Mobius syndrome
Encyclopedia
Möbius syndrome 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
and cannot close their eyes or form facial expressions. Limb and chest wall abnormalities sometimes occur with the syndrome. Most 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 neurologist who first described the syndrome in 1888.
cranial nerves
. The VI cranial nerve controls lateral eye movement, and the VII cranial nerve controls facial expression. People with Möbius syndrome are born with facial paralysis and the inability to move their eyes laterally. 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 that is detectable during crying or laughing and by an inability to suck while nursing because of paresis
(palsy) 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.
Other symptoms that sometimes occur with Möbius syndrome are:
Children with Möbius syndrome may have delayed speech because of paralysis of the lips. 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
. However, some children with Möbius syndrome are mistakenly labeled as mentally retarded or autistic because of their expressionless faces, strabismus
, and frequent drooling.
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.
) or lack of oxygen (hypoxia
) to a developing fetus. Some cases are associated with reciprocal translocation between chromosome
s 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 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 (making the incidence of Möbius syndrome with misoprostal use, less than one in 1000 births). 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.
Genetic links to 13q12.2 and 1p22 have been suggested.
(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), because 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.
(baby) 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 (enamel hypoplasia
) that makes the teeth more vulnerable to caries (cavities). There may be missing teeth eruptions. If the infant is not closing down properly, the lower jaws become more noticeably deficient (micrognathia or retrognathia). 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.
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 (lips together) allows the gingiva
(gums) to get dry and may get inflamed and irritated.
(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.
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
and cannot close their eyes or form facial expressions. Limb and chest wall abnormalities sometimes occur with the syndrome. Most 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
Paul Julius Möbius
Paul Julius Möbius was a German neurologist who was born in Leipzig. Prior to entering the medical field in 1873, he studied philosophy and theology at the Universities of Leipzig, Jena and Marburg....
, a neurologist who first described the syndrome in 1888.
Clinical features
Möbius syndrome results from the underdevelopment of the VI and VIIFacial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
cranial nerves
Cranial nerves
Cranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of cranial nerves...
. The VI cranial nerve controls lateral eye movement, and the VII cranial nerve controls facial expression. People with Möbius syndrome are born with facial paralysis and the inability to move their eyes laterally. Often, the upper lip is retracted due to muscle shrinkage. Occasionally, the cranial nerves V
Trigeminal nerve
The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...
and VIII
Vestibulocochlear nerve
The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...
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 that is detectable during crying or laughing and by an inability to suck while nursing because of paresis
Paresis
Paresis is a condition typified by partial loss of voluntary movement or by impaired movement. When used without qualifiers, it usually refers to the limbs, but it also can be used to describe the muscles of the eyes , the stomach , and also the vocal cords...
(palsy) 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.
Other symptoms that sometimes occur with Möbius syndrome are:
- Limb abnormalities—clubbed feet, missing fingers or toes
- Chest-wall abnormalities (Poland SyndromePoland syndromePoland syndrome is a rare birth defect characterized by underdevelopment or absence of the chest muscle on one side of the body and webbing of the fingers of the hand on the same side mostly common on the right...
) - Crossed eyes (strabismusStrabismusStrabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...
) - Difficulty in breathing and/or in swallowing
- Corneal erosion resulting from difficulty in blinking
Children with Möbius syndrome may have delayed speech because of paralysis of the lips. 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
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
. However, some children with Möbius syndrome are mistakenly labeled as mentally retarded or autistic because of their expressionless faces, strabismus
Strabismus
Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...
, 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. 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 corneaCornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
via tarsorraphy, and improve limb and jaw deformities. Sometimes called smile surgery
Smile surgery
Smile surgery or smile reconstruction is a surgical procedure that restores the smile for people with facial nerve paralysis. Facial nerve paralysis is a relatively common condition with a yearly incidence of 0.25% leading to function loss of the mimic muscles. The facial nerve gives off several...
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.
