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

Super-selective injection of propofol into the intracranial arteries enables Patient's self-evaluation of expected neurological deficit

INTRODUCTION

It is hard to realize the extent of the expected postoperative neurological deficit for patients themselves. The provision of appropriate information can contribute not only to examining surgical indications but also to filling the gap between patient and expert expectations. We hypothesized that propofol infusion into the intracranial arteries (ssWada) could induce focal neurological symptoms with preserved wakefulness, enabling the patients to evaluate the postsurgical risk subjectively.

METHODS

Presurgical evaluation using ssWada was performed in 28 patients with drug-resistant epilepsy. Based on anatomical knowledge, propofol was super-selectively infused into the intracranial arteries including the M1, M2, and M3 segments of the middle cerebral artery (MCA), A2 segment of the anterior cerebral artery, and P2 segment of the posterior cerebral artery to evaluate the neurological and cognitive symptoms. We retrospectively analyzed a total of 107 infusion trials, including their target vessels, and elicited symptoms of motor weakness, sensory disturbance, language, unilateral hemispatial neglect (UHN), and hemianopsia. We evaluated preserved wakefulness which enabled subjective evaluations of the symptoms and comparison of the subjective experience to the objective findings, besides adverse effects during the procedure.

RESULTS

Preserved wakefulness was found in 97.2% of all trials. Changes in neurological symptoms were positively evaluated for motor weakness in 51.4%, sensory disturbance in 5.6%, language in 48.6%, UHN in 22.4%, and hemianopsia in 32.7%. Six trials elicited seizures. Multivariate analysis showed significant correlations between symptom and infusion site of language and left side, language and MCA branches, motor weakness and A2 or M2 superior division, and hemianopsia and P2. Transient adverse effect was observed in 8 cases with 12 infusion trials (11.2 %).

CONCLUSION

The ssWada could elicit focal neurological symptoms with preserved wakefulness. The methodology enables specific evaluation of risk for cortical resection and subjective evaluation of the expected outcome by the patients.

Methohexital - Induced lateralized periodic discharges during Wada test

•

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

•

Ipsilateral LPDs may impair memory testing during the Wada.

•

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.

Beyond the Wada: An updated approach to pre-surgical language and memory testing: An updated review of available evaluation techniques and recommended workflow to limit Wada test use to essential clinical cases

The Intracarotid amobarbital test (IAT), also called Wada test, is considered the "gold standard" for lateralizing language dominance in the pre-surgical evaluation of patients with epilepsy. In addition, it has been further modified to assess the postoperative risk of amnesia in patients undergoing temporal lobectomy. Since then it has been utilized to lateralize language and assess pre-surgical memory function. Over the years, its popularity has declined due to several limitations and availability of alternative procedures like fMRI and MEG. A survey of its use in the pre-surgical evaluation for epilepsy surgery has not been performed since the 2008 international survey by Baxendale et al. and it was heavily skewed due to data from European and North American countries. Only approximately 12% of the epilepsy centers indicated that they used the Wada test in every patient to assess preoperative memory function and language lateralization before temporal lobectomy. Nowadays, we have many functional mapping tools at our disposal. It has become somewhat unsuitable to have epilepsy patients undergo an invasive test such as the Wada test for the risks associated with it outweigh the benefits. Our objective is to review the Wada Test and alternative methods of assessing language and memory dominance, as it is past its prime and should only be used in specific circumstances.

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.

Comparing the North American Adult Reading Test (NAART) and the Test of Premorbid Functioning (TOPF) to estimate premorbid Wechsler Adult Intelligence Scale - 4th edition FSIQ in a clinical sample with epilepsy

