Prevalence and clinical significance of epileptiform EEG discharges in a large memory clinic cohort.

Background: Although EEG is not considered as standard in memory clinics, evidence indicates that epileptiform discharges are of value in diagnosing cognitive complaints as epilepsy.
Objective: To determine prevalence and significance of epileptiform discharges in a memory clinic.
Methods: 1,674 consecutive patients underwent routine EEGs [mean age 66 years, diagnoses: Alzheimer disease (AD; n = 510), other dementia (n = 193), mild cognitive impairment (MCI; n = 225), subjective complaints (n = 368), and other disorders (n = 378)]. Database statistics, charts and EEG reports were reviewed.
Results: Epileptiform discharges were present in 42 (3%) patients, of which 60% lacked clinical seizures. All discharges were focal and predominantly temporally localized. Epileptiform activity was not associated with a dementia diagnosis (2% in AD and 1% in other dementia vs. 2% in MCI, 2% in subjective complaints and 5% in other disorders, p = 0.07) or with lower Mini-Mental State Examination scores (p = 0.69). Two (diagnoses: AD, vascular dementia) of 20 patients with epileptiform activity without clinical seizures developed first seizures after 2 years.
Conclusion: In a memory clinic cohort, epileptiform discharges are rare, nonspecific and indicate a moderate risk of first-ever seizures in demented patients. These findings should be taken into account when routinely evaluating memory clinic patients with EEG.