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Physical phenomenon that involves jaw movements and upper eyelid. Controversies exist about sensibility to malignant hyperthermia.

Jaw-Winking Syndrome; Marcus Gunn Syndrome; Trigemino Oculomotor Synkinesis Syndrome.

Gunn syndrome is estimated to account for approximately 5% of all congenital cases of blepharophimosis.

Several presentations have been suggested: sporadic cases, and autosomal dominant transmissions.

Caused by an aberrant connection between the motor branches of the trigeminal nerve (innervating the external pterygoid muscle) and the fibers of the superior division of the oculomotor nerve that innervate the levator superioris muscle of the upper eyelid.

Generally possible to evocate at birth or after a few weeks when facing a child with unilateral congenital ptosis and rapid, exaggerated elevation of the ptotic lid on moving of the lower jaw.

Principal features are ophthalmic with strabismus (50-60% of cases), anisometropia (5-25% of cases), and amblyopia (30-50% of cases). Superior rectus palsy is found in 25% of cases and double elevator palsy in another 25% of cases.

Obtain full personal and familial history with regard to malignant hyperthermia reaction in the past. Laboratory investigations may include preoperative creatine phosphokinase level because of the potential for malignant hyperthermia, although normal levels do not exclude a predisposition to malignant hyperthermia.

Relation with malignant hyperthermia susceptibility has been evocated on the findings of rare cases of histologic muscle anomalies. Close monitoring for signs of beginning malignant hyperthermia is therefore recommended, although to the best of our knowledge, no such care has been reported in connection with this disorder.

Avoid halogenated agents and succinylcholine if possible.

Bullock JD: Marcus-Gunn jaw-winking ptosis: Classification and surgical management. J Pediatr Ophthalmol Strabismus 17:375, 1980.  [PubMed: 7205518]
Pratt SG, Beyer CK, Johnson CC: The Marcus Gunn phenomenon. A review of 71 cases. Ophthalmology 91:27, 1984.  [PubMed: 6709318]

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