Physical phenomenon that involves jaw movements and
upper eyelid. Controversies exist about sensibility to malignant
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
Bullock JD: Marcus-Gunn jaw-winking ptosis: Classification and surgical
management. J Pediatr Ophthalmol Strabismus
Pratt SG, Beyer CK, Johnson CC: The Marcus Gunn phenomenon. A review of 71