Clozapine-induced seizures, electroencephalography abnormalities, and clinical responses in Japanese patients with schizophrenia

PURPOSE We describe electroencephalography (EEG) abnormalities and seizures associated with clozapine treatment in Japanese patients with schizophrenia and retrospectively compare EEG results and total Positive and Negative Syndrome Scale (PANSS [T]) scores before and after treatment. METHODS Twenty-six patients with treatment-resistant schizophrenia were enrolled in this study. EEG measurements were obtained prior to clozapine treatment and every 4 weeks thereafter. EEG measurements were also obtained at the time of seizure. After seizures or EEG abnormalities were noted, additional EEGs were performed every 2 weeks. PANSS (T) scores were used to determine clozapine treatment outcome. RESULTS All 26 patients had normal baseline EEG measurements, and ten patients (38.5%) later manifested EEG abnormalities. The mean age was significantly lower than in the abnormal EEG group. Six patients (23.1%) experienced seizures. The mean dose of clozapine at the first occurrence of seizure was 383.3 mg/day. Five of six patients who experienced seizures in this study were successfully treated with valproate or lamotrigine without discontinuation of clozapine. The one patient who continued to experience seizures was successfully treated without antiepileptic drugs. The mean baseline PANSS (T) scores were not significantly different between the normal and abnormal EEG groups, but the mean score in the abnormal EEG group was significantly lower than that in the normal EEG group at the final follow-up (P=0.02). CONCLUSION EEG abnormalities may appear in younger patients, and our findings indicate that there is no need to discontinue clozapine when seizures occur. EEG abnormalities that appeared after clozapine treatment were associated with a good clinical response.