Cerebellar Anatomy

Lobes

  • The anterior cerebellar lobe
  • The posterior cerebellar lobe
The primary fissure separates the the anterior lobe from the posterior lobe.
  • The flocculonodular lobe: nodule in midline and flocculus out laterally.
The posterolateral fissure separates the corpus cerebelli from the flocculonodular lobe.

Zones

  • The midline cerebellum is the vermis (which means wormlike)
  • Lateral to it, lies the paravermis (aka the intermediate zone)
  • Lateral to it, lies the hemisphere (aka the lateral zone)

FUNCTIONAL MODULES

Clinical Correlation: Ataxia & Incoordination

Vestibulocerebellum

  • Phylogenetically the oldest portion of the cerebellum and is referred to as the archicerebellum.
  • It is derived from the flocculonodular lobe and the anterior tip of the vermis (the lingula).
  • The vestibulocerebellum receives its name because of its midline vestibulo- and olivocerebellar fibers, which project to the deep, medial-lying cerebellar fastigial nuclei.
  • It is important for equilibrium and eye movements.

Clinical Correlation – Nystagmus

Spinocerebellum

  • Phylogenetically the next oldest and is referred to as the paleocerebellum.
  • It is derived from the anterior lobe and the majority of the vermian and paravermian posterior lobe.
  • The spinocerebellum receives its name from its major input fibers: the spinocerebellar tracts.
  • It plays a major role in postural stability.

Clinical Correlations – Truncal ataxia, Gait Ataxia

Pontocerebellum

  • Phylogenetically the newest portion of the cerebellum and is referred to as the neocerebellum.
  • It is derived from the remainder of the posterior lobe.
  • The pontocerebellum receives its name because it acts through the corticopontocerebellar pathway.
  • It is geared towards fine motor movements, which are typically goal-oriented.

Clinical Correlation – Incoordination

ALCOHOL TOXICITY & CEREBELLAR DEGENERATION

Acute alcohol intoxication, the entire cerebellum is affected (vestibulo-, spino-, pontocerebellum).
  • Nystagmus occurs from toxicity to the vestibulocerebellum, truncal ataxia occurs from toxicity to the spinocerebellum, and incoordination occurs from toxicity to the pontocerebellum.

Alcoholic cerebellar degeneration

Clinical Correlation: Chronic Alcoholic Cerebellar Degeneration

  • The pathology is predominantly restricted to the anterior superior cerebellar vermis. Because of this restricted area of injury, truncal ataxia is sometimes the sole deficit.
We may miss this exam finding, if we fail to ask our patients to stand during the exam.

GENERAL SOMATOTOPIC ORGANIZATION OF THE CEREBELLUM

  • Unilateral cerebellar lesions affect the ipsilateral side of the body.
  • The midline cerebellum plays a role in posture whereas the lateral cerebellum assists in fine motor, goal-oriented skills.
  • For instance, to stand upright, you need the midline cerebellum, and to play the piano, you need the lateral cerebellar hemispheres.
  • The somatotopic map of the cerebellum is in concert with its functional layout: the role of the spinocerebellar, anterior lobe is to provide postural stability, which requires the limbs and trunk, and the role of the neocerebellar, posterior lobe is to provide goal-oriented, fine motor movements, such as those of the fingers and mouth.

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