Abstracts

Results of recent studies suggest that the temporal lobe is involved in attention and executive functioning. However, few studies have assessed these functions in TLE patients, and no single study has comprehensively assessed different aspects of attention and executive functioning in this population. Within this group, we compared patients with and without MTS. Given the earlier age of onset typically associated with MTS, we hypothesized that patients with MTS would perform more poorly on these measures due to longer duration of irritative activity in the temporal region. Eighty-nine TLE patients (51 non-MTS, onset 24 yrs; 38 MTS, onset 13 yrs, p[lt].001) underwent comprehensive neuropsychological evaluation. Measures used to assess attention and executive functions included Symbol Search, Digit Symbol Coding (psychomotor speed, selective attention), Digit Span, Arithmetic and Letter-Number Sequencing (working memory), and Similarities (abstract reasoning) subtests of the WAIS-III; Controlled Oral Word Association Test ([quot]COWAT[quot], verbal fluency); Trail Making A and B (tracking, selective attention, psychomotor speed, set shifting, sequencing); Wisconsin Card Sorting Test ([quot]WCST[quot]) concept formation, mental flexibility, problem solving); and Stroop Color-Word Naming Test (mental processing speed, response inhibition). A one-way multivariate ANOVA was used to compare group means. Scores greater than one standard deviation below the normative sample mean were considered clinically meaningful. A chi square test indicated comparable numbers of left and right TLE patients in each group. Both non-MTS and MTS patients performed within normal limits on most measures, with the exception of reduced performance on Trails B (non-MTS=1 SD below mean, MTS=1.16 SD below mean). Performance on the COWAT approached our criterion (non-MTS=0.9 SD below mean; MTS=0.7 SD below mean). Patients with MTS were slower than non-MTS patients on the Stroop color naming task (p=0.01). The number of WCST [ldquo]loss of set[rdquo] errors approached significance (p=0.06), with greater loss of set in the MTS group. There were no other significant differences between groups. Additionally, there were no differences between right and left TLE patients on any measures employed. These findings suggest that regardless of MTS status, attention and executive functions are compromised in TLE patients, to a limited extent. Additionally, as predicted, TLE patients with MTS exhibited slower mental processing speed and greater difficulty maintaining cognitive set than patients without MTS. Thus, longer duration of epilepsy, and/or other factors associated with MTS, appear to be detrimental to some aspects of attention and executive functioning.