Question

A patient with ptosis presents with retraction of the ptotic eyelid on chewing. This represents:

• A. Marcus Gunn jaw-winking syndrome
• B. Third nerve misdirection syndrome
• C. Abducent palsy
• D. Oculomotor palsy

Hint:

A trigeminal-oculomotor cross-wiring makes the drooping lid lift during jaw movement.

Answer 1

The Correct Option is A

Step 1: The key clinical clue is a drooping (ptotic) eyelid that suddenly lifts (retracts) when the patient chews or moves the jaw.
Step 2: This is a synkinesis between the trigeminal nerve (motor branch to the pterygoid muscles, which move the jaw) and the oculomotor nerve branch to the levator palpebrae superioris (which lifts the lid).
Step 3: When the patient activates the pterygoids during chewing or lateral jaw movement, the abnormal connection co-fires the levator, so the ptotic lid elevates. This is the Marcus Gunn jaw-winking phenomenon, a congenital trigemino-oculomotor synkinesis.
Step 4: Third nerve misdirection (aberrant regeneration) follows oculomotor nerve injury and links eye movements to lid or pupil behaviour, but it is not triggered by jaw movement; so Option B is wrong.
Step 5: Abducent palsy (Option C) causes failure of lateral gaze, and a simple oculomotor palsy (Option D) causes ptosis with a fixed dilated eye, but neither shows lid retraction on chewing.
Hence the answer is Option A (Marcus Gunn jaw-winking syndrome).