Abstracts

Rationale: The intracarotid amobarbital (Wada) test is a standard measure of hemispheric dominance for language and memory. It has been used to reveal contralateral neurocognitive weakness and risk of catastrophic memory outcomes (i.e. amnesia) from ipsilateral surgery for medial temporal lobe epilepsy (MTLE). By sedating the ipsilateral frontal and temporal lobe broadly, however, the standard Wada likely overestimates cognitive risk of surgery that targets only the medial temporal lobe, as in cases of selective laser amygdalohippocampotomy (SLAH). When MTLE patients fail a standard Wada memory test, we employ a selective posterior cerebral artery (PCA) injection preferentially targeting amobarbital to the distribution including the hippocampus. We examined memory outcomes in 5 SLAH patients who failed the standard Wada but passed the selective PCA test. Methods: We reviewed all SLAH patients in our practice (2011-2016) who had an ipsilateral Wada test administered (sodium amobarbital 100-125 mg injected into internal carotid artery) and the subset of patients who were also administered the selective PCA injection (50 mg). Ipsilateral failure was defined as < 4/8 correctly recognized objects. Pre- and post-surgical (1 y) measures used 1 standard deviation to define significant change on Rey Auditory Verbal Learning Test, Visual Reproduction and Logical Memory subtests of the Wechsler Memory Scale, and Rey Complex Figure Test. Results: Of 21 SLAH patients that underwent a standard Wada, 5 failed and underwent a selective PCA test. Of these 5 patients (4 female), all were left language dominant (4 underwent left SLAH), 3 had ipsilateral mesial temporal sclerosis (none had contralateral sclerosis or dual pathology identified), and 4 had poor baseline ipsilateral memory scores. None developed amnesia after SLAH, 2 patients showed mild decline in visual and verbal memory, and 3 remained stable or slightly improved. The sole patient with average or better baseline memory did not decline after SLAH. Conclusions: Memory outcomes of SLAH are superior to open temporal lobe surgery that also impacts extrahippocampal structures (DLD, this meeting). The standard Wada test targets the hemisphere while the selective PCA injection may better target the hippocampus. Failing the standard Wada but passing the selective PCA injection was not associated with amnesia after SLAH. Since we do not offer SLAH in the setting of failed selective PCA injection, predictive validity cannot be determined. The epileptic hippocampus, a target of both selective PCA injection and SLAH, may be less critical for recognition memory than other ipsilateral structures. Larger sample sizes, comparison of patient characteristics to memory outcomes, and better understanding of the amobarbital distribution following selective PCA injection are needed to further characterize the utility of this approach. Funding: National Institutes of Health