Hippocampal memory function as reflected by the intracarotid sodium methohexital Wada test

The intracarotid amobarbital procedure (IAP) determines lateralization of memory function for predicting the risk of amnesia after epilepsy surgery. Shortages of amobarbital led to its substitution with sodium methohexital in the intracarotid methohexital procedure (IMP). We compared IAP scores (32 patients) with IMP scores (20 patients). Wada ipsilateral and contralateral memory scores were analyzed and compared, as was the relationship of these scores to the results of standard neuropsychological memory tests. There was no significant difference in Wada contralateral memory scores (first injection) between the IAP and IMP. Differences between the IAP and IMP in memory scores for the hemisphere ipsilateral to the epileptogenic focus (second injection) were significant (P=0.01), patients who underwent the IMP manifesting a higher ipsilateral memory reserve. IAP scores related better to standard neuropsychological memory test scores than did IMP scores. The anesthetic drug used in Wada testing may affect lateralized memory assessment and prediction of postsurgical memory changes.     

A comparison of propofol and amobarbital for use in the Wada test

129 Wada procedures were reviewed to examine the suitability of propofol (n=54) as a replacement to amobarbital (n=75) for use as an anaesthetic in the Wada test. Suitability was considered with respect to length of hemiplegia induced, the frequency of side effects and patient memory scores. Data was retrospectively collected from records of patients who had undergone the Wada procedure between 2004 and 2009 in Beaumont Hospital, Dublin. No significant differences were found between the two drugs on any of the measures. The results suggest that propofol represents a suitable alternative to amobarbital for use in the Wada procedure.     

Sodium methohexital (brevital) as an anesthetic in the Wada test

PURPOSES: We report our experience with sodium methohexital (Brevital) as an anesthetic used in the Wada test for language and memory in 86 epilepsy surgery patients (173 procedures). METHODS: The methods are compared with those of the more commonly used anesthetic sodium amobarbital (Amytal). RESULTS: Despite differences between the methohexital and amobarbital test protocols, the behavioral and neurologic effects of the two anesthetics are similar. Because of the brief duration of methohexital, two successive injections are made on each side rather than one, to lengthen the time available for testing both language and memory. Behavioral and EEG indices return to baseline more quickly and more completely with methohexital than with amobarbital, allowing several repetitions of the procedure without incremental drowsiness, and the total time taken for the procedure is less with methohexital than with amobarbital. CONCLUSIONS: The results of language and memory testing in the Wada test are equivalent for amobarbital and methohexital, except that methohexital has a briefer duration of action and is associated with less sedation.     

Hippocampal memory function as reflected by the intracarotid sodium methohexital Wada test

The intracarotid amobarbital procedure (IAP) determines lateralization of memory function for predicting the risk of amnesia after epilepsy surgery. Shortages of amobarbital led to its substitution with sodium methohexital in the intracarotid methohexital procedure (IMP). We compared IAP scores (32 patients) with IMP scores (20 patients). Wada ipsilateral and contralateral memory scores were analyzed and compared, as was the relationship of these scores to the results of standard neuropsychological memory tests. There was no significant difference in Wada contralateral memory scores (first injection) between the IAP and IMP. Differences between the IAP and IMP in memory scores for the hemisphere ipsilateral to the epileptogenic focus (second injection) were significant (P = 0.01), patients who underwent the IMP manifesting a higher ipsilateral memory reserve. IAP scores related better to standard neuropsychological memory test scores than did IMP scores. The anesthetic drug used in Wada testing may affect lateralized memory assessment and prediction of postsurgical memory changes.     

Bilateral Wada test: Amobarbital or propofol?

