[Clinical and electrophysiological study of 2 familial cases of Marcus Gunn phenomenon]

Two cases of jaw-winking synkinesia or Marcus Gunn (MG) phenomenon are reported, with electromyographic and genetic studies. In the first patient a right eyelid ptosis which had been occurring since birth was associated with a bilateral MG phenomenon confirmed by electromyography. An examination of other family members revealed 3 other cases in the mother's family. The second patient had a congenital left eyelid ptosis associated with an MG phenomenon. His maternal uncle and his mother also had this "jaw-winking" synkinesia. The authors discuss the physiopathology of this complex phenomenon up to now without known neurological lesions. Concerning the genetic aspect of the MG phenomenon, they conclude that in their patients the hereditary pattern was that of an incomplete autosomal dominant trait with varied expressivity in the two families.