Marcus Gunn phenomenon

Marcus Gunn phenomenon is an autosomal dominant condition with incomplete penetrance, in which nursing infants will have rhythmic upward jerking of their upper eyelid.

[citation needed] Marcus Gunn jaw-winking is an exaggeration of a very weak physiologic co-contraction that has been disinhibited secondary to a congenital brain stem lesion.

The stimulation of the trigeminal nerve by contraction of the pterygoid muscles of jaw results in the excitation of the branch of the oculomotor nerve that innervates the levator palpebrae superioris ipsilaterally (on the same side of the face), so the patient will have rhythmic upward jerking of their upper eyelid.

[4] Inverse Marcus Gunn phenomenon is a rare condition[5] that causes the eyelid to fall upon opening of the mouth.

In this case, trigeminal innervation to the pterygoid muscles of the jaw is associated with an inhibition of the branch of the oculomotor nerve to the levator palpebrae superioris, as opposed to stimulation in Marcus Gunn jaw-winking.

Marcus Gunn phenomenon: the woman cannot control her eyelids while drinking. This is a particularly mild case.}
An affected young woman demonstrating the Marcus Gunn Jaw Wink Phenomenon. The woman cannot control her eyelids while sucking on a straw. This is a particularly mild case.