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 other people may have difficulty recognizing the emotions of people with Möbius. A person with Möbius syndrome who cannot smile may appear unfriendly or uninterested in a conversation. However, friends and family who are familiar with the person with Möbius syndrome learn to recognize other signals of emotion such as body language, and they sometimes report forgetting that the person has facial paralysis altogether. People with Möbius syndrome can use alternative methods to communicate emotion—such as 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 (ischemiaIschemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
) or lack of oxygen (hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
) to a developing fetus. Some cases are associated with reciprocal translocation between chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s 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
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
and a traumatic pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
may also be linked to the development of Mobius syndrome. The use of the drugs misoprostol
Misoprostol
Misoprostol is a drug that is used for the prevention of non steroidal anti inflammatory drug induced gastric ulcers, for early abortion, to treat missed miscarriage, and to induce labor. The latter use is controversial in the United States. Misoprostol was invented and marketed by G.D...
or thalidomide
Thalidomide
Thalidomide was introduced as a sedative drug in the late 1950s that was typically used to cure morning sickness. In 1961, it was withdrawn due to teratogenicity and neuropathy. There is now a growing clinical interest in thalidomide, and it is introduced as an immunomodulatory agent used...
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 (making the incidence of Möbius syndrome with misoprostal use, less than one in 1000 births). The use of cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...
(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
Hypoplasia
Hypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...
or agenesis
Agenesis
In medicine, agenesis refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue...
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.
Genetic links to 13q12.2 and 1p22 have been suggested.
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 fasciculateFasciculation
A fasciculation , or "muscle twitch", is a small, local, involuntary muscle contraction and relaxation visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers...
(quiver) or be hypotonic
Hypotonia
Hypotonia is a state of low muscle tone , often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength...
(low muscle tone). The tongue may be larger or smaller than average. There may be low tone of the muscles of the soft palate
Soft palate
The soft palate is the soft tissue constituting the back of the roof of the mouth. The soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone....
, pharynges
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
, and the masticatory system
Mastication
Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...
. The palate may be arched excessively (a high palate), because 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 primaryDeciduous teeth
Deciduous teeth, otherwise known as reborner teeth, baby teeth, temporary teeth and primary teeth, are the first set of teeth in the growth development of humans and many other mammals. In some Asian countries they are referred to as fall teeth as they will eventually fall out, while in almost all...
(baby) 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
Tooth eruption
Tooth eruption is a process in tooth development in which the teeth enter the mouth and become visible. It is currently believed that the periodontal ligaments play an important role in tooth eruption...
timing varies greatly. There may be an incomplete formation of the enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
on the teeth (enamel hypoplasia
Hypoplasia
Hypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...
) that makes the teeth more vulnerable to caries (cavities). There may be missing teeth eruptions. If the infant is not closing down properly, the lower jaws become more noticeably deficient (micrognathia or retrognathia). 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 (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. When a tooth is lost prematurely, removable or fixed spacersOrthodontic spacer
Orthodontic separators are rubber bands or metal appliances used in orthodontics. Spacers are placed between the molars at the second orthodontic appointment, before a palatal expander or braces are applied.Spacers are circular rubber bands about a centimeter in diameter placed between top and...
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 (lips together) allows the gingiva
Gingiva
The gingiva , or gums, consists of the mucosal tissue that lies over the mandible and maxilla inside the mouth.-General description:...
(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. OrthognathicOrthognathic surgery
Orthognathic surgery is surgery to correct conditions of the jaw and face related to structure, growth, sleep apnea, TMJ disorders, malocclusion problems owing to skeletal disharmonies, or other orthodontic problems that cannot be easily treated with braces. Originally coined by Dr. Harold...
(jaw) surgery may be indicated. This should be completed in most situations before the smile surgery where the gracilis muscle
Gracilis muscle
The gracilis is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above, narrow and tapering below.-Origin and insertion:...
is grafted to the face.