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masticatory system

Möbius syndrome

Möbius syndrome (also spelled Moebius) is an extremely 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, which means they cannot close their eyes or form facial expression. Limb and chest wall abnormalities sometimes occur with the syndrome. Most people with Möbius syndrome have normal intelligence, and others should take care not to confuse their lack of facial expression with dullness or unfriendliness. It is named for Paul Julius Möbius, a neurologist who first described the syndrome in 1888.

Clinical features

Möbius syndrome results from the underdevelopment of the VI and VII cranial nerves. The VI cranial nerve controls lateral eye movement, and the seventh cranial nerve controls facial expression. People with Möbius syndrome are born with facial paralysis and the inability to move their eyes lateraly. Often, the upper lip is retracted due to muscle shrinkage. Occasionally the cranial nerves V and VIII are affected. If cranial VIII is affected the person experiences hearing loss.

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 detectable during crying or laughing and inability to suck while nursing due to paresis (palsy) of the sixth and seventh cranial nerves. Additionally, people with Möbius syndrome cannot follow objects moving side to side with the eye; the child turns his or her head instead.

Other symptoms that sometimes occur with Möbius syndrome:

  • Limb abnormalities: clubbed feet, missing fingers or toes
  • Chest wall abnormalities (Poland Syndrome)
  • Crossed eyes (strabismus)
  • Difficulty breathing and/or swallowing
  • corneal erosion resulting from difficulty blinking

Children with Möbius syndrome may have delayed speech due to paralysis of the lips. However, with speech therapy, most people with Möbius syndrome can develop understandable speech. Möbius syndrome has been linked to increased occurrence of the symptoms of autism. However, some children with Möbius syndrome are mistakenly labeled as mentally retarded or autistic due to their expressionless faces, strabismus, and frequent drooling.

Treatment

There is no single course of medical treatment or cure for Möbius syndrome. Treatment is supportive and in accordance with symptoms. Infants may require feeding tubes or special bottles to maintain sufficient nutrition if they have difficulty nursing. Physical, occupational, and speech therapy can improve motor skills and coordination, and lead to better control of speaking and eating abilities. Often, frequent lubrication with eye drops is sufficient to combat dry eye resulting 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. While "smile surgery" may provide the ability to smile, the procedure is complex and can take twelve hours for each side of the face. Additionally, the surgery cannot be considered a "cure" for Möbius syndrome since it does not improve the ability to form other facial expressions.

Living with Möbius syndrome

Many people with Möbius syndrome lead full lives and experience personal and professional success. Facial expression is important in social interaction, and others may have difficulty recognizing the emotions of people with Möbius. A person with Möbius syndrome who cannot smile may appear unfriendly or disinterested in a conversation. However, friends and family who are familiar with the person with Möbius syndrome learn to recognize other signals of emotion like body language, and sometimes report forgetting that the person has facial paralysis altogether. People with Möbius syndrome can use alternative methods to communicate emotion like body language, posture, and vocal tone.

Pathological picture

The causes of Möbius syndrome are poorly understood. Möbius syndrome is thought to result from a vascular disruption (temporary loss of bloodflow) in the brain during prenatal development. There could be many reasons that a vascular disruption leading to Möbius syndrome might occur. 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 (Ischemia) or lack of oxygen (Hypoxia) 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 (palsy) occurs without associated limb abnormalities.

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 Möbius syndrome in some cases. Misoprostol is used to induce abortions in Brazil, where the drug is cheap and readily available and elective abortions are illegal. Misoprostol abortions are not very effective and 80% result in the pregnancy going to term. Möbius syndrome appears in 20% of children born after failed misoprostol abortions. The use of cocaine (which also has vascular effects) 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 Period

When a child is born with Möbius syndrome, there may be difficulty in closing the mouth or swallowing. The tongue may faciculate (quiver) or be hypotonic (low muscle tone). 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 (a high palate) since the tongue does not form a suction that would normally shape the palate down further. The palate may have a groove (this may be partially due to intubation early on if it is for an extended period of time) or may be cleft (incompletely formed). 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 (baby) teeth generally start coming in by the first birthday and all 20 teeth may be in by the second birthday. The eruption timing varies greatly. There may be an incomplete formation of the enamel on the teeth (enamel hypoplasia) that makes the teeth more vulnerable to caries (cavities). There may be missing teeth eruptions. The lower jaws become more noticeably deficient (micrognathia or retrognathia) if the infant is not closing down properly. The front teeth may not touch when the child closes down because the back teeth have overerrupted. 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 (fall out) 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. Removable or fixed spacers may be needed to prevent the shifting of teeth when a tooth is lost prematurely. 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 (lips together) allows the gingiva (gums) 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 (jaw) surgery may be indicated. This should be completed in most situations before the smile surgery where the gracilis muscle is grafted to the face.

References

External links

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