PurposeThe Wada test is still the gold standard procedure to predict language and memory deficits before temporal lobe epilepsy surgery. As amobarbital was no longer available, our aim was to validate propofol as an alternative.MethodWe retrospectively studied 47 patients who underwent a bilateral intracarotid procedure, performed with amobarbital (18), or propofol (29), between 2000 and 2010 during the preoperative evaluation of temporal lobe epilepsy.ResultsThe number of patients experiencing an adverse event (mostly transient disturbance of consciousness or benign ocular symptoms) during both injections did not differ significantly between amobarbital and propofol. Hemispheric dominance was successfully determined in 96.5% patients with propofol vs. 94.4% with amobarbital for language, and in 72.4% under propofol vs. 77.7% under amobarbital for memory with no significant difference between groups.ConclusionPropofol can be used for the Wada test with an efficacy and safety comparable to amobarbital.     

FMRI reveals functional cortex in a case of inconclusive Wada testing

OBJECTIVES: The intracarotid amobarbital test (Wada test) currently represents the gold standard for preoperative lateralization of hemispheric dominance. Here, we report an epileptic patient with a longstanding extended lesion of the left hemisphere showing absence of motor and speech dysfunction with left carotid amobarbital injection, but tetraplegia and speech arrest with right carotid injection interpreted as a neuroplastic shift of motor and language functions to the right hemisphere. In contrast to the Wada results, motor functional magnetic resonance imaging (fMRI) showed a strong left hemispheric activation with right hand movements. METHODS: Right and left hand motor fMRI was performed. FMRI results and neurophysiological information obtained by motor and sensory evoked potential measurements were compared with the Wada test results. RESULTS: Initial interpretation of neuroplastic shifts of intrinsic left hemisphere functions to the right brain was revised after fMRI results which were confirmed by motor and sensory evoked potentials. CONCLUSION: As motor inactivation usually is thought to be the most robust feature of the Wada test, this case demonstrates that fMRI may reveal residual functional cortex in cases of inconclusive Wada results.     

Integration of Perceptual and Mnemonic Dysfunction: Sensory Auras Are Associated with Left Hemispheric Memory Impairment

Memory function during the intracarotid amobarbital test was studied to test the hypothesis that left hemisphere memory impairment is associated with sensory auras. In a series of 37 patients undergoing preoperative evaluation for epilepsy surgery, the quantitative memory scores during amobarbital inactivation of right and left hemisphere were analyzed for correlation with habitual epileptic auras classified as either (a) experiential, forced emotion, or whole-body dysphoria or (b) sensory hallucinations and/or illusions or localized dysesthesias. The left hemispheric memory score impairment was significantly worse in association with auras classified as sensory hallucinations and/or illusions or localized dysesthesias compared with auras classified as experiential, forced emotion, or whole-body dysphoria (P < 0.05). This finding may assist in predicting left-sided hemispheric memory dysfunction in patients with seizures beginning as auras involving sensory material. The results suggest an integration of perceptual and mnemonic dysfunction in which sensory auras are associated with left hemispheric memory impairment.     

Hemispheric language dominance testing by means of fMRI.

Presurgical evaluation of patients with intractable epilepsy routinely includes hemispheric language dominance (HLD) testing. Commonly, HLD is assessed by the intracarotid amobarbital (Wada) test.¹ The advent of functional magnetic resonance imaging (fMRI) has generated considerable interest in this technique as an alternative to HLD testing.^2–6 Functional MRI mapping of the brain relies on the detection of focal changes in the concentrations of deoxyhemoglobin.⁷     

The safety and efficacy of propofol as a replacement for amobarbital in intracarotid Wada testing of presurgical patients with epilepsy

ObjectiveThe intracarotid sodium amytal procedure (the “Wada test”) has for many years been the gold standard for language and memory lateralization and remains an important part of presurgical analysis for patients with medically intractable seizures. Due to shortages in the key sedative (amobarbital), neuropsychologists have turned to alternatives such as propofol. Our aim was to investigate the safety and efficacy of propofol relative to amobarbital in the Wada test.MethodsWe performed a retrospective review of the 97 Wada procedures performed at University of Iowa Hospitals and Clinics from 2007 through mid-2015.ResultsPropofol produced similar lateralization rates as amobarbital for both language and memory. Similar rates of patients in each group went on to have the resection surgery. With regard to safety, there were no differences found in average rate or severity of adverse effects. None of the demographic characteristics reviewed were predictive of increased risk for either drug.SignificanceThese findings support previous studies indicating that propofol is as safe and efficacious as amobarbital, and can continue to be used in Wada procedures with confidence.     

