Medical Q&As

Marcus Gunn Syndrome - explain?

Can you give me information on Marcus Gunn Syndrome?

Marcus Gunn Syndrome is a rare congenital syndrome that was originally described by Marcus Gunn in 1883. It is also known by the colloquial name of jaw winking. The affected person has ptosis, which means a drooping eyelid. This lid then winks if the lower jaw moves. The condition usually occurs on one side of the face but in rare cases it can present on both sides. The winking effect is triggered by opening the mouth, protruding the jaw or by chewing or sucking. It is usually noticed by parents early in infancy as the baby winks one of its eyelids while sucking at breast or bottle. The syndrome is due to an aberrant connection between two of the cranial nerves namely the third and fifth cranial nerves. The fifth cranial nerve is also known as the trigeminal nerve and it innervates the pterygoid muscles, which are involved in chewing and sucking. Normally these two nerves are not connected to each other but the aberrant connection associated with Marcus Gunn Syndrome means that electrical impulses discharging through the trigeminal nerve also discharge through the third cranial nerve resulting in intermittent contraction of the muscles in the upper eyelid. The syndrome can be associated with weakness of the extraocular muscles, which are the muscles that control movement of the eyeball. This weakness can give rise to strabismus or squint. If you require further detailed information on this syndrome it would be best to attend an ophthalmologist since the condition is quite rare.