Estimating premorbid general cognitive functioning is an essential component to the neuropsychological evaluation process. The North American Adult Reading Test (NAART) is a method to predict premorbid general cognitive functioning based on word reading skills developed using the Wechsler Adult Intelligence Scale-Revised (WAIS-R), which is currently in its fourth edition (WAIS-IV). The Test of Premorbid Function (TOPF) was developed using the WAIS-IV, based on the same method as the NAART, to estimate premorbid intellectual ability. There is a paucity of research comparing estimates of premorbid general intellectual ability between the NAART and TOPF. This study evaluated the clinical utility of premorbid estimates of FSIQ derived from the NAART and TOPF in a sample of 101 patients with temporal lobe epilepsy (TLE). Differences between NAART-derived premorbid FSIQs and TOPF simple demographic predicted FSIQs were significant (p < .001) with large effect sizes. NAART estimated premorbid FSIQ (M = 104.04, SD = 8.42) was significantly greater than TOPF premorbid estimates (M = 99.83, SD = 9.26). Results suggested NAART-derived estimates of premorbid FSIQ may be more accurate than TOPF-based estimates, which likely underestimated premorbid FSIQ in this sample of patients with epilepsy. Limitations and future directions are discussed.

Experience of adverse events with cerebral propofol testing in patients with drug resistant epilepsy

The aim of this study was to assess the type and frequency of adverse events during the Wada test conducted with propofol as an anaesthetic agent. In total, 122 patients with temporal lobe epilepsy underwent the Wada test with propofol between 2006 and 2016 as part of presurgical evaluation at the Department of Neurosurgery of the Medical University of Warsaw. The Wada test was conducted bilaterally on 118 patients (236 cases). In four cases, due to complications, the test was conducted only unilaterally, which resulted in a total of 240 cases. Those cases were further analysed for the presence of adverse events. In all cases, intracranial circulation angiography (via the transfemoral approach) was performed before memory and language testing. Of the 122 patients, adverse events were observed in 75 patients (61.4%). Serious complications were notably rare and observed only in two patients (1.6%): one patient had a carotid artery dissection, and the other had a pseudoaneurysm at the puncture site. Mild adverse events (e.g., shivers or pain of the eye) were highly common - we observed them in 71 patients (58%), but they were short-term and well-tolerated by the subjects. Two patients (1.6%) had a seizure during the Wada test. Most of the adverse events occurring during the Wada test with propofol were mild and short-lived. Considering a small risk of serious damage to health, this procedure can be perceived as a good method for assessing language and memory in a fraction of the epilepsy surgery candidates.

An improved qEEG index for asymmetry detection during the Wada test

The Wada test is commonly used to evaluate language and memory lateralization in candidates for epilepsy surgery. The spatial Brain Symmetry Index (BSI) quantifies inter-hemispheric differences in the EEG. Its application has been shown to be feasible during Wada testing. We developed a method for the quantification of EEG asymmetry that matches visual assessments of the EEG better than BSI. Fifty-three patients' EEG data, with a total of 85 injections were analyzed. In a step-wise, data-driven manner, multiple electrode and frequency band combinations were evaluated. Eventually, BSI, calculated using only the frontal electrodes F3 and F4, was combined with a temporal measure of delta power in the central electrodes, C3 and C4, into a new measure: cBSI. Using the area under the ROC curve (AUC), we showed that cBSI performs significantly better relative to BSI (median AUC 0.98 versus 0.96, p=0.0015, Wilcoxon signed rank test). Our results showed that asymmetry detection was significantly improved by combining temporal with spatial qEEG measures. In the future, our combined qEEG measure could allow for a more objective way of monitoring EEG asymmetry, thereby increasing the feasibility of using EEG as a monitoring tool during the Wada test. Future studies should, however, validate our cBSI method in real time in the operating room or radiology suite.

Utility of Green's Word Memory Test Free Recall Subtest as a Measure of Verbal Memory: Initial Evidence from a Temporal Lobe Epilepsy Clinical Sample

This study investigated the Word Memory Test (WMT) Free Recall (FR) subtest as a conventional memory measure. Nineteen participants with pharmacoresistant left temporal lobe epilepsy (LTLE) and 16 with right temporal lobe epilepsy (RTLE) completed the WMT, Rey Auditory Verbal Learning Test (RAVLT), and Wechsler Memory Scale-Fourth Edition Logical Memory (LM) subtest during presurgical evaluation. LTLE participants performed significantly worse on FR subtest (p < .05, [Formula: see text]) and RAVLT Trial 7 (p < .01, [Formula: see text]), but not on LM subtest. Age was a significant covariate for FR (p < .01, [Formula: see text]). Logistic regression revealed FR plus age and RAVLT age-adjusted T-scores both yielded 77.1% classification accuracy and respective diagnostic odds ratios of 11.36 and 11.84. Receiver operating characteristic curves to classify seizure laterality found that RAVLT and FR were significant (area under the curve [AUC] = 0.82 and 0.74), whereas LM was nonsignificant (AUC = 0.67). Cut scores and positive/negative predictive values were established for improved clinical classification.

