One center's experience with complications during the Wada test

Cortico-cortical evoked potential and language mapping: A meta-analysis

PURPOSE

The purpose of this meta-analysis was to determine the best available evidence for the use of cortico-cortical evoked potential (CCEP) for language mapping.

METHODS

PubMed/Medline/Google Scholar/Cochrane and Scopus electronic databases were searched for articles using CCEP for language mapping. CCEP data was obtained including the area of the cortex generating CCEP, resection data, and post-resection language outcomes. Inclusion criteria were clinical articles reporting the use of CCEP in language regions of the brain, reporting language outcomes and whether there was final resection of the cortex, studies with more than five patients, and studies in either English or Spanish. Review articles, systematic reviews, meta-analyses, or case series with less than five patients were excluded.

RESULTS

Seven studies with a total of 59 patients were included in this meta-analysis. The presence of CCEPs from stimulation of Broca's area or posterior perisylvian region in the resection predicts language deficits after surgery. The diagnostic odds ratio shows values greater than 0 perioperatively (0.69-5.82) and after six months (1.38-11), supporting a high likelihood of a language deficit if the presence of CCEPs from stimulation of Broca's area or posterior perisylvian region are included in the resection and vice versa. The True Positive rate varied between 0.38 and 0.87. This effect decreases after six months to 0.61 (0.30-0.86). However, the True Negative rate increased from 0.53 (0.32-0.79) to 0.71 (0.55-0.88).

CONCLUSION

This meta-analysis supports the utility of CCEP to predict the probability of having long-term language deficits after surgery. .

Determination of language areas in patients with epilepsy using the super-selective Wada test

The Wada test is the gold standard for determining language-dominant hemisphere. However, the precise determination of language areas in each patient requires more invasive methods, such as electrocortical stimulation. Some studies have reported the use of anesthetic injection into selective cerebral arteries to predict postoperative function. To assess the function of the anterior and posterior language areas separately, we developed an advanced test named the “super-selective Wada test” (ssWada). The ssWada procedure is as follows: an endovascular neurosurgeon identifies the arterial branches of the middle cerebral artery (MCA) perfusing the anterior language area of the inferior frontal gyrus and the posterior language area of the posterior part of the superior temporal gyrus using angiography. Behavioral neurologists assess language symptoms before and after propofol administration using a microcatheter tip in the selected arterial branch. From 30 serial patients with epilepsy who underwent ssWada test at Tohoku University Hospital, we retrospectively reviewed patients in whom multiple areas in the bilateral MCA region was examined. Eight cases were identified in this study. All eight cases had been considered for resection of the area overlapping the classical language area. Three of the eight cases were left-dominant, and the within-hemisphere distribution was also considered typical. One case was determined to be left-dominant but atypical in the intra-hemispheric functional distribution. Two cases were right-dominant, and the intra-hemispheric functional distribution was considered a mirror image of the typical pattern. The remaining two cases were considered atypical, not only in terms of bilateral language function, but also in terms of anterior-posterior functional distribution. This case series demonstrates the potential utility of ssWada in revealing separate function of the anterior and posterior language areas. The ssWada allows simulation of local surgical brain resection and detailed investigation of language function, which potentially contributes to planning the resection area. Although indications for ssWada are quite limited, it could play a complementary role to noninvasive testing because it provides information related to resection using a different approach.

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The super-selective Wada test (ssWada) injects anesthetic locally into the brain.

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The ssWada simulates states of post-resection functional impairment.

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The ssWada successfully localized different components of language separately.

Roles of fMRI and Wada tests in the presurgical evaluation of language functions in temporal lobe epilepsy

Surgical treatment of pharmacoresistant temporal lobe epilepsy (TLE) carries risks for language function that can significantly affect the quality of life. Predicting the risks of decline in language functions before surgery is, consequently, just as important as predicting the chances of becoming seizure-free. The intracarotid amobarbital test, generally known as the Wada test (WT), has been traditionally used to determine language lateralization and to estimate their potential decline after surgery. However, the test is invasive and it does not localize the language functions. Therefore, other noninvasive methods have been proposed, of which functional magnetic resonance (fMRI) has the greatest potential. Functional MRI allows localization of language areas. It has good concordance with the WT for language lateralization, and it is of predictive value for postsurgical naming outcomes. Consequently, fMRI has progressively replaced WT for presurgical language evaluation. The objective of this manuscript is to review the most relevant aspects of language functions in TLE and the current role of fMRI and WT in the presurgical evaluation of language. First, we will provide context by revising the language network distribution and the effects of TLE on them. Then, we will assess the functional outcomes following various forms of TLE surgery and measures to reduce postoperative language decline. Finally, we will discuss the current indications for WT and fMRI and the potential usefulness of the resting-state fMRI technique.

