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At a glance

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.

Synonyms

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

History

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).

Incidence

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

Classification

There are two major groups of trigemino-oculomotor synkinesis:

  • External Pterygoid Levator Synkinesis: The most common group) is present when the eyelid raises upon:

    • Jaw thrust to opposite side (homolateral external pterygoid)

    • Jaw is projected forward (bilateral external pterygoid)

    • Mouth is opened widely

  • Internal Pterygoid Levator Synkinesis: Diagnosed when the eyelid raises upon teeth clenching.

Genetic inheritance

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

Pathophysiology

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.

Diagnosis

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.

Clinical aspects

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.

Anesthetic considerations

Relation with ...

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