Intracarotid Amobarbital Procedure Research Articles

Surgery: All Ages

Surgery: All Ages

September 13 Highlight and Commentary

Kirsch et al. examine the clinical value of Wada memory asymmetry to predict postoperative seizure freedom and postoperative verbal memory. Wada memory asymmetry in the unexpected direction may signal increased risk of poor surgical outcome after nondominant temporal lobectomy. It is not a predictor of persistent postoperative verbal memory decline. see page 676 Commentary by Kimford J. Meador, MD, and David W. Loring, PhD For over 50 years, the Wada test has been a component of the preoperative evaluation for epilepsy surgery. Juhn Wada introduced the intracarotid amobarbital procedure to lateralize language in 1949, and soon thereafter, Brenda Milner included memory testing during the procedure to help determine risk for postoperative amnesia. …

Lateralized Anterior Mesiotemporal Lobe Activation: Semirandom Functional MR Imaging Encoding Paradigm in Patients with Temporal Lobe Epilepsy—Initial Experience

To prospectively demonstrate anterior mesiotemporal lobe (MTL) activation in healthy volunteers by using a semirandom memory-encoding paradigm and to prospectively compare lateralized functional magnetic resonance (MR) imaging activation with intracarotid amobarbital procedure (IAP) memory test results in patients with temporal lobe epilepsy (TLE) who were scheduled to undergo surgery. The study was approved by a local ethics committee, and written informed consent was obtained from all subjects. Eight healthy volunteers and 18 patients with TLE who were scheduled for surgery were included in the functional MR imaging study involving the use of a memory-encoding paradigm with variable epoch lengths. Subjects were instructed to memorize new pictures that were mixed among pictures that they had seen before. Data analysis entailed computations of the contrast between the MTL activation induced by the new pictures and the MTL activation induced by the old pictures and of the lateralization index, defined as the relative difference in the number of activated voxels between the left and right MTLs. Lateralization indexes were compared between the patients and the volunteers and statistically correlated with the patients' IAP memory test results. To study deviations from perfect correspondence between the functional MR imaging- and IAP-derived lateralization indexes, orthogonal regression analysis was applied. Proportional relations for the patients with left-sided TLE and for those with right-sided TLE were calculated separately. The memory paradigm consistently activated the posterior and anterior MTL structures in both the healthy volunteers and the patients. Regression analysis revealed that functional MR imaging activation was stronger than the IAP results when it was lateralized to the contralateral MTL. This analysis also revealed a significant (P < .001) correlation between the functional MR imaging results and the IAP results in the patients with right-sided TLE but not in those with left-sided TLE (P > .1). The functional MR imaging memory-encoding paradigm consistently yielded MTL activation in the volunteers and the patients with TLE, but lateralized functional MR imaging activation was in concordance with the IAP results in only those patients with right-sided TLE.

Language and arithmetic – a study using the intracarotid amobarbital procedure

The intracarotid amobarbital procedure is used as a standard procedure in presurgical evaluation to assess hemispheric lateralization of language and memory, but has not been applied to investigate numerical processing. Patients with medically intractable epilepsy (n=20) were consecutively recruited during a presurgical evaluation programme. All 14 patients with left-lateralized language showed better arithmetic performance with the left hemisphere (intracarotid amobarbital procedure right), while five out of six patients with bilateral or right-hemispheric language representation showed better performance with the right hemisphere (intracarotid amobarbital procedure left). Furthermore, in patients with left-lateralized language, an interaction between intracarotid amobarbital procedure and type of arithmetic operation was found. The study suggests a close association between language lateralization and hemispheric specialization for arithmetic processing.

