Advantages of methohexital over amobarbital in determining hemispheric language and memory lateralization in the Wada test - A retrospective study

OBJECTIVE

Due to supply shortage, amobarbital, the traditional anesthetic agent in Wada testing, was replaced by methohexital in many epilepsy centers. This study aimed to compare the two barbiturates to identify possible advantages or disadvantages of methohexital as compared to amobarbital with regard to the adequacy of language and memory testing during the Wada test.

METHODS

Data from 75 patients with temporal lobe epilepsy who underwent bilateral Wada tests using either amobarbital (n = 53) or methohexital (n = 22) as part of presurgical work-up were analyzed retrospectively. The two subgroups were compared regarding hemispheric language and memory lateralization results and Wada testing characteristics, and the adequacy of language and memory testing was assessed.

RESULTS

We observed shorter durations of motor-, speech-, and EEG recovery after each injection in patients receiving methohexital compared to amobarbital. In addition, significantly more items could be presented during effective hemispheric inactivation in the methohexital group. Moreover, significant correlations of Wada memory scores with standard neuropsychological memory test scores could be found in the methohexital group.

SIGNIFICANCE

Our findings confirm that methohexital is not only equally suitable for Wada testing but has several advantages over amobarbital. Wada testing can be performed more efficiently and under more constant hemispheric inactivation using methohexital. Furthermore, the adequacy of language and memory testing during the Wada test might be affected by the anesthetic agent used.

Hemispheric language lateralization in presurgical patients with temporal lobe epilepsy: Improving the retest reliability of functional transcranial Doppler sonography

Since its introduction, functional transcranial Doppler sonography (fTCD) has been extensively applied in research and clinical settings and has now become part of the routine presurgical work-up of patients with epilepsy. Because of its importance in planning neurosurgical interventions and predicting possible cognitive risks, the reproducibility of fTCD in determining hemispheric language lateralization (HLL) has to be ensured. In the present study, fTCD was performed twice in 33 initially lateralized patients with temporal lobe epilepsy (TLE) as part of their presurgical work-up, using a standard word generation paradigm. Initially, the standard analysis, including only the statistical examination of fTCD data, was applied, and a rather poor retest reliability of r = 0.41 was obtained (p = 0.017). Because of doubts concerning appropriate task performance in some patients, subsequently, a two-step data analysis was introduced, including an additional qualitative evaluation of fTCD data regarding (1) instruction-compliant task performance, (2) sufficient quality of the baseline phase, and (3) adequate increase in cerebral blood flow velocity (CBFV) during the activation phase. Attributable to a more valid interpretation of fTCD data after the application of the qualitative step, the reproducibility of HLL significantly improved (p = 0.007) to a high retest reliability of r = 0.84 (p < 0.000). In clinical settings, psychological and situational factors seem to strongly influence the reproducibility of fTCD determining HLL. Accordingly, we highly recommend the complementation of the standard statistical examination of fTCD data by an additional qualitative evaluation (two-step data analysis), as this extra security is particularly desirable because of its direct implications for the further evaluation of neurosurgical interventions. This article is part of the Special Issue "Individualized Epilepsy Management: Medicines, Surgery and Beyond".