Commentary: Epilepsia's Wada survey.

Abstract

The potential equivalence of non-invasive approaches for establishing language and memory representation to invasive methods (e.g., Wada testing, cortical simulation mapping) in epilepsy surgery candidates is an important topic of discussion, and we thank the editors of EPILEPSIA for the opportunity to present our rationale as to why we consider it premature to make broad pronouncements that invasive approaches should be abandoned. Our comments were intended to be balanced, acknowledging the differences in backgrounds and skills across epilepsy surgery programs, and thus were couched in probabilistic rather than absolute terms to reflect this variability. We recognize that the readership poll on the initial controversy dialogue was never intended to be scientific, and indeed, the sample size is insufficient to allow any broad generalizations. The goals of such polls, however, are to encourage greater participation of EPILEPSIA readers on topics for which there is a lack of consensus, and the equivalence of invasive and non-invasive measures of language and memory during preoperative evaluation is such a topic. No exchanges will convince persons with strongly held beliefs to abandon them, although commentary and dialogue are important to articulate the clinical rationale behind choice of methods. From our perspective, the survey questions addressing the persuasiveness of our clinical rationale could be improved upon, and perhaps future EPILEPSIA controversy authors could supply several questions similar to what is typically necessary in continuing education courses. For example, neither Papanicolaou nor our manuscript directly addressed the necessity of Wada testing as part of the evaluation for temporal lobe epilepsy, but rather, discussed whether existing non-invasive approaches to language and memory provide information that is sufficiently equivalent to Wada results so that Wada testing itself becomes unnecessary, a comparison that was explicitly probed regarding MEG and fMRI vs. intracranial grids. That over half of responders indicated intracranial grids are still necessary for cortical localization despite MEG and fMRI is a valuable data point reflecting diverse clinical practice. It would be interesting to have included a question as to whether MEG and fMRI were sufficiently developed so that Wada testing should be fully abandoned across all epilepsy programs. While we never argued whether Wada testing should or should not be performed on all temporal lobe epilepsy surgical candidates, the survey findings that no European responders felt that the Wada is necessary reflects the greater emphasis of using fMRI to minimize Wada testing by epilepsy clinicians in Europe in the epilepsy literature. We reassert our belief, though, that it is premature to develop position statements asserting that the Wada test (or stimulation mapping) is unnecessary due to the availability of non-invasive measures of language and memory fMRI or MEG since non-invasive approaches have important limitations that are not always fully appreciated or acknowledged by non-expert users, and that such a position does not reflect the opinion of many clinicians who actively manage and follow epilepsy patients to optimize their epilepsy care.