1 Motility Disorders Internuclear Ophthalmoplegia Supranuclear Internuclear MLF

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1 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Internuclear MLF Fascicular Subarachnoid Infranuclear Cavernous sinus Orbital

1 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Internuclear MLF Fascicular Subarachnoid Infranuclear Cavernous sinus Orbital CN 6 Nucleus ^ CN 3 Nucleus ^ Nuclear This slide captures one way to think about the motility disorders. If it is unfamiliar, I strongly suggest you review the slide-set entitled ‘Motility disorders: Overview’ before proceeding. Neuromuscular junction Extraocular muscle CN 4 Nucleus

2 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear In this slide-set we will address internuclear ophthalmoplegia

2 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear In this slide-set we will address internuclear ophthalmoplegia (INO), along with several related conditions (that’s what the ‘+’ refers to in the title) Internuclear MLF CN 6 Nucleus ^ CN 3 Nucleus ^ Nuclear Fascicular Subarachnoid Infranuclear Cavernous sinus Orbital Neuromuscular junction Extraocular muscle CN 4 Nucleus

3 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus

3 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus What does MLF stand for in this context? Medial longitudinal fasciculus Again in this context, what does the word fasciculus mean? It means ‘a small fascicle’ OK then, in context, what does fascicle refer to? It refers to a bundle of nerve fibers running together within the substance of the brainstem. In other words, it’s a cranial nerve that’s left its nucleus, but has yet to ‘break out’ into the subarachnoid space

4 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus

4 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus What does MLF stand for in this context? Medial longitudinal fasciculus Again in this context, what does the word fasciculus mean? It means ‘a small fascicle’ OK then, in context, what does fascicle refer to? It refers to a bundle of nerve fibers running together within the substance of the brainstem. In other words, it’s a cranial nerve that’s left its nucleus, but has yet to ‘break out’ into the subarachnoid space

5 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus

5 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus What does MLF stand for in this context? Medial longitudinal fasciculus Again in this context, what does the word fasciculus mean? It means ‘a small fascicle’ OK then, in context, what does fascicle refer to? It refers to a bundle of nerve fibers running together within the substance of the brainstem. In other words, it’s a cranial nerve that’s left its nucleus, but has yet to ‘break out’ into the subarachnoid space

6 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus

6 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus What does MLF stand for in this context? Medial longitudinal fasciculus Again in this context, what does the word fasciculus mean? It means ‘a small fascicle’ OK then, in context, what does fascicle refer to? It refers to a bundle of nerve fibers running together within the substance of the brainstem. In other words, it’s a cranial nerve that’s left its nucleus, but has yet to ‘break out’ into the subarachnoid space

7 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus

7 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus What does MLF stand for in this context? Medial longitudinal fasciculus Again in this context, what does the word fasciculus mean? It means ‘a small fascicle’ OK then, in context, what does fascicle refer to? It refers to a bundle of nerve fibers running together within the substance of the brainstem. In other words, it’s a cranial nerve that’s left its nucleus, but has yet to ‘break out’ into the subarachnoid space

8 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus

8 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus What does MLF stand for in this context? Medial longitudinal fasciculus Again in this context, what does the word fasciculus mean? It means ‘a small fascicle’ OK then, in context, what does fascicle refer to? It refers to a bundle of nerve fibers running together within the substance of the brainstem. In other words, it’s a cranial nerve that’s left its nucleus, but has yet to ‘break out’ into the subarachnoid space.

9 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Internuclear MLF CN 6 Nucleus ^ CN 3

9 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Internuclear MLF CN 6 Nucleus ^ CN 3 Nucleus ^ Nuclear What does MLF stand for in this context? Medial longitudinal fasciculus Fascicular Subarachnoid Infranuclear Cavernous Again in this context, what does the word sinusfasciculus mean? It means ‘a small fascicle’ But you knew this already. Recall that the first segment Orbital OK then, in context, doesnerve fascicle refer to? of the Infranuclear portion of thewhat cranial pathway Itjunction refers to a bundle of nerve fibers running Neuromuscular is the Fascicular , followed by the Subarachnoid Extraocular together within the substance of the brainstem. muscle In other words, it’s a cranial nerve that’s left its nucleus, but has yet to ‘break out’ into the subarachnoid space.

10 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus

10 Motility Disorders: Internuclear Ophthalmoplegia+ MLF CN 6 Nucleus ^ ^ CN 3 Nucleus From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

11 MLF CN 6 Nucleus ^ CN 3 Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+

11 MLF CN 6 Nucleus ^ CN 3 Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? ipsi- v contralateral From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

12 MLF CN 6 Nucleus ^ CN 3 Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+

12 MLF CN 6 Nucleus ^ CN 3 Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

13 MLF CN 6 Nucleus ^ ? CN 3 R M SN Nucleus ^

13 MLF CN 6 Nucleus ^ ? CN 3 R M SN Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, EOM to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

14 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility

14 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

15 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility

15 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

16 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility

16 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

17 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility

17 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into ipsilateral gaze together

18 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility

18 MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ Motility Disorders: Internuclear Ophthalmoplegia+ From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What purpose does the MLF serve? To allow coordinated lateral gaze of both eyes How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

