Glossopharyngeus vagus accessory and hypoglossus nerves Mark Kozsurek

Glossopharyngeus, vagus, accessory and hypoglossus nerves Mark Kozsurek, M. D. , Ph. D. mark@kozsurek. hu EM II. , 28/10/2019.

Glossopharyngeus nerve (CN IX. )

Why is it good to have a glossopharyngeal nerve? n n n swallowing: Stylopharyngeus muscle, pharyngeal constrictor muscles general somatosensory innervation: oral part of pharynx (e. g. sore throat!) taste sensation: at the root of the tongue salivation: parotid gland blood pressure, p. H, O 2, CO 2: carotid sinus and glomus Clinical consideration: Isolated damage of the glossopharyngeal nerve is rare and difficult to identify, as only some difficulty of swallowing might be present.

ambiguus nucl. : branchialmotor inferior salivatory nucl. : general visceromotor (parasympathetic) spinal trigeminal nucl. : general somatosensory lateral nucl. of ala cinerea: general viscerosensory solitary nucl. : special viscerosensory (taste)

jugular gangl. petrosal gangl. At its cranial exit the glossopharyngeal nerve possesses two sensory ganglia with pseudounipolar neurons: the upper one is within the jugular foramen, pars nervosa, while the inferior one fits into the petrosal fossula. The first branch, the tympanic nerve ascends into the tympanic cavity through the tympanic canaliculus.

Tympanic nerve creates a plexus on the medial wall of the tympanic cavity together with those postganglionic sympathetic fibres which arrive along the internal carotid artery. Fibres of this plexus reunite to constitute the lesser petrosal nerve entering infratemporal fossa through the foramen lacerum.

Lesser petrosal nerve terminates within the otic ganglion found lateral to the mandibular division of trigeminal arriving into the infratemporal fossa through the foramen ovale. This is an autonomic ganglion with multipolar neurons which give arise to axons joining auriculotemporal nerve as guest fibres to reach the parotid gland.

Main trunk of the glossopharyngeal nerve further descends along the stylopharyngeus muscle (one of the levators of the pharynx) innervates this muscle and constitutes the pharyngeal plexus together with the branches of the vagus nerve and postganglionic sympathetic fibres derived from the superior cervical ganglion.

While descending along the pharyngeal wall gives off branches to the isthmus of the fauces, the palatine tonsils and the root of the tongue (tonsillary and lingual branches).

The most caudally descending fibres terminate close to the bifurcation of the common carotid artery where they innervate the carotid glomus and sinus (Hering nerve!)

Summary:

Vagus nerve (CN X. )

Why do we need the vagus nerve? (What are the symptomes in vagus insufficiency? ) n swallowing: Levator veli palatini muscle, pharyngeal constrictors, esophageal muscles n phonation: laryngeal muscles n viscera: lungs, heart, esophagus, stomach, liver, biliary system, pancreas, small and large intestine, kidney Clinical symptomes: dysphagia, aspiration, dysphonia, deviation of uvula.

ambiguus nucl. : branchialmotor dorsal vagal nucl. : general visceromotor (parasympathetic) spinal trigeminal nucl. : general somatosensory lateral nucl. of ala cinerea: general viscerosensory solitary nucl. : special viscerosensory (taste)

Brainstem, dural and cranial exit of the vagus nerve

I. Branches on the head and neck Posterior meningeal branch Auricular branch of vagus nerve superior or jugular ggl. inferior or nodose ggl. 1. Posterior meningeal branch 2. Auricular branch of vagus nerve inferoposterior wall of the external auditory meatus, posterior surface of the auricle (mastoid canaliculus: jugular fossa → tympanomastoid fissure) Both of these branches contain exclusively general somatosensory fibres!

