Mobius syndrome is caused by abnormal development of the cranial nerves. This rare disorder has a number of causes. Most often affected are the cranial nerves VI and VII. Occasionally the cranial nerves V and VIII are affected.

If the cranial nerve VI is affected, the patient suffers from loss of lateral gaze. If cranial nerve VII is affected, the patient suffers from bilateral facial palsy — mask-like expressionless face with mouth constantly held open. If cranial VIII is affected the patient suffers from hearing loss.

Although its rarity often leads to late diagnosis, 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. Other characteristics include:

abnormalities in the limbs — their fingers may be webbed, shorter than usual or they may have more than 5 fingers on their hand
impaired sucking ability
inability to follow objects with the eye—instead the child turns his or her head to follow
crossed eyes
inability to smile
limitation of tongue movement

Later on, the child may develop speech difficulties, crossed eyes, abnormally small eyes, and fluid building up in the lungs, causing bronchopneumonia.

Treatment

There is no specific course of treatment for Mobius syndrome. Treatment is supportive and in accordance with symptoms. Infants may require feeding tubes or special bottles, such as the Haberman Feeder, to maintain sufficient nutrition. Surgery may correct crossed eyes and improve limb and jaw deformities. Physical and speech therapy often improves motor skills and coordination, and leads to better control of speaking and eating abilities. Plastic reconstructive surgery may be beneficial in some individuals. Nerve and muscle transfers to the corners of the mouth have been performed to provide limited ability to smile.

Pathological picture

The causes of Mobius syndrome are poorly understood. Many cases have no obvious cause. Others may be genetic.

Some cases are associated with reciprocal translocation between chromosomes or maternal illness. Some maternal trauma may result in impaired or interrupted blood flow (Ischemia) or lack of oxygen (Hypoxia) to a developing fetus. The use of drugs and a traumatic pregnancy may also be linked to the development of Mobius syndrome. The use of the drugs Misoprostol or Thalidomide by women during pregnancy has been linked to the development of Mobius syndrome in some cases.

Some researchers have suggested that the underlying problem of this disorder could be congenital hypoplasia or agenesis of the cranial nerve nuclei. Certain symptoms associated with Mobius syndrome may be caused by incomplete development of facial nerves, other cranial nerves, and other parts of the central nervous system.