19 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

19 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? CN 6 nucleus to the contralateral So From if thethe depicted CN 6 nucleus is on a pt’s. CN 3 left nucleus—specifically, side, the depicted MLF to to its her medial (MR) subnucleus runs rightrectus MR subnucleus. When the pt endeavors to look to her left, the left CN 6 nucleus causes the left LR to contract while also What purpose does the MLF serve? sending impulses (via lateral the MLF) To allow coordinated gazetoofher bothright eyes. MR subnucleus, which in turn causes the right MR to contract simultaneously—and both eyes shift intodoes left the gaze in facilitate coordinated How MLF lateralfashion gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

20 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

20 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? CN 6 nucleus to the contralateral So From if thethe depicted CN 6 nucleus is on a pt’s. CN 3 left nucleus—specifically, side, the depicted MLF to to its her medial (MR) subnucleus runs rightrectus MR subnucleus. When the pt endeavors to look to her left, the left CN 6 nucleus causes the left LR to contract while also What purpose does the MLF serve? sending impulses (via lateral the MLF) To allow coordinated gazetoofher bothright eyes. MR subnucleus, which in turn causes the right MR to contract simultaneously—and both eyes shift intodoes left the gaze in facilitate coordinated How MLF lateralfashion. gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

21 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L ^ MLF CN 6 To To

21 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L ^ MLF CN 6 To To the MLF LR LR ^ CN 3 R M SN Nucleus ^ MR Note that the CN 6 nucleus consists of two subpopulations of do neurons: those that innervate the ipsilateral LR, and From where to where the fascicles of the MLF run? those whose MLF and innervate the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, So From if thethe depicted CN 6 nucleus isaxons on awill pt’sform leftthe side, the depicted MLF MR subnucleus to to its her medial (MR) subnucleus runs rightrectus MR contralateral subnucleus. When the pt endeavors to look to her left, the left CN 6 nucleus causes the left LR to contract while also What purpose does the MLF serve? sending impulses (via lateral the MLF) To allow coordinated gazetoofher bothright eyes. MR subnucleus, which in turn causes the right MR to contract simultaneously—and both eyes shift intodoes left the gaze in facilitate coordinated How MLF lateralfashion. gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

22 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

22 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in appropriate ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

23 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

23 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in appropriate ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

24 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

24 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. . allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in appropriate ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

25 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

25 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing the contralateral MR to fire simultaneously with the ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

26 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

26 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

27 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

27 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR Would this be considered a right INO, or a left INO? What is the rule for naming INOs? From where to where do the fascicles of the MLF run? By convention, INOs are named based on the side with impaired ADduction. From the nucleus to the contralateral nucleus—specifically, Therefore, the. CN 6 scenario as presented would represent. CN 3 a right INO. to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

28 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

28 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR Would this be considered a right INO, or a left INO? What is the rule for naming INOs? From where to where do the fascicles of the MLF run? By convention, INOs are named based on the side with impaired ADduction. From the nucleus to the contralateral nucleus—specifically, Therefore, the. CN 6 scenario as presented would represent. CN 3 a right INO. to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

29 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

29 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR Would this be considered a right INO, or a left INO? What is the rule for naming INOs? From where to where do the fascicles of the MLF run? By convention, INOs are named based on the side with impaired ADduction. From the nucleus to the contralateral nucleus—specifically, Therefore, the. CN 6 scenario as presented would represent. CN 3 a right INO. to its medial rectus (MR) subnucleus What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? a right By causing the MR to fire simultaneously with(INO) the This iscontralateral an internuclear ophthalmoplegia ^ (LR), thus ensuring both eyes turn into ipsilateral rectus lateral gaze together

30 Motility Disorders: Internuclear Ophthalmoplegia+ ? R L LR MLF CN 6 Nucleus ^

30 Motility Disorders: Internuclear Ophthalmoplegia+ ? R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? What form does. From this ‘impairment’ take? That is, oncontralateral attempted lateral gaze in an the CN 6 nucleus to the CN 3 nucleus—specifically, INO pt, what does the adducting eye do? to aitsmuch medial rectus (MR) subnucleus It adducts, What but ateffect slower velocity than. MLF that of the on abduction movement of does a lesion of the have lateral gaze? the fellow If eye. The Neuro book refers to this to slowed-saccade the(Take MLF note: is bagged, the impulse intended result in the firing of the contralateral What purpose does the MLF serve? phenomenon “cardinal sign” an INO. ) MRas is the affected…but theof impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

31 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN

31 Motility Disorders: Internuclear Ophthalmoplegia+ R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? What form does. From this ‘impairment’ take? That is, oncontralateral attempted lateral gaze in an the CN 6 nucleus to the CN 3 nucleus—specifically, INO pt, what does the adducting eye do? to aitsmuch medial rectus (MR) subnucleus It adducts, What but ateffect slower velocity than. MLF that of the on abduction movement of does a lesion of the have lateral gaze? the fellow If eye. The Neuro book refers to this to slowed-saccade the(Take MLF note: is bagged, the impulse intended result in the firing of the contralateral What purpose does the MLF serve? phenomenon “cardinal sign” an INO. ) MRas is the affected…but theof impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