Does memory assessment during amobarbital testing predict postsurgical amnesia?

The intracarotid amobarbital procedure (Wada test) is an integral part of the preoperative evaluation for epilepsy surgery. Originally employed to identify patients with atypically cerebral language representation, it has evolved into a technique designed to also assess the capacity of a single temporal lobe to sustain recent memory function. Despite its importance in patient evaluation, this procedure remains unstandardized and varies among surgery centers. Thus, conclusions regarding the risk of a postsurgical amnestic syndrome can differ based solely on amobarbital procedural variations. We examine the theoretical assumptions associated with the memory component of intracarotid amobarbital assessment, review the available validity and reliability studies, and highlight the behavioral and methodologic limitations inherent in clinical reports of this technique.     

Effects of topiramate on memory performance on the intracarotid amobarbital (Wada) test

We evaluated the effects of topiramate (TPM) on memory function in the intracarotid amobarbital (Wada) test in nine patients with mesial temporal lobe epilepsy (MTLE) whose antiepileptic drugs (AEDs) included TPM and compared their scores with those of 16 patients with MTLE on AEDs not including TPM. Sodium amobarbital was injected first into the hemisphere ipsilateral to the seizure focus and then into a contralateral site, and the patients were tested for naming and memorization. There was no statistical difference in percentage memory scores between the two patient groups following the contralateral injection. After the ipsilateral injection, however, TPM patients had significantly lower percentage memory scores compared with non-TPM patients (P < 0.02). We conclude that a possible adverse effect of TPM on memory performance should be considered when evaluating the Wada test memory scores of patients on TPM therapy.     

Intracarotid amobarbital (Wada) test for language dominance: correlation with results of cortical stimulation

Eighty-eight patients had bilateral intracarotid amobarbital (Wada) testing to determine hemispheric dominance for language in preparation for epilepsy surgery, as well as unilateral extraoperative cortical electrical stimulation using subdural electrode arrays. In none of the patients with left dominance by Wada testing were language areas found with right-sided stimulation, but two patients with right dominance by Wada testing had language areas mapped on the left side. These findings suggest that left dominance by Wada testing is strong evidence for exclusive lateralization of language function in the left hemisphere, but there is concern about the ability of the Wada test to exclude the possibility of some left-sided language function despite apparent right-sided dominance. Patients with left dominance on Wada testing do not need cortical stimulation before extensive right temporal lobectomy, but we believe that patients with right or bilateral dominance on Wada testing should have cortical stimulation for localization of language areas if extensive left or right temporal or frontal resection is planned.     

Memory performance during the intracarotid amobarbital procedure and neuropsychological assessment in medial temporal lobe epilepsy: the limits of material specificity

We investigated the relationship between material-specific memory performance elicited during the Wada test, or intracarotid amobarbital procedure (IAP), and classic neuropsychological assessment in 89 surgical candidates with refractory medial temporal lobe epilepsy (MTLE). The neuropsychological battery included measures of simple and complex verbal and visual memory, whereas the IAP material consisted of verbal and dually encodable stimuli. Neuropsychological testing revealed that reduced verbal memory performance was associated with left-sided MTLE, whereas visual memory tasks revealed no differences between patients with left-sided and right-sided MTLE. During IAP, memory performance was worse with the ipsilesional hemisphere, regardless of lesion side. Most importantly, performance on verbal memory tests was significantly, but moderately, correlated with left hemispheric IAP performance, indicating that memory tasks using verbal material are a valid marker of left hemispheric integrity in left language-dominant MTLE patients and significantly predict left hemispheric memory performance during IAP. In contrast, performance on classic visual memory tests is unrelated to right hemispheric IAP performance, suggesting that the currently used visual memory stimuli do not reflect right hemispheric sensitivity.     

