Correlations Between Cognitive Aspects and Quantitative EEG in Adults With Epilepsy

Abstract

Introduction. Cognitive impairment frequently occurs in adult patients with epilepsy (PWE), but its pathophysiological basis is not well known. This study assessed cognition and its correlations with quantitative EEG coherence (QEEG) of patients with epilepsy. Method. Eighty PWE seen consecutively in the clinic and 40 normal subjects (NC) were assessed by neurological evaluation, Mini Mental State Examination, immediate and delayed recall of 10 simple figures, phonemic verbal fluency (FAS), category fluency test (VF animals), clock drawing, and QEEG. The mean global inter- and intrahemispheric coherences for the delta, theta, alpha, and beta bands were calculated. Cognitive functions and QEEG coherence of the PWE and the NC were compared, and logistic regression analysis determined the factors associated with impaired cognitive functions in PWE. The significance level was set at P < .05. Results. Regression analysis showed that FAS impairment (14.5 ± 8.6 vs 24.3 ± 15.7, respectively) and delayed recall of figures in PWE (7.3 ± 2.07 vs 8.6 ± 1.48) differed significantly between the PWE and the NC (Nagelkerke R2 = 0.266). Absolute power was greater in all the frequency bands in PWE. Interhemispheric and intrahemispheric beta coherences in the theta frequency was higher in the PWE than in the NC. Logistic regression analysis showed a significant association between interhemispheric delta coherence and VF animal impairment (cutoff point of 12), and between an interhemipheric beta coherence with level of education and delayed recall of figures impairment (cutoff point of 7) (Nagelkerke R2 = 0.297). Other variables were not associated. Conclusions. There was cognitive impairment of PWE and it was significantly associated with QEEG, which suggests that QEEG measures may contribute to the understanding of physiopathological events and as a marker for cognitive alterations in epilepsy.