32 Motility Disorders: Internuclear Ophthalmoplegia+ ? ? R L LR MLF CN 6 Nucleus

32 Motility Disorders: Internuclear Ophthalmoplegia+ ? ? R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral nucleus—specifically, While it abducts normally, the LR in CN 3 INO often manifests an uncommon finding-to its medialwhat rectus (MR) subnucleus is it? What effect does a lesion of the MLF have on lateral gaze? The abducting eye often exhibits end-point nystagmus If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both. ABduction eyes Thus, Toattempted lateral gaze results in normal of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

33 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

33 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral nucleus—specifically, While it abducts normally, the LR in CN 3 INO often manifests an uncommon finding-to its medialwhat rectus (MR) subnucleus is it? What effect does a lesion of the MLF have on lateral gaze? The abducting eye often exhibits end-point nystagmus If the MLF is bagged, the impulse intended to result in the firing of the contralateral What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both. ABduction eyes Thus, Toattempted lateral gaze results in normal of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

34 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

34 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? What about convergence movements? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, In theory, convergence should be unaffected by an INO (in practice, to its medial rectus (MR) subnucleus it may be impaired) What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Why would one the expect convergence What purpose does MLF serve? to be unaffected by an INO? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Because neural inputs controlling convergence movements do not To allow coordinated lateral gaze of both eyes Thus, attempted results normal reach lateral the MRgaze subnuclei viain the MLF ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

35 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

35 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? What about convergence movements? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, In theory, convergence should be unaffected by an INO (in practice, to its medial rectus (MR) subnucleus it may be impaired) What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Why would one the expect convergence What purpose does MLF serve? to be unaffected by an INO? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Because neural inputs controlling convergence movements do not To allow coordinated lateral gaze of both eyes Thus, attempted results normal reach lateral the MRgaze subnuclei viain the MLF ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

36 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

36 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? What about convergence movements? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, In theory, convergence should be unaffected by an INO (in practice, to its medial rectus (MR) subnucleus it may be impaired) What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Why would one the expect convergence What purpose does MLF serve? to be unaffected by an INO? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Because neural inputs controlling convergence movements do not To allow coordinated lateral gaze of both eyes Thus, attempted results normal reach lateral the MRgaze subnuclei viain the MLF ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

37 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

37 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? What about convergence movements? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, In theory, convergence should be unaffected by an INO (in practice, to its medial rectus (MR) subnucleus it may be impaired) What effect does a lesion of the MLF have on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Why would one the expect convergence What purpose does MLF serve? to be unaffected by an INO? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Because neural inputs controlling convergence movements do not To allow coordinated lateral gaze of both eyes Thus, attempted results normal reach lateral the MRgaze subnuclei viain the MLF ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

38 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

38 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the eyes evidence another alignment issue, one not to its medial rectus (MR)may subnucleus What effect does a lesionbased of theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral. ADducting, gaze results in normal ABduction ipsilateral eye, but Which eye--the or the ABducting--tend to of be the hyper? impaired. The ADduction of the contralateral eye. ADducting How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

39 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

39 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the eyes evidence another alignment issue, one not to its medial rectus (MR)may subnucleus What effect does a lesionbased of theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral. ADducting, gaze results in normal ABduction ipsilateral eye, but Which eye--the or the ABducting--tend to of be the hyper? impaired. The ADduction of the contralateral eye. ADducting How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

40 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

40 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

41 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

41 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

42 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

42 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

43 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear? ((( ))) R L CN 3 R M

43 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear? ((( ))) R L CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ Nuclear? ^ Internuclear? MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting be internuclear, but it is actually supranuclear Infranuclear? How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

44 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear? ((( ))) R L CN 3 R M

44 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear? ((( ))) R L CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ Nuclear? ^ Internuclear? MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear Infranuclear? How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

45 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear ((( ))) R L LR MLF CN 6

45 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

46 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear

46 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Those from the cortex, cerebellum, vestibular system, and a number of brainstem nuclei ( (( MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ An important rule-of-thumb can be stated regarding ))) supranuclear motility. Rdisorders L and diplopia--what is it? It is this: With four important exceptions, supranuclear pts do not complain of diplopia LR MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

47 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear

47 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Those from the cortex, cerebellum, vestibular system, and a number of brainstem nuclei ( (( MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ An important rule-of-thumb can be stated regarding ))) supranuclear motility. Rdisorders L and diplopia--what is it? It is this: With four important exceptions, supranuclear pts do not complain of diplopia LR MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

48 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear

48 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Those from the cortex, cerebellum, vestibular system, and a number of brainstem nuclei ( (( MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ An important rule-of-thumb can be stated regarding ))) supranuclear motility. Rdisorders L and diplopia--what is it? It is this: With four important exceptions, supranuclear pts do not complain of diplopia LR MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

49 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear

49 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Those from the cortex, cerebellum, vestibular system, and a number of brainstem nuclei ( (( MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ An important rule-of-thumb can be stated regarding ))) supranuclear motility. Rdisorders L and diplopia--what is it? It is this: With four important exceptions, supranuclear pts do not complain of diplopia LR MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

