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Ophthalmology · Eyelid: ptosis
Sample itemA newborn has drooping of the right upper eyelid, which retracts briskly when the baby sucks or moves the jaw to the left. What is the diagnosis?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
C. Marcus Gunn jaw-winking syndrome
Marcus Gunn jaw-winking is a congenital synkinesis in which the levator palpebrae superioris is abnormally innervated by branches of the trigeminal (pterygoid) nerve, so the ptotic lid lifts on chewing or jaw movement to the opposite side. Treatment depends on the degree of ptosis, to prevent amblyopia and improve appearance.
Option by option
A. Myasthenia gravis
Myasthenia gravis causes fatigable ptosis that is not linked to jaw movement.
B. Horner syndrome
Horner syndrome gives mild ptosis, miosis and anhidrosis without synkinesis.
C. Marcus Gunn jaw-winking syndrome (correct)
Correct. Lid elevation with jaw movement is characteristic.
D. Third nerve palsy
Third nerve palsy gives ptosis with an eye deviated down and out.
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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