Mobius syndrome
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Mobius syndrome (also spelled Moebius) is an extremely rare neurological disorder.
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Clinical features
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 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.
There appears to be an increased incidence of Mobius in children of parents with Mobius, implying a genetic cause. In some rare cases, it is thought that Mobius syndrome may be inherited as an autosomal dominant trait. Human traits including the classic genetic diseases are the product of the interaction of two genes for that condition, one received from the father and one from the mother. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.
In the majority of cases of Moebius syndrome in which autosomal dominant inheritance is suspected, sixth and seventh cranial nerve paralysis (palsy) occurs without associated limb abnormalities.
External links
- Moebius Syndrome Information (http://goldbamboo.com/topic-t3369-moebius_syndrome.html)
- Moebius Syndrome Foundation & International Conference Information (http://www.moebiussyndrome.com)fr:Syndrome de Möbius