50 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear

50 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Those from the cortex, cerebellum, vestibular system, and a number of brainstem nuclei ( (( An important rule-of-thumb can be stated regarding ))) supranuclear motility. Rdisorders L and diplopia--what is it? It is this: With four important exceptions, supranuclear pts do not complain of diplopia LR MR ^ ^ What are the four supranuclear disorders in which pts c/o diplopia? -CN 3 R CN 6 MLF -M SN Nucleus --- From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

51 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear

51 What sorts of inputs comprise the supranuclear pathways? Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear Those from the cortex, cerebellum, vestibular system, and a number of brainstem nuclei ( (( An important rule-of-thumb can be stated regarding ))) supranuclear motility. Rdisorders L and diplopia--what is it? It is this: With four important exceptions, supranuclear pts do not complain of diplopia LR MR ^ ^ What are the four supranuclear disorders in which pts c/o diplopia? --Skew deviation CN 3 R CN 6 MLF --Divergence insufficiency M SN Nucleus --Convergence insufficiency --Convergence spasm From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the. What eyes may evidence another alignment issue, one not to its medial rectus (MR)is subnucleus skew deviation? What effect does a lesionbased of acquired theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? An vertical misalignment 2 ndry to disruption of vestibular input If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. Is skew deviation supranuclear, internuclear, or infranuclear? To allow coordinated lateral gaze of both eyes Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, butyou’d think Which eye--the ADducting, ABducting--tend to be hyper? When it isorathe component of an internuclear ophthalmoplegia, impaired. The ADduction of theit contralateral eye. ADducting would be internuclear, but it is actually supranuclear How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

52 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

52 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the eyes evidence another alignment issue, one not to its medial rectus (MR)may subnucleus What effect does a lesionbased of theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral. ADducting, gaze results in normal ABduction the ipsilateral eye, but Which eye--the or ABducting--tends to beof hyper in INO skew? impaired. The ADduction of the contralateral eye. ADducting How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

53 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

53 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR From where to where do the fascicles of the MLF run? From the CN 6 nucleus to the contralateral CN 3 nucleus—specifically, Finally: In INO, the eyes evidence another alignment issue, one not to its medial rectus (MR)may subnucleus What effect does a lesionbased of theon. MLF have on lateral gaze? easily anticipated pathology of the MLF. What is it? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Skew deviation What purpose does the MLF serve? MR is affected…but the impulse to the ipsilateral LR gets through unscathed. allow coordinated lateral gaze of both eyes Thus, Toattempted lateral. ADducting, gaze results in normal ABduction the ipsilateral eye, but Which eye--the or ABducting--tends to beof hyper in INO skew? impaired. The ADduction of the contralateral eye. ADducting How does the MLF facilitate lateral gaze coordination? By causing MR to fire simultaneously with(INO) the Thistheiscontralateral an internuclear ophthalmoplegia ipsilateral rectus (LR), thus ensuring both eyes turn into lateral gaze together

54 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

54 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Is bilateral (BINO) thing? MR is affected…but the impulse to the. INO ipsilateral LRa gets through unscathed. Indeed it is Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. a bilateral This is an internuclear ophthalmoplegia (INO) ? ^

55 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

55 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the MLF is bagged, the impulse intended to result in the firing of the contralateral Is bilateral (BINO) thing? MR is affected…but the impulse to the. INO ipsilateral LRa gets through unscathed. Indeed it is Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, but impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

56 Motility Disorders: Internuclear Ophthalmoplegia+ ? ? R L MR CN 3 R M

56 Motility Disorders: Internuclear Ophthalmoplegia+ ? ? R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the MLF is bagged, impulse intended to result in the firing of the contralateral Does BINOthe present with… Is bilateral (BINO) thing? MR is affected…but the impulse to the. INO ipsilateral LRa gets through unscathed. …slow saccade of the ADducting eye in lateral gaze bilaterally? Yes Indeed it is Thus, attempted lateral gaze results in normal ABduction of the ipsilateral …nystagmus of the ABducting eye in lateral gaze bilaterally? Yes eye, but impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

57 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

57 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the MLF is bagged, impulse intended to result in the firing of the contralateral Does BINOthe present with… Is bilateral (BINO) thing? MR is affected…but the impulse to the. INO ipsilateral LRa gets through unscathed. …slow saccade of the ADducting eye in lateral gaze bilaterally? Yes Indeed it is Thus, attempted lateral gaze results in normal ABduction of the ipsilateral …nystagmus of the ABducting eye in lateral gaze bilaterally? Yes eye, but impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

58 Motility Disorders: Internuclear Ophthalmoplegia+ ? ? R L MR CN 3 R M

58 Motility Disorders: Internuclear Ophthalmoplegia+ ? ? R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the MLF is bagged, impulse intended to result in the firing of the contralateral Does BINOthe present with… Is bilateral (BINO) thing? MR is affected…but the impulse to the. INO ipsilateral LRa gets through unscathed. …slow saccade of the ADducting eye in lateral gaze bilaterally? Yes Indeed it is Thus, attempted lateral gaze results in normal ABduction of the ipsilateral eye, but …nystagmus of the ABducting eye in lateral gaze bilaterally? impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

