The intracarotid amobarbital or Wada test: unilateral or bilateral?

New insights for predicting surgery outcome in patients with temporal lobe epilepsy. A systematic review

Resective surgery is the treatment of choice for one-third of adult patients with focal, drug-resistant epilepsy. This procedure is associated with substantial clinical and cognitive risks. In clinical practice, there is no validated model for epilepsy surgery outcome prediction (ESOP). Meta-analyses on ESOP studies assessing prognostic factors report discrepancies in terms of study design. Our review aims to systematically investigate methodological and analytical aspects of studies predicting clinical and cognitive outcomes after temporal lobe epilepsy surgery. A systematic review of ESOP studies published between 2000 and 2022 from three databases (MEDLINE, Web of Science, and PsycINFO) was completed by following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. It yielded 4867 articles. Among them, 21 corresponded to our inclusion criteria and were therefore retained in the final review. The risk of bias was assessed using A Tool to Assess Risk of Bias and Applicability of Prediction Model Studies (PROBAST). Data extracted from the 21 studies were analyzed using narrative synthesis and descriptive statistics. Our findings show an increase in the use of multimodal datasets and machine learning analyses in recent ESOP studies, although regression remained the most frequently used approach. We also identified a more frequent use of network notions in recent ESOP studies. Nevertheless, several methodological issues were noted, such as small sample sizes, lack of information on the follow-up period, variability in seizure outcome, and the definition of neuropsychological postoperative change. Of 21 studies, only one provided a clinical tool to anticipate the cognitive outcome after epilepsy surgery. We conclude that methodological issues should be overcome before we move towards more complete models to better predict clinical and cognitive outcomes after epilepsy surgery. Recommendations for future studies to harness the possibilities of multimodal datasets and data fusion, are provided. A stronger bridge between fundamental and clinical research may result in developing accessible clinical tools.

Wada test results contribute to the prediction of change in verbal learning and verbal memory function after temporal lobe epilepsy surgery

In recent years, the clinical usefulness of the Wada test (WT) has been debated among researchers in the field. Therefore, we aimed to assess its contribution to the prediction of change in verbal learning and verbal memory function after epilepsy surgery. Data from 56 patients with temporal lobe epilepsy who underwent WT and subsequent surgery were analyzed retrospectively. Additionally, a standard neuropsychological assessment evaluating attentional, learning and memory, visuospatial, language, and executive function was performed both before and 12 months after surgery. Hierarchical linear regression analyses were used to determine the incremental value of WT results over socio-demographic, clinical, and neuropsychological characteristics in predicting postsurgical change in patients' verbal learning and verbal memory function. The incorporation of WT results significantly improved the prediction models of postsurgical change in verbal learning (∆R2 = 0.233, p = .032) and verbal memory function (∆R2 = 0.386, p = .005). Presurgical performance and WT scores accounted for 41.8% of the variance in postsurgical change in verbal learning function, and 51.1% of the variance in postsurgical change in verbal memory function. Our findings confirm that WT results are of significant incremental value for the prediction of postsurgical change in verbal learning and verbal memory function. Thus, the WT contributes to determining the risks of epilepsy surgery and, therefore, remains an important part of the presurgical work-up of selected patients with clear clinical indications.

The Optimal Dose of Amobarbital in the Wada Test for the Presurgical Evaluation of Patients With Temporal Lobe Epilepsy

OBJECTIVE

The use of amobarbital in the Wada test varied between epilepsy centers, with no unified dosing or protocols available in the literature to standardize its use. We aimed to determine the dose of amobarbital in the presurgical evaluations of patients with temporal lobe epilepsy.

METHODS

A retrospective study of patients with temporal lobe epilepsy seen between January 2004 and December 2018 in King Faisal Specialist Hospital and Research Centre in Jeddah, Saudi Arabia, was conducted, and those who successfully underwent a Wada test were studied. A neuropsychologist or a neurologist will assess the memory and language, using standardized testing.

RESULTS

A total of 90 patients were studied. The mean age was 30 years (range, 16-52 years), where 49 (57%) of them were men. All patients had a routine neurological examination, including language and memory. The average dose of amobarbital given was 10.1.1 mg (range, 65.7-150 mg). There was no statistical difference between the dosing given to patients who passed or failed the memory testing (101.4 mg vs 94.7 mg, P = 0.1). Multivariate regression analysis showed that amobarbital dose needed an adjustment to patient's weight only for those older than 30 years, (P < 0.05; 95% confidence interval, 0.1-0.5), where an increase in the dose by 0.3 mg·kg·y was required to execute Wada test successfully.

CONCLUSION

It was only the patient's age that could influence the modification of Amobarbital dose in the Wada test, yet establishing a universal protocol is challenging because of the lack of well-defined dose determinants.