In a patient with ptosis, which of the following is the cause of retraction of the ptotic eye lid on chewing?

Patient in the question is showing features of Marcus gunn jaw winking syndrome. It is seen in 5% cases of congenital ptosis. It is characterized by the presence of abnormal synkinetic movement of the upper eyelid with contraction of muscles of mastication, most commonly external pterygoids. The condition is typically unilateral and the lid fold is generally better maintained than in other types of congenital ptosis. It is believed to be due to a congenital error of neuronal wiring in the brainstem. It sometimes occur as an autosomal dominant familial trait. The risk is increased in infants after a pregnant woman uses misoprostol as an aboifacient. Ref: Merritt's Neurology By Lewis P. Rowland, Page 695; Pg Ophthalmology : V. I and Volume 2 By Zia Chaudhari, Page 1358; Oculoplastic Surgery Atlas : Eyelid Disorders By Geoffrey J. Gladstone, Page 41; Adams and Victor's Principles Of Neurology By Allan H. Ropper, 8th Edition, Page 230