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Cerebellum: Anterior Aspect Lateral hemisphere Posterior Lobe Vermis Primary Fissure Anterior Lobe The cerebellum has three lobes: anterior, posterior, and flocculonodular. Each lobe has a vermal portion and a hemispheric portion. Midbrain Cerebellum, Posterior View Vermis Posterior Lobe Hemisphere Pyramis Uvula Tonsils of cerebellum Medulla Foramen of Magendie (opening in post. medullary velum from 4th ventricle) The flocculus is the hemispheric part of the flocculonodular lobe of the cerebellum. The nodule is the vermal part of the flocculonodular lobe. Primary fissure Ant Post Tonsil Posterolateral fissure Prenodular fissure Cerebellar Vermis The cerebellar vermis has ten sublobules. Primary fissure Anterior lobe vernis Posterior lobe vermis Midbrain Fourth ventricle Pons Nodule Prenodular fissure Medulla Tonsil Cerebellar Peduncles: connect the cerebellum to the brainstem; each pair of peduncles connects the cerebellum to a separate division of the brainstem: SCP to midbrain, MCP to pons, and ICP to medulla. Inferior cerebellar peduncle- afferents (input) spinocerebellars, cuneocerebellars, vestibulocerebellars, and olivocerebellars Middle cerebellar peduncle- afferent, pontocerebellars Superior cerebellar peduncle- primarily efferent (output) cerebellorubrals (to red nucleus) and cerebellothalamics (to VL nucleus of thalamus) The cerebellar cortex contains three layers: molecular, Purkinje cell, and granular layers Molecular layer Cerebellum Purkinje cell layer Cell body of Purkinje cell Granular layer Primary dendrite Vermis Abundant dendritic spines on dendrites Dendrites H&E Cerebellar Cortex Axon Cell body of Purkinje neuron Intrinsic Cerebellar Cortex Connections Granule cells give rise to parallel fibers Mossy fibers terminate on granule cells Climbing fibers terminate on Purkinje cells Purkinje cells Purkinje cells project to deep cerebellar nuclei Vermis Paravermal cortex Lateral Hemisphere E G F D SCP CL Red nucleus VL Nucleus Inferior Spinal olivary cord nucleus Motor cortex JRB Vestibular complex Purkinje cells of the cerebellar cortex project in topographic order to deep cerebellar nuclei. Cerebellar efferents from the dentate, globose, and emboliform nuclei join the SCP to project to the contralateral (CL) red nucleus and VL nucleus of the thalamus. The fastigial nucleus has reciprocal connections with the vestibular complex thru the juxtarestiform body. Cerebellar Afferents: Spinocerebellars Cuneocerebellars Vestibulocerebellars Pontocerebellars Olivocerebellars All of these inputs enter the cerebellum thru the inferior & middle cerebellar peduncles. All (except olivocerebellars) terminate as “mossy fibers” on granule cells. Olivocerebellars terminate as “climbing fibers” directly on Purkinje cells. Cerebellar Afferents Pontocerebellars terminate in the posterior lobe Spinocerebellar and cuneocerebellar tracts primarily terminate in the anterior lobe Olivocerebellars go to all lobes Vestibulocerebellars terminate in the flocculonodular lobe Pontocerebellar Connections Corticopontine tract relay information from motor cortex about ongoing movements Posterior lobe (neocerebellum) Basilar pontine nuclei Olivocerebellar fibers terminate in all lobes Pontocerebellar fibers terminate primarily in the posterior lobe. Vermis Paravermal cortex Lateral Hemisphere E G F D SCP CL Red nucleus VL Nucleus Inferior Spinal olivary cord nucleus Motor cortex JRB Vestibular complex Purkinje cells of the cerebellar cortex project in topographic order to deep cerebellar nuclei. Cerebellar efferents from the dentate, globose, and emboliform nuclei join the SCP to project to the contralateral (CL) red nucleus and VL nucleus of the thalamus. The fastigial nucleus has reciprocal connections with the vestibular complex thru the juxtarestiform body. Cerebellar Connections: Principle of Lateralization Spinocerebellar and Vestibulocerebellar Inputs are primarily ipsilateral (conveying information about the same side of the body) Cerebellar efferents project to the contralateral VL nucleus of the thalamus and motor cortex. Corticopontines project to basilar pons, and pontocerebellar afferents cross back to the original side. Hence, clinical deficits resulting from cerebellar lesions are expressed ipsilaterally. Cerebellar Lesions: deficits expressed ipsilaterally Ataxia- tendency to fall toward side of lesion Intention Tremor (Action Tremor) Dysdiadokinesia- inability to produce alternating antagonistic actions Past-pointing Nystagmus- flocculonodular lobe lesion
