Abstracts

Rationale: Recent functional mapping studies have identified highly localized regions within the temporal lobe neocortex that underlie specific functions, such as number, faces, and word form recognition. This study examines neuropsychological test performance of patients with temporal lobe epilepsy (TLE) to determine whether seizure onset zones in these regions are associated with corresponding neuropsychological deficits in these functions.  Methods: This study retrospectively examined presurgical neuropsychological testing data in patients with medically refractory TLE undergoing surgical evaluation. Data from 36 subtests of our standard neuropsychological testing battery were evaluated in an exploratory fashion. 34 subjects were grouped based on intracranial EEG localization of seizure onsets using an anterior-posterior axis (left anterior=9, right anterior=7, left posterior=10, and right posterior=8) and a mesial-lateral axis (left mesial=8, right mesial=6, left lateral=11, right lateral=9). Mean age of subjects was 32 years (SD=16.3); mean age of seizure onset was 17 (SD=13.6); 26 were right handed with mean education level of 15.2 years (SD=3.2).  Results: Performance on the Digit Symbol WAIS III and IV Test (which relies on identification of visual numerals and symbols) was significantly higher in patients with right anterior temporal lobe foci when compared to patients with right posterior temporal lobe foci (right anterior M=8.2, SD=1.86; right posterior M=5.8, SD=1.9; p < 0.05 on indepedent samples t-test). This result persisted when patients with right posterior temporal lobe foci were compared to all other subgroups in the anterior-posterior axis (right posterior M=5.8, SD=1.9; other M=8.2, SD=2.0; p < 0.05). Facial Recognition Delayed WMS III Test performance tended to be lower in patients with lateral TLE compared to mesial TLE (lateral M=8.4, SD=2.7; mesial M=10.3, SD=2.6), though this finding was not statistically significant. No test was found to elicit different performance measures between patients with left anterior and posterior TLE. Conclusions: Impairment on the WAIS Digit Symbol Test in patients with right posterior TLE is consistent with recent functional mapping studies that have localized the visual number form area (vNFA) to the ventral posterior temporal lobe neocortex. The trend toward impaired performance in a facial recognition memory task may also represent subtle involvement of the fusiform face area (FFA), also located in this region. None of our tests were found to elicit different performances between patients with left anterior versus posterior TLE, even though specialized regions such as the visual word form area (vWFA) have been reported in that region. This may be due to broader language impairments in this population, lack of specific tests addressing this function, or masking of subtle findings when patients are grouped by lateralization only. These findings underscore the potential utility of incorporating specific neuropsychological testing that more accurately target specific functional regions. Funding: Intramural Research Program of the NINDS, NIH