Abstracts

Rationale: The Wada test, or Intracarotid Amobarbital Procedure (IAP), is a relatively safe and commonly used tool for evaluation of language and memory lateralization in the pre-surgical work up for patients with epilepsy or brain tumor (1). Although the Wada test was first done using amobarbital, many institutions now use methohexital because of several factors, including drug availability and a shorter recovery time compared to amobarbital.Historically, methohexital has been used to induce interictal discharges during intraoperative electrocorticography (ECoG) but fell out of favor because of inappropriate activation in about 43% of the cases (2). Methohexital has also been used in the past to induce epileptiform activity at doses of 0.3-0.6 mg/kg (3). Methohexital is also commonly used as an anesthetic in electroconvulsive therapy (ECT) due to its propensity to lower the seizure threshold (4) and in some cases, it can induce seizures even before the treatment (5).   The exact effect of methohexital on interictal activity during the Wada test has not been described. Our hypothesis is that methohexital may activate interictal epileptiform discharges on electroencephalography (EEG) recordings during the Wada test and that this may have an impact on cognitive performance during evaluation of language and memory. Methods: A retrospective review of  6 years of consecutive Wada tests was completed at Michigan Medicine. This time period was included for analysis due to the ease of retrospectively reviewing EEG recordings during the Wada test. EEG recordings were reviewed for evidence of baseline epileptiform discharges and presence of induced  epileptiform discharges following administration of methohexital. Results: A total of 114 patient were included in the analysis, 84 patients had epilepsy and 30 patients had brain tumors as the primary indication for having the Wada test done as a part of their presurgical evaluation. There were two (1.75 %) cases identified where intra-arterial methohexital administration was associated with activation of epileptiform discharges within 2-7 seconds of the injection. The epileptiform discharges in these two cases were abundant and were consistent with periodic discharges (PD). The PD resolved 3-10 minutes after injection. The LPDs were similar to the patients’ regular interictal epileptiform discharges and did not induce any new pattern. There were no seizures recorded in any of the patients.      Conclusions: #NAME? Funding: No funding was received.