Marcus Gunn syndrome, or mandibulopalpebral synkinesis, is a congenital movement of the upper eyelid when the mouth is opened. The cause is a paradoxical ipsilateral innervation between the eyelid retractor and the lateral pterygoid muscle. Clinically, there is ptosis of the affected eyelid, which disappears when the mouth is opened.
The inverse Marcus-Gunn phenomenon describes an ipsilateral closure of the eyelid when the lateral pterygoid muscle contracts. The combination of both phenomena is also known as ‘See-Saw’ Marcus Gunn syndrome. This is a congenital condition that leads to lifting of the upper eyelid on one side and lowering of the upper eyelid on the opposite side when the mouth is opened. This condition is considered an extreme rarity.
In this case report, we show a twenty-year-old woman who has had the condition from birth. At rest, there is incomplete ptosis of the right eye. When the mouth is opened, the right eyelid lifts involuntarily and the left upper eyelid lowers almost completely. In addition, she shows a bilateral involuntary pupil movement to the left caudal side. A causal therapy is not yet known, genetic counselling is recommended. Therapeutic approaches relate to independent conscious training of the dysinervated eyelid in front of the mirror; in severe cases, surgical correction may be considered.