Alternatives to the Wada test: a critical view of functional magnetic resonance imaging in preoperative use

The Wada or intracarotid amobarbital procedure is already in its fifties and, despite its invasive character, still routine for determining the lateralization of language and memory prior to epileptic surgery. Among the new techniques available, functional magnetic resonance imaging is one of the most promising alternatives. This non-invasive method has several advantages including the possibility of mapping relevant areas within the hemispheres and being able to prolong examination time in case of discordant results. Many functional magnetic resonance imaging studies have focused on correlations with the intracarotid amobarbital procedure as the gold standard and found an agreement of about 90%. More importantly, recent studies demonstrated a significant correlation between presurgical functional magnetic resonance imaging testing and postsurgical outcome for functional magnetic resonance imaging activations in frontal language areas. In some studies, prediction for outcome is already higher for functional magnetic resonance imaging than for the intracarotid amobarbital procedure. Current data support functional magnetic resonance imaging as a valid alternative to the intracarotid amobarbital procedure. Small sample sizes in outcome studies and restrictions to certain sites of operation, however, still call for caution. A standardized series of tasks to activate the whole language and memory system paired with good comparability between medical centres is needed.

Right hemisphere language mapping in patients with bilateral language

Purpose The configuration of language cortex in the dominant left hemisphere has been well described in the literature. However, language representation in the right hemisphere, particularly in patients with some degree of bilateral language, remains unclear. Herein, we report six patients who underwent electrocortical stimulation (ECS) for language mapping following implantation of a right subdural electrode array (SEA). Methods The medical records of six bilateral language patients with right SEA implantation at the Minnesota Epilepsy Group between January 1996 and July 2004 were retrospectively reviewed. Language lateralization was based on the results of the intracarotid amobarbital procedure performed preoperatively. Anatomical localization of the SEA for each patient was verified using colored photographs of the cortical surface before and after SEA placement and by review of MRI scans taken with the SEA in place. Frontal and temporal language areas were identified by errors in any language modality including automatic speech, reading, naming, repetition, and comprehension during ECS. Results Language maps revealed the presence of frontal and/or temporal language areas analogous to the classic essential language areas of the dominant left hemisphere in four of six patients. One patient had a widespread distribution of single-language-error sites over the right temporal lobe. One patient had a silent language map. Conclusion Our results identified the presence of language cortex in the right hemisphere in five of six patients classified with bilateral language based on intracarotid amobarbital procedure. These areas are assumed to be accessory language zones in relation to the left hemisphere. Further exploratory studies are needed to evaluate their clinical significance.

Removing Eye‐movement Artifacts from the EEG during the Intracarotid Amobarbital Procedure

The EEG is often recorded during the intracarotid amobarbital procedure (IAP) to help in the assessment of the spatial extent and the duration of the effect of the drug. In scalp recordings, the EEG is always heavily contaminated with eye movement artifacts as the patient actively performs visual tasks. Independent component analysis (ICA) is a new technique for blind source separation. In this study, we separated the EEG data recorded during the IAP into independent components using ICA. The EEG signal was reconstructed by excluding the components related to eye movement and eye blinks. EEGs from 10 IAP tests were analyzed. The experimental results indicate that ICA is very efficient at subtracting eye-movement artifacts, while retaining the EEG slow waves and making their interpretation easier. ICA appears to be a generally applicable and effective method for removing ocular artifacts from EEG recordings during IAP, although slow waves and ocular artifacts share similar frequency distributions.

Language laterality determined by MEG mapping with MR-FOCUSS

Magnetoencephalography recordings were made on 27 patients with localization related epilepsy during two different language tasks involving semantic and phonological processing (verb generation and picture naming). These patients underwent the semi-invasive intracarotid amobarbital procedure (IAP), also referred to as the Wada test, to determine the language-dominant hemisphere. Magnetoencephalography (MEG) data were analyzed by MR-FOCUSS, a current density imaging technique. A laterality index (LI) was calculated from this solution to determine which hemisphere had more neural activation during these language tasks. The LIs for three separate latencies, within each language task, were calculated to determine the latency that correlated best with each patient’s IAP result. The LI for all language processing was calculated for the interval 150–550 ms, the second LI was calculated for the interval 230–290 ms (Wernicke’s activation), and the third LI was calculated for the interval 396–460 ms (Broca’s activation). In 23 of 24 epilepsy patients with a successful IAP, the LIs for Broca’s activation, during the picture naming task, were in agreement with the results of the IAP (96% agreement). One of three patients who had an undetermined or bilateral IAP had an LI calculated for Broca’s activation (396–460 ms) that agreed with intracranial mapping and clinical testing. These results indicate an 89% agreement rate (24 of 27) for magnetoencephalographic LI determination of the hemisphere of language dominance.