59 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L MR CN 3 R M

59 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the MLF is bagged, impulse intended to result in the firing of the contralateral Does BINOthe present with… Is bilateral (BINO) thing? MR is affected…but the impulse to the. INO ipsilateral LRa gets through unscathed. …slow saccade of the ADducting eye in lateral gaze bilaterally? Yes Indeed it is Thus, attempted lateral gaze results in normal ABduction of the ipsilateral …nystagmus of the ABducting eye in lateral gaze bilaterally? Yes eye, but impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

60 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

60 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the BINO MLF is bagged, impulse intended toofresult in the firing of the contralateral can presentthe with. Is two other findings interest: bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical Indeed it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

61 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

61 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the BINO MLF is bagged, impulse intended toofresult in the firing of the contralateral can presentthe with. Is two other findings interest: bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical Indeed it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

62 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

62 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the BINO MLF is bagged, impulse intended toofresult in the firing of the contralateral can presentthe with. Is two other findings interest: bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical Indeed it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. Broadly speaking, what is the etiology of the vertical nystagmus? Like the skew deviation that can accompany INO, the nystagmus BINO a bilateral is 2 ndry to disruption of input from the (vestibular This is an internuclear ophthalmoplegia INO) ^ system

63 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

63 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the BINO MLF is bagged, impulse intended toofresult in the firing of the contralateral can presentthe with. Is two other findings interest: bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical Indeed it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. Broadly speaking, what is the etiology of the vertical nystagmus? Like the skew deviation that can accompany INO, the nystagmus BINO a bilateral is 2 ndry to disruption of input from the (vestibular This is an internuclear ophthalmoplegia INO) ^ system

64 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

64 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the BINO MLF is bagged, impulse intended toofresult in the firing of the contralateral can presentthe with. Is two other findings interest: bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical Indeed it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. Broadly speaking, what is the etiology of the vertical nystagmus? Like the skew deviation that can accompany INO, the nystagmus BINO a bilateral is 2 ndry to disruption of input from the (vestibular This is an internuclear ophthalmoplegia INO) ^ system

65 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

65 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the BINO MLF is bagged, impulse intended toofresult in the firing of the contralateral can presentthe with. Is two other findings interest: bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical Indeed it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

66 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

66 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What effect does a lesion of the MLFshave on lateral gaze? If the BINO MLF is bagged, impulse intended toofresult in the firing of the contralateral can presentthe with. Is two other findings interest: bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical Indeed it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

67 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

67 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN both What term is useddoes to describe the of appearance of effect a lesion the MLFshave on lateral gaze? individuals with exotropia in BINO? If the BINO MLF is bagged, the impulse intended toofresult in the firing of the contralateral can present with two other findings interest: The term is ‘wall eyed. ’ Thus, these individuals are Is bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical said to have a ‘wall-eyed bilateral. Indeed INO’ (WEBINO) it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

68 R L MR CN 3 R M SN Nucleus MLF LR CN 6

68 R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR Left wall Right wall Motility Disorders: Internuclear Ophthalmoplegia+ CN 3 Nucleus MR SN both What term is useddoes to describe the of appearance of effect a lesion the MLFshave on lateral gaze? individuals with exotropia in BINO? If the BINO MLF is bagged, the impulse intended toofresult in the firing of the contralateral can present with two other findings interest: The term is ‘wall eyed. ’ Thus, these individuals are Is bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical said to have a ‘wall-eyed bilateral. Indeed INO’ (WEBINO) it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. a bilateral BINO This is an internuclear ophthalmoplegia (INO) ^

69 R L MR CN 3 R M SN Nucleus MLF LR CN 6

69 R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR Left wall Right wall Motility Disorders: Internuclear Ophthalmoplegia+ CN 3 Nucleus MR SN both What term is useddoes to describe the of appearance of effect a lesion the MLFshave on lateral gaze? individuals with exotropia in BINO? If the BINO MLF is bagged, the impulse intended toofresult in the firing of the contralateral can present with two other findings interest: The term is ‘wall eyed. ’ Thus, these individuals are Is bilateral INO (BINO) a thing? MR is. One affected…but the impulse to the ipsilateral LRisgets throughnystagmus unscathed. finding concerns a vertical-gaze issue. What it? Vertical said to have a ‘wall-eyed bilateral. Indeed INO’ (WEBINO). it is Thus, The attempted gaze issue. results. What in normal ABduction of the ipsilateral eye, but other is lateral a strabismic is it? Large-angle exotropia impaired ADduction of the contralateral eye. wall-eyed WEBINO a bilateral ^ This is an internuclear ophthalmoplegia (INO) ^

70 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

70 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? This is an internuclear ophthalmoplegia (INO)

71 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

71 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: age? gender? ethnicity? This is an internuclear ophthalmoplegia (INO)

72 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

72 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: This is an internuclear ophthalmoplegia (INO)

73 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

73 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: --In a teen/young adult, it is likely… This is an internuclear ophthalmoplegia (INO)

74 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

74 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: --In a teen/young adult, it is likely…demyelinating dz This is an internuclear ophthalmoplegia (INO)

