Cerebellum The cerebellum fills most of the posterior cranial fossa It is the largest part of the hindbrain
The cerebellum ("little brain") has convolutions similar to those of cerebral cortex, only the folds are much smaller. Cerebellum = little brain literally
The cerebellum is covered superiorly by the tentorium cerebelli It is separated from Pons & medulla oblongata by 4 th ventricle occipital lobe of Cerebral hemisphere Pons MO Tentorium cerebelli Cerebellum 4 th ventricle
Superior surface Anterior notch Lingula Inferior surface superior vermis Nodule Post. notch inferior vermis It has 2 hemispheres 2 surfaces 2 vermis 2 notches 3 lobes
Inferior surface Nodule Uvula Tonsil Pyramid Retrotonsillar fissure Vallecula Inferior vermis
medulla Tonsillar herniation oblongata Tonsil If the pressure in cranial, spinal parts of subarachnoid space is abnormally high, with sudden decompression of spinal part may forcibly displace the tonsil downwards and become impacted in foramen magnum with compression on vital centers of medulla
Surfaces A- Superior surface, - The middle part is raised and called superior vermis. - The lingua is the most anterior part of the superior vermis. B- Inferior surface, - The middle part is called inferior vermis and lies in the bottom of a depression between the two hemispheres called Vallecula. - The inferior vermis consists of nodule, uvula and pyramid. - The inferior surface of each hemisphere rests on the floor of the posterior cranial fossa. - Tonsil is a small part of the cerebellar hemisphere that lies lateral to the inferior vermis.
Notches Separated from the Pons, and upper part of medulla oblongata by the 4 th ventricle containing cerebellar peduncles (MIS) Wide Anterior cerebellar notch Containing the falx cerebelli of the dura mater Narrow Posterior cerebellar notch
These cerebellar peduncles pass into the white core of The cerebellum through Anterior notch Superior Cerebellar peduncle Middle Cerebellar peduncle Inferior Cerebellar peduncle Anterior cerebellar notch 4 th ventricle The cerebellum is connected to the posterior aspect of the brainstem by three symmetrical bundles of nerve fibers called the superior, middle, and inferior cerebellar peduncles
Notches A- Anterior notch; - It is a large median depression separated from the back of the pons and open medulla by the 4 th ventricle. - It contains 3 cerebellar peduncles that connecting the cerebellum with the brain stem (MIS) middle, inferior and superior from lateral to medial. B- Posterior notch is a smaller median depression containing falx cerebelli.
1 - Primary fissure on Superior surface Anterior lobe Primary fissure Upper part of Middle lobe It is a wide V-shaped fissure which separates the anterior lobe from the middle lobe behind it
2 - Secondary fissure, posterolateral Flocculonodular lobe Secondary fissure Lower part of Middle lobe Inferior surface On the inferior surface, It separates the middle lobe from the Flocculonodular lobe.
3 - Transverse Fissures The external Surface Folia Great number of transverse (horizontal) fissures on the superior and inferior surfaces. The part of the cerebellum between the transverse fissures called folia.
The most marked of these fissures 4 - Horizontal fissure extends from anterior to posterior notches along the margin of the cerebellum and separates the superior from the inferior surfaces.
The anterior lobe is seen on superior surface of cerebellum and is separated from the middle lobe by a wide V-shaped fissure called primary fissure Anterior lobe Primary fissure Middle lobe The middle lobe (sometimes called posterior lobe), which is the largest part of the cerebellum, is situated between the primary and Posterolateral Fissure, seen on the superior & inferior surfaces
Flocculonodular peduncle Flocculonodular lobe Flocculus Posterolateral fissure Nodule Middle lobe inferior vermis The flocculonodular lobe is situated anterior to Posterolateral fissure
• Lobes and functions of the Cerebellum (PNA) 1 - Anterior lobe (Pa. Ieo-cerebellar) - It receives afferent proprioceptive impulses from spinal cord. - It is concerned with the muscle tone. 2 - Middle (Posterior) lobe (Neo-cerebellar) - It receives afferent impulses from the cerebral cortex. - It is concerned with the coordination of the action of different groups of muscles. So that the movements are done smoothly and accurately (Computer like organ) 3 - Flocculonodular lobe (Archi-cerebellum) - It receives afferent impulse from the vestibular apparatus. - It is concerned with equilibrium.
1 superior Blood supply of cerebellum cerebellar artery 2 Anterior inferior cerebellar artery Basilar artery 3 Posterior inferior cerebellar artery 4 th part of vertebral artery
** Blood supply * Arterial blood supply; 3 arteries on each side: 1 - Superior cerebellar artery from the basilar artery and supplies the superior surface. 2 - Anterior inferior cerebellar artery from the basilar artery and supplies the anterior part of the inferior surface. 3 - Posterior inferior cerebellar artery; from the vertebral artery and supply the posterior part of the inferior surface. * Venous drainage, into the dural venous sinuses.
Like the cerebrum, the cerebellum has an outer cortex, an inner white matter, in which deep nuclei are embedded outer Cerebellar cortex inner white matter Central core of White matter Nuclei of cerebellum Folia T. fissure
Cerebellar nuclei (DEFG)
Deep cerebellar nuclei 4 th ventricle Inferior medullary velum Dentate Fastigial Globose Emboliform
Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle The cerebellum is connected to the posterior aspect of the brainstem by three symmetrical bundles of nerve fibers called the cerebellar peduncles cerebellum
• Afferent of Inferior cerebellar peduncle; - It connects the spinal cord & medulla oblongata with the cerebellum. It integrates the proprioceptive sensation (Afferent) with vestibular functions (Efferent) as balance and posture maintenance. PCR-OVA 1 - Posterior spinocerebellar tract; from Clark's nucleus of the spinal cord - It carrying proprioceptive sensation from the lower 1/2 of the body. (same side) 2 - Cuneo-cerebellar tract; from accessory cuneate nucleus of medulla(same side) - It carrying proprioceptive sensation from the upper limb and neck. 3 - Reticulo-cerebellar tract. from the reticular formation in the medulla (same side 4 - Olivo-cerebellar tract. from the inferior olivary nucleus of medulla (only from the opposite side). 5 - Vestibulo-cerebellar tract; from the vestibular nuclei (same side) - It carries the equilibrium impulses. 6 - Anterior external arcuate fibres arise from arcuate nucleus a small nucleus in front of pyramid. (same side)
• Efferent of inferior cerebellar peduncles 1 - Cerebello- Vestibular tract; to the vestibular nuclei (The most important). 2 - Cerebello- Reticular tract; to the nuclei of reticular formation.
2 1 3 4 Anterior external arcuate fibres arise from arcuate nucleus a small nucleus in front of pyramid. Afferents fibers (same side) Inferior cerebellar peduncle
Afferents fibers 5 Vestibulocerebellar Inferior cerebellar peduncle cerebellum vestibular nuclei Inferior cerebellar Peduncle
Inferior cerebellar peduncle Afferents fibers 6 Reticulocerebellar fiber Reticular formation cerebellum Inferior cerebellar peduncle
Efferent fibers 1
Efferent fibers 2 Cerebelloreticular fiber Inferior cerebellar peduncle Reticular formation cerebellum
Middle cerebellar peduncle Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle The Middle cerebellar peduncle connects the cerebellum to the Pons Is the largest of the cerebellar peduncles, it enters the anterior notch of the cerebellum lateral to the other cerebellar peduncles
Middle cerebellar peduncle Corticopontocerebellar Pathway Crosses the opposite side
Superior cerebellar peduncle inferior colliculus Superior cerebellar peduncle Middle peduncle Inferior peduncle The superior cerebellar peduncle connects the cerebellum to the midbrain Is the smallest and most medial of the cerebellar peduncles
• Afferent of Superior cerebellar peduncle START 1 - Tecto-cerebellar tract; from the tectum (superior and inferior colliculi) of the midbrain - It carries the visual and auditory impulses to the cerebellum. 2 - Anterior spino-cerebellar tract, from the Clark's nucleus of the spinal cord - It carrying proprioceptive sensation from the lower limb. - In the spinal cord, the fibres cross to the opposite side and ascend in the opposite side of brainstem. -In cerebellum, fibres retain gain to ipsilateral cerebellar hemisphere. 3 - Rubrocerebellar from the red nucleus of the midbrain 4 - Trigeminocerebellar from the mesencephalic nucleus of trigeminal nerve
** Efferent of superior cerebellar peduncle - It forms the majority of fibers and decussated in the midline (Decussation of SCP) ROT 1 - Dentato- Rubral tract to the red nucleus (opposite side). 2 - Dentato- Reticular; to the reticular formation of the brain steam (opposite side). . 3 - Dentato- Olivary tract; from the dentate nucleus to the inferior olivary nucleus (opposite side). . 4 - Dentato-Thalamic tract from the dentate nucleus to the thalamus (opposite side). .
Afferent fibers Superior cerebellar peduncle
Afferents fibers Superior cerebellar peduncle
Trigeminocerebellar tract Mesencephalic nucleus of trigeminal nerve Superior cerebellar Peduncle cerebellum Superior cerebellar peduncle Red nucleus rubrocerebellar fibers Afferents fibers
Ventral nucleus of thalamus Red nucleus Inferior olivary nucleus Decussationof Superior cerebellar peduncle Decussation of Superior cerebellar peduncle Dentate nucleus Reticular nuclei of brainstem
Cerebellar lesions • 1 - Disturbance of equilibrium. • 2 - Hypotonia of the muscle. • 3 - Cerebellar ataxia, in the form of intermittent jerky movements. • 4 - Intention tremor, absent at rest, best seen at the end of the finger-nose test. • 5 - Nystagmus, in the form of jerky movements. • 6 - Dysdiadokokinesis, ask the patient to do rapidly alternating movements as supination and pronation of the forearm.
Th ank Qu you est ion s I/Azzam - 2004