Mobius syndrome is a congenital and rare neurological disorder that affects approximately 2 individuals in every 1 million births worldwide (1 individual in every 50,000 births in the United States). This disorder is characterized by facial muscle weakness/paralysis due to paralysis (palsy) of the sixth (abducens) and seventh (facial) cranial nerves. These nerves enter and exit from the back of the brain in the brainstem and are critical for the movement of facial muscles and in particular back and forth (lateral) eye movement. One of the distinguishing symptoms of Mobius syndrome is the inability to look left and right and the need to turn one’s head to see to either side of the body. In some individuals the eighth (vestibulocochlear) cranial nerve is also involved. At this point, there is no known effective treatment for this disorder.
Mobius syndrome is named after Paul Julius Mobius (1853—1907), a German neurologist who fully described this syndrome in 1892. Mobius syndrome is a congenital disease and not something that an individual can develop after birth. Individuals born with Mobius syndrome have significant weakness or paralysis of the facial muscles and as a result are often unable to frown, move their eyebrows, smile, and have significant difficulty with feeding early in life due to a smaller than average mouth size and weakness in the muscles associated with sucking. These individuals also tend to have smaller than average chins (micrognathia) and smaller than normal tongues. In addition, these individuals often have difficulty with speech and exhibit significant dental problems.
There are currently four classifications/groups of Mobius syndrome. Group I individuals often exhibit simple hypoplasia or atrophy of the cranial nerve nuclei. Group II individuals will exhibit more significant lesions in the peripheral cranial nerves. Group III individuals start to show focal (localized) necrosis (death) of neuronal nuclei in the brainstem, and group IV individuals exhibit primary myopathies with no central nervous system or cranial nerve lesions.
In addition to defects seen in the face and skull, individuals with Mobius syndrome can also have general skeletal system defects. These include the presence of clubbed feet, shorter than average tibial and fibular lengths, and scoliosis. It is not uncommon to also find defects specifically of the hand including syndactyly (webbing of the fingers), absence of some fingers, and/or underdevelopment of the fingers. Lastly, some individuals may also demonstrate lack of development of the pectoral muscles of the chest. This in conjunction with scoliosis is a contributing factor to the respiratory problems that some individuals with this syndrome exhibit.
While there is no specific known cause for Mobius syndrome, there is a growing body of evidence that the cause is most likely a combination of both environmental and genetic factors. No specific genes have been identified to date that may be the cause of this syndrome, but there is evidence that there may be changes in chromosomes 3, 10, and/or 13 in some families. There is also a growing body of evidence that this syndrome could be due in part to a disruption of blood flow to the brainstem during early fetal development, which could be a leading cause of the atrophy of the sixth and seventh cranial nerves. It is important to note that this evidence is very preliminary and much more research needs to be performed.
There is also evidence that some medications, if taken during pregnancy, could contribute to the development of this syndrome. In particular, studies completed in Brazil have shown that mothers who take misoprostol, which is a drug that is occasionally used to induce labor, or thalidomide, which was used to treat nausea during pregnancy, increase their chances of giving birth to a fetus with Mobius syndrome by a factor of 30.
While there is no specific treatment today that can be used to prevent this syndrome, it is not uncommon to treat the secondary symptoms and difficulties that arise from this syndrome. Treatment teams often consist of neurologists, orthopedic surgeons, and plastic surgeons, to name a few. If a patient has involvement of cranial nerve VIII, an audiologist is also often part of the treatment team. Experimental surgeries that are designed to increase nervous system innervation of affected muscles as well as increase vascular supply to affected areas continue to be examined as a possible mode of treatment for this syndrome (https://www.youtube.com/watch?v=zj6om25_KX4). For individuals with significant skeletal system defects, the use of physical therapy has been shown to relieve some of the symptoms of this syndrome. Research continues to try to determine the exact cause of this syndrome and to develop more specific treatments.
Charles A. Ferguson
See also: Brain Anatomy; Brainstem; Facial Nerve; National Organization for Rare Disorders; Sacks, Oliver Wolf; Visual System
Bogart, Kathleen R. (2014). “People are all about appearances”: A focus group of teenagers with Moebius syndrome. Journal of Health Psychology. http://dx.doi.org/10.1177/1359105313517277
Koren, G., & L. Schuler. (2001). Taking drugs during pregnancy. How safe are the unsafe? Canadian Family Physician, 47, 951—953.
National Organization for Rare Disorders (NORD). (2014). Moebius syndrome. Retrieved from http://rarediseases.org/rare-diseases/moebius-syndrome/
St. Louis Children’s Hospital. (2014). Dawson’s smile: Facial reanimation surgery for a child with Mobius syndrome. Retrieved from https://www.youtube.com/watch?v=zj6om25_KX4