Transient global amnesia triggered by the intracarotid amobarbital procedure

The emergence of a sudden, global, and fully reversible amnestic state during an intracarotid amobarbital procedure (IAP) performed in a patient with a right temporal tumor is described. Forms of amnesia during the IAP are discussed, and it is argued that because of its appearance, the associated behavioral abnormalities, and EEG findings, this state was a transient global amnesia (TGA). In addition to other origins such as bitemporal lesions, increased barbiturate levels, seizures, and epileptic amnesia, TGA may triggered by stress or angiography during the IAP.

Reduced Anesthetization during the Intracarotid Amobarbital (Wada) Test in Patients Taking Carbonic Anhydrase–Inhibiting Medications

Failure to show adequate anesthetization during the intracarotid amobarbital procedure (IAP or "Wada test") is a rare complication. After an unusually high rate of recent anesthetization failures, we sought to determine the frequency of reduced anesthetization and any common factors underlying these failures. We reviewed the records of all patients who underwent IAP tests through the UCLA Seizure Disorder Center between September 1999 and May 2002. Age, date, epileptogenic focus, radiologist, and current medications were all considered. Of a total of 56 patients who underwent our intracarotid amobarbital examination, 11 (19.6%) showed either very rapid recovery (<or=1 min) or anesthetization failure. Of these, 10 (91%) of 11 were taking a medication with some carbonic anhydrase-inhibiting (CAI) properties (topiramate (TPM), n=7; zonisamide (ZNS), n=2; hydrochlorothiazide and furosemide, n=1 each). The only patient of 40 (2.5%) who was not taking any CAI drugs and showed an early IAP recovery (55 s) had recently discontinued TPM. IAPs performed on patients after weaning from TPM showed a correlation between length of drug discontinuation and duration of anesthesia effect. Our data strongly suggest that recent failures of anesthetization during the IAP are associated with a possible interaction between amobarbital and medications possessing CAI properties. We suggest that the IAP be performed only after >/=8 weeks after discontinuation of such medications.

Atypical language cortex in the left temporal lobe

The intracarotid amobarbital procedure (IAP) is widely used in the preoperative evaluation for epilepsy surgery to lateralize language dominance and memory functions. However, language mapping has most often been accomplished with cortical brain stimulation. To examine left temporal lobe language cortex representation using this technique in patients with bilateral language (BL) as compared with patients with left language dominance (LD). The language maps of each patient were reviewed retrospectively. Group I consisted of 10 patients with BL and Group II consisted of 10 matched control patients with LD. Each stimulation trial included a brief assessment of confrontation naming, automatic speech, reading, repetition, and comprehension. Clusters of errors that included comprehension, repetition, and naming defined primary temporal lobe language areas. Mapping revealed two distinct language areas in 60% of patients in Group I and 10% in Group II (p = 0.019). In Group I, two patients had both language areas in the same gyrus (either the superior or the middle temporal gyrus), whereas two showed one language area each in the superior and middle temporal gyri and the remaining two had one in the superior temporal gyrus and the other intermixed between the superior and middle temporal gyri. In Group II, both language areas were intermixed between the superior and middle temporal gyri. Bilateral language (BL) representation in the intracarotid amobarbital procedure is frequently associated with more than one noncontiguous language area in the left temporal lobe. A careful search for multiple language areas, particularly in patients with BL, is prudent prior to surgical resection.

Probabilistic map of blood flow distribution in the brain from the internal carotid artery