Quantitative EEG is an objective, sensitive, and reliable indicator of transient anesthetic effects during Wada tests

The intracarotid amobarbital or Wada procedure is a component of the presurgical evaluation for refractory epilepsy, during which monitoring the onset and offset of transient anesthetic effects is critical. In this study, the authors characterized changes of 8 quantitative measures during 26 Wada tests, which included alpha, beta, theta, and delta powers, alpha/delta power ratio, beta/delta power ratio, median amplitude-integrated EEG, and 90% spectral edge frequency (SEF90), and correlated them with contralateral hemiplegia. The authors found that on the side of injection, delta and theta powers, alpha/delta power ratio, beta/delta power ratio, and SEF90 peaked within 1 minute after injection of 70 to 150 mg amobarbital or 4 to 7 mg methohexital. When contralateral arm strength returned to 3/5, delta power and amplitude-integrated EEG decayed on average 24% and 19%, respectively, for amobarbital, similar to that of methohexital (27% and 18%). Because delta power resolution most closely mirrored that of the hemiplegia and amplitude-integrated EEG had the highest signal/noise ratio, these quantitative values appear to be the best measures for decay of anesthetic effects. Increase in alpha power persisted longest, and therefore may be the best measure of late residual anesthetic effects.

The intracarotid etomidate Wada test: a 54-patient series

Hemispheric language dominance and isolated hemispheric memory function evaluation can be undertaken with the intracarotid injection of a general anesthetic agent (Wada test). Amobarbital has been traditionally used as the anesthetic agent, but legal and commercial constraints limit its use. We evaluated the use of etomidate as an alternative agent for the Wada test in a series of 54 consecutive adult patients with mesial temporal sclerosis undergoing presurgical evaluation for epilepsy surgery. Language lateralization and hemispheric memory function evaluation were successfully achieved in all cases. Side effects (somnolence, tremor, and dystonia) were infrequent, minor, and transient and did not require interruption of the procedure. Etomidate appears to be a safe and effective alternative agent to amobarbital in the Wada test. Similarly to the amobarbital Wada test, the ability of the etomidate Wada test to predict postoperative memory decline remains unclear.

Feasibility of the superselective test with propofol for determining eloquent brain regions in the endovascular treatment of arteriovenous malformations

The superselective test for determining eloquent brain areas, carried out prior to the embolization treatment for arteriovenous malformations (AVMs), is a tool contributing to increase the safety of endovascular procedures. Taking into account amobarbital unavailability, it was decided to carry out the present study to demonstrate the efficacy and safety of propofol as an alternative to amobarbital to perform this test. A group of 58 patients were treated in 91 embolization sessions for brain AVMs using endovascular surgery between February 2006 and February 2011. The superselective test was performed prior to embolization with Histoacryl, using the intra-arterial administration of 20 mg propofol through a microcatheter positioned near the AVM nidus. Ten (7.8%) of the 128 superselective tests were positive. Neurological deficits appeared immediately after propofol administration, lasted for one minute and disappeared after five minutes. Only one of the patients showing a negative test result developed neurological deficits after embolization, for 99.2% negative predictive vale. Despite their positive test results, six patients were embolized and five developed post-embolization neurological deficits, for 83.3% positive predictive value. The test showed 83.3% sensitivity and 99.2% specificity. The use of propofol to perform the superselective test during brain AVM embolization is a safe and effective alternative to amobarbital, and may predict the occurrence of post-embolization ischemic complications.

