What are the other Names for this Condition? (Also known as/Synonyms)

• Jaw-Winking Syndrome
• Marcus Gunn Ptosis (with Jaw-Winking)
• Maxillopalpebral Synkinesis

What is Marcus Gunn Phenomenon? (Definition/Background Information)

• Marcus Gunn Phenomenon is a rare and unusual congenital disorder that is characterized by abnormalities affecting the eye and jaw
• In this disorder, the upper eyelid of one eye rises and drops rapidly and repeatedly, whenever the individual moves their jaw, such as while eating, talking, or smiling. This jaw-movement induced involuntary winking of the eye is also known as Jaw-Winking Syndrome
• Marcus Gunn Phenomenon is normally present at birth and most cases are not associated with a family history of the condition; some are inherited as an autosomal dominant trait
• The exact cause of Marcus Gunn Phenomenon is not known, but it is believed to be caused by unusual interactions between the nerves that connect the eye to the jaw. This phenomenon may be associated with other abnormalities affecting the eye
• The treatment of Marcus Gunn Phenomenon depends upon the severity of the condition. In some cases, the jaw movement-eye winking symptoms may simply becoming less noticeable with age; while for severe conditions, a surgery to correct the defect may be undertaken
• Most individuals diagnosed with Marcus Gunn Phenomenon are able to live their full lives and learn to cope with the symptoms quite well. The prognosis is generally good

Who gets Marcus Gunn Phenomenon? (Age and Sex Distribution)

• Marcus Gunn Phenomenon is usually present from birth and first noticed when a baby is feeding or suckling
• It is a very rare disorder and presently, there have been only 300 cases of Marcus Gunn Phenomenon reported
• Both males and females are affected and no gender bias is noted
• There is also no racial or ethnic predilection noticed

What are the Risk Factors for Marcus Gunn Phenomenon? (Predisposing Factors)

The risk factors for Marcus Gunn Phenomenon may be described as:

• Family history of the condition: Some cases of inheritance of Marcus Gunn Phenomenon have been reported, though this is very rare
• Generally, sporadic cases are seen to occur randomly in individuals with no family history of the condition. In such cases, the risks are unidentified

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases the chance of getting a condition in comparison to an individual without any risk factors. Some risk factors are more important than others. 

At the same time, not having a risk factor does not mean one will not get a condition. For more clarity, discuss with your healthcare provider the effects of risk factors.

What are the Causes of Marcus Gunn Phenomenon? (Etiology)

The exact cause of Marcus Gunn Phenomenon development is unknown.

• Some study reports inform that this condition may be due to a stray connection between nerves essential for chewing and winking. Here, the trigeminal nerve, which controls a jaw muscle, and the oculomotor nerve, which controls a muscle of the upper eyelid, is involved
• Many cases occur randomly and no preceding family history of the condition is observed
• Some cases are genetic in nature and in such cases, a family history of Marcus Gunn Phenomenon is observed. Familial inheritance occurs in an autosomal dominant manner
• Some types of facial nerve injuries are known to produce symptoms similar to Marcus Gunn Phenomenon

Autosomal dominant: Autosomal dominant conditions are traits or disorders that are present when only one copy of the mutation is inherited on a non-sex chromosome. In these types of conditions, the individual has one normal copy and one mutant copy of the gene. The abnormal gene dominates, masking the effects of the correctly functioning gene. If an individual has an autosomal dominant condition, the chance of passing the abnormal gene on to their offspring is 50%. Children, who do not inherit the abnormal gene, will not develop the condition or pass it on to their offspring.

What are the Signs and Symptoms of Marcus Gunn Phenomenon?

The main indication of Marcus Gunn Phenomenon is the association of jaw movement with eyelid movement, mostly restricted one eye.

• Movement of the jaw in any manner, such as while talking, eating/chewing, yawning, sideways movement, or smiling, can cause rapid movement of the eyelid appearing like repeated winking
• This involuntary eye action may be severe when the individual is bending down or looking to the floor
• Drooping of upper eyelid of only one eye, called ptosis
• Typically only a single eye is involved; involvement of both the eyes is extremely rare

How is Marcus Gunn Phenomenon Diagnosed?

The symptoms of Marcus Gunn Phenomenon are usually evident following birth of the child, during feeding sessions. This may be picked up by the parent(s) or the assisting/attending healthcare provider.

• The healthcare provider can make a diagnosis based on the characteristic symptom associated with jaw movement and eyelid movement. However, a complete physical examination and family history evaluation may be requested
• Eye examination to detect any other associated eye abnormalities may be undertaken
• In case signs and symptoms associated with Marcus Gunn Phenomenon is noted after birth of the child (for any reason such as due to an injury), the healthcare provider may call forth for further tests and exams

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Marcus Gunn Phenomenon?

The complications may depend upon the severity of Marcus Gunn Phenomenon and may include:

• Presence of other eye abnormalities or vision defects
• Strabismus, when both the eyes do not look in the same direction (or are cross-eyed)
• Reduced vision in the affected eye (compared to the other eye), known as ‘lazy eye’
• Treatment-related complications: Some issues after surgery to correct ‘jaw-winking’ condition include unequal eyelid levels, partial correction of the defect, loss of the lid crease, and overhanging skin folds that can cause cosmetic issues

How is Marcus Gunn Phenomenon Treated?

Marcus Gunn Phenomenon is normally less noticeable with age. In many cases, individuals often learn to mask it by controlling their facial movements. In case the disorder is severe and needs to be treated, then the following measures may be considered:

• Associated eye defects often need to be corrected before managing Marcus Gunn Phenomenon. These can normally be rectified using glasses, medications, or surgery
• Muscle reattachment surgery or symptom management through observation are suggested for mild conditions
• In case of severe cases, the condition can be corrected through surgery on the affected eyelid

How can Marcus Gunn Phenomenon be Prevented?

Sporadic cases of Marcus Gunn Phenomenon are not preventable. However, if the disorder is genetically inherited, then the following factors may be considered.

• Genetic testing of the expecting parents (and related family members) followed by prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks prior to childrearing
• Active research is currently being performed in order to explore both treatment and prevention methods for genetic disorders such as Marcus Gunn Phenomenon

What is the Prognosis of Marcus Gunn Phenomenon? (Outcomes/Resolutions)

• The prognosis of individuals diagnosed with Marcus Gunn Phenomenon is overall good, because it is not a life-threatening condition
• Anxiety and stress as a result of the condition can affect the individuals, sometimes for a long period of time
• Severe eye conditions associated with Marcus Gunn Phenomenon can be corrected through various treatment options including surgery

Additional and Relevant Useful Information for Marcus Gunn Phenomenon:

There have been a few cases of Marcus Gunn Phenomenon-like condition occurring in adulthood. Eye symptoms of the condition have been seen through movement of lips, whistling, clenching teeth, chewing, smiling and swallowing.