Safety of pediatric cerebral angiography

OBJECTIVE

Catheter-based cerebral angiography is commonly used for neurovascular diagnosis in children. In this work, the authors aimed to quantify the complication rate of cerebral angiography in children, characterize these complications, and identify risk factors for complications.

METHODS

Relevant clinical data were retrospectively obtained for 587 consecutive cerebral angiography procedures performed in 390 children from March 2002 to March 2020. Complications were categorized as neurological or nonneurological, and severity was graded using a standard schema. Incidences of complications were reported as point estimates. Associations between risk factors and complications were characterized in univariate analysis using the two-tailed Fisher exact test and in multivariate analysis using multiple logistic regression with bidirectional elimination based on the Akaike information criterion. In both univariate and multivariate analyses, statistical significance was corrected for multiple comparisons using the Benjamini-Hochberg method.

RESULTS

Complications occurred in 6.5% of procedures, including neurological complications in 1.9% and nonneurological complications in 4.8%. Permanent deficits occurred in only 0.2% of cases. Overall, 0.5% of procedures resulted in major complications, while 6.0% resulted in minor complications. Female sex and a history of hypertension or ischemic stroke were associated with an increased risk of complications, while femoral artery access was associated with a decreased risk of complications.

CONCLUSIONS

Pediatric cerebral angiography was shown to have a low rate of major or permanent complications. Children who were female and those with a history of hypertension or ischemic stroke were shown to be at higher risk of complications, while the use of femoral access carried a lower risk of complications.

Methohexital - Induced lateralized periodic discharges during Wada test

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Methohexital-induced LPDs occur rarely during Wada testing in epilepsy.

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Ipsilateral LPDs may impair memory testing during the Wada.

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EEG monitoring during the Wada test is recommended.

Objective

The Wada test is used to evaluate language lateralization and memory performance after inactivation of an isolated cerebral hemisphere. Methohexital a short-acting barbiturate has a history of use to induce interictal discharges during intraoperative corticography. We report a new finding of activation of lateralized periodic discharges (LPDs) after Methohexital injection.

Methods

We retrospectively reviewed 174 consecutive adult patients who underwent Wada testing in preparation for epilepsy surgery (N = 129, 74%) or brain tumor resection (N = 45, 26%) at the University of Michigan to determine the frequency of induced periodic discharges by methohexital.

Results

Four epilepsy patients (2.29%) had methohexital-induced LPDs within a median of 2 s (1–99 s) of the injection and lasting a median of 4 min (3–10 min) after a total of 7 injections. All LPDs occurred ipsilateral to the injection hemisphere in the known region of interictal epileptiform discharges. LPDs were not induced in brain tumor patients. In one patient, LPDs occurred during memory testing, and this patient's memory performance was below expectation based on pre-test neuropsychological testing.

Conclusions

Methohexital can induce LPDs in ipsilateral hemisphere and that can potentially affect memory performance.

Significance

This observation indicates that concurrent EEG monitoring during the Wada test is important and that induced discharges should be considered when interpreting Wada test results.

Classification of complications of epilepsy surgery and invasive diagnostic procedures: A proposed protocol and feasibility study

OBJECTIVE

In epilepsy surgery, which aims to treat seizures and thereby to improve the lives of persons with drug-resistant epilepsy, the chances of attaining seizure relief must be carefully weighed against the risks of complications and expected adverse events. The interpretation of data regarding complications of epilepsy surgery and invasive diagnostic procedures is hampered by a lack of uniform definitions and method of data collection.

METHODS

Based on a review of previous definitions and classifications of complications, we developed a proposal for a new classification. This proposal was then subject to revisions after expert opinion within E-pilepsy, an EU-funded European pilot network of reference centers in refractory epilepsy and epilepsy surgery, later incorporated into the ERN (European Reference Network) EpiCARE. This version was discussed with recognized experts, and a final protocol was agreed to after further revision. The final protocol was evaluated in practical use over 1 year in three of the participating centers. One hundred seventy-four consecutive procedures were included with 35 reported complications.

RESULTS

This report presents a multidimensional classification of complications in epilepsy surgery and invasive diagnostic procedures, where complications are characterized in terms of their immediate effects, resulting permanent symptoms, and consequences on activities of daily living.

SIGNIFICANCE

We propose that the protocol will be helpful in the work to promote safety in epilepsy surgery and for future studies designed to identify risk factors for complications. Further work is needed to address the reporting of outcomes as regards neuropsychological function, activities of daily living, and quality of life.

