Some people have a drooping upper eyelid that lifts on its own when the jaw moves. Not from a tic, not from effort, but as a fixed reflex tied to chewing, sucking, smiling, or pushing the jaw sideways. The lid jumps upward, sometimes higher than the unaffected one, then drops back.
A case report published in January in the International Journal of Medicine in Developing Countries is the latest to document the phenomenon, noting that it is classically elicited by voluntary jaw movements such as opening the mouth or moving the jaw sideways. The diagnosis is Marcus Gunn jaw-winking syndrome, and what makes it worth a reader's attention is less the wink itself than what occasionally comes with it.
