A patient presents with intention tremor, dysdiadochokinesia, hypotonia, and scanning dysarthria on the right side only. The lesion is most likely in which cerebellar structure?

• A Right cerebellar hemisphere (neocerebellum) ✓
• B Left cerebellar hemisphere (neocerebellum)
• C Flocculonodular lobe (archicerebellum)
• D Cerebellar vermis (paleocerebellum)

Explanation

The cerebellar hemispheres project ipsilaterally: cerebellar output crosses in the superior cerebellar peduncle, decussates in the midbrain, but then crosses again through the corticospinal system back to the ipsilateral limbs — net result is ipsilateral ataxia from hemisphere lesions. A right hemisphere lesion produces right-sided limb ataxia (intention tremor, dysdiadochokinesia). Vermis lesions cause truncal and gait ataxia. Flocculonodular lesions cause vestibulo-cerebellar dysfunction (nystagmus, truncal ataxia, tendency to fall).

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.