According to the National Institute of Neurological Disorders and Stroke, Moebius syndrome is a rare birth defect that affects the sixth cranial nerve, which moves muscles of the face, and the seventh cranial nerve, which moves eyes side-to-side. In some cases, additional cranial nerves are also affected. People with Moebius syndrome are unable to make facial expressions, have trouble blinking and swallowing and may have crossed eyes. It is rare and is estimated to affect 1 in every 50,000 to 500,000 people. The cause of Moebius syndrome is unknown.
Vascular Disruption
In "Clinical Genetics," researcher W. Briegel states that the most accepted cause of Moebius syndrome is vascular disruption. Vascular disruption causes a temporary loss of blood flow to the brain. Researchers believe this occurs early in development, at some time during the first trimester. This loss of blood flow, and the oxygen it carries, causes errors in the development of the cranial nerves, leading to the facial paralysis of Moebius syndrome.
Maternal Drug Use
Maternal drug use can cause vascular disruption. Drugs associated with Moebius syndrome include cocaine, alcohol, benzodiazepines, thalidomide and ergotamines. Misoprostol is the most extensively studied drug associated with Moebius syndrome, and woman in some countries use it for self-induced abortion. Studies suggest its use largely increases a woman's chances of having a child with Moebius syndrome.
Maternal Illness & Trauma
According to Briegel in "Clinical Genetics," maternal illness and trauma, both of which are associated with Moebius syndrome, can cause vascular disruption. This includes hyperthermia during pregnancy, which is an elevated body temperature caused, for example, by heat stroke. Electric shock is also associated with Moebius syndrome, as is chorionic villus sampling, which is a method used to determine genetic disorders in the fetus.
Genetic
Researchers suggest genetic abnormalities could also cause errors in the cranial nerves. Some studies have found errors in chromosomes, the part of cells made up of genes, in patients with Moebius syndrome. This is an ongoing area of research, and experts are still not certain how large a role genes may play.
References
- National Institute of Neurological Disorders and Stroke: Moebius Syndrome Information Page
- Clinical Genetics: Neuropsychiatric findings of Mobius sequence - a review
- Pediatric Neurology: Poland Mobius syndrome and cocaine abuse: A relook at vascular etiology
- The New England Journal of Medicine: Use of Misoprostol during Pregnancy and Mobius' Syndrome in Infants
- Journal of Medical Genetics: Deletion of chromosome 13 in Moebius Syndrome
