Abstracts

Rationale: Temporal lobe resection is considered the gold standard for the treatment of individuals with intractable temporal lobe epilepsy; however, postoperatively patients can experience deficits in multiple cognitive domains, especially memory and language. Hippocampal volume has been shown to correlate with memory outcome following standard temporal lobectomy; however, the effects of hippocampal volume on other aspects of cognitive functioning have received less attention. The following study examines the use of high resolution MRI-based hippocampal volume to predict postoperative memory, language, and intellectual performances of individuals undergoing subtemporal selective amygdalohippocampectomy. Methods: 30 adults (21 female; mean sd age = 38.67 10.97; mean sd education = 13.42 1.98) with intractable temporal lobe epilepsy were included in the dataset. Participants underwent pre and post-surgical comprehensive neuropsychological assessment (verbal/visual learning and memory, confrontation naming, phonemic/semantic fluency, verbal/visuospatial intelligence), as well as 1.5 or 3T quantitative MRI using FreeSurfer for postprocessing of hippocampal volume. Seizure onset was determined for each participant via consensus conference using video-EEG monitoring, neuropsychological testing, Wada testing, and structural and functioning imaging. 12 participants were found to have right temporal lobe epilepsy while 18 had left sided onset. Of those, 7 of 12 right and 12 of 18 left TLE participants were found to have mesial temporal sclerosis. All participants underwent subtemporal selective amygdalohippocampectomy for treatment of their seizures. Multiple regression was used to determine the relationship between hippocampal volume and postoperative performance on neuropsychological testing. Results: Neither right nor left presurgical hippocampal volume predicted postoperative memory, language, or intellectual outcome; however, left hippocampal volume did show a trend in the prediction of verbal memory (p = 0.069). The model s ability to predict postoperative confrontation naming, visual memory, phonemic and semantic fluency, and verbal and nonverbal intellectual functioning remained insignificant.Conclusions: After controlling for age, our findings suggest that left hippocampal volume may predict verbal memory performance following subtemporal selective amygdalohippocampectomy. Hippocampal volume does not appear, however, to affect other cognitive abilities such as verbal/nonverbal intellect, visual memory, fluency, and naming. These results suggest that postoperative cognitive deficits other than memory are likely the result of surgical resection of extrahippocampal tissue.