Mobius syndrome

Clinical features

Mobius syndrome is caused by an abnormal neurodevelopment of the cranial nerves. This is quite a rare disorder and it has a number of different causes. The cranial nerves VI and VII are the most commonly affected nerves. Cranial nerves V and VIII are only affected occasionally. If the cranial nerve VI is affected, the patient will suffer from loss of lateral gaze. If cranial nerve VII is affected, the patient will suffer from bilateral facial palsy i.e. mask-like expressionless face with mouth constantly held open. The patient will suffer from hearing loss if cranial VIII is affected. Infants with this disorder can be identified at birth, by a "mask-like" expression detectable during crying or laughing due to paralysis (palsy) of the sixth and seventh cranial nerves. Along with this, infants also suffer from abnormalities in their limbs i.e their fingers may be webbed, shorter than usual or they may have more than 5 fingers on their hand. Later on, the child may develop speech difficulties, crossed eyes, abnormally small eyes, and fluid building up in lungs causing bronchopneumonia.

Pathological picture

The exact cause of this disorder is not known. Most of the cases seen are sporadic but there is a few that may be of a genetic cause. In some cases, this syndrome may be due to the reciprocal translocation between chromosomes or due to maternal illness. The use of drugs and a traumatic pregnancy may also be linked to the development of Mobius syndrome. Some researchers have suggested that the underlying problem of this disorder could be due to congenital hypoplasia or agenesis of the cranial nerve nuclei.