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Marcus Gunn syndrome

Also known as: Marcus Gunn Jaw-winking syndrome, Marcus Gunn's Phenomenon, Gunn syndrome, Marcus Gunn Ptosis

Overview

Marcus Gunn syndrome causes involuntary facial movement, including 'jaw winking'. This characteristic jaw winking occurs as a brief rising of the eyelid to equal or above normal level followed by a quick return to a lower position. The winking response can be triggered by opening the mouth, chewing, sucking, moving the jaw from side-to-side, clenching the teeth or pushing the jaw forward. Jaw winking generally does not improve with age, although sometimes patients are able to mask it after learning to control facial movement. Individuals with the condition also exhibit drooping eyelids (also known as ptosis), which usually only occurs on one side of the face. Other eye abnormalities, such as strabismus (where the eyes do not look in the same direction, also called 'squint' or 'cross eyed') and other vision difficulties may also occur. The cause of Marcus Gunn syndrome is thought to be due to a stray connection between the motor branches of nerves essential for chewing and winking. Diagnosis is made by observation of the jaw winking response, which is often evident from birth; parents may first notice it when the baby is feeding. If the condition is acquired, symptoms may be evident at any age. All patients should have continuous follow-up by an ophthalmologist. Surgery can be carried out to correct or improve the ptosis. Any amblyopia (see entry Vision disorders in Childhood) must be treated prior to surgical intervention. Good results are normally achieved and the condition becomes manageable.

Credits

Medical text approved February 2015 by Dr Jenny Fisken (retired), formerly Associate Specialist in Community Paediatrics, North Yorkshire and York PCT, UK.

What are the symptoms?

Individuals with Marcus Gunn syndrome exhibit eyelid droops (also known as ptosis), this usually occurs on one side of the face. The characteristic jaw winking occurs as a brief rising of the eyelid to equal or above normal level followed by a quick return to a lower position. The winking response can be triggered by opening the mouth, chewing, sucking, moving the jaw from side-to-side, clenching the teeth or pushing the jaw forward. The condition can occur on both sides of the face in very rare cases.

Eye abnormalities such as strabismus (where the eyes do not look in the same direction, also called 'squint' or 'cross eyed') and other vision difficulties may also occur.

What are the causes?

The cause of Marcus Gunn syndrome is thought to be due to a stray connection between the motor branches of nerves essential for chewing and winking. The nerves involved are the trigeminal nerve, which controls the external pterygoid muscle of the jaw and the oculomotor nerve, which controls the levator muscle of the upper eyelid.

How is it diagnosed?

Diagnosis is made by observation of the jaw winking response. This is often evident from birth and parents may first notice it when the baby is feeding. If the condition is acquired symptoms may be evident at any age.

How is it treated?

All patients should have continuous follow-up by ophthalmologist. Surgery can be carried out to correct or improve the ptosis. Any amblyopia (see entry Vision disorders in Childhood) must be treated prior to surgical intervention. With treatment good results are normally achieved and the condition becomes manageable.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
Usually sporadic but familial cases have been reported with an irregular autosomal dominant inheritance pattern.

Prenatal diagnosis
Not available.

Is there support?

There is no support group for Marcus Gunn syndrome in the UK. Cross referrals to other entries in The Contact a Family Directory are intended to provide relevant support for those particular features of the disorder. Organisations identified in those entries do not provide support specifically for Marcus Gunn syndrome.

Families can use Contact a Family's freephone helpline for advice, information and, where possible, links to other families. Contact a Family's web-based linking service can be accessed at community.cafamily.org.uk

References

Chang-Hsu L, Yaw-Don H, Chang-Hung H, et al. Electromyographic findings of Marcus Gunn phenomenon. J Med Sci. 2003;23:307-10.

Khwarg SI, Tarbet KJ, Dortzbach RK, et al. Management of moderate-to-severe Marcus-Gunn Jaw-winking ptosis. Ophthalmology. 1999;106:1191-96.

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