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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. This condition is characterized as a synkinesis: when two or more muscles that are independently innervated have either simultaneous or coordinated movements. Common physiologic examples of synkineses occur during sucking, chewing, or conjugate eye movements. There are also several abnormal cranial nerve synkineses, both acquired and congenital. Marcus Gunn jaw-winking is an example of a pathologic congenital synkinesis. First described by the ophthalmologist Marcus Gunn in 1883,〔Gunn RM. Congenital ptosis with peculiar associated movements of the affected lid. Trans Ophthal Soc UK. 1883;3:283-7.〕 this condition presents in approximately 5% of neonates with congenital ptosis. This condition has been associated with amblyopia (in 54% of cases), anisometropia (26%), and strabismus (56%). ==Pathophysiology== It has been postulated that the synkinesis is due to damage to cranial nerve nuclei, caused by peripheral nerve injury and the nuclear lesion releases evolutionarily older () mechanisms with their tendency toward associated movements, and so primitive reflexes are not inhibited. 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. There are two major groups of trigemino-oculomotor synkineses: 1) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Marcus Gunn phenomenon」の詳細全文を読む スポンサード リンク
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