Moebius Syndrome

 

Moebius Syndrome (also spelled Möbius) is an extremely rare congenital neurological disorder that primarily affects the muscles that control facial expression and eye movement. Signs and symptoms of the condition may include weakness or paralysis of the facial muscles; feeding, swallowing, and choking problems; excessive drooling; crossed eyes; lack of facial expression; eye sensitivity; high or cleft palate; hearing problems; dental abnormalities; bone abnormalities in the hands and feet; and/or speech difficulties. Moebius syndrome is caused by the absence or underdevelopment of the 6th and 7th cranial nerves, which control eye movement and facial expression. As of now, there is no cure for Moebius syndrome, but proper care and treatment give many individuals a normal life expectancy. The exact cause of the syndrome is unknown. It appears to occur randomly (sporadically) in most cases; however, some cases occur in families suggesting that there may be a genetic component.

 Symptoms

The abnormalities and severity of Moebius syndrome vary greatly from one person-to-another. The classically accepted diagnostic criteria include: 1) Facial paralysis or weakness affecting at least one but usually both sides of the face (7th cranial nerve) 2) Paralysis of sideways (lateral) movement of the eyes (6th cranial nerve) and 3) Preservation of vertical movements of the eyes. Less often, other cranial nerves, including the 5th, 8th, 9th, 10th, 11th, and 12th may be affected. Other symptoms that occur with Möebius syndrome are:

• Limb abnormalities—clubbed feet, missing fingers or toes
• Chest-wall abnormalities (Poland syndrome)
• Crossed eyes (strabismus)
• Difficulty in breathing and/or in swallowing
• Corneal erosion resulting from difficulty in blinking

 Causes

Many of the signs and symptoms of Moebius syndrome result from the absence or underdevelopment of cranial nerves VI and VII. Abnormal development of cranial nerves leads to the facial muscle weakness or paralysis that is characteristic of Moebius syndrome.

The causes of Moebius syndrome are unknown, although the condition probably results from a combination of environmental and genetic factors. Sporadic mutations in PLXND1 and REV3L genes have also been identified in a number of patients. In rare cases, familial patterns have been reported. In familial cases, there is evidence that Moebius syndrome is inherited as an autosomal dominant trait. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy.

 

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 Möebius syndrome. Some specialized tests may be carried out to rule out other causes of facial palsy.

 

Treatment and Management

There is no single course of medical treatment or cure for Möebius syndrome. Treatment is supportive and in accordance with symptoms. Usually these children are managed by a multidisciplinary team involving pediatricians, neurologists, otolaryngologists, orthopedists, dental specialists, speech pathologists, audiologists, ophthalmologists and other healthcare professionals.

• Frequent lubrication for dry eyes is often necessary
• Physical therapy may be needed for individuals with various orthopedic abnormalities.
• Occupational therapy may also be beneficial, especially in patients with abnormalities of the hands, fingers and toes.
• Speech therapy may be necessary for some affected children.
• Strabismus is usually surgically correctable
• Specialized procedures to correct abnormalities and/or underdevelopment of the chest wall and breast are available.
• Splints, braces and prostheses may be necessary for individuals with congenital limb abnormalities.
• Corrective procedures for facial paralysis involve transfer of muscle and/or graft nerves from another area of the face or the body. The most recent procedure, called “the smile operation”, involves transfer of a muscle from the thigh to the face. This operation has shown remarkable results in terms of speech, facial mobility and self-esteem.
• Genetic counseling may benefit affected individuals and their families.

 

Resources

1. Moebius Syndrome Foundation:https://moebiussyndrome.org/about-moebius-syndrome/what-is-moebius-syndrome/
2. Orphanet:https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Expert=570/
3. Genetics and Rare Disease Information Center: https://rarediseases.info.nih.gov/diseases/8549/moebius-syndrome/
4. National Organization for Rare Diseases: https://rarediseases.org/rare-diseases/moebius-syndrome/
5. Genetics Home: https://ghr.nlm.nih.gov/condition/moebius-syndrome/

 

If you know anyone with Moebius Syndrome, or if you are a physician interested in collaboration, please get in touch with the ORDI team.