cerebellum D.Nimer D.Rania Gabr D.Safaa D.Elsherbiny

Objectives Identify the major lobes and regions of cerebellum. Summarize the structure of the cerebellar cortex Identify the deep cerebellar nuclei and their connections. List the afferent and efferent connections of the cerebellum and their arrangement in cerebellar peduncles. Describe the major functions of the cerebellum and how each side of the cerebellum controls the ipsilateral side of the body. Explain the effects of lesions of cerebellum and motor disorder associated with cerbellar lesions.

Cerebellum Position: Lies behind Pons & Medulla Situated in the posterior cranial fossa It is covered by “tentorium cerebelli “ Separated from pons and medulla by 4th ventricle. Separated from cerebrum by tentorium cerebelli.

EXTERNAL FEATURES Its surface is highly convoluted forming the gyri called Folia, separated by Fissures. It consists of two Cerebellar Hemispheres joined in midline by the Vermis. Vermis: Superior vermis: on superior surface. Inferior vermis: on inferior surface

Inferior vermis N U T P N: Nodule U: Uvula P:Pyramid T:Tuber

EXTERNAL FEATURES Folia: Transversely oriented folia or gyri 3 lobes in each hemisphere: Anterior, Posterior, Flocculonodular Neural arrangement: Gray matter (Cortex), White matter (Internal), Arbor vitae (tree of life): distinctive treelike pattern of the white matter Folium

CONNECED TO THE BRAIN STEM BY: 3 peduncles Superior cerebellar peduncle: with midbrain Middle cerebellar peduncle: with pons Inferior cerebellar peduncle: with medulla

2 Notches Anterior notch. Posterior notch.

Fissures Horizontal fissure. Primary fissure. Postero-lateral fissure= Secondary or uvulonodular fissure Posterolateral fissure

Anatomical classification Anterior lobe:in front of primary fissure, on the superior surface. Posterior lobe (middle) lobe : behind primary fissure (Between Primary & posterolateral ) Flocculonodular lobe: : in front of Posterolateral Posterolateral fissure

Posterior lobe Anterior lobe Flocculonodular lobe Anterior lobe

Structure of the cerebellum Outer grey matter: cerebellar cortex. Inner white matter: cerebellar medulla. Deeply seated nuclei (grey matter) in white matter: from medial to lateral: Fastigeal nucleus. Globose nucleus. Emboliform nucleus. Dentate nucleus: largest one.

Longitudinal classification Vermal zone: projects to Fastigial nucleus. Paravermal zone(= Intermediate zone): projects to interposed nuclei( Globose and Emboliform). Lateral zone: projects to dentate nucleus. VERMAL ZONE = Paravermal zone

Functional classification Archicerebellum (vestibulocerebellum) Consists of flocculonodular lobe. Connected with vestibular system Concerned with equilibrium

Functional classification 2. Paleocerebellum (spinocerebellum) Consists of vermal and paravermal zones. Connected with spinal cord. Concerned with ms coordination and regulation of ms tone. 3. Neocerebellum (cerebrocerebellum) Consists of lateral zone. Connected with cerebral hemisphere. Concerned with planning and skills.

Arterial supply of cerebellum SCA (superior cerebellar artery): from basilar artery. PICA (posterior inferior cerebellar artery): from vertebral artery. AICA (anterior inferior cerebellar artery): from basilar artery.

CEREBELLAR CONNECTIONS INFERIOR CEREBELLAR PEDUNCLE AFFERENT FIBERS INFERIOR CEREBELLAR PEDUNCLE Restiform Body: It contains: Olivocerebellar fibers: from the inferior olivary nucleus of the opposite side. It carries information from the spinal cord and the cerebral cortex for the control of movement. Terminates as climbing fibers to cerebellar cortex. Dorsal spinocerebellar tract: from Clarke’s nucleus of the same side. It carries proprioceptive information from the TRUNK AND LOWER LIMB. Cuneocerebellar tract (dorsal external arcuate fibers): from the accessory cuneate nucleus of the same side. It carries proprioceptive information from the UPPER LIMB.

3. Arcuatocerebellar fibers: from the arcuate nuclei of the 2 sides 3. Arcuatocerebellar fibers: from the arcuate nuclei of the 2 sides. They reach the cerebellum by the ventral external arcuate fibers and stria medullaris of the 4th ventricle. 4. Reticulocerebellar tract: from the reticular formation. It carries motor information from the cerebral cortex and sensory information from the spinal cord. 5. Trigeminocerebellar tract: from the spinal nucleus and the main sensory nucleus of the trigeminal nerve. It carries sensory information from the face.

B. Juxtarestiform Body: Vestibulocerebellar fibers: From the vestibular nerve and vestibular nuclei for maintaining equilibrium. 2. Cerebellovestibular Fibers: To the vestibular nuclei to maintain the equilibrium and regulate muscle tone. 3. Cerebelloreticular Fibers: To the reticular formation to maintain equilibrium and regulate the muscle tone.

MIDDLE CEREBELLAR PEDUNCLE SUPERIOR CEREBELLAR PEDUNCLE It contains pontocerebellar fibers only (arise from the pontine nuclei of the opposite side). SUPERIOR CEREBELLAR PEDUNCLE AFFERENT FIBERS: Ventral spinocerebellar tract: It carries proprioceptive information from the muscles of the lower limb. Tectocerebellar tract: from the tectum. It carries visual and auditory stimuli. Trigeminocerebellar tract: from the mesencephalic nucleus of the trigeminal nerve. It carries proprioceptive information from the muscles of the face, eye and palate

Efferent Fibers: Dentatorubral tract: to red nucleus of the opposite side to regulate the muscle tone. Dentatothalamic tract: to the ventral lateral thalamic nucleus of the opposite side for moment-to-moment control of movement.

Functions of cerebellum  Maintenance of Equilibrium - balance, posture, eye movement  Coordination of half-automatic movement of walking and posture maintenace - posture, gait  Adjustment of Muscle Tone  Motor Leaning – Motor Skills  Cognitive Function

CEREBELLAR LESIONS Intention tremor: the tremor is absent at rest. It appears when the patient moves his limb. Incoordination: Ataxia Ipsilateral: is due to incoordination of the lower limb muscles. Nystagmus: rapid jerky eye movements due to incoordination of the extraocular muscles. 3. Disturbance in the range of movement (dysmetria): inability to measure distances.

Cerebellar Ataxia Ataxic gait and position: Left cerebellar tumor a. Sways to the right in standing position b. Steady on the right leg c. Unsteady on the left leg d. ataxic gait Remember: IPSILATERAL