Methods for determination of language dominance: The wada test and proposed noninvasive alternatives

The intracarotid amobarbital procedure, also known as the Wada test, helps to lateralize language dominance by deactivating the language cortex with an intracarotid injection of an anesthetic agent. Although it has been the gold standard for determining language dominance for more than four decades, its invasiveness has prompted a search for noninvasive alternatives. Potential replacements have included neuropsychological techniques, measurements of anatomic brain asymmetries, magnetic stimulation for deactivation of language cortex, measurement of the electrical or magnetic neurophysiologic response to language activation, and methods that detect the hemodynamic response to activation of language cortex, namely increased local blood flow or increased local oxygenation. Based on widespread availability and the ability to provide localizing as well as lateralizing information, functional MRI will likely be the most widely used alternative.     

Seizures during intracarotid methohexital and amobarbital testing

BackgroundMethohexital and amobarbital have been used as agents for Wada testing in the presurgical evaluation of patients with epilepsy. Previous experience with methohexital as an anesthetic indicates that methohexital may decrease seizure threshold and may trigger seizures.MethodsA retrospective chart review of 760 intracarotid amobarbital and methohexital tests was performed to determine the frequency of seizures associated with preoperative intracarotid barbiturate testing for language and memory lateralization.ResultsSixteen patients (2.1%) who had seizures were found. In 3 patients, seizures occurred prior to barbiturate injection, and in 13, following barbiturate injection. After injection of amobarbital, 4 of 538 patients (0.7%) had a seizure. Nine of 222 patients had a seizure after methohexital injection (4.1%) (P = 0.001).ConclusionPatients with a previous history of epilepsy may be at higher risk for seizures after methohexital injection as compared with amobarbital injection.     

The Wada test in Austrian, Dutch, German, and Swiss epilepsy centers from 2000 to 2005: a review of 1421 procedures

Twenty-six Austrian, Dutch, German, and Swiss epilepsy centers were asked to report on use of the Wada test (intracarotid amobarbital procedure, IAP) from 2000 to 2005 and to give their opinion regarding its role in the presurgical diagnosis of epilepsy. Sixteen of the 23 centers providing information had performed 1421 Wada tests, predominantly the classic bilateral procedure (73%). A slight nonsignificant decrease over time in Wada test frequency, despite slightly increasing numbers of resective procedures, could be observed. Complication rates were relatively low (1.09%; 0.36% with permanent deficit). Test protocols were similar even though no universal standard protocol exists. Clinicians rated the Wada test as having good reliability and validity for language determination, whereas they questioned its reliability and validity for memory lateralization. Several noninvasive functional imaging techniques are already in use. However, clinicians currently do not want to rely solely on noninvasive functional imaging in all patients.     

Language assessment in Wada test: Comparison of methohexital and amobarbital

IntroductionMethohexital has replaced amobarbital during Wada testing at many centers. The objective of our study was to compare the use of methohexital and amobarbital during Wada testing regarding language and memory lateralization quotients as well as speech arrest times.MethodsA chart review of 582 consecutive patients undergoing 1041 Wada-procedures was performed (left = 60, right = 63, bilateral = 459). Language lateralization was calculated based on duration of speech arrest using a laterality index, defined as (L ? R)/(L + R). Memory lateralization was expressed as percentage of retained objects and laterality quotient.ResultsLanguage and memory lateralization revealed a similar distribution with amobarbital and methohexital. Speech arrest after left and right-sided injection was significantly longer in the amobarbital group as compared to the methohexital group. Language lateralization did not differ in the two groups. Percentage of retained memory items was higher in the methohexital group and there were fewer presented test items in the methohexital group.DiscussionLanguage and memory testing during the Wada test can successfully be performed with methohexital instead of amobarbital. The shorter half-life of methohexital allows repeated injections and shorter interhemispheric testing intervals, but also shortens the testing window.     

