INTRODUCTION The Marcus Gunn Jaw Winking Syndrome is a form of congenital synkinetic ptosis that is typically unilateral and non-hereditary, although bilateral and familial cases have been reported. The cause remains unknown, but appears to result from a misdirection of either the efferent motor innervation or the afferent proprioceptive fibers of the third and fifth cranial nerves. This results in inappropriate contraction of muscle fibers of the eye or eyelid during mastication.
CLINICAL CHARACTERISTICS The involved upper eyelid typically shows ptosis that may be mild to severe.
In most patients the synkinesis is used to reduce the true degree of ptosis which often is greater than appears clinically. With contraction of the masticatory muscles, most commonly the external pterygoid muscle, the ptotic eyelid shows coordinated elevation or even retraction. The characteristic appearance is a "winking" of the eyelid during eating or chewing. The degree of ptosis and the amount of kinetic lid elevation are related proportionately. Aberrant and sometimes bizarre synkinetic movements between the eyelid and other muscles, such as the masseter or temporalis, may be seen. Levator muscle function may be normal or somewhat decreased. Unlike congenital myogenic ptosis, the eyelid crease is usually normal in position. Various types of strabismus may be seen in 25% to 35% of cases, and amblyopia in 35% to 60%. An association between the Marcus Gunn Jaw Winking syndrome and Duane's Retraction syndrome, another neural miswiring disorder, has been reported.
TREATMENT Therapy is surgical and is often challenging. Preoperatively attention must be paid to any associated strabismus and amblyopia. If the ptosis is the major concern with minimal synkinetic movement, levator surgery alone will usually give good results. For patients with larger amplitude winking, however, it is better to disinsert the levator muscle and elevate the lid with a frontals suspension procedure. There remains some controversy as to the benefit of also disinserting and slinging the contralateral normal eyelid for symmetry. In most cases we prefer unilateral surgery.
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