Neuroanatomy: Horner syndrome: 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: Horner syndrome

Sample item

A 62-year-old smoker with an apical lung mass has a drooping right upper eyelid, a small right pupil and absent sweating on the right side of the face. Paralysis of which muscle explains the drooping eyelid?

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

The answer and the reasoning

A. Superior tarsal muscle (Muller)

Horner syndrome results from interruption of the cervical sympathetic pathway, here by a Pancoast tumour. Sympathetic fibres supply the superior tarsal muscle, which gives a small part of eyelid elevation, so paralysis produces mild ptosis, and the dilator pupillae, whose paralysis produces miosis. Sweating is lost through sudomotor fibres.

Option by option

  • A. Superior tarsal muscle (Muller) (correct)

    The superior tarsal muscle is smooth muscle with sympathetic supply, and its paralysis causes partial ptosis.

  • B. Levator palpebrae superioris

    Levator palpebrae superioris is supplied by the oculomotor nerve and is spared, which is why ptosis is mild.

  • C. Orbicularis oculi

    Orbicularis oculi is supplied by the facial nerve and paralysis produces lagophthalmos, not ptosis.

  • D. Dilator pupillae

    The dilator pupillae is paralysed in Horner syndrome, but it causes miosis and not ptosis.

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 A, Superior tarsal muscle (Muller). Horner syndrome results from interruption of the cervical sympathetic pathway, here by a Pancoast tumour.

Why is "Levator palpebrae superioris" not the answer?

Levator palpebrae superioris is supplied by the oculomotor nerve and is spared, which is why ptosis is mild.

Why is "Orbicularis oculi" not the answer?

Orbicularis oculi is supplied by the facial nerve and paralysis produces lagophthalmos, not ptosis.

Why is "Dilator pupillae" not the answer?

The dilator pupillae is paralysed in Horner syndrome, but it causes miosis and not ptosis.

What concept does this question test?

It tests Neuroanatomy: Horner syndrome in Anatomy. Sympathetic fibres supply the superior tarsal muscle, which gives a small part of eyelid elevation, so paralysis produces mild ptosis, and the dilator pupillae, whose paralysis produces miosis. Sweating is lost through sudomotor fibres.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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: Horner syndrome?

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.