This article includes discussion of paroxysmal dyskinesias, paroxysmal choreoathetosis of Mount and Reback, paroxysmal kinesigenic dystonia, paroxysmal choreoathetosis precipitated by prolonged exercise, paroxysmal exertion-induced dyskinesia, paroxysmal hypnogenic dyskinesia, paroxysmal kinesigenic choreoathetosis, paroxysmal kinesigenic dyskinesia, paroxysmal nocturnal dystonia, and paroxysmal nonkinesigenic dyskinesia. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Paroxysmal dyskinesias are a relatively rare subset of hyperkinetic movement disorders that are defined by their episodic nature. They may be categorized into paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, and paroxysmal exertion-induced dyskinesia. Advances in the genetic causes of paroxysmal dyskinesias, particularly in the familial forms, have allowed further studies of phenotype-genotype correlation. Paroxysmal dyskinesias can also occur secondarily in the setting of other neurologic or systemic diseases. Psychogenic movement disorders, which may also be paroxysmal and abrupt in onset, should be considered in the differential diagnosis of paroxysmal dyskinesias. In this article, the authors review the expanding genetic advances and clinical characteristics of these disorders. Treatment strategies are reviewed.
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• Paroxysmal dyskinesias may be categorized into paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, and paroxysmal exertion-induced dyskinesia.
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• Paroxysmal dyskinesias may be sporadic, genetic, or caused by metabolic or structural etiologies.
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• Another common cause of paroxysmal dyskinesias is psychogenic movement disorders.
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• Paroxysmal kinesigenic dyskinesia typically responds well to antiepileptic medications.
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• Mutations in PRRT2 are associated with several childhood-onset episodic syndromes including paroxysmal kinesigenic dyskinesia, infantile convulsions, paroxysmal kinesigenic dyskinesia or infantile convulsions, and hemiplegic migraine.
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• ADCY5 mutations are being increasingly recognized as a cause of paroxysmal dyskinesias.
Historical note and terminology
Paroxysmal dyskinesias are a relatively rare subset of hyperkinetic movement disorders that are defined by their episodic nature. Mount and Reback were the first to use the term "paroxysmal choreoathetosis" (138). They reported a familial form of intermittent, periodic dystonia and chorea in which the proband had infantile-onset prolonged dyskinesia induced by alcohol and other agents. The episodes were characterized by an aura of a tight sensation in the neck and abdomen and a sense of fatigue followed by involuntary flexion of the arms and extension of the legs (dystonia). The spells progressed to involuntary choreoathetosis and dysarthria despite normal consciousness. Mount and Reback called the condition "familial paroxysmal choreoathetosis." Kertesz described a group of patients who primarily had a childhood onset of movement-induced paroxysmal choreoathetosis (95). He highlighted the kinesigenic component and coined the term "paroxysmal kinesigenic choreoathetosis" as a specific entity within the paroxysmal choreoathetosis syndrome. A striking feature of the kinesigenic form was the brief (seconds to minutes) duration of the episode, whereas the nonkinesigenic form was said to be longer lasting (minutes to hours). Richards and Barnett coined the term “paroxysmal dystonic choreoathetosis of Mount and Reback” to help delineate it from the more common paroxysmal kinesigenic choreoathetosis (156). Lance reported a family with intermediate-duration attacks that were precipitated by prolonged exercise (107). Lance’s kindred also pointed out a common feature of the nonkinesigenic phenotype that is distinctive from the kinesigenic: failure to respond to anticonvulsants other than benzodiazepines. Lance comprehensively summarized the various forms of paroxysmal movement disorders that were often labeled as paroxysmal kinesigenic choreoathetosis, including (familial) paroxysmal choreoathetosis, periodic dystonia, reflex epilepsy, movement induced seizures, conditionally responsive extrapyramidal syndrome, and hereditary kinesthetic reflex epilepsy. For a more detailed review of the history, see the review by Fahn (55).