Motility: internuclear ophthalmoplegia: practice question

A Ophthalmology 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.

Try it

Ophthalmology · Motility: internuclear ophthalmoplegia

Sample item

A young woman with multiple sclerosis cannot adduct her right eye on left gaze, while the left eye abducts with nystagmus. Where is the lesion?

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

The answer and the reasoning

C. Right medial longitudinal fasciculus

Internuclear ophthalmoplegia is named for the side of the lesion in the MLF, which fails to carry signals from the contralateral abducens nucleus to the ipsilateral medial rectus subnucleus. Convergence is typically preserved.

Option by option

  • A. Right abducens nucleus

    An abducens nucleus lesion causes a conjugate gaze palsy.

  • B. Left medial longitudinal fasciculus

    A left MLF lesion impairs left adduction.

  • C. Right medial longitudinal fasciculus (correct)

    Correct. Failure to adduct on the right indicates a right MLF lesion.

  • D. Right oculomotor nerve

    An oculomotor nerve lesion would impair convergence as well.

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.

More Ophthalmology questions

Questions about this Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is C, Right medial longitudinal fasciculus. Internuclear ophthalmoplegia is named for the side of the lesion in the MLF, which fails to carry signals from the contralateral abducens nucleus to the ipsilateral medial rectus subnucleus.

Why is "Right abducens nucleus" not the answer?

An abducens nucleus lesion causes a conjugate gaze palsy.

Why is "Left medial longitudinal fasciculus" not the answer?

A left MLF lesion impairs left adduction.

Why is "Right oculomotor nerve" not the answer?

An oculomotor nerve lesion would impair convergence as well.

What concept does this question test?

It tests Motility: internuclear ophthalmoplegia in Ophthalmology. Convergence is typically preserved.

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 Motility: internuclear ophthalmoplegia?

Group the red eye by what to examine and what the pupil does. Then use the flashcards and the other Ophthalmology 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.