Two years after severe head trauma, a 30-year-old man who had a left third nerve palsy now shows elevation of the left upper eyelid when he attempts to look to the right or downward, and constriction of the left pupil on attempted adduction. This phenomenon is best explained by:

• A Marcus Gunn jaw-winking synkinesis
• B Aberrant regeneration of the oculomotor nerve ✓
• C Duane retraction syndrome type I
• D Ocular myasthenia with fatigable ptosis

Explanation

After traumatic or compressive third nerve injury, regenerating axons may be misdirected to wrong targets, producing aberrant regeneration. Classic patterns include lid-gaze dyskinesis (lid elevates on attempted adduction or depression, the pseudo-Graefe sign), adduction-constriction synkinesis (pupil constricts on adduction), and pseudo-ductions. Marcus Gunn jaw-winking is a congenital trigemino-oculomotor synkinesis present since birth, not acquired after trauma, which eliminates option A. Myasthenia fluctuates and does not produce fixed synkinetic movements.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.