Abstracts

RATIONALE: The Wada test, used to assess unilateral memory and language functioning and predict post surgical outcome, has traditionally used the drug amobarbital (Amytal). Due to reduced availability of Amytal we initiated the use of sodium methohexital (Brevital). Brevital, being shorter acting, limits the time to test language and memory, but patients clear more quickly and, if there are questions about the validity of the procedure, it can be repeated without significant concern about over sedation. Using these two anesthetics necessitates procedural differences and it is possible that this could result in different findings.
Objective: This summary of our experience with Brevital and Amytal, including two cases who had both a Brevital and an Amytal Wada, is presented to compare the time required and findings in Wada testing.
METHODS: 15 Amytal patients and 5 Brevital patients, referred for Wada testing as part of a presurgical evaluation, were compared. Our Amytal procedure (AP) involved assessing language by having patients verbally identify and then remember a colored geometric shape, a phrase, 2 pictures, 2 words, a math problem, and a nursery rhyme. Our Brevital procedure (BP) is modeled after the procedure described by Buchtel et al. (2002). Language is assessed by naming objects during the first injection. To be remembered stimuli are presented following a second injection and include 2 objects, 2 words, a math problem, and a nursery rhyme. Memory testing includes recall and recognition testing and does not proceed until the patient[ssquote]s EEG is back to baseline and the patient reliably performs effortful cognitive tasks. The two procedures are compared in time from injection until patients can tested for memory and time from injection until memory testing is completed. Results from both procedures were included when both hemispheres were tested in the patient. The results from two patients who had repeat Wada[ssquote]s are also compared.
RESULTS: Time from initial injection until patients could be tested for memory was significantly different (mean minutes for AP vs. BP of 9.4 vs. 5.4, p[lt].01) as was total time for testing (mean minutes for AP vs. BP of 14.1 vs. 9.5, p[lt].01). For both patients who had both AP and BP the results were equivalent. In one case the Wada was repeated due to concerns about the validity of the AP. This patient remembered 60% with the left hemisphere injection and 80% with the right during the AP and 80% and 100% with the BP. In the case of a BP following a left temporal lobectomy and before additional surgery, the patient remembered 80% with the AP and 83% with the BP following a left hemisphere injection. All patients showed significant language impairment with left hemisphere injections and little to no language impairment with right hemisphere injections with both AP and BP. The total time necessary to complete the procedures were dramatically different since with the AP we waited a minimum of an additional 30 minutes before testing the alternate hemisphere.
CONCLUSIONS: Our preliminary experience with the BP suggests that this offers significant advantages over the use of the AP. The BP procedure can be completely much more quickly with an average savings of more than 35 minutes, could be more easily repeated if there are questions regarding validity, and yielded equivalent results to the AP.