Alternatives to sodium amobarbital in the Wada test

OBJECTIVE

To review the literature and identify alternatives to sodium amobarbital for use in the Wada test.

DATA SOURCES

A search of PubMed (1960-October 2010) was performed using the following key words alone or in combination: Wada test, intracarotid amobarbital procedure, intracarotid, intraarterial, sodium amobarbital, methohexital, Brevital, pentobarbital, etomidate, propofol, and alternative anesthetics. References of the identified articles were reviewed for relevant information.

STUDY SELECTION AND DATA EXTRACTION

All articles in English identified from the data sources were evaluated. Review included comparative, prospective, and retrospective studies along with case series and case reports.

DATA SYNTHESIS

Methohexital, pentobarbital, etomidate, and propofol have all been studied as alternatives to sodium amobarbital in the Wada test. Four controlled experimental trials, 1 uncontrolled experimental trial, 6 retrospective chart reviews, and 2 case reports were reviewed. Methohexital, pentobarbital, and propofol required a second injection due to their short duration of action. Etomidate was studied as a bolus injection followed by a continuous infusion until the critical speech and memory tests were administered, which differed from the standard Wada test procedure. Patients had an increased risk of seizures with methohexital, whereas 1 patient developed transient respiratory depression immediately after receiving pentobarbital. Furthermore, propofol caused increased tone with twitching and rhythmic movements, which interfered with the completion of the Wada test for 1 patient. All authors concluded that these agents were equivalent to amobarbital for the Wada test.

CONCLUSIONS

Methohexital, pentobarbital, etomidate, and propofol are viable alternatives to sodium amobarbital for use in the Wada test, but each has shortcomings.

Intravenous methylprednisolone reduces the risk of propofol-induced adverse effects during Wada testing

The adverse effects and risks associated with intracarotid propofol injection during Wada testing were retrospectively compared in two groups of patients with (n = 75) and without (n = 58) intravenous methylprednisolone administered before intracarotid propofol injection. The incidences of all adverse effects were decreased in the methylprednisolone group. In particular, severe adverse effects such as increased muscle tone with twitching and rhythmic movements or tonic posture, which could adversely affect Wada test results, were seen in one patient in the methylprednisolone group and seven patients in the control group, indicating 92% risk reduction. This study suggests that Wada testing using intravenous methylprednisolone administration prior to propofol injection is a safe approach to the preoperative evaluation of brain tumors, epilepsy, and arteriovenous malformations.

Wada test using secobarbital sodium (Ional) to determine language dominance

The intracarotid sodium amobarbital (Amytal) test, the Wada test, remains an efficient test for evaluation of language and memory function. However, due to a world shortage of amobarbital, it has become necessary to investigate the use of alternatives. We report the efficacy of the Wada test using secobarbital sodium (Ional) in determining language dominance. An accurate determination of language dominance was required in 43 patients preoperatively at our institution. Patients underwent the Wada test using secobarbital sodium, effectiveness and safety were assessed. Patients were monitored for vital signs (blood pressure, respiratory rates, heart rates and saturation of oxygen). Ten patients were further monitored for continuous intra-arterial blood pressure and monitored with scalp electroencephalography (EEG). Language dominance was determined by the Wada test with secobarbital sodium in all patients. Total volume of secobarbital sodium injected was 10-25 mg (mean 16.5 ± 3.2 mg). Changes in vital signs were minimal and any induced neurological deficits completely disappeared within 8 min. On EEG records, induced theta waves immediately appeared on the ipsilateral side of the intra-arterial injection and disappeared within 6 min. One patient described a scintillating scotoma (sensation of shimmering light in his eyes) at the moment of injection; another experienced an epileptic episode during the test and recovered after 6 min. No adverse events were observed in the remaining 41 cases. We propose secobarbital sodium as a safe and reliable alternative to sodium amobarbital used in the Wada test to determine language dominance.