1. Post. meningeal branch 2. Auricular branch 3. Pharyngeal branches PHARYNGEAL PLEXUS

1. Posterior meningeal branch 2. Auricular branch 3. Pharyngeal branches 4. Superior laryngeal branch - external br. (Cricothyroid m. ) - internal br. 5. Inferior and recurrent laryngeal nerve

6. CARDIAC PLEXUS - superior cervical cardiac branches - inferior cervical cardiac branches - (thoracic cardiac branches)

II. Thoracic branches - thoracic cardiac branches - bronchial branches - pericardiac branches - esophageal branches

III. Abdominal branches * Cannon-Böhm’s point - gastric plexus - hepatic plexus The most distal branches follow the celiac trunk and the superior mesenteric artery to reach their targets. - celiac plexus - renal plexus

posterior meningeal br. : general somatosensory auricular branch of vagus nerve: general somatosensory head, neck rr. pharyngei: branchialmotor (striated muscles), general visceromotor (glands), general somatosensory (mucosa) superior laryngeal nerve: external br. – branchialmotor; iternal br. – general somatosensory (mucosa), special viscerosensory (taste sensing), general visceromotor (glands) fibres inferior and recurrent laryngeal nerve: branchialmotor, general somatosensory (mucosa), general visceromotor (glands) abdomen thorax cardiac plexus: general visceromotor and viscerosensory (blood pressure, heart rate) bronchial, pulmonary, pericardiac and esophageal plexus: general visceromotor and viscerosensory gastric, coeliac, hepatic, renal plexus: general visceromotor and viscerosensory

General viscerosensory and visceromotor functions of the vagus nerve n Vagus controls the autonomic functions of the thoracic and abdominal viscera. inferior ganglion (pseudounipolar neurons) (caudal part of the solitary nucleus) lateral nucleus of ala cinerea viscera dorsal vagus nucleus parasympathetic (intramural) ganglia submucous and myenteric plexus multipolar neurons

Accessory nerve (CN XI. )

What does the accessory nerve do? n phonation: fibres joining the vagus mainly innervate the interarythenoid muscles. n innervation of trapezius and sternocleidomastoid muscles Clinical symptoms: abnormal, asymmetrical position of the head or neck („wry neck”), abduction of the upper limb over the horizontal plane is difficult.

ambiguus nucleus: branchialmotor (fibres arising from this nucleus constitute the cranial roots which exit in the lateral parolivary sulcus and than join the vagus nerve as internal branches) spinal accessory nucleus: general somatomotor nucleus in the lateral portion of the ventral horn of C 1 -C 6 spinal segments. (fibers coming from the nucleus give the spinal roots of the accessory nerve which enter the skull through the foramen magnum exit again through the pars nervosa of the jugular foramen and target sternocleidomastoid and trapezius muscles as external branches)

Hypoglossal nerve (CN XII. )

Functions: 1. Somatomotor innervation of extrinsic and intrinsic muscles of the tongue. 2. Contributes to the innervation of infrahyoid muscles (and the geniohyoid) by taking guest fibres from the cervical plexus. hypoglossal nucleus: general somatomotor

Clinical consideration: Peripheral injury of the hypoglossal nerve results in deviation of the protruded tongue toward the side of injury. Tongue might be atrophic. Chewing, swallowing, talking is difficult.

deep cervical ansa: a branch of C 1 spinal nerve joins the hypoglossus as a guest fibre and later leaves that as the superior root of cervical ansa. This will form a loop with the inferior root of ansa cervicalis arrising from the ventral branches of C 2 -3 spinal nerves. Deep cervical ansa innervates infrahyoid muscles and the Geniohyoid.

Pirogov’s triangle is formed by the intermediate tendon of the digastric muscle, the posterior border of the mylohyoid muscle and the hypoglossal nerve. Béclard's triangle is an area whose boundaries are the posterior border of the hyoglossus, the posterior belly of the digastric/stylohyoid muscles and the greater horn of the hyoid bone.

Hypoglossus nerve is found in the lateral sulcus of the tongue bellow the lingual nerve and the submandibular duct.

Thank you for your attention!