The clinical characteristics of paroxysmal dystonic choreoathetosis (PDC) in 20 affected members of a large British family are reported from the Institute of Neurology, Queen Square, and the MR Unit, Hammersmith Hospital, London, UK. The findings are compared with those in 11 other PDC families cited in the literature. This hyperkinetic movement disorder consists of episodic attacks of chorea, dystonia, and ballism, beginning in infancy or childhood, and persisting with lesser frequency and severity into adulthood. Speech is frequently involved, diplopia may also occur, but consciousness is not disturbed. Frequency may be up to 3 times daily in childhood, mainly afternoon or evening, and yearly in adults. Attack duration in children is usually 30 min to 2 hours. Precipitants include stress, anger, and excitement, caffeine, alcohol, sleep deprivation, hunger, intercurrent illness, cold, prolonged exercise, and menstruation. Sudden movement or startle do not provoke attacks. Attacks are aborted by short periods of sleep, sometimes prevented by clonazepam, but are unaffected by various other antiepileptic drugs. Epilepsy and hysteria are common misdiagnoses. CSF monoamine metabolite levels may increase during attacks. MRI and PET scans are normal. Inheritance is autosomal dominant with high penetrance and linked to chromosome 2q. Male to femal ratio is 1.7:1. 
COMMENT. In addition to paroxysmal dystonic choreoathetosis (PDC) that is non-kinesigenic, two further hyperkinetic movement disorders are described: 1) paroxysmal kinesigenic choreoathetosis (PKC), the most common, with attacks occurring frequently (100 or more daily), precipitated by sudden movement, and controlled by anticonvulsant drugs; and 2) paroxysmal exercise-induced dystonia (PED), of intermediate duration (5-30 min), the least common type. In addition, Nocturnal paroxysmal dystonia has been described (Lugaresi et al. 1986), usually misdiagnosed as nightmares, and generally treated as a complex partial seizure of frontal lobe origin. (see Progress in Pediatric Neurology II, PNB Publ, 1994, pp 193-4). Attacks of PDC, unlike PKC, were not benefited by anticonvulsants. PKC is sometimes referred to as PKD, and is often associated with infantile convulsions and epilepsy.