Marcus Gunn phenomenon

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Marcus Gunn phenomenon is a rare congenital condition characterized by an abnormal connection between the nerves that control the muscles of the jaw and the muscles of the eyelid. This condition is also known as Marcus Gunn jaw-winking syndrome or jaw-winking ptosis.

Presentation

The most distinctive feature of Marcus Gunn phenomenon is the involuntary movement of the upper eyelid in response to certain jaw movements. Typically, when the affected individual chews, sucks, or opens their mouth, the upper eyelid on the same side will elevate. This is due to an aberrant connection between the trigeminal nerve (which controls the muscles of mastication) and the oculomotor nerve (which controls the muscles of the eyelid).

Diagnosis

Diagnosis of Marcus Gunn phenomenon is primarily clinical, based on the characteristic jaw-winking motion of the eyelid. A thorough ophthalmologic examination and neurologic examination are essential to rule out other conditions that may present with similar symptoms. Electromyography (EMG) and nerve conduction studies may be used to further evaluate the abnormal nerve connections.

Treatment

Treatment for Marcus Gunn phenomenon is often not necessary unless the condition causes significant functional or cosmetic issues. In severe cases, surgical intervention may be considered. Surgical options include ptosis surgery to correct the drooping eyelid or procedures to weaken the connection between the jaw and eyelid muscles.

Prognosis

The prognosis for individuals with Marcus Gunn phenomenon is generally good. The condition is usually stable and does not progress over time. Most individuals adapt to the jaw-winking motion, and it does not typically interfere with vision or daily activities.

Related Conditions

Marcus Gunn phenomenon can be associated with other congenital conditions such as congenital ptosis, strabismus, and amblyopia. It is important for individuals with Marcus Gunn phenomenon to have regular follow-ups with an ophthalmologist to monitor for these associated conditions.

History

The condition is named after the Scottish ophthalmologist Robert Marcus Gunn, who first described the phenomenon in 1883.

See Also

• Congenital ptosis
• Strabismus
• Amblyopia
• Oculomotor nerve
• Trigeminal nerve