Clinical characteristics of 26 children diagnosed with paroxysmal dyskinesias between 1980 and 2000 were evaluated retrospectively at the National Neurological Institute “C Besta” of Milan, Italy. Patients were categorized according to precipitating factors: 14 had paroxysmal kinesigenic dyskinesia (PKD), 6 had paroxysmal non-kinesigenic dyskinesia (PNKD), and 6 had paroxysmal exercise-induced dyskinesia (PED). None had paroxysmal hypnogenic dyskinesia (PHD), a form of nocturnal frontal lobe epilepsy. Patients with PKD had a mean age at onset of 7.1 years (range l.5-14 years); 13 were idiopathic, with a positive family history in 9 and autosomal-dominant inheritance; and one was associated with Chiari type 1 malformation. Of the 6 with PNKD, 1 had multiple sclerosis, 2 had cerebral palsy, 1 had a left basal ganglia stroke. 1 an acute inflammatory encephalopathy, and only 1 was idiopathic. Six with PED were all idiopathic, and attacks of dystonia or choreoathetosis were triggered by prolonged exercise, usually running or walking. Antiepileptic drugs, especially carbamazepine, were most effective in treatment of the PKD type, with benefit obtained in 70%. The occasional co-occurrence of epilepsy and PKD may be explained by a common ion channel dysfunction, and a gene locus mapped to chromosome 16. 
COMMENT. Paroxysmal dyskinesias refer to brief attacks of dystonia or choreoathetosis, alone or combined, with return to normal between episodes. Cases are classified according to precipitating factors. Paroxysmal kinesthetic dyskinesia (PKD) is the most frequent form of paroxysmal dyskinesia, it is usually familial and idiopathic, often responds to treatment with carbamazepine, and may resolve spontaneously by age 30. PNKD is relatively rare, it is often symptomatic of illnesses including cerebral palsy, infection, or vascular lesion, and response to treatment is poor. Exercise-induced (PED) cases are rare, usually in response to running, and dystonia is generalized or focal, affecting the foot. Antiepileptic drugs, including carbamazepine, clonazepam, and acetazolamide, L-Dopa, and trihexyphenidyl are reported of benefit in some cases.