Clozapine-induced seizures and EEG abnormalities in ambulatory psychiatric patients

OBJECTIVE: To examine the seizure characteristics and electroencephalogram (EEG) abnormalities in psychiatric patients taking clozapine, given the estimate of a 10% cumulative risk of generalized seizures in this population. DESIGN: We reviewed all consecutive EEGs of ambulatory psychiatric patients taking clozapine performed at our laboratory during 1996 and 1997. SETTING: A university-affiliated urban teaching hospital. SUBJECTS: Twelve patients (4 F/8 M; mean age 40.1 y, range 20-63) had either presented with de novo ictal events within the first month of clozapine therapy (n = 8) or had EEGs recorded to assess seizure risk (n = 4). RESULTS: According to clinical history and interictal EEG findings, the patients were subdivided as follows: three patients with generalized tonic-clonic seizures, two with generalized myoclonic jerks (1 associated with simple partial seizures), two with complex partial seizures, and one with simple partial seizures. The EEGs revealed interictal epileptiform abnormalities (IEDs) in eight patients, two of whom had not had seizures. IEDs were focal or multifocal, with a predominance of left temporal foci. One patient showed a paroxysmal response to photic stimulation. CONCLUSIONS: Patients taking clozapine may be prone to partial seizures and focal EEG abnormalities as well as to generalized seizures and EEG abnormalities, as previously reported.