75 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

75 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: --In a teen/young adult, it is likely…demyelinating dz --In an older adult, it is likely 2 ndry to a… This is an internuclear ophthalmoplegia (INO)

76 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

76 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: --In a teen/young adult, it is likely…demyelinating dz --In an older adult, it is likely 2 ndry to a…CVA This is an internuclear ophthalmoplegia (INO)

77 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

77 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: --In a teen/young adult, it is likely…demyelinating dz --In an older adult, it is likely 2 ndry to a…CVA What condition/etiology must always be considered? This is an internuclear ophthalmoplegia (INO)

78 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

78 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: --In a teen/young adult, it is likely…demyelinating dz --In an older adult, it is likely 2 ndry to a…CVA What condition/etiology must always be considered? abb. A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

79 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

79 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? That is usually a function of pt age: --In a teen/young adult, it is likely…demyelinating dz --In an older adult, it is likely 2 ndry to a…CVA What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

80 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

80 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is likely…demyelinating dz --In a teen/young --The absence of--In end-point nystagmus in likely the ABducting an older adult, it is 2 ndry toeye a…CVA --The presence of MG-related lid signs What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

81 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

81 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is likely…demyelinating dz --In a teen/young --The absence of--In end-point nystagmus in likely the ABducting an older adult, it is 2 ndry toeye a…CVA --The presence of MG-related lid signs What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

82 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

82 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is likely…demyelinating dz --In a teen/young --The absence of--In end-point nystagmus in likely the ABducting an older adult, it is 2 ndry toeye a…CVA --The presence of MG-related lid signs What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

83 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

83 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is likely…demyelinating dz --In a teen/young --The absence of--In end-point nystagmus in likely the ABducting an older adult, it is 2 ndry toeye a…CVA --The presence of MG-related lid signs What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

84 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

84 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is likely…demyelinating dz --In a teen/young --The absence of--In end-point nystagmus in likely the ABducting an older adult, it is 2 ndry toeye a…CVA --The presence of MG-related lid signs What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

85 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

85 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is. What --In a teen/young likely…demyelinating dz are the lid signs implicating MG? --The absence of--In end-point nystagmus in the ABducting eye an older adult, it is likely -- 2 ndry to a…CVA --The presence of MG-related lid signs -- What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

86 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

86 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is. What --In a teen/young likely…demyelinating dz are the lid signs implicating MG? --The absence of--In end-point nystagmus in the ABducting eye eponym an older adult, it is likely 2 ndry to --Cogan lid a…CVA twitch --The presence of MG-related lid signs --Fatiguability of ptosis What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

87 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

87 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is the etiology underlying INO? What aspects of That the presentation an ‘INO’ that would is usually of a function of pt age: indicate that it’s pseudo-INO 2 ndry toadult, MG? it is. What --In a teen/young likely…demyelinating dz are the lid signs implicating MG? --The absence of--In end-point nystagmus in the ABducting eye an older adult, it is likely 2 ndry to --Cogan lid a…CVA twitch --The presence of MG-related lid signs --Fatiguability of ptosis What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

88 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

88 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is Cogan lid twitch? A phenomenon in which, when the eye shifts from down- to upgaze, What is the etiology underlying INO? its normal upgaze resting position before the upper lid overshoots What aspects of That the presentation of an ‘INO’ that would is usuallysettling a function of pt age: into that position indicate that it’s pseudo-INO 2 ndry toadult, MG? it is. What --In a teen/young likely…demyelinating dz are the lid signs implicating MG? --The absence of--In end-point nystagmus in the ABducting eye an older adult, it is likely 2 ndry to --Cogan lida…CVA twitch --The presence of MG-related lid signs --Fatiguability of ptosis What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

89 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus

89 Motility Disorders: Internuclear Ophthalmoplegia+ ((( ))) R L LR MLF CN 6 Nucleus ^ CN 3 R M SN Nucleus ^ MR What is Cogan lid twitch? A phenomenon in which, when the eye shifts from down- to upgaze, What is the etiology underlying INO? its normal upgaze resting position before the upper lid overshoots What aspects of That the presentation of an ‘INO’ that would is usuallysettling a function of pt age: into that position indicate that it’s pseudo-INO 2 ndry toadult, MG? it is. What --In a teen/young likely…demyelinating dz are the lid signs implicating MG? --The absence of--In end-point nystagmus in the ABducting eye an older adult, it is likely 2 ndry to --Cogan lida…CVA twitch --The presence of MG-related lid signs --Fatiguability of ptosis What condition/etiology must always be considered? A pseudo-INO 2 ndry to MG This is an internuclear ophthalmoplegia (INO)

90 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear In this slide-set we will address internuclear ophthalmoplegia

90 Motility Disorders: Internuclear Ophthalmoplegia+ Supranuclear In this slide-set we will address internuclear ophthalmoplegia (INO), along with several related conditions (that’s what the ‘+’ refers to in the title) ^ ^ Internuclear We will now turn to the ‘several CN 3 related conditions ’MLF alluded. CN 6 to at Nuclear Nucleus the beginning of the slide-set Fascicular Subarachnoid Infranuclear Cavernous sinus Orbital Neuromuscular junction Extraocular muscle CN 4 Nucleus

91 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

91 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In the present context, what is the one-and-a-half syndrome?

