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At a glance

It is a hereditary familial disease characterized by attacks of choreoathetosis and body torsion without loss of consciousness. Each episode usually lasts from a few minutes to several hours. Alcoholic beverages, coffee, hunger, fatigue, emotional stress, and tobacco are the precipitating factors. The presence of an atypical Kayser-Fleischer ring is the principal ocular feature.


Mount Syndrome; Paroxysmal Nonkinesigenic Dyskinesia (PNKD); Paroxysmal Dystonic Choreoathetosis (PDC).


This medical condition was first described in 1940 by Lester A. Mount, an American physician, and Stan Reback, also an American physician, in a family with many members over five generations affected with paroxysmal choreoathetosis.


There are no epidemiological studies establishing the exact incidence or prevalence. There are only few cases that have been reported in the literature.

Genetic inheritance

It is believed inherited as autosomal dominant. Gene locus is 2q33-2q35.


Unknown; has been suggested it could be an anomaly of the sodium channel even though it is not a seizure disorder.


Movement disorder can be recognized in the first week of life. Usually, attacks of choreoathetosis lasting only a few minutes and occurring several times per day are not associated with loss of consciousness. The attacks never occur during sleep and at their height are similar to those occurring in Huntington chorea. Attacks are precipitated by fatigue, hunger, alcohol, tobacco, or coffee, but not by movement, contrary to kinesigenic choreoathetosis. Attacks are usually preceded by an aura. The presence of an atypical Kayser-Fleischer ring is the principal ocular feature.

Clinical aspects

Usually discovered during the first week of life. Patients are automatically place on benzodiazepine (diazepam or clonazepam) therapy to decrease the incidence of crisis and risk.

Precautions before anesthesia

Administration of benzodiazepines must be continued up to the operation.

Anesthetic considerations

No specific anesthetic experience reported. No specific medication regimen required; surgery usually performed under general anesthesia. Bradycardias following small doses of opiates respond to atropine at normal doses. Monitoring of the level of neuromuscular blockade is helpful. Maintain normothermia by adequately warming up the room and infused fluids to prevent shivering. If preoperative or postoperative sedation is needed, use benzodiazepines. Remember this is not a seizure disorder.

Pharmacological implications

No specific drug required or to be avoided. However, benzodiazepines are part of the normal therapy.

Other condition to be considered

  • Huntington Chorea: Inherited disease characterized by choreiform movements and progressive dementia. First described in 1872 by George Huntington, ...

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