Predictive value of Wada memory scores on postoperative learning and memory abilities in patients with intractable epilepsy

Abstract

Surgery for refractory epilepsy often bestows significant relief but may cause memory impairment. The risk of postoperative memory loss can be determined by the intracarotid amobarbital procedure, or the Wada test. Chemical inactivation of the hemisphere on the side of the lesion is usually performed first, followed by inactivation of the contralateral hemisphere. Patients who demonstrate adequate memory capacity of the contralateral hemisphere following deactivation of the ipsilateral hemisphere are considered good candidates for anterior temporal lobectomy. Evidence for the contribution of deactivating the contralateral healthy hemisphere remains inconclusive. The authors analyzed results in 32 patients with intractable epilepsy who had undergone a bilateral Wada test followed by an anterior temporal lobectomy and in whom the findings of both pre- and postsurgical neuropsychological evaluations were available. The Wada memory scores were correlated with the difference in scores between pre- and postsurgical standardized memory test scores. Analyses revealed no significant relationship between the Wada memory scores in the contralateral hemisphere and postsurgical changes in memory abilities. There was, however, a significant negative correlation between the Wada memory score in the ipsilateral hemisphere and postsurgical memory changes, particularly in patients with right hemisphere epileptogenic lesions (p = 0.0007). The results of this study are discussed vis-à-vis two theories of hippocampal function, and the authors stress the importance of the functional status of the surgical hemisphere in the prediction of postsurgical memory changes.