92 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

92 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In the present context, what is the one-and-a-half syndrome? A clinical condition in which one eye is incapable of horizontal movement (the ‘one’) and the other is capable only of ABduction (the ‘half’)

93 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

93 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In the present context, what is the one-and-a-half syndrome? A clinical condition in which one eye is incapable of horizontal movement (the ‘one’) and the other is capable only of ABduction (the ‘half’) What is the cause?

94 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

94 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In the present context, what is the one-and-a-half syndrome? A clinical condition in which one eye is incapable of horizontal movement (the ‘one’) and the other is capable only of ABduction (the ‘half’) What is the cause? A lesion that bags the MLF on one side along with the ipsilateral CN 6 nucleus (or ipsilateral PPRF)

95 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

95 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN How would a lesion bagging both the CN 6 and MLF on one side of the brainstem lead to one eye without horizontal movements, and the other with ABduction only? Obviously, knocking out the CN 6 nucleus will bag the ipsilateral LR. However, recall that the CN 6 nucleus consists of two subpopulations of neurons, one of which gives rise to the MLF heading to the contralateral CN 3 MR subnucleus. Thus, a nuclear CN 6 lesion is a de facto MLF lesion as well, knocking out lateral-gaze input to the contralateral MR in addition to the ipsilateral LR. Finally, involvement of the ipsilateral MLF (ie, the one carrying innervation from the contralateral CN 6 nucleus to the ipsilateral CN 3 MR subnucleus), knocks out lateral-gaze innervation to the ipsilateral MR. Thus, we are left with a one-and-a-half syndrome, with the only ABduction of the contralateral eye being intact.

96 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MR MLF ^ ^ CN 6

96 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MR MLF ^ ^ CN 6 Nucleus MLF CN 6 To the Nucleus MLF LR ^ CN 3 R M SN Nucleus ^ MR ^ LR CN 3 Nucleus MR SN How would a lesion bagging both the CN 6 and MLF on one side of the brainstem lead to one eye without horizontal movements, and the other with ABduction only? Obviously, knocking out the CN 6 nucleus will bag the ipsilateral LR. However, recall that the CN 6 nucleus consists of two subpopulations of neurons, one of which gives rise to the MLF heading to the contralateral CN 3 MR subnucleus. Thus, a nuclear CN 6 lesion is a de facto MLF lesion as well, knocking out lateral-gaze input to the contralateral MR in addition to the ipsilateral LR. Finally, involvement of the ipsilateral MLF (ie, the one carrying innervation from the contralateral CN 6 nucleus to the ipsilateral CN 3 MR subnucleus), knocks out lateral-gaze innervation to the ipsilateral MR. Thus, we are left with a one-and-a-half syndrome, with the only ABduction of the contralateral eye being intact.

97 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MR MLF ^ ^ CN 6

97 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MR MLF ^ ^ CN 6 Nucleus MLF CN 6 To To the MLF LR LR ^ CN 3 R M SN Nucleus ^ MR ^ LR CN 3 Nucleus MR SN How would a lesion bagging both the CN 6 and MLF on one side of the brainstem lead to one eye without horizontal movements, and the other with ABduction only? Obviously, knocking out the CN 6 nucleus will bag the ipsilateral LR. However, recall that the CN 6 nucleus consists of two subpopulations of neurons, one of which gives rise to the MLF heading to the contralateral CN 3 MR subnucleus. Thus, a nuclear CN 6 lesion is a de facto MLF lesion as well, knocking out lateral-gaze input to the contralateral MR in addition to the ipsilateral LR. Finally, involvement of the ipsilateral MLF (ie, the one carrying innervation from the contralateral CN 6 nucleus to the ipsilateral CN 3 MR subnucleus), knocks out lateral-gaze innervation to the ipsilateral MR. Thus, we are left with a one-and-a-half syndrome, with the only ABduction of the contralateral eye being intact.

98 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MR MLF ^ ^ CN 6

98 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MR MLF ^ ^ CN 6 Nucleus MLF CN 6 To To the MLF LR LR ^ CN 3 R M SN Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In thebagging present context, is theonone-and-a-half syndrome? How would a lesion both the CN 6 what and MLF one side of the brainstem lead to one eye without horizontal movements, and the otherin with ABduction only? A clinical condition which one eye is incapable of horizontal movement Obviously, knocking out theand CN 6 the nucleus bag the ipsilateral LR. However, recall that the CN 6 nucleus (the ‘one’) otherwill is capable only of ABduction (the ‘half’) consists of two subpopulations of neurons, one of which gives rise to the MLF heading to the contralateral CN 3 MR subnucleus. Thus, a nuclear CN 6 lesion is a de facto MLF lesion as well, knocking out lateral-gaze What is the cause? input to the contralateral MR in addition to the ipsilateral LR. Finally, involvement of the ipsilateral MLF (ie, the A lesionfrom thatthe bags the MLFCN 6 on nucleus one side along with CN 3 the ipsilateral CN 6 knocks one carrying innervation contralateral to the ipsilateral MR subnucleus), (ortoipsilateral PPRF) out lateral-gazenucleus innervation the ipsilateral MR. Thus, we are left with a one-and-a-half syndrome, with the only ABduction of the contralateral eye being intact.

