<unk>  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<unk>  are poorly understood. It is thought to result from a vascular disruption (temporary loss of bloodflow) in the brain during prenatal development. There can be many reasons for vascular disruption leading to<unk> . 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<unk>  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<unk> . The use of the drugs misoprostol or thalidomide by women during pregnancy has been linked to the development of<unk>  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<unk>  by a factor of 30. While this is a dramatic increase in risk, the incidence of<unk>  without misoprostal use is estimated at one in 50000 to 100000 births (making the incidence of<unk>  with misoprostol use, less than one in 1000 births). The use of cocaine (which also has vascular effects) has been implicated in<unk> . 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<unk>  may be caused by incomplete development of facial nerves, other cranial nerves, and other parts of the central nervous system. Oral/dental concerns Sagittal magnetic resonance imaging scan showing a markedly underdeveloped (hypoplastic) tongue Neonatal When a child is born with<unk> , there may be difficulty in closing the mouth or swallowing. The tongue may fasciculate (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, pharynx, 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. Primary dentition The primary (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. 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 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<unk>  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. Genetic links to 13q12.2 and 1p22 have been suggested.
Möbius syndrome
Otocephaly
Morquio syndrome
Poland syndrome
Eiken syndrome
Hashimoto's encephalopathy
Creutzfeldt–Jakob disease
Wilson's temperature syndrome