Cerebellum

Overview

Introduction

• Function
  • to smoothly coordinate movement
  • to play a role in motor planning and balance
• Anatomy
  • the cerebellum is derived from the metencephalon and is found
    • dorsally to the pons and rostral medulla which are attached by cerebellar peduncles
      • between the cerebellum and this portion of the brainstem you will find the
        • fourth ventricle
  • the cerebellum contains
    • the vermis and flocculonodular lobes which play an important role in
      • proximal and truncal muscle control (vermis)
      • vestibulo-ocular control (flocculonodular lobes)
    • cerebellar hemisphere can be divided into
      • intermediate hemisphere which plays an important role in
        • distal appendicular muscle control
      • lateral hemisphere which plays an important role in
        • motor planning
    • cerebellar peduncles
      • superior cerebellar peduncles
        • mainly carries output signals
      • middle and inferior cerebellar peduncles
        • mainly carries input signals to the cerebellum
  • deep cerebellar nuclei can be arranged from lateral → medial as
    • Dendate nuclei
    • Eboliform
    • Globos
    • Fastigial
    • mnemonic: “Dont Eat Greasy Food”
• Circuitry
  • input
    • brain (via the pontocerebellar and climbing fiber) to the cerebellum via the
      • middle cerebellar peduncle
    • spinal cord (via the spinocerebellar and climbing fibers) to the cerebellum via the
      • inferior cerebellar peduncle (there are exceptions)
    • vestibular system to the cerebellum via
      • juxtarestiform body (in the inferior cerebellar peduncle)
  • output
    • all cerebellar outputs are carried by Purkinje cells which synapse in the
      • deep cerebellar nuclei or vestibular nuclei
        • which deep cerebellar nuclei the Purkinje cell synapse with is dependent on where the Purkinje cell arose from
          • Purkinje cells from
            • lateral cerebellum synapse to the dendate nucleus which 
              • exits the cerebellum via the superior cerebellar  peduncle → contralateral VL of the thalamus → motor cortex and supplementary motor areas to influence the corticospinal system for motor planning
            • intermediate cerebellum synapses to the eboliform and globose nucleus
              • exits the cerebellum via the superior cerebllar pendcuncle → contralateral VL of the thalamus → motor cortex and supplementary motor areas to influence the lateral corticospinal tract
            • vermis synapses to the fastigial nucleus
              • eventually influencing the medial motor system
            • flocculonodular lobe synapses to the vestibular nucleus
              • eventually leading to vestibulo-ocular control
• Clinical correlate
  • cerebellar disorders typically results in 
    • nausea, vomiting, and vertigo
    • slurred speech
    • uncoordinated limb movements
      • dysmetria (under- or over-shooting towards a target)
      • dysrhythmia
    • unsteadiness
  • lesion localization 
    • lesions to the vermis results in
      • truncal ataxia
    • lesions to the flocculonodular lobe results in
      • eye movement abnormalities
    • lesions to the cerebellar hemispheres results in
      • ipsilateral ataxia
• Physical exam
  • physical exam maneuvers to test the cerebellum include
    • finger-to-nose and heel-to-shin test
    • finger tapping
    • rapid alternating movement
    • gait testing
      • truncal ataxia can present with
        • a wide-based and unsteady gait
    • testing for ocular dysmetria and nyastagmus