Material-specific memory changes after anterior temporal lobectomy as predicted by the intracarotid amobarbital test

Abstract

Purpose: The intracarotid amobarbital test (IAT) has been shown to predict verbal memory changes after anterior temporal lobectomy (ATL). Seeking to extend these findings we examined two questions: (a) What is the relationship between material-specific aspects of IAT memory and material-specific memory changes after ATL? and (b) Which IAT memory score(s) optimally predict memory changes after surgery, the memory score after injection ipsilateral to the seizure focus or at the IAT asymetry score, comprising the ipsilateral minus contralateral injection scores? Methods: Seventy left hemisphere language-dominant patients undergoing ATL for treatment of medically refractory seizures were administered a verbal and visouspatial recognition memory test before surgery and 3 weeks after surgery. IAT memory recognition scores for words and designs were used to predict verbal and visouspatial memory changes after surgery. Results: After surgery, left ATL patients declined in verbal memory, whereas ATL patients declined visuospatial memory. IAT total recognition memory scores (collapsed across all types of materials) and IAT word memory scores were associated with postoperative verbal memory decline. This relationship was significant for the IAT ipsilateral injection memory scores and the IAT hemispheric asymetry scores. IAT memory performances were not related to visouspatial memory changes. Conclusions: Results indicate IAT memory measures to be related to postoperative verbal, but not visouspatial memory change. A specific relationship was found between postoperatuive verbal memory change and IAT verbal memory after injection ipsilateral to the seizure focus, when relying primarily on the contralateral hemisphere. This finding is consistent with the functional reserve model of memory change in ATL.