Neuroanatomy: cerebellar lesions: practice question

A Anatomy question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Anatomy · Neuroanatomy: cerebellar lesions

Sample item

A 55-year-old man has an infarct of the right cerebellar hemisphere. On which side are the finger-nose incoordination and falls, and what explains this?

ABoth sides equally, because the cerebellum acts through the vermisBLeft side, because the corticospinal tract crosses at the pyramidsCRight side, because cerebellar output crosses to the cortex and the corticospinal tract crosses againDLeft side, because the cerebellar peduncles cross the midline

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Right side, because cerebellar output crosses to the cortex and the corticospinal tract crosses again

A cerebellar hemisphere controls the ipsilateral limbs. Its output leaves through the superior cerebellar peduncle and crosses to the contralateral thalamus and motor cortex, and the corticospinal tract then crosses again at the pyramids, a double decussation. A hemispheric lesion thus causes ipsilateral dysmetria, intention tremor and ataxia.

Option by option

A. Both sides equally, because the cerebellum acts through the vermis
The vermis controls midline trunk balance, and a hemispheric lesion affects the ipsilateral limbs.
B. Left side, because the corticospinal tract crosses at the pyramids
Considering only the pyramidal crossing ignores the earlier cerebellar crossing.
C. Right side, because cerebellar output crosses to the cortex and the corticospinal tract crosses again (correct)
Correct. Two crossings return the control to the same side as the lesioned hemisphere.
D. Left side, because the cerebellar peduncles cross the midline
Crossed pontocerebellar fibres are part of input, but the net control remains ipsilateral.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is C, Right side, because cerebellar output crosses to the cortex and the corticospinal tract crosses again. A cerebellar hemisphere controls the ipsilateral limbs.

Why is "Both sides equally, because the cerebellum acts through the vermis" not the answer?

The vermis controls midline trunk balance, and a hemispheric lesion affects the ipsilateral limbs.

Why is "Left side, because the corticospinal tract crosses at the pyramids" not the answer?

Considering only the pyramidal crossing ignores the earlier cerebellar crossing.

Why is "Left side, because the cerebellar peduncles cross the midline" not the answer?

Crossed pontocerebellar fibres are part of input, but the net control remains ipsilateral.

What concept does this question test?

It tests Neuroanatomy: cerebellar lesions in Anatomy. Its output leaves through the superior cerebellar peduncle and crosses to the contralateral thalamus and motor cortex, and the corticospinal tract then crosses again at the pyramids, a double decussation. A hemispheric lesion thus causes ipsilateral dysmetria, intention tremor and ataxia.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Neuroanatomy: cerebellar lesions?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.