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Marcus Gunn Syndrome – Causes, Symptoms & Treatment

Marcus Gunn Syndrome is a rare congenital condition in which a drooping eyelid involuntarily lifts when the jaw is moved, such as during chewing or opening the mouth.

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Things worth knowing about "Marcus Gunn Syndrome"

Marcus Gunn Syndrome is a rare congenital condition in which a drooping eyelid involuntarily lifts when the jaw is moved, such as during chewing or opening the mouth.

What is Marcus Gunn Syndrome?

Marcus Gunn Syndrome – also referred to as the Jaw-Winking Phenomenon or Marcus Gunn Phenomenon – is a rare, congenital neurological eye condition. It is characterized by an involuntary lifting of a drooping upper eyelid (ptosis) that occurs in response to jaw movements, such as chewing, sucking, or opening the mouth. The condition was first described in 1883 by Scottish ophthalmologist Robert Marcus Gunn.

It represents a form of synkinetic ptosis, caused by an abnormal neural connection between the nerve supplying the chewing muscles (trigeminal nerve) and the muscle responsible for lifting the upper eyelid (levator palpebrae superioris).

Causes

Marcus Gunn Syndrome is predominantly congenital and usually affects only one eye. The underlying cause is an aberrant nerve connection (misdirected innervation) between the third cranial nerve (oculomotor nerve), which normally controls the eyelid elevator, and the third branch of the fifth cranial nerve (trigeminal nerve), which innervates the jaw muscles.

In most cases, the syndrome occurs sporadically, without a family history.
Rare familial cases with an autosomal dominant inheritance pattern have been reported.
It is estimated to account for approximately 2–13% of all congenital ptosis cases.
There is no known sex predilection.

Symptoms

The hallmark symptom of Marcus Gunn Syndrome is the characteristic involuntary eyelid elevation in response to jaw movement. Other symptoms may include:

Congenital ptosis: The affected eyelid droops at rest.
Jaw-winking: The eyelid suddenly rises when the jaw is opened, moved sideways, or engaged in chewing or sucking movements.
Amblyopia (lazy eye): Prolonged ptosis can reduce visual development in the affected eye due to insufficient light stimulation.
Anisometropia: A difference in the refractive power between the two eyes.
Strabismus (squinting): Present in a proportion of affected individuals.
Psychosocial impact: The visible eyelid twitching can be a source of social distress, particularly in older children and adults.

Diagnosis

The diagnosis of Marcus Gunn Syndrome is primarily clinical, based on observation and physical examination. Specialized imaging or laboratory tests are generally not required.

Diagnostic Steps

Medical history: Questions about the onset and progression of symptoms, including family history.
Inspection: The physician observes the eyelid at rest and during jaw movements (e.g., opening the mouth wide, chewing, moving the jaw sideways).
Ptosis measurement: Quantification of the eyelid elevation deficit.
Visual acuity testing and eye examination: Assessment for amblyopia, binocular vision, and ocular muscle function.
Slit-lamp examination: Evaluation of the anterior segment of the eye.
Neurological assessment: If needed to exclude other neurological conditions.

Treatment

Not all patients require surgical intervention. The treatment decision depends on the severity of the ptosis, the degree of jaw-winking, and the presence of amblyopia.

Conservative Management

Amblyopia therapy: Patching (occlusion therapy) of the healthy eye to stimulate the weaker eye.
Spectacle correction: If associated refractive error or anisometropia is present.
Observation: In mild cases without functional impairment, a watchful waiting approach may be appropriate.

Surgical Treatment

In cases of significant ptosis or disturbing jaw-winking, surgical correction is indicated. Two main approaches are used:

Levator resection: Tightening of the eyelid elevator muscle on the affected side, suitable for mild jaw-winking.
Bilateral levator disinsertion with frontalis suspension: In pronounced jaw-winking, the levator muscle is disinserted on both sides and the eyelid is suspended from the frontalis muscle using a sling material. This is the preferred approach for achieving a more symmetrical cosmetic result.

Surgery is generally performed during childhood once the child has reached sufficient maturity and stable ocular alignment has been established.

Prognosis

With early diagnosis and appropriate management, the prognosis for visual function is generally good. Regular ophthalmological follow-up is essential to detect and treat amblyopia in a timely manner. Cosmetic and functional outcomes following surgery are generally satisfactory.

References

Bhatt, A. et al. - Marcus Gunn Jaw-Winking Synkinesis: A Review. Survey of Ophthalmology, 2012.
Doucet, T.W. & Crawford, J.S. - The quantification, natural course, and surgical results in 57 eyes with Marcus Gunn (jaw-winking) syndrome. American Journal of Ophthalmology, 1981.
World Health Organization (WHO) - International Classification of Diseases (ICD-11), Entry for Congenital Ptosis and Synkinetic Disorders. Geneva, 2022.

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