A patient has a cerebellar hemisphere lesion on the right side. Which of the following clinical signs is expected?
- A Intention tremor and dysmetria on the right side ✓
- B Intention tremor and dysmetria on the left side
- C Contralateral limb ataxia with normal gait
- D Truncal ataxia with absent limb signs
Correct answer: A. Intention tremor and dysmetria on the right side
Explanation
Cerebellar hemisphere lesions produce ipsilateral limb ataxia because the cerebellum controls ipsilateral motor activity via a double-crossing pathway: the cerebellar output crosses to the contralateral red nucleus/thalamus, then the corticospinal tract crosses again at the medullary decussation, resulting in net ipsilateral control. Truncal ataxia (gait ataxia without significant limb signs) is characteristic of vermis lesions.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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