Abstracts

Anterior temporal lobe resection for seizure control involving the language dominant hemisphere carries the risk of postoperative naming decline. This decline, however, is minimal in patients with the syndrome of medial TLE ([quot]MTLE,[quot] i.e., patients with medial temporal sclerosis, [quot]MTS[quot]) compared to that observed in patients with non-medial TLE ([quot]nonMTLE[quot]. To explain this finding, it has been theorized that the earlier age of onset in MTLE patients elicits reorganization of cortical function. Specifically, cortical sites essential for naming might shift away from the region of seizure onset, and therefore, would less likely be included within the boundaries of an anterior temporal resection. To test this hypothesis, we compared the topographical distribution of auditory and visual naming sites identified by direct cortical stimulation in preoperative left (i.e., language dominant) MTLE and nonMTLE patients. Subjects were 25 left TLE patients (10 MTLE, 15 nonMTLE) who underwent preoperative cortical language mapping (9 intraoperative, 16 extraoperative) utilizing visual and auditory naming tasks (mean age of on seizure onset: MTLE = 16.6, SD = 11.3, nonMTLE = 21.8, SD = 10.6). Naming was tested at 11-44 sites per patient, depending on time constraints (intraoperative) or extent of implantation (extraoperative). The anterior temporal region was defined as [le] 5cm from the temporal pole, and the posterior temporal region as [gt] 5 cm from the temporal pole. The proportion of auditory and visual naming sites in the anterior and posterior temporal regions was compared in MTLE and nonMTLE patients using Fisher[apos]s exact test. In the MTLE group, 16 auditory naming and 3 visual naming sites were found in the anterior region, whereas 2 auditory naming and 8 visual naming sites were found in the posterior temporal region. In the nonMTLE group, 13 auditory naming and 5 visual naming sites were found in the anterior region, whereas 2 auditory naming and 16 visual naming sites were found in the posterior temporal region. Fisher[apos]s exact test comparing the distribution of naming sites indicated no significant differences in the distribution of auditory (p [gt] .05) or visual (p [gt] .05) naming sites between MTLE and nonMTLE groups. Results of independent sample T tests also showed no group differences in mean number of auditory naming sites, visual naming sites, or number of sites removed with resection (all p [gt] .05). These preliminary findings do not provide evidence of reorganization of naming sites within the lateral temporal region in MTLE patients. It remains possible, however, that MTLE patients develop additional naming sites in areas outside this region, such as the basal temporal area, more posterior temporoparietal cortex, or in homologous areas in the contralateral hemisphere. (Supported by NINDS Grant Number R01NS035140 to M. J. Hamberger)