The contribution of neuropsychology to diagnostic assessment in epilepsy

Neuropsychology plays a vital role in the treatment of epilepsy, providing information on the effects of seizures on higher cortical functions through the measurement of behavioral abilities and disabilities. This is accomplished through the design, administration and interpretation of neuropsychological tests, including those used in functional neuroimaging or cortical mapping and in intracarotid anesthetic procedures. The objective of this paper is to define and summarize in some detail the role and methods of neuropsychologists in specialized epilepsy centers. Included are information and recommendations regarding basic ingredients of a thorough neuropsychological assessment in the epilepsy setting, as well as suggestions for an abbreviated alternative exam when needed, with emphasis on functions associated with specific brain regions. The paper is intended for novice and experienced neuropsychologists to enable them to develop or evaluate their current practices, and also for other clinicians, who seek a better understanding of the methodology underlying the neuropsychological input to their work.

Provocative test with propofol: experience in patients with cerebral arteriovenous malformations who underwent neuroendovascular procedures

BACKGROUND AND PURPOSE

Provocative testing before AVM embolization has been shown to be a predictor of a successful endovascular treatment without neurologic deficits. Propofol has been used previously as an alternative agent in Wada testing with adequate results. The purpose of this study was to show our experience with the use of propofol as a safe and effective alternative to barbiturate provocative testing in AVM embolization procedures.

MATERIALS AND METHODS

A series of 20 patients, undergoing 38 embolization sessions, was treated for cerebral AVMs between November 2007 and February 2009 by endovascular methods. All patients were treated under conscious sedation. Pre-embolization neurologic assessment was performed with provocative testing by using propofol at 7-mg doses by an intra-arterial route after microcathether placement in or near the AVM nidus.

RESULTS

Among these 20 patients, 3 developed transient neurologic deficits after provocative testing, precluding initial or further embolization. One of the patients passing the provocative test developed slight paresis as a result of embolization with n-BCA, resulting in a PPV of 97%.

CONCLUSIONS

Propofol use during provocative testing in AVM embolization procedures represents an effective alternative to barbiturate testing and can have a positive impact in improving safety under sedation.

Language assessment in Wada test: comparison of methohexital and amobarbital

INTRODUCTION

Methohexital 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.

METHODS

A 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.

RESULTS

Language 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.

DISCUSSION

Language 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.

Multispectral molecular imaging of capillary endothelium to facilitate preoperative endovascular brain mapping

OBJECT

Brain mapping aims to localize neurological function to specific regions of the human brain. Preoperative endovascular brain mapping (PEBM) is a novel approach that allows clear visualization of nonfunctional (silent) brain parenchyma in real time during a resection. It has potential to improve neurosurgical guidance because brain shift does not alter the maps, and the map is visualized directly on the brain in situ rather than on a nearby image. Therefore, the risk of a new neurological deficit should be reduced. The authors report the first PEBM approach that combines selective molecular targeting of brain endothelium with multispectral (optical) imaging in preclinical animal models.

METHODS

Sprague-Dawley rats and New Zealand white rabbits were selectively catheterized, and a fluorescein isothiocyanate-derivatized tomato lectin-based imaging probe was administered into the carotid artery or posterior cerebral artery, measuring < 500 microm in diameter. After binding/uptake of the imaging probe, and removal of unbound probe, a craniotomy was performed to directly visualize the "brain map."

RESULTS

Selective localization of the imaging probe to the right hemisphere in rats or right posterior cerebral artery in rabbits was clearly visualized after craniotomy. Cross-sections of stained capillaries demonstrated that the imaging probe did not cause vascular occlusion. Gross regional selectivity of the imaging probe was documented by multispectral molecular imaging of intact brains, with discrete localization and endothelium-directed targeting validated by histological examination.

CONCLUSIONS

The authors have demonstrated the first molecular endothelium-targeted approach to PEBM that does not require manipulation of the intact blood-brain barrier or result in vascular occlusion. Furthermore, the presented multispectral molecular imaging technique appears to be a suitable methodology for the generation of region-selective brain maps of vascularized brain parenchyma. Further refinement of the PEBM approach, as well as the development of improved imaging probes, may result in clinical advancement of PEBM where direct visual discrimination of nonfunctional silent brain parenchyma at the time of resection could significantly improve neurosurgical outcomes.