99 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MLF ^ ^ ^ CN 6

99 Motility Disorders: Internuclear Ophthalmoplegia+ ^ R L MLF ^ ^ ^ CN 6 Nucleus MLF LR ^ CN 3 R M SN Nucleus CN 6 To To the MLF LR ^ MR MR CN 3 Nucleus MR SN ^ LR How would a lesion bagging both the CN 6 and MLF on one side of the brainstem lead to one eye without horizontal movements, and the other with ABduction only? Obviously, knocking out the CN 6 nucleus will bag the ipsilateral LR. However, recall that the CN 6 nucleus consists of two subpopulations of neurons, one of which gives rise to the MLF heading to the contralateral CN 3 MR subnucleus. Thus, a nuclear CN 6 lesion is a de facto MLF lesion as well, knocking out lateral-gaze input to the contralateral MR in addition to the ipsilateral LR. Finally, involvement of the ipsilateral MLF (ie, the one carrying innervation from the contralateral CN 6 nucleus to the ipsilateral CN 3 MR subnucleus), knocks out lateral-gaze innervation to the ipsilateral MR. Thus, we are left with a one-and-a-half syndrome, with the only ABduction of the contralateral eye being intact.

100 Motility Disorders: Internuclear Ophthalmoplegia+ MR ^ MLF ^ ^ CN 6 Nucleus MLF

100 Motility Disorders: Internuclear Ophthalmoplegia+ MR ^ MLF ^ ^ CN 6 Nucleus MLF CN 6 To To the MLF LR LR ^ CN 3 R M SN Nucleus ^ MR ^ LR CN 3 Nucleus MR SN ^ ^ ^ R L How would a lesion bagging both the CN 6 and MLF on one side of the brainstem lead to one eye without horizontal movements, and the other with ABduction only? Obviously, knocking out the CN 6 nucleus will bag the ipsilateral LR. However, recall that the CN 6 nucleus consists of two subpopulations of neurons, one of which gives rise to the MLF heading to the contralateral CN 3 MR subnucleus. Thus, a nuclear CN 6 lesion is a de facto MLF lesion as well, knocking out lateral-gaze input to the contralateral MR in addition to the ipsilateral LR. Finally, involvement of the ipsilateral MLF (ie, the one carrying innervation from the contralateral CN 6 nucleus to the ipsilateral CN 3 MR subnucleus), knocks out lateral-gaze innervation to the ipsilateral MR. Thus, we are left with only ABduction of the contralateral eye being preserved.

101 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

101 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In the present context, what is the eight-and-a-half syndrome?

102 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

102 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In the present context, what is the eight-and-a-half syndrome? A clinical condition consisting of a one-and-a-half syndrome plus an ipsilateral CN 7 palsy (7 + 1. 5 = 8. 5 --get it? )

103 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

103 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 3 Nucleus MR SN In the present context, what is the eight-and-a-half syndrome? A clinical condition consisting of a one-and-a-half syndrome plus an ipsilateral CN 7 palsy (7 + 1. 5 = 8. 5 --get it? ) What is the anatomic relationship that makes this possible?

104 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

104 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 7 Nucleus CN 3 Nucleus MR SN In the present context, what is the eight-and-a-half syndrome? A clinical condition consisting of a one-and-a-half syndrome plus an ipsilateral CN 7 palsy (7 + 1. 5 = 8. 5 --get it? ) What is the anatomic relationship that makes this possible? Recall that, after leaving its nucleus, the CN 7 fascicle loops around the CN 6 nucleus before exiting the brainstem. Thus, any lesion that bags the CN 6 nucleus is likely to get the CN 7 fascicle as well.

105 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

105 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 7 Nucleus CN 3 Nucleus MR SN In the present context, what is the eight-and-a-half syndrome? A clinical condition consisting of a one-and-a-half syndrome plus an ipsilateral CN 7 palsy (7 + 1. 5 = 8. 5 --get it? ) What is the most common cause of the one-and-a-half and eight-and-a-half syndromes? CVA What is the anatomic relationship that makes this possible? Recall that, after leaving its nucleus, the CN 7 fascicle loops around the CN 6 nucleus before exiting the brainstem. Thus, any lesion that bags the CN 6 nucleus is likely to get the CN 7 fascicle as well.

106 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus

106 Motility Disorders: Internuclear Ophthalmoplegia+ R L MR CN 3 R M SN Nucleus MLF LR CN 6 Nucleus ^ ^ CN 6 Nucleus ^ MR ^ LR CN 7 Nucleus CN 3 Nucleus MR SN In the present context, what is the eight-and-a-half syndrome? A clinical condition consisting of a one-and-a-half syndrome plus an ipsilateral CN 7 palsy (7 + 1. 5 = 8. 5 --get it? ) What is the most common cause of the one-and-a-half and eight-and-a-half syndromes? CVA What is the anatomic relationship that makes this possible? Recall that, after leaving its nucleus, the CN 7 fascicle loops around the CN 6 nucleus before exiting the brainstem. Thus, any lesion that bags the CN 6 nucleus is likely to get the CN 7 fascicle as well.