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

Marcus Gunn phenomenon (external pterygoid-levator synkinesis)

Almost all cases of synkinesis develop as a sequel to nerve trauma (the exception is when it is congenitally acquired as in Duane-Retraction Syndrome and Marcus Gunn phenomenon).

Marcus Gunn (Jaw-Winking) Syndrome Marcus Gunn Ptosis (with jaw-winking) Maxillopalpebral Synkinesis None Marcus Gunn phenomenon is a rare genetic disorder that is usually present at birth.

Marcus Gunn phenomenon (a.k.a. Marcus Gunn Jaw-Winking or Trigemino-oculomotor Synkineses) is an autosomal-dominant condition with incomplete penetrance, in which nursing infants will have rhythmic upward jerking of their upper eyelid.