Intracarotid propofol testing: a comparative study with amobarbital

Twenty-five consecutive patients who underwent the Wada test using propofol as anesthetic were compared with 15 randomly selected patients who were tested using amobarbital. Time to verbal and nonverbal responses and time to motor power 3/5 did not differ between the two groups (P>0.05). The number of doses received by each patient and the percentage of patients needing more than one dose were significantly greater in the propofol group (P<0.005). Only one patient developed confusion, combativeness, and agitation. Despite the need for multiple doses, our patients had no residual drowsiness within 10 to 15 minutes of the propofol injection. This allowed us to perform the test on both sides on the same day separated only by 45 minutes. Propofol is an effective alternative to amobarbital in the Wada test, and may be used successfully in multiple repeated injections within the same test without significant residual sedation or significant adverse effects.

Can pentobarbital replace amobarbital in the Wada test?

To investigate the usefulness of pentobarbital (PTB) in the Wada test, 32 patients injected with PTB and 28 patients injected with amobarbital (AMB) were retrospectively analyzed. The AMB and PTB groups did not significantly differ with respect to mean time for recovery to grade III or V motor activity and duration of EEG delta slowing. The incidence of drowsiness or confusion after injection was lower in the PTB group (P=0.043). Language lateralization was well established in both groups. Fifty-three percent of patients in the PTB group and 46.2% in the AMB group with unilateral temporal lobe epilepsy had memory dominance in the nonepileptic hemisphere. The usefulness of PTB in terms of language and memory lateralization was found to be equivalent to that of AMB. Moreover, PTB produced drowsiness and confusion less frequently than AMB, although one patient in the PTB group experienced transient respiratory depression without any sequelae.

An update on determination of language dominance in screening for epilepsy surgery: the Wada test and newer noninvasive alternatives

The intracarotid amobarbital procedure or Wada test has been the gold standard for lateralization of language dominance before epilepsy surgery. It is based on deactivation of language cortex with intracarotid anesthesia. However, it is an invasive test with risks and discomforts, and it also has limitations. There has been great interest in replacing the Wada test with a noninvasive procedure. One alternative, repetitive magnetic stimulation works by deactivating language cortex, but most other promising alternatives are based on brain activation. Functional magnetic resonance imaging (fMRI), 15O-water positron emission tomography, single photon emission computerized tomography, transcranial Doppler, and near infrared spectroscopy detect hemodynamic responses to language cortex activation, while magnetoencephalography more directly measures event-related physiological activation. Some of the techniques also provide localization of language functions, whereas the Wada test is strictly a lateralization method. Based on widespread availability, fMRI will likely be the most widely used alternative.

Seizures during intracarotid methohexital and amobarbital testing

BACKGROUND

Methohexital 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.

METHODS

A 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.

RESULTS

Sixteen 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).

CONCLUSION

Patients with a previous history of epilepsy may be at higher risk for seizures after methohexital injection as compared with amobarbital injection.

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.

Neurosurgery for the treatment of epilepsy

PURPOSE OF REVIEW

Epilepsy is a common condition that is estimated to afflict 0.5-1.0% of the world's population. Frequently commencing in childhood, it is often associated with life-long disability. Approximately one-third of patients with epilepsy are refractory to antiepileptic drug therapy and many of these patients are candidates for surgical treatment. A growing body of evidence supports the safety and efficacy of surgery for the treatment of selected patients with epilepsy. Little information is available in the anesthesia literature regarding the presurgical assessment of candidates for surgical treatment.

RECENT FINDINGS

The presurgical identification of suitable candidates involves a multidisciplinary approach to assessment. Recent advances, particularly in neuroimaging techniques, are dramatically enhancing the capacity to accurately identify patients who are most likely to benefit from surgery. Epilepsy surgery is underused worldwide and in developed countries. In view of current efforts to increase opportunities to provide surgical treatment to more patients and to offer surgery earlier in the course of the disorder, the number of patients requiring specialized perioperative anesthetic care is expected to increase.

SUMMARY

This article provides anesthesiologists with an overview of the assessment process, investigation techniques and current rationale that influence the selection of appropriate candidates for surgical treatment and the associated need for specialized anesthetic care.