Prediction of verbal memory decline after epilepsy surgery in children: effectiveness of Wada memory asymmetries

PURPOSE: Differences in Wada memory performance after left and right amobarbital injection are powerful predictors of pre- to postoperative memory change among adult epilepsy patients after anterior temporal lobectomy. It is unknown, however, whether these Wada memory asymmetries apply to children who undergo focal cortical resection or to epilepsy surgery patients who undergo resection outside the temporal lobes. METHODS: To investigate these issues, Wada memory asymmetries and pre- to postoperative neuropsychological memory test performances were examined in 132 children who underwent some form of resective epilepsy surgery. Ninety-three (70%) children showed Wada memory asymmetries in the predicted direction (memory after injection ipsilateral to side of surgery better than memory after contralateral injection), and 39 (30%) did not. RESULTS: Children with Wada memory asymmetries showed significant improvement in verbal memory after surgery as compared with children without Wada memory asymmetries who showed significant verbal memory decline. This result was also obtained when individual cases were examined: 77% of children with Wada memory asymmetries in predicted direction showed no verbal memory decline after surgery, whereas 80% of children without asymmetries had lower postoperative verbal memory (passage recall) test scores. Wada memory asymmetries had no value in predicting postoperative changes in visual-spatial memory. CONCLUSIONS: Wada memory asymmetries may be used as one of the factors to assess risk for verbal memory decline after epilepsy surgery in children.     

Functional magnetic resonance imaging in the determination of dominant language cerebral area

Functional magnetic resonance imaging (fMRI) is a technique for detecting minimal changes in brain perfusion and oxygenation secondary to neuronal activation. Its application in the pre-surgical evaluation of epileptic patients with temporal mesial sclerosis is currently being under investigation in several centers. This study aims to describe an activation paradigm for the evaluation of language and memory functions, as an alternative to the worldwide used Wada test, which is an invasive procedure. In order to propose a paradigm adapted to the Portuguese language, we report our experience in determining the dominant cerebral area for language through fMRI with a verbal fluency task. The results of the fMRI from 19 patients studied in Curitiba in a period of approximately two years were studied. Sixteen of them presented with left hemispheric cerebral language dominance. In five patients, results from fMRI and Wada test could be compared and agreed in localization. Our results reinforce the view that fMRI may become an essential tool for medical practice, perhaps for the determination of eloquent areas in the evaluation of candidates for epilepsy surgery.     

Determination of language dominance: Wada test confirms functional transcranial Doppler sonography.

OBJECTIVE: To determine the efficacy of the invasive Wada test in determining language dominance, and to validate the functional transcranial Doppler sonography (fTCD) examination in patients. BACKGROUND: Previous work shows that simultaneous bilateral fTDC may identify cognitive hemispheric dominance in healthy individuals. METHOD: fTDC and the Wada test were performed prospectively in 14 patients with various diseases (tumors, cerebrovascular events, head injury, intractable epilepsy). fTDC hemispheric dominance was determined based on the hemispheric blood flow velocity shift for language and visuospatial tasks. Results: fTDC was performed easily in patients. One patient could not be examined by fTDC because of absent temporal bone window for ultrasonic transmission. Two Wada tests were inconclusive due to patient somnolence. One of these patients suffered from right frontal tumor and had aphasia remitted under steroids when examined. fTDC indicated a bilateral language dominance. In the remaining 11 patients the correlation between fTDC and Wada language lateralization indices was 0.75 (p = 0.008). If a post hoc cutoff score was taken for the fTDC language lateralization index, in eight patients, both fTDC and Wada testing determined the left hemisphere to be dominant for language; in the other three patients, language function was bilateral in both examinations. CONCLUSION: Although the current results are preliminary and require replication in a larger sample, fTDC seems to be able to assess hemispheric language dominance not only in healthy individuals, but also in patients. It might become an alternative noninvasive or complementary tool to the Wada test, particularly in patients in whom the Wada test is impractical or gives inconclusive results.