Marcus-Gunn Jaw Winking
Marcus-Gunn jaw-winking ptosis was first described in 1883 as unilateral upper eyelid ptosis with eyelid retraction associated with activation of the pterygoid muscle (i.e. movement of the jaw) (see Figures 4 and 5). This is a congenital condition thought to be caused by pterygoid-levator synkinesis. The exact abnormal neurological pathway has yet to be described, but it is postulated that fibers of the fifth cranial nerve are responsible for either directly or indirectly innervating the levator. Electromyographic studies have reported that the impulses generating levator activation originate from the proprioceptive receptors of the pterygoid muscles, thereby linking pterygoid movement to elevation of the eyelid. The condition is almost always unilateral and affects males and females in equal proportion (Demirci 2010). There is associated superior rectus weakness in over half of cases (Beard 1976).
In evaluating a patient with what appears to be isolated unilateral ptosis, it is valuable to ask if the infant's ptosis varies with nursing or eating. This may be a clue to look carefully for this synkinetic condition.
|Figure 4: Note the ptosis of the right upper eyelid||Figure 5: Note the dramatic eyelid retraction with jaw opening|