Preoperative endovascular brain mapping for intraoperative volumetric image guidance: preliminary concept and feasibility in animal models

Object

The authors describe a novel concept for brain mapping in which an endovascular approach is used, and they demonstrate its feasibility in animal models. The purpose of endovascular brain mapping is to delineate clearly the nonfunctional brain parenchyma when a craniotomy is performed for resection. The nonfunctional brain will be stained with sharp visual margins, differentiating it from the functional, nonstained brain. The authors list four essential criteria for developing an ideal endovascular mapping agent, and they describe seven potential approaches for accomplishing a successful endovascular brain map.

Methods

Four Sprague–Dawley rats and one New Zealand white rabbit were used to determine initial feasibility of the procedure. The animals were anesthetized, and the internal carotid artery was catheterized. Four potential brain mapping agents were infused into the right hemisphere of the five animals. Afterward, the brains were removed and each was analyzed both grossly and histologically.

Fluorescein and FD&C Green No. 3 provided good visual clarity and margins, but required blood–brain barrier (BBB) manipulation. Tantalum particles enabled avoidance of BBB manipulation, but provided inadequate visual clarity, probably because of their size. A Sudan black “cocktail” provided excellent clarity and margins despite remaining in the brain capillaries.

Conclusions

This is a novel application of the endovascular approach, and has broad potential for clinical neurosurgical brain mapping. The animal models in this study establish the feasibility of the procedure. However, further study is required to demonstrate safety, minimize toxicity, investigate stain durability, and improve the characteristics of potential mapping agents. The authors are planning to conduct future studies for identification of mapping agents that do not require BBB manipulation or vascular occlusion.

Tratamento cirúrgico da epilepsia do lobo temporal: análise de 43 casos consecutivos

Quarenta e três pacientes com epilepsia refratária ao tratamento medicamentoso foram submetidos à cirurgia de epilepsia do lobo temporal no Instituto de Neurologia de Curitiba, entre os anos de 1998 a 2003. Trinta e nove (90,6%) pacientes apresentavam esclerose mesial temporal, e quatro (9,4%), tumores cerebrais. Dos trinta e sete pacientes que possuíam avaliação pós-operatória completa, 83,7% apresentaram classificação I, segundo Engel (livres de crises incapacitantes). Complicações pós-operatórias ocorreram em 18,6%: uma infecção da ferida operatória, um caso de hidrocefalia, um de fístula liquórica, dois casos de paralisia transitória do IV nervo craniano e um de hemiparesia transitória. Não houve nenhum óbito relacionado à cirurgia de epilepsia no presente estudo.

Bilateral bispectral index monitoring during suppression of unilateral hemispheric function

Bispectral Index (BIS) has been used to monitor level of "sedation" based on the electroencephalogram (EEG). Patients evaluated for surgery to control a seizure disorder undergo Wada testing, during which one hemisphere is rendered functionally inactive after injecting a short-acting barbiturate. We surmised that the BIS values would reflect these functional changes. Eight epileptic patients were enrolled. A full array of 21 EEG electrodes and 2 BIS XP (Quatro) strips over each frontal region of the scalp were applied. The EEG was continuously recorded. BIS values from each hemisphere were recorded every minute. Angiography was performed by advancing a catheter into each internal carotid artery. Amobarbital or methohexital was injected until the patient developed a hemiparesis. The EEG confirmed a significant lateralized cortical effect of the barbiturate. Repeated measures analysis of variance was used to analyze the differences between the BIS values from monitor electrode strips placed on the left (left BIS) and the right (right BIS) sides of the head as well as the differences in the left and right BIS values before and after each injection of the barbiturate. Injection of barbiturate into either the left or right internal carotid artery produced a significant change on the 21-electrode EEG. However, there was no difference between left BIS to right BIS values (P = 0.84). With repeated injections of barbiturates, some patients became sedated. At these times, both left BIS and right BIS values decreased together before and after injection of barbiturate. The BIS monitor was unable to distinguish significant hemispheric EEG and clinical functional changes except when the patient became sedated.