Neuro-ophthalmology and pupils: downbeat nystagmus: 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.

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Ophthalmology · Neuro-ophthalmology and pupils: downbeat nystagmus

Sample item

A 40-year-old woman has a vertical nystagmus with the fast phase downward, worst on lateral and downgaze, with oscillopsia. Where should imaging concentrate?

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

The answer and the reasoning

C. The craniocervical junction, for Chiari malformation

Downbeat nystagmus localises to the craniocervical junction and cerebellum, as in Arnold-Chiari malformation, and may also result from drugs or vitamin deficiency. A pontine reticular lesion produces horizontal gaze palsy, and an MLF lesion produces internuclear ophthalmoplegia.

Option by option

  • A. The medial longitudinal fasciculus

    An MLF lesion causes internuclear ophthalmoplegia with failed adduction.

  • B. The optic chiasm

    A chiasmal lesion causes bitemporal field loss and may produce see-saw nystagmus.

  • C. The craniocervical junction, for Chiari malformation (correct)

    Correct. Downbeat nystagmus suggests a craniocervical or cerebellar lesion such as Chiari malformation.

  • D. The paramedian pontine reticular formation

    A paramedian pontine reticular formation lesion causes ipsilateral horizontal gaze palsy.

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 Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is C, The craniocervical junction, for Chiari malformation. Downbeat nystagmus localises to the craniocervical junction and cerebellum, as in Arnold-Chiari malformation, and may also result from drugs or vitamin deficiency.

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

An MLF lesion causes internuclear ophthalmoplegia with failed adduction.

Why is "The optic chiasm" not the answer?

A chiasmal lesion causes bitemporal field loss and may produce see-saw nystagmus.

Why is "The paramedian pontine reticular formation" not the answer?

A paramedian pontine reticular formation lesion causes ipsilateral horizontal gaze palsy.

What concept does this question test?

It tests Neuro-ophthalmology and pupils: downbeat nystagmus in Ophthalmology. A pontine reticular lesion produces horizontal gaze palsy, and an MLF lesion produces internuclear ophthalmoplegia.

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 Neuro-ophthalmology and pupils: downbeat nystagmus?

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.