At 5 months old, doctors diagnosed Marcus Gunn jaw-winking phenomenon, a congenital miswiring between the nerves that control chewing and the eyelid. The case, published Aug. 18, 2025, in the International Medical Case Reports Journal by Amjad Fiusal H. Alharthe, Naif M. ALAli, and colleagues at the University of Tabuk in Saudi Arabia, carries a striking twist. In its classic form, the condition pairs jaw-triggered eyelid movement with a droopy eyelid. This baby had the movement without the droop.
Eyelid Movement Without the Expected Droop
The full-term girl was examined at a private outpatient clinic. Doctors saw her left eyelid repeatedly lift during sucking, but it did not droop when she looked straight ahead.
Both eyes moved fully, her corneas were clear, her pupils were normal, and a cover test for eye misalignment was normal. Her physical and neurological exams were unremarkable. The authors reported that the eyelid movement was evident during suckling and during near accommodation, when the eyes adjust to focus up close.
This pattern differs from textbook descriptions. StatPearls, a peer-reviewed clinical reference, places jaw-winking among people with congenital ptosis, where it represents roughly 2% to 13% of cases.
Jaw-winking without the droop is uncommon. In a 2017 study in Ophthalmic Plastic and Reconstructive Surgery, researchers identified 72 jaw-winking patients among 848 congenital ptosis cases. Only four, about 6%, had no ptosis, and the authors described them as the first case series of the pattern.
Developmental Nerve Crossings
The Scottish ophthalmologist Robert Marcus Gunn first described the phenomenon in 1883, in a 15-year-old girl. It is thought to result from abnormal connections between the trigeminal nerve, which drives the jaw muscles, and the oculomotor nerve, which supplies the muscle that raises the upper eyelid. When the jaw moves, the eyelid moves with it.
Sucking is a classic trigger, which is why many cases surface during infant feeding. According to Nemours KidsHealth, the eyelid can also lift when a child opens the mouth, chews, smiles, sticks the jaw out, or moves it to the side.
The report includes one additional detail that raises questions. The girl’s parents are blood relatives, though no one else in the family had a similar condition. The authors noted that most cases are sporadic, but familial cases with autosomal dominant inheritance have been reported. They did not perform genetic testing and listed that as a limitation.
Vision, Not the Wink, May Be the Bigger Question
The eyelid movement itself is rarely the main concern. The authors cite estimates that strabismus, or eye misalignment, occurs in 50% to 60% of patients with jaw-winking, differences in focusing power between the eyes in 5% to 25%, and amblyopia, or lazy eye, in 30% to 60%.
Testing with dilating drops showed that the baby was farsighted with astigmatism in both eyes. The report did not describe glasses or other treatment for those findings.
Her doctors chose observation, with follow-up by an ophthalmologist to watch for progression or complications. They outlined clinic visits every four to six months with photographs to track the eyelid movement, astigmatism checks at each visit and monitoring of visual development. Surgery, they wrote, may be considered in extreme cases or when a patient has severe psychological or social distress. Any amblyopia should be treated first with patching, and the authors warned that fixing a droop without also addressing the wink can make the abnormal movement more noticeable.
Surgery brings its own considerations. StatPearls notes that an atypical oculocardiac reflex, a heart-rate response to pressure on the eye, is easily triggered in these patients and recommends an ECG before surgery. It also reports weakness of the muscle that raises the eye in about a quarter of patients, another reason specialists check eye movements closely.
Feeding-Time Clue for Parents
The report has limits. It describes one infant; it does not include long-term follow-up, and the family’s genetic background was not explored.
Its practical message is simple. An eyelid that moves with feeding is a visible clue to a wiring difference that may come with vision problems, even when the eyelid looks normal at rest. KidsHealth notes that the wink usually becomes less noticeable as a child grows and that treatment is generally needed only for eye or vision problems, or by choice for appearance.
The authors called jaw-winking underdiagnosed and urged pediatricians to stay alert for it and recommend routine eye exams.
Parents who notice an eyelid that moves with sucking, chewing, or jaw movement should mention it to their pediatrician, who may recommend a full eye exam by a pediatric ophthalmologist.
Key Questions Answered
What did the baby’s parents notice?
From one month of age, her left upper eyelid repeatedly lifted whenever she sucked on her bottle.
What was the diagnosis?
Marcus Gunn jaw-winking phenomenon, a congenital condition in which jaw movement triggers eyelid movement.
Why is this case unusual?
Jaw-winking usually comes with a droopy eyelid, but this baby had no droop when looking straight ahead. One series found that pattern in about 6% of jaw-winking patients.
Is jaw-winking dangerous?
The wink itself is not harmful, but it is linked to strabismus, amblyopia and focusing differences that can affect vision.
How was the baby managed?
With observation and regular eye exams. Surgery is generally reserved for severe cases or significant distress.
What should parents do if they notice something similar?
Tell a pediatrician, who may refer the child for a full eye exam by a pediatric ophthalmologist.