During a cerebellar examination, a patient shows intention tremor, dysdiadochokinesia, and ipsilateral limb ataxia but NO truncal ataxia or falling. The lesion most likely involves which part of the cerebellum?

• A Flocculonodular lobe (archicerebellum)
• B Anterior vermis
• C Lateral hemisphere (neocerebellum / pontocerebellum) ✓
• D Posterior vermis

Explanation

The lateral cerebellar hemispheres (pontocerebellum) coordinate ipsilateral skilled limb movements; their damage produces intention tremor, dysdiadochokinesia, and limb ataxia without disturbing equilibrium or truncal stability. The flocculonodular lobe governs balance and vestibular reflexes, so its damage causes truncal ataxia and nystagmus. Vermian lesions preferentially impair axial and gait coordination.

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

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