A concordance study determining language dominance between navigated transcranial magnetic stimulation and the Wada test in patients with drug-resistant epilepsy

OBJECTIVE

It remains unclear whether transcranial magnetic stimulation (TMS) can replace the Wada test to determine language hemisphere dominance (HD). Using the Wada test as the gold standard, this study aimed to investigate the accuracy of navigated TMS (nTMS) in determining language HD.

METHODS

This study enrolled nine right-handed patients with drug-resistant epilepsy. We hypothesized that application of nTMS to language-related areas of the language-dominant hemisphere would induce positive manifestation of language dysfunction (LD). To test our hypothesis, the patients were instructed to perform a visual object-naming task while nTMS was applied to the anterior (e.g., Broca's area) and posterior (e.g., Wernicke's area) regions, which are closely related to language processing. The Wada test result was used as the gold standard, and the diagnostic value of nTMS was assessed using the Kappa consistency test.

RESULTS

The nTMS-induced LD positive rate for the bilateral anterior language areas (85.7%) was higher than that for the posterior language areas (57.1%). There was high consistency between nTMS stimulation of the left anterior and posterior language areas and the Wada test results for determining language HD. In contrast, the consistency of stimulation of the right anterior and posterior transfer sites was moderate (Kappa value = 0.545, P = 0.171) and low, respectively. For the latter, no statistical calculation was performed because stimulation of the right posterior speech area was negative in all patients compared with the Wada test results.

CONCLUSIONS

Our findings revealed that using nTMS to stimulate language-related left anterior and posterior areas could predict language HD with high accuracy. When the stimulation performance of these areas is positive, nTMS and the Wada test are equally accurate. Observing only negative performance may indicate that language HD has been transferred to the right side.

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.

A voxel-based asymmetry study of the relationship between hemispheric asymmetry and language dominance in Wada tested patients

Determining the anatomical basis of hemispheric language dominance (HLD) remains an important scientific endeavor. The Wada test remains the gold standard test for HLD and provides a unique opportunity to determine the relationship between HLD and hemispheric structural asymmetries on MRI. In this study, we applied a whole‐brain voxel‐based asymmetry (VBA) approach to determine the relationship between interhemispheric structural asymmetries and HLD in a large consecutive sample of Wada tested patients. Of 135 patients, 114 (84.4%) had left HLD, 10 (7.4%) right HLD, and 11 (8.2%) bilateral language representation. Fifty‐four controls were also studied. Right‐handed controls and right‐handed patients with left HLD had comparable structural brain asymmetries in cortical, subcortical, and cerebellar regions that have previously been documented in healthy people. However, these patients and controls differed in structural asymmetry of the mesial temporal lobe and a circumscribed region in the superior temporal gyrus, suggesting that only asymmetries of these regions were due to brain alterations caused by epilepsy. Additional comparisons between patients with left and right HLD, matched for type and location of epilepsy, revealed that structural asymmetries of insula, pars triangularis, inferior temporal gyrus, orbitofrontal cortex, ventral temporo‐occipital cortex, mesial somatosensory cortex, and mesial cerebellum were significantly associated with the side of HLD. Patients with right HLD and bilateral language representation were significantly less right‐handed. These results suggest that structural asymmetries of an insular‐fronto‐temporal network may be related to HLD.

Concordance between the Wada test and neuroimaging lateralization: Influence of imaging modality (fMRI and MEG) and patient experience

The Wada test remains the traditional test for lateralizing language and memory function prior to epilepsy surgery. Functional imaging, particularly functional MRI (fMRI), has made progress in the language domain, but less so in the memory domain. Magnetoencephalography (MEG) has received less research attention, but shows promise, particularly for language lateralization. We recruited a consecutive sample of 19 patients with epilepsy who had completed presurgical work-up, including the Wada test, and compared fMRI (memory) and MEG (language and memory) with Wada test results. The main research question was the concordance between Wada and these two imaging techniques as preepilepsy surgery investigations. We were also interested in the acceptability of the three techniques to patients. Concordance rates (N=16) were nonsignificant (Cohen's Kappa) between fMRI and Wada test (memory) and between MEG and Wada test (memory and language). The Wada test was a well-established protocol used at several epilepsy surgery centers in the UK. Patients generally found the Wada test an odd, but not aversive procedure. Sixteen (84%) patients who were scanned reported some level of obtundation in MEG. We present these discordant findings in support of the position that functional imaging and the Wada test are distinctive procedures, with little in the way of overlapping mechanisms, and that patient's experience should be taken into account when procedures are selected and offered to them.