Abstracts

Rationale: With the increasing availability of marijuana products, there are concerns about what impact it may have on cognition in patients with epilepsy. The effect of marijuana on Wada or intracarotid amobarbital testing (IAT) has not previously been described.Methods: A retrospective observational study using chart review to assess marijuana consumption and possible effects on IATwas performed. The hospital electronic medical record system was searched for patients 18 years or older who underwent IAT as part of pre-surgical work-up for epilepsy between January 2012 and December 2013. The time frame was chosen as it coincided with more consistent documentation of marijuana use in the charts, but before marijuana abstinence became mandatory prior to IAT at our institution. We reviewed demographics, epilepsy duration and ictal onset area on EEG, MRI findings, marijuana consumption, and IAT comments and results.Results: 58 patients underwent IAT, of which 16 patients (28%) indicated regular (at least monthly) marijuana use. Of those, 12 (75%) reported frequent use (at least twice weekly). During IAT, five frequent users had poor memory bilaterally or on the healthy side indicating the potential for an amnestic syndrome post-operatively. Inadequate performance related to marijuana was suspected and led to repeat IAT in three patients after abstinence from marijuana for 4 weeks. In all, the second IAT revealed sufficient memory function when using the healthy temporal lobe (data for all five patients shown in Table 1). Results suggested that epilepsy surgery would be feasible without an unacceptably high risk for severe memory impairment.Conclusions: The findings raised concerns that frequent marijuana use may alter IAT results leading to incorrect assessments regarding potential post-operative cognitive deficits. We have since implemented a process that includes inquiring about marijuana use and informing all patients to abstain from it for four weeks prior to the procedure.