Möbius syndrome


Möbius syndrome is a rare congenital neurological disorder which is characterized by facial paralysis and the inability to move the eyes from side to side. Most people with Möbius syndrome are born with complete facial paralysis and cannot close their eyes or form facial expressions. Limb and chest wall abnormalities sometimes occur with the syndrome. People with Möbius syndrome have normal intelligence, although their lack of facial expression is sometimes incorrectly taken to be due to dullness or unfriendliness. It is named for Paul Julius Möbius, a German neurologist who first described the syndrome in 1888.

Signs and symptoms

People with Möbius syndrome are born with facial paralysis and the inability to move their eyes laterally. Often, their upper lip is retracted due to muscle shrinkage. Occasionally, the cranial nerves V and VIII are affected. If cranial nerve VIII is affected, the person experiences hearing loss.
Other symptoms that sometimes occur with Möbius syndrome are:
Children with Möbius syndrome may have delayed speech because of paralysis of muscles that move the lips, soft palate and tongue root. However, with speech therapy, most people with Möbius syndrome can develop understandable speech. Möbius syndrome has been associated with increased occurrence of the symptoms of autism. Some children with Möbius syndrome are mistakenly labeled as intellectually disabled because of their expressionless faces, strabismus and frequent drooling.

Pathogenesis

Möbius syndrome results from the underdevelopment of the VI and VII cranial nerves. The VI cranial nerve controls lateral eye movement, and the VII cranial nerve controls facial expression.
The causes of Möbius syndrome are poorly understood. It is thought to result from a vascular disruption in the brain during prenatal development. There can be many reasons for vascular disruption leading to Möbius syndrome. Most cases do not appear to be genetic. However, genetic links have been found in a few families. Some maternal trauma may result in impaired or interrupted blood flow or lack of oxygen to a developing fetus. Some cases are associated with reciprocal translocation between chromosomes or maternal illness. In the majority of cases of Möbius syndrome in which autosomal dominant inheritance is suspected, sixth and seventh cranial nerve paralysis occurs without associated limb abnormalities.
The use of drugs and a traumatic pregnancy may also be linked to the development of Möbius syndrome. The use of the drugs misoprostol or thalidomide by women during pregnancy has been linked to the development of Möbius syndrome in some cases. Misoprostol is used to induce abortions in Brazil and Argentina as well as in the United States. Misoprostol abortions are successful 90% of the time, meaning that 10% of the time the pregnancy continues. Studies show that the use of misoprostal during pregnancy increases the risk of developing Möbius syndrome by a factor of 30. While this is a dramatic increase in risk, the incidence of Möbius syndrome without misoprostal use is estimated at one in 50000 to 100000 births. The use of cocaine has been implicated in Möbius syndrome.
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 Möbius syndrome may be caused by incomplete development of facial nerves, other cranial nerves, and other parts of the central nervous system.

Oral/dental concerns

Neonatal

When a child is born with Möbius syndrome, there may be difficulty in closing the mouth or swallowing. The tongue may fasciculate or be hypotonic. The tongue may be larger or smaller than average. There may be low tone of the muscles of the soft palate, pharynges, and the masticatory system. The palate may be arched excessively, because the tongue does not form a suction that would normally shape the palate down further. The palate may have a groove or may be cleft. The opening to the mouth may be small. Feeding problems may become a critical issue early on if adequate nutrition is difficult.

Primary dentition

The primary teeth generally start coming in by 6 months of age, and all 20 teeth may be in by two and a half years of age. The eruption timing varies greatly. There may be an incomplete formation of the enamel on the teeth that makes the teeth more vulnerable to caries. There may be missing teeth eruptions. If the infant is not closing down properly, the lower jaws become more noticeably deficient. The front teeth may not touch when the child closes down because the back teeth have overerrupted or because of incomplete formation of the maxilla. This condition is called an anterior open bite and has facial/skeletal implications. The saliva may be thick, or the infant may have a dry mouth.

Transitional dentition

Between age 5 and 7, most children start losing their primary teeth. Occasionally, some primary teeth are slow to exfoliate, and the dentist may want to remove a primary tooth early to prevent orthodontic problems. Likewise, premature loss of primary teeth may create orthodontic problems later on. When a tooth is lost prematurely, removable or fixed spacers may be needed to prevent the shifting of teeth. Interceptive orthodontic treatment can be initiated at this stage of development to help with crowding or to help relate the upper and lower jaws. Consistent with a high palate is a narrow arch shape of the upper teeth as they line up in the mouth. This may cause the upper front teeth to flare out and become more prone to fracture if accidentally hit. Interceptive orthodontics has an important role in this situation. Appliances that expand the upper arch tend to bring the front teeth back into a more-normal position. Some appliances can even help allow the front teeth to close to normal in an open-bite situation. The mouth and lips may tend to get dry with the Möbius patient. Lack of a good oral seal allows the gingiva to get dry and may get inflamed and irritated.

Permanent dentition

After the last primary tooth is lost, usually around the age of twelve, final orthodontic treatment can be initiated. A patient that has not been able to close or swallow well probably will have an open bite, deficient lower-jaw growth, a narrow archform with crowded teeth, and upper anterior flaring of teeth. Orthognathic surgery may be indicated. This should be completed in most situations before the smile surgery where the gracilis muscle is grafted to the face.
Genetic links to 13q12.2 and 1p22 have been suggested.

Diagnosis

Diagnosis is typically made by the physical characteristics and symptoms, patient history and a thorough clinical evaluation. There is no specific diagnostic test that confirms Möbius syndrome. Some specialised tests may be carried out to rule out other causes of facial palsy.

Treatment

There is no single course of medical treatment or cure for Möbius syndrome. Treatment is supportive and in accordance with symptoms. If they have difficulty nursing, infants may require feeding tubes or special bottles to maintain sufficient nutrition. Physical, occupational, and speech therapy can improve motor skills and coordination and can lead to better control of speaking and eating abilities. Often, frequent lubrication with eye drops is sufficient to combat dry eye that results from impaired blinking. Surgery can correct crossed eyes, protect the cornea via tarsorraphy, and improve limb and jaw deformities. Sometimes called smile surgery by the media, muscle transfers grafted from the thigh to the corners of the mouth can be performed to provide the ability to smile. Although "smile surgery" may provide the ability to smile, the procedure is complex and can take twelve hours for each side of the face. Also, the surgery cannot be considered a "cure" for Möbius syndrome, because it does not improve the ability to form other facial expressions.

Epidemiology

It is estimated that there are, on average, 2 to 20 cases of Möbius syndrome per million births. Although its rarity often leads to late diagnosis, infants with this disorder can be identified at birth by a "mask-like" lack of expression that is detectable during crying or laughing and by an inability to suck while nursing because of paresis of the sixth and seventh cranial nerves. Also, because a person with Möbius syndrome cannot follow objects by moving their eyes from side to side, they turn their head instead.

Social and lifestyle effects

Möbius syndrome does not prevent individuals from experiencing personal and professional success. Due to the importance of facial expression and smiling in social interaction, the inability to form either can lead to individuals with Möbius being perceived as unhappy, unfriendly or uninterested in conversations. Individuals who are familiar with Möbius patients such as family or friends can recognize other signals of emotion such as body language, to the point that they sometimes report forgetting that the person has facial paralysis. Indeed, people with Moebius syndrome are often adept at compensating for a lack of expression by using body language, posture, and vocal tone to convey emotion.

In popular culture

Literature and media with mentions of Möbius syndrome include: