The inverse Marcus Gunn phenomenon. An electromyographie contribution

Area of Science:

• Ophthalmology
• Neurology
• Anatomy

Background:

• Marcus Gunn anomaly is a rare congenital condition characterized by synkinesis between the eyelid and jaw.
• Inverse Marcus Gunn anomaly presents with eyelid elevation during jaw depression.

Observation:

• Electromyographic (EMG) studies were performed on a patient with inverse Marcus Gunn anomaly.
• The study investigated the neural pathways responsible for the aberrant eyelid movement.

Findings:

• The closing of the affected eye during contralateral jaw movement was not mediated by the seventh cranial nerve's stimulation of the orbicularis oculi muscle.
• Instead, the observed phenomenon was attributed to the inhibition of the homolateral levator palpebrae superioris muscle.

Implications:

• This finding clarifies the neurophysiological mechanism underlying inverse Marcus Gunn anomaly.
• Understanding this mechanism allows for the development of specific and effective surgical interventions.
• Accurate diagnosis and targeted treatment can improve patient outcomes for this rare condition.