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Infantile convulsions and choreoathetosis
Infantile Convulsions and paroxysmal ChoreoAthetosis (ICCA) syndrome is a neurological condition characterized by the occurrence of seizures during the first year of life (Benign familial infantile epilepsy ; see this term) and choreoathetotic dyskinetic attacks during childhood or adolescence.
This disorder is rare but the exact prevalence is unknown.
Benign familial infantile epilepsy begins at 3 to 12 months of age with a family history of the same type of seizures. Seizures are afebrile, partial or sometimes generalized, and normally disappear after the first year of life. During childhood or adolescence, affected individuals present with paroxysmal kinesigenic dyskinesia with frequent and recurrent episodic choreathetotic or dystonic movements that last less than 1 minute. The attacks are triggered by the initiation of voluntary movements or startle. The association with other paroxysmal disorders such as migraine, with or without aura, hemiplegic migraine, episodic ataxia and tics has also been described. Psychomotor development is normal.
The genetic loci of ICCA syndrome have been described on chromosomes 16p11.2-q12.1, 16q13-q22.1 and 3q29-29. Mutations in the Proline-rich transmembrane protein 2 (PRRT2) gene, located on 16p11.2, have recently been found in families affected by ICCA syndrome. This gene encodes a membrane protein that interacts with the presynaptic protein SNAP-25 but the mechanism leading to the disease remains unknown.
The diagnosis is mainly clinical, based on the appearance of infantile convulsions with benign evolution followed by kinesigenic dyskinesia attacks later on. Genetic testing confirms the diagnosis.
Differential diagnosis includes other paroxysmal dystonias such as paroxysmal exertion-induced dyskinesia and paroxysmal non-kinesigenic dyskinesia (see these terms) triggered by drugs or food intake (such as caffeine and alcohol).
ICCA syndrome can present as sporadic or familial; in the latter case, it is transmitted as an autosomal dominant trait that can be variably expressed within the same family.
Management and treatment
Antiepileptic drugs, mainly phenytoin or carbamazepine, are effective in controlling seizures and dyskinesia during the active phase of the disorder.
ICCA has a good outcome. Without treatment, dyskinetic attacks tend to disappear during adulthood.