Abstracts

Rationale: The intracarotid amobarbital procedure (IAP) or Wada test is routinely used to determine memory and language lateralization in candidates for epilepsy surgery. Several studies have been published about the complications of Wada testing, reported in as many as 10.9% of patients (Epilepsy Behav 2008;13:551-553). With improvement in noninvasive functional neuroimaging methods, the continued use of the Wada test has become controversial (Epilepsia 2014;55:629-632). The purpose of this study is to accurately report complications of the Wada test observed at a single major academic medical center for comparison to previously published complication rates. Methods: A database of patients who underwent Wada testing between April 1991 and June 2013 at the University of Michigan was used to perform a retrospective chart review. Data were collected on the occurrence of any unexpected clinical event that occurred at the time of Wada testing, during the post-operative period, or within 1 month of the procedure. A procedure complication was defined as an unintended adverse and undesirable event in a patient that was clinically significant, requiring additional resources or prolonged hospitalization. Neurologic changes related to the patient's underlying illness were not considered procedure-related complications. Arteriotomy-related hematomas were considered complications if they required consultative evaluation, treatment, or inpatient admission. Patients undergoing procedures immediately following Wada testing were excluded. Results: A total of 436 patients underwent Wada testing between April 1991 and June 2013 at the University of Michigan. Five patients were excluded from review (see Figure 1). A total of 8/431 patients (1.9%) had a complication associated with Wada testing (see Table 1). Complications included encephalopathy, anesthetic injection into the external carotid artery, internal carotid artery vasospasm, seizure, and status epilepticus. None of the complications resulted in long-term morbidity. Conclusions: A total of 8/431 patients (1.9%) undergoing Wada testing at the University of Michigan between April 1991 and June 2013 had a complication, which is significantly lower than that of previous studies (Epilepsy Behav 2008;13:551-553). One explanation for these discordant data is that we distinguished clinically insignificant events from complications, similar to publications on general cerebral angiography (J Vasc Interv Radiol 2009;20:442-447). A strict definition of complication should be used when considering the safety of the Wada test and non-invasive alternatives. The risk of incompletely localizing language and memory with non-invasive methods in patients undergoing epilepsy surgery is potentially a greater hazard than the risk of complications associated with Wada testing, as demonstrated in this study. The Wada test is a relatively safe and uniquely useful diagnostic tool in the presurgical workup of patients with refractory epilepsy and should continue to be used as the primary or complementary modality of determining language and memory lateralization.