Brain single photon emission computed tomographic (SPECT) images acquired after injecting Tc-99m-HMPAO into the internal carotid artery (ICA) during an intracarotid amobarbital procedure (IAP SPECT) provide anatomical information on the blood flow distribution from the ICA. In this study, probabilistic maps of the distribution of blood supply from the ICA were developed using the IAP SPECT images. Twenty-two sets of basal and IAP SPECT were collected from an existing database. IAP SPECT images were coregistered to basal SPECT images, and spatial normalization parameters used for basal SPECT images were reapplied to IAP SPECT for anatomical standardization. Pixel counts of IAP SPECT images were then normalized, and the probabilistic map of cerebral perfusion distribution (perfusion probabilistic map) for each hemisphere was determined by averaging the spatial/count-normalized IAP SPECT images. Population-based probabilistic maps representing the extent of ICA territory (extent probabilistic map) were also composed by averaging the binary images obtained by thresholding the spatially normalized IAP SPECT images. The probabilistic maps were used to quantify cerebral perfusion and reserve change after arterial bypass surgery in 10 patients with ICA stenosis. In the probabilistic maps, blood supply from the ICA was found to be most likely in the dorsolateral frontal lobe, the anterosuperior portion of the temporal lobe, and in the frontoparietal area. Of the subcortical regions, the striatum was found to be most likely to derive its blood supply from ICA. In patients with cerebral occlusive disease, improvements in basal perfusion and perfusion reserve in the bypass-grafted ICA territory were well identified and were increased by 6.2% and 4.6%, respectively, on average. The probabilistic maps developed in this study illustrate the perfusion distribution and extent of vascular territory for ICA and would be useful for objective evaluations of perfusion status in cerebrovascular disease.

Contralateral Cerebral Blood Flow Velocity Changes after Intracarotid Amobarbital Injection

The intracarotid amobarbital procedure (IAP) leads to a prompt decrease in ipsilateral middle cerebral artery (MCA) mean blood flow velocity (MFV). Little is known about contralateral MFV changes. The authors investigated bilateral MCA MFV using transcranial Doppler sonography (TCD) in 8 patients with epilepsy undergoing IAP. Measurements were excluded from analysis if angiography revealed any signs of interhemispheric cross-flow. With in 64 seconds after amobarbital injection, ipsilateral MFV decreased to a mean of 44.4% +/- 7.5% of baseline value (P < .01). In the absence of interhemispheric cross-flow and within 68 seconds, contralateral MFV decreased to 83.1% +/- 7.9% (P < .01). The observed decrease of contralateral MFV was not caused by amobarbital cross-perfusion. A possible underlying mechanism may be interhemispheric deafferentation.

Contralateral Cerebral Blood Flow Velocity Changes after Intracarotid Amobarbital Injection

ABSTRACT Background and Purpose. The intracarotid amobarbital procedure (IAP) leads to a prompt decrease in ipsilateral middle cere bral artery (MCA) mean blood flow velocity (MFV). Little is known about contralateral MFV changes. Methods. The authors investigated bilateral MCA MFV using transcranial Doppler sonography (TCD) in 8 patients with epilepsy undergoing IAP. Measurements were excluded from analysis if angiography revealed any signs of interhemispheric cross‐flow. Results. With in 64 seconds after amobarbital injection, ipsilateral MFV decreased to a mean of 44.4%± 7.5% of baseline value (P &lt; .01). In the absence of interhemispheric cross‐flow and within 68 seconds, contralateral MFV decreased to 83.1%± 7.9% (P &lt; .01). Conclusions. The observed decrease of contralateral MFV was not caused by amobarbital cross‐perfusion. A possible underlying mechanism may be interhemispheric deafferentation.

Under which Condition can fMRI Replace the Intracarotid Amobarbital Procedure (IAP) for Presurgical Language Lateralization?

Introduction: There is a large body of evidence showing that functional magnetic resonance imaging (fMRI) is able to lateralize cortical language representations. Across activation protocols, many studies show good congruence of fMRI-based language lateralization with the gold standard, IAP. However, in up to 25% of patients, fMRI and IAP are discordant. This can be due to a variety of factors. Hence, we developed a simple algorithm that identifies individuals with one strongly dominant hemisphere in whom fMRI can actually replace IAP for language lateralization. Patients and Methods: Forty-five patients with pharmacoresistant epilepsy and suspected atypical language dominance received presurgical language lateralization by fMRI and IAP. For fMRI, we used a semantic-perceptual contrast designed to activate frontal as well as parieto-temporal language areas. It provides an active control condition as well as a continuous performance control. IAP was performed unilaterally on the side of intended surgery. Results: The algorithm: 1) exclusion of patients with possibly BOLD-interfering lesions (n=8); 2) exclusion of patients with non-compliance or protocol atypical activation patterns (n=1); 3) identification of unilateral language dominance across both frontal and parieto-temporal activations according