Neuroanatomy: caloric test in coma: 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: caloric test in coma

Sample item

In a comatose patient with an intact brainstem, 30 mL of ice-cold water is irrigated into the right ear canal. What is the expected eye response?

ABoth eyes remain central with no movement at allBBoth eyes deviate slowly toward the left earCBoth eyes deviate slowly toward the irrigated right earDThe right eye abducts while the left eye fails to adduct

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

The answer and the reasoning

C. Both eyes deviate slowly toward the irrigated right ear

Cold water lowers the firing of the ipsilateral vestibular nerve, so the tone from the opposite labyrinth dominates and drives the eyes slowly toward the cold ear. In an awake patient a fast corrective phase gives nystagmus away from the cold ear, but in coma the cortical fast phase is absent and only the tonic deviation remains.

Option by option

A. Both eyes remain central with no movement at all
No movement indicates failure of the vestibulo-ocular pathway and a poor brainstem prognosis.
B. Both eyes deviate slowly toward the left ear
Deviation toward the opposite ear is the response to warm water in a comatose patient.
C. Both eyes deviate slowly toward the irrigated right ear (correct)
Correct. Slow tonic deviation toward the cold ear shows an intact vestibulo-ocular arc in the brainstem.
D. The right eye abducts while the left eye fails to adduct
An internuclear ophthalmoplegia pattern implies medial longitudinal fasciculus damage, not an intact brainstem.

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, Both eyes deviate slowly toward the irrigated right ear. Cold water lowers the firing of the ipsilateral vestibular nerve, so the tone from the opposite labyrinth dominates and drives the eyes slowly toward the cold ear.

Why is "Both eyes remain central with no movement at all" not the answer?

No movement indicates failure of the vestibulo-ocular pathway and a poor brainstem prognosis.

Why is "Both eyes deviate slowly toward the left ear" not the answer?

Deviation toward the opposite ear is the response to warm water in a comatose patient.

Why is "The right eye abducts while the left eye fails to adduct" not the answer?

An internuclear ophthalmoplegia pattern implies medial longitudinal fasciculus damage, not an intact brainstem.

What concept does this question test?

It tests Neuroanatomy: caloric test in coma in Anatomy. In an awake patient a fast corrective phase gives nystagmus away from the cold ear, but in coma the cortical fast phase is absent and only the tonic deviation remains.

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: caloric test in coma?

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.