Head and neck: corneal reflex pathway: 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 · Head and neck: corneal reflex pathway

Sample item

Touching the left cornea with cotton wool produces no blink in either eye, but touching the right cornea makes both eyes blink. Where is the lesion?

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

The answer and the reasoning

D. Left trigeminal (ophthalmic) afferent limb

The corneal reflex has an afferent limb in the nasociliary branch of the ophthalmic nerve and an efferent limb in the facial nerve to orbicularis oculi. A left afferent lesion abolishes the response to left corneal stimulation in both eyes, while the right eye can still be stimulated. A facial efferent lesion would spare the contralateral blink.

Option by option

  • A. Right trigeminal afferent limb

    A right trigeminal lesion would abolish blinks to right corneal stimulation, which are present.

  • B. Right facial nerve efferent limb

    A right facial lesion would stop the right eye blinking, but both eyes blinked.

  • C. Left facial nerve efferent limb

    A left facial lesion would still allow the right eye to blink when the left cornea is touched.

  • D. Left trigeminal (ophthalmic) afferent limb (correct)

    Correct. Stimulating the left cornea fails in both eyes only if the left afferent limb is cut.

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.

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Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Left trigeminal (ophthalmic) afferent limb. The corneal reflex has an afferent limb in the nasociliary branch of the ophthalmic nerve and an efferent limb in the facial nerve to orbicularis oculi.

Why is "Right trigeminal afferent limb" not the answer?

A right trigeminal lesion would abolish blinks to right corneal stimulation, which are present.

Why is "Right facial nerve efferent limb" not the answer?

A right facial lesion would stop the right eye blinking, but both eyes blinked.

Why is "Left facial nerve efferent limb" not the answer?

A left facial lesion would still allow the right eye to blink when the left cornea is touched.

What concept does this question test?

It tests Head and neck: corneal reflex pathway in Anatomy. A left afferent lesion abolishes the response to left corneal stimulation in both eyes, while the right eye can still be stimulated. A facial efferent lesion would spare the contralateral blink.

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 Head and neck: corneal reflex pathway?

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.