The impact of cannabis use on intracarotid amobarbital testing

Chronic cannabis use impacts memory functioning, even while users are not acutely intoxicated. The impact of cannabis use on Wada or intracarotid amobarbital testing (IAT) has not previously been described. We reviewed cannabis consumption in epilepsy patients undergoing IAT during pre-surgical work-up. Of 58 patients reviewed, 16 patients (28%) indicated regular use. During IAT, five regular cannabis users with suspected temporal lobe epilepsy exhibited poor memory while testing their presumptively healthy temporal lobe (i.e., the side opposite that targeted for epilepsy surgery), indicating the potential for an amnestic syndrome post-operatively. It was suspected that the pattern of IAT results for these patients was attributable to the deleterious impact of cannabis use on cognition. Thus, three of the five underwent repeat IAT after a period of enforced abstinence. On repeat IAT, each of the three patients exhibited improved memory performance while testing their healthy temporal lobe, suggesting that the healthy temporal lobe of each mediated sufficient memory ability to allow for epilepsy surgery. These findings raised concerns that frequent cannabis use may alter IAT results, leading to incorrect assessments regarding potential post-operative cognitive deficits, and led to a mandate at our institution that patients must stop cannabis use before IAT.