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ICCA syndrome
- Infantile Convulsions and Paroxysmal Choreoathetosis (ICCA) syndrome is a neurological disorder marked by seizures beginning in infancy (benign familial infantile epilepsy), followed later in childhood or adolescence by episodes of choreoathetotic, dyskinetic movements.
Synonyms
- Infantile convulsions and choreoathetosis
- Paroxysmal kinesigenic dyskinesia and infantile convulsions
Inheritance: Autosomal dominant
Age of onset: Infancy, Neonatal
What are the symptoms of ICCA syndrome?
Very frequent symptoms
- Normal interictal EEG
Frequent symptoms
- Athetosis
- Chorea
- Choreoathetosis
- Dystonia
- Focal impaired awareness autonomic seizure
- Focal impaired awareness seizure
- Focal-onset seizure
- Involuntary movements
- Paroxysmal dyskinesia
- Seizure
Occasional symptoms
- Complex febrile seizure
- Experiential auras
Clinical description
- Benign familial infantile epilepsy typically begins between 3 and 12 months of age and is often associated with a family history of similar seizures. These seizures are afebrile, partial or occasionally generalized, and usually resolve within the first year of life.
- Later in childhood or adolescence, individuals develop paroxysmal kinesigenic dyskinesia, characterized by frequent, brief (less than one minute) episodes of choreathetotic or dystonic movements triggered by sudden voluntary motion or startle.
- Some individuals may also experience other paroxysmal conditions such as migraine (with or without aura), hemiplegic migraine, episodic ataxia, or tics. Psychomotor development remains normal.
What causes ICCA syndrome?
- Genetic loci associated with ICCA syndrome have been identified on chromosomes 16p11.2–q12.1, 16q13–q22.1, and 3q29. Mutations in the PRRT2 (Proline-Rich Transmembrane Protein 2) gene, located on 16p11.2, have recently been discovered in families with ICCA syndrome.
- This gene encodes a membrane protein that interacts with the presynaptic protein SNAP-25, although the precise mechanism by which these mutations lead to the disorder remains unclear.
How is this condition diagnosed?
- Diagnosis is primarily clinical, based on the presence of benign infantile seizures followed by the onset of kinesigenic dyskinesia during later childhood or adolescence. Genetic testing can be used to confirm the diagnosis by identifying causative mutations, most commonly in the PRRT2 gene.
Differential diagnosis
Differential diagnosis includes other paroxysmal dystonias such as
- paroxysmal exertion-induced dyskinesia and
- paroxysmal non-kinesigenic dyskinesia triggered by drugs or food intake (such as caffeine and alcohol)
Genetic counseling
- 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 – How is this condition treated?
- Antiepileptic drugs, mainly phenytoin or carbamazepine, are effective in controlling seizures and dyskinesia during the active phase of the disorder.
What is the Prognosis of ICCA syndrome?
- ICCA has a good outcome.
- Without treatment, dyskinetic attacks tend to disappear during adulthood.
