[Epidemiological and clinical study of West syndrome in Nagasaki Prefecture, Japan].

To determine the occurrence, outcome, and prognostic factors of West syndrome (WS), we performed a retrospective epidemiological study of WS occurred in 47 children (26 boys and 21 girls) in Nagasaki prefecture during a recent 10-year period from 1989 to 1998. The incidence of WS was 3.1/10,000 live births. The mean age at onset of spasm is 6.3 months (range: 2 to 12 months). Thirty-nine patients (83%) had symptomatic WS, in which the prenatal causes (patients) were most frequent, followed by low-birth weight infants (patients), perinatal (patients) and postnatal (patients). The brain CT was performed in 37 patients, and revealed congenital brain malformations (9 patients), destructive brain disorders (12 patients), and no structural abnormalities (16 patients). The seizure outcome was worse in the symptomatic WS than in the cryptogenic WS; seizure/disappeared in 39% of the former and in 75% of the latter/developmental delay before the onset of WS, relapse of WS and persistence of seizures were associated with poor seizure outcomes. Among the remaining seizures at the time of this surveillance, a tonic seizure was most frequently observed, followed by the partial seizures. Lennox-Gastaut syndrome was observed in 2 patients only. Epileptic discharge in the latest interictal EEG were diffuse in 4.3%, focal or multifocal in 60.7%, and absent in 35%, suggesting that many patients with WS had cortical epileptogenic foci. The developmental outcome was very poor in both the symptomatic and cryptogenic WS. The mean DQ in all the patients was 25, and only 4 patients (11%) had a normal DQ (> 75). DQ was lower in patients with congenital brain malformations than in those with destructive brain disorders.