Objective: To characterize the nature and degree of cognitive morbidity in patients with chronic temporal lobe epilepsy compared with healthy control subjects, determine the association between the duration of epilepsy and cognitive morbidity, and ascertain whether there are factors that moderate the association between duration of disorder and cognitive impairment.
Methods: Temporal lobe epilepsy (n = 96) and healthy control (n = 82) subjects were assessed with a comprehensive neuropsychological battery. Test performances were adjusted for age, gender, and education and transformed to a common metric (z scores). Analyses included group comparisons and correlations of duration of epilepsy with cognitive morbidity.
Results: Patients with temporal lobe epilepsy exhibited not only worse memory function (p < 0.05) but worse performance across measures of intelligence, language, executive function, and motor speed (p < 0.05). Chronicity of epilepsy was related to worsening mental status (r = 0.42, p < 0.001). This relationship was particularly evident among those individuals with less (r = 0.58, p < 0.001) compared with more (r = 0.25, NS) cerebral reserve, operationally defined by years of formal education.
Conclusions: Neuropsychological morbidity in chronic temporal lobe epilepsy is widespread in nature despite a focal epileptic process. Cross-sectional analyses demonstrate that increasing duration of epilepsy is associated with worsening mental status. Individuals with less educational attainment (low cerebral reserve) exhibit especially poor cognitive function in association with chronicity of epilepsy.