Abstracts

Course and etiology of cognitive impairments in chronic epilepsy still remains controversial. By using a factorial model of cognitive domains, a new approach to characterize the effects of age at onset and duration of epilepsy on cognition was chosen. A comprehensive neuropsychological test battery including measures of intelligence, language, spatial abilities, verbal and nonverbal memory, executive function, and psychomotor processing was administered to a sample of n = 158 patients with medically intractable epilepsy. Patients were tested in the context of preoperative evaluation. A factor analysis with varimax rotation was calculated, and factor scores were correlated to age at onset/duration of epilepsy while controlling for age and other variables. Factor analysis using test scores adjusted for age, gender, and education disclosed seven factors accounting for 62% of variance. Factors were: verbal episodic memory, attention, language based knowledge system, executive function, numerical, visuospatial and visual memory functions, and a seventh, bad defined factor. At least four of these factors can be seen as meaningful according to the factor loadings. Duration of epilepsy and onset of disease were significantly associated only with language based knowledge [age at onset: r = .190, p = 0.017 (positive association); duration: r = -.203, p = .011 (negative association)]. This relationship remains significant after controlling for several other factors (e.g., polytherapy, side and site of lesion, verbal episodic memory). As a trend, the effect seems to be stronger in patients with left-sided lesions. Factor analysis of an extensive neuropsychological test battery for the preoperative evaluation of patients with focal epilepsy resulted in 7 cognitive domains, with the first four factors representing verbal episodic memory, attention, language based knowledge system, and executive functions. Partialling out the effects of ageing, education and gender on performance in these domains, an earlier onset of chronic epilepsy was associated with significantly poorer performance in language based knowledge. Results can be discussed in the framework of Cattell[apos]s theory of fluid and crystallized abilities: Focal epilepsy first of all impairs fluid intelligence (Gf), and this diminishes the potential to acquire crystallized intelligence (Gc). Following this, the cumulative development of Gc through the life span is reduced particularly in association with an early onset of disease. Taking into account earlier results from our center, it can be concluded that impaired Gc in association with an early onset is mainly caused by reduced Gf rather than by reduced episodic memory. The former may be associated with neocortical damage.