Interictal epileptiform activity in elderly patients with epilepsy

Objective: To examine the frequency of interictal epileptiform activity (LEA) in elderly patients with epilepsy. Design and Methods: From a consecutive 13905 EEGs recorded over 5 years at a university hospital EEG laboratory, 558 studies were performed on outpatients aged 60 years or more. Medical record review identified 125 patients in whom a confident clinical diagnosis of epilepsy was made by a board-certified neurologist. The EEG findings in these patients were reviewed. The effects of various variables on the likelihood of detecting IEA were calculated using Fisher's test and chi-square analysis. Results: IEA were present on the first EEG in 35% of 55 patients (mean age 65 years) with pre-existing epilepsy, and 26% of 70 patients (mean age 70 years) with seizure onset after 60 years. There were no significant differences in the frequency of IEA in patients with late onset epilepsy in the 7th or in the 8th decades of life. Most IEA were focal. Activation procedures added little additional information. Patients with more than one seizure per month were significantly more likely to have IEA (P = 0.016). There were no major differences in likelihood of IEA detection depending on the underlying cause of the seizures. Conclusions: The frequency of IEA in elderly patients with epilepsy is substantially lower than that reported in epileptic populations as a whole. This low rate of lEA in routine EEG studies must be recognized when considering the diagnosis of an epileptic syndrome for episodic events happening in the elderly. (C) 1998 Elsevier Science Ireland Ltd.