Chronic periodic lateralized epileptiform discharges.

Six patients with chronic epilepsy had persistent periodic lateralized epileptiform discharges (PLEDs) in their interictal electroencephalographic recordings. Three patients had complex partial seizures, two had infantile spasms, and one had multifocal seizures. Four patients had cerebral pathologic changes consisting of tuberous sclerosis (two patients), a porencephalic cyst (one patient), and a chronic brain abscess (one patient). Although PLEDs are usually seen in association with an acute or subacute disturbance of cerebral function, the findings in this group of patients show that chronic PLEDs also can occur in patients with long-standing seizure disorders or chronic brain lesions.