Physical phenomenon that involves jaw movements and upper eyelid. This medical condition presents in approximately 5% of neonates with congenital ptosis. It is associated with amblyopia, anisometropia, and strabismus. Controversies exist about sensibility to malignant hyperthermia.
Jaw-Winking Syndrome; Marcus Gunn Jaw-Winking Syndrome; Trigemino Oculomotor Synkinesis Syndrome.
This medical condition was first described in 1883 by Robert Marcus Gunn (1850-1909), a Scottish ophthalmologist. Dr Gunn is remembered for his discovery of the Gunn’s Sign (characterized by a retinal vascular arteriovenous nicking observed during fundus examination where an arteriole can be seen crossing a venule causing compression of the vein and leading to vascular bulging on either side of the crossing. It is most commonly seen in hypertensive retinopathy) and the Marcus Gunn pupil (is characterized by a medical sign related to a “relative afferent pupillary defect” that can be observed during the “Swinging-Flashlight Test.” The patient’s pupils constrict less and therefore appear to dilate when a bright light is beamed to the eye. The affected eye presents a reduced pupillary sphincter constriction).
Gunn Syndrome is estimated to account for approximately 5% of all congenital cases of blepharophimosis.
There are two major groups of trigemino-oculomotor synkinesis:
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 innervates 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.
Precautions before anesthesia
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.