The role of the Wada test in the surgical treatment of temporal lobe epilepsy: An international survey—Commentary on Baxendale et al.

Baxendale and colleagues (in this issue) report the results of a Web-based survey that they conducted to determine the current practice of performing intraarterial anesthetic procedures (IAPs) in patients who are candidates for resection from the temporal lobe as treatment for intractable epilepsy. Individuals were selected to participate in the survey if they had published on the subject of surgery for temporal lobe epilepsy between 2000 and 2007. Response rate to the survey was 40%, raising in my mind a note of caution regarding how representative the survey results may be. A list of respondents who contributed to the survey would have been informative. According to the authors, the survey was kept simple “to maximize the response rate.” Thus the main issue addressed was to learn whether the frequency of performing IAPs has changed since the survey published by Rausch and colleagues in 1993 (Rausch et al., 1993), and indeed the new survey finds that fewer IAPs are done. Whereas 85% of Rausch et al.'s sample carried out an IAP on all surgical candidates, 12% of Baxendale et al.'s 92 respondents reported performing the procedure on all candidates, or 29% if one includes those who do so in more than 95% of their patients. The survey is useful in providing what I interpret as a sign that the field is maturing. In writing and talking about the IAP for the past 20 years, I have always maintained that this procedure should be performed only in selected cases, and I have specified the selection criteria in several publications (e.g., Jones-Gotman, 1991, 1996). The practice that many centers had of testing all surgical candidates may reflect insecurity about noninvasive measures of language and memory that precede the decision for surgery. I think that the reduction in number of centers that still test all patients reflects greater confidence in those measures, and thus the ability to rely upon them to select for IAP only patients who need it. The authors have an obvious bias against the IAP in the way they have presented the results, and reporting in the form of selected quotes does not help advance the cause of evidence-based medicine. Although no question on the survey was directed specifically at the use of fMRI in place of the IAP, the authors suggest that fMRI is replacing the IAP based on selected quotations from respondents. It is true that fMRI is used increasingly for the language application of the IAP, as many centers are including an fMRI language test in their investigation. However, few seem to actually replace the IAP completely, even for language, and no reliable paradigm has yet been designed for the memory application (Jones-Gotman et al., 2008). A future survey is needed to provide quantitative evidence on the replacement of IAP by fMRI. It is obvious that it would be best if a noninvasive procedure could fully replace the IAP. Many centers outside of the United States have faced problems of access to amobarbital, some chronically and some intermittently, owing to shortages. Performing an intracarotid anesthetic procedure with etomidate circumvents that problem. The etomidate speech and memory (eSAM) procedure (Jones-Gotman et al., 2005) also provides a more reliable test, as in the eSAM the hemianesthesia is maintained by infusion until the critical postinjection memory items have all been introduced. The Baxendale et al. paper alludes to “greater adverse reactions in newer compounds,” referring to etomidate, propofol, and brevital together, but that statement is not supported for etomidate, nor is the problem with brevital about adverse reactions. Our own experience with etomidate remains very positive, and we are receiving positive feedback from others who have started to use the test. The paper by Baxendale and colleagues (2008) began with a reference to Juhn Wada's original 1949 publication, in Japanese. For those who would like to read this paper, a Wada-approved English translation (Wada, 1997) exists in a special issue of Brain and Cognition devoted to the IAP.

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