Marcus Gunn Syndrome is a rare, congenital condition involving a drooping eyelid that moves in sync with the jaw. First described in 1883 by ophthalmologist Marcus Gunn, it is often called the “jaw-winking phenomenon.” The condition usually affects only one eye, though in rare instances, both are involved. This connection results in the affected eyelid lifting when the jaw is moved for activities like chewing or talking.
Causes and Symptoms of Jaw-Winking
The cause of Marcus Gunn Syndrome is an abnormal neural connection that forms in the nervous system before birth. Specifically, the trigeminal nerve, which controls the muscles for chewing (pterygoid muscles), forms a faulty link with a branch of the oculomotor nerve. This branch of the oculomotor nerve is meant to control the levator palpebrae superioris, the muscle that lifts the upper eyelid.
The most prominent sign is the involuntary lifting, or retraction, of the affected eyelid whenever the jaw is stimulated. This “wink” can be triggered by common actions such as chewing, sucking, smiling, swallowing, or moving the jaw from side to side. When the jaw is at rest, the primary symptom is ptosis, which is a noticeable drooping of the upper eyelid.
The severity of both the ptosis and the jaw-winking action can vary significantly. For some, the movement is subtle and may become less obvious over time as they learn to control facial movements. Parents often first notice the condition in infancy, particularly when the baby is feeding or sucking. The amount of wink can also appear more exaggerated when the person is looking downward.
The Diagnostic Process
The diagnosis of Marcus Gunn Syndrome is made through a clinical examination by an ophthalmologist or a pediatric specialist. No complex imaging or blood tests are required; the diagnosis relies on careful observation of the patient’s facial and eye movements. The specialist will watch the patient’s eyelids while instructing them to perform jaw motions like opening and closing the mouth, clenching the teeth, and moving the jaw side-to-side.
A thorough diagnostic process also involves screening for other eye conditions that are frequently associated with the syndrome. Among the most common associated conditions is amblyopia, often called a “lazy eye,” where vision in one eye does not develop properly. Strabismus, a misalignment of the eyes where they do not look in the same direction, is another frequent finding. Anisometropia, a condition where the two eyes have significantly different refractive power, can also be present.
Treatment and Management Options
Managing Marcus Gunn Syndrome depends on the severity of the symptoms and their impact on vision. In many mild cases, where the ptosis is not severe and the winking is not cosmetically significant, no medical intervention is recommended. The course of action is observation, with regular follow-up appointments with an ophthalmologist to monitor vision.
For individuals with more severe symptoms, surgical options may be considered to improve the function and appearance of the eyelid. The goal of surgery is not to correct the underlying abnormal nerve connection, but to create better eyelid height and symmetry. The decision for surgery is based on factors like the degree of ptosis and the prominence of the wink, and any associated conditions like amblyopia must be treated before surgical intervention.
One of the primary surgical procedures involves weakening or detaching the levator muscle—the one responsible for the winking—to stop the aberrant movement. Following this, a procedure called a frontalis sling, or frontalis suspension, is performed. This technique connects the eyelid to the frontalis muscle in the forehead, allowing the patient to use their forehead to help lift the eyelid. This can provide a more stable and symmetric eyelid position, but it requires learning a new way to open the eye.