Abstracts

Rationale: As naming is mediated by perisylvian cortex in the left (dominant) hemisphere, left anterior temporal lobe resection (ATL) for treatment of intractable TLE carries the risk of postoperative naming decline. Interestingly, this risk is lower in patients with hippocampal sclerosis (HS) relative to those without HS (nonHS). Although the hippocampus has traditionally been considered critical for memory, without contribution to naming, this pattern might implicate direct hippocampal involvement in naming. Alternatively, these different postoperative naming patterns might reflect group differences in the cortical organization of naming. Critical naming sites have been found in anterior, lateral temporal neocortex, the region typically removed with “standard” TLE resection. Thus, we hypothesized that the relative preservation of naming in HS patients might reflect reorganization of language to areas outside this region. Methods: Subjects were 12 patients with HS and 12 patients without structural brain pathology (nonHS) who underwent pre-resection, stimulation language mapping using auditory and visual naming tasks. Baseline naming was assessed preoperatively and approximately one year postoperatively. Related samples T tests compared pre and postoperative naming in HS and nonHS patients. Independent samples T tests compared HS and nonHS patients with respect to clinical data, number of naming sites, and distance of naming sites from the temporal pole. Fisher's exact test assessed group differences in the proportion of naming sites in specified perisylvian areas.Results: Consistent with previous work, nonHS patients exhibited significant naming decline (P =.03) whereas HS patients did not decline postoperatively. As hypothesized, HS patients had proportionally fewer overall naming sites in anterior temporal cortex, whereas nonHS patients exhibited a more even distribution of naming sites in anterior and posterior temporal regions (P =.03). Although both groups showed the previously reported pattern of auditory naming sites anterior to visual naming sites, auditory naming sites had a significantly more posterior distribution in HS (mean=4.5 cm, SD=1.0) than in nonHS patients (mean=3.5 cm, SD=1.2; P=.02). Additionally, nonHS patients exhibited a greater proportion of visual naming sites above the superior temporal sulcus, whereas visual naming sites in HS patients were scattered across superior and inferior temporal cortex. The mean number of naming sites identified per patient was higher among HS patients (HS: 3.7, SD=2.1; nonHS: 1.9. SD=1.4, P =.03). Conclusions: Results suggest that preserved naming ability in HS patients following ATL might be related to intrahemispheric reorganization of language in response to the likely, early development of hippocampal sclerosis. These results hold theoretical implications regarding the role of the dominant hippocampus in determining the cortical representation of linguistic information, and could potentially improve the efficiency by which naming sites are identified during the time constrained process of stimulation mapping. (NIH Grant RO1NS35140)