Abstracts

Rationale: Individuals who undergo anterior temporal lobectomy in the left, language dominant hemisphere are at risk for postoperative verbal memory decline. It has recently been shown that the extent of language dominance in the left hemisphere can predict postoperative verbal memory outcome in these left language dominant ATL patients. Additionally, research has shown that left language dominant patients who undergo a non-dominant, right ATL are not at risk for postoperative verbal memory decline. However, studies of memory outcome in L-ATL patients with bilateral or right dominant language representation are more rare, and whether or not L-ATL patients remain at risk for verbal memory decline has not been conclusively determined. In the present study, we examined verbal memory outcome in L-ATL patients who had right dominant or bilateral language representation as determined by the Intracarotid Amobarbital Procedure (IAP). Methods: Patients who met the following criteria of 1) bilateral or right language dominance as determined by a valid intracarotid sodium amytal test, 2) left anterior temporal lobe resection, and 3) valid pre and 1 year postoperative neuropsychological assessment with a verbal list learning test (12 trial Selective Reminding Test) were examined in the present study. A total of 12 patients were identified who met these criteria. Of these patients, 9 of 12 were right hemisphere dominant and 3 of the 12 were classified as bilateral according to the intracarotid amobarbital test. IAP methodology and classification criteria at our center have been previously published. Results: A significant decline in verbal memory was determined as a greater than 2 standard deviation decline from pre to postoperative assessment on one or more subscales of the Selective Reminding Test. With this criteria, 5 of the 12 (42%) L-ATL patients with atypical language representation showed significant decline on one or more of the SRT scales. 4 of these patients (33%) were right hemisphere dominant for language as determined by the IAP. Conclusions: While the number of patients with bilateral and right hemisphere language in the sample is small, there appears to be a risk for postoperative verbal memory decline after L-ATL with atypical language. Surprisingly, 4 of the 9 patients with right hemisphere language dominance showed a significant postoperative verbal memory decline after undergoing a supposedly non-dominant L-ATL. This is in contrast to individuals who are left language dominant who undergo a R-ATL, who are at minimal risk for verbal memory decline. Further studies of organization of atypical language representation in left and right ATL patients and its relationship to verbal memory outcome are needed not only from a scientific standpoint, but to aid in surgical planning in temporal lobe epilepsy patients.