Chronically Impaired Frontal Lobe Function from Subclinical Epileptiform Discharges.

Subclinical epileptiform discharges (SEDs) are a common occurrence on electroencephalograms (EEGs). Their potential for acutely disrupting cognitive functions has been well documented, but detailed studies of cognitive performance by patients with chronic exposure to disruptive SEDs have been lacking and scant data have been available to guide treatment decisions or to assist in predicting recovery. We identified a patient with frequent frontotemporally (FT) predominant SEDs and monitored cognitive performance over time with periodic neuropsychological testing and EEGs. Over a 16-year period, Full Scale IQ rose 23 points and Verbal IQ rose 30 as SEDs were suppressed. Severity of impairment, reflected by the marked increase in cognitive performance over time, was not predicted by his appearance and performance on routine tests of cognitive functions in the clinic. Quantitating total SED duration per EEG provided an objective marker to track severity over time. The cumulative effects of chronic exposure to disruptive SEDs may create a sustained "cognitive burden" or encephalopathic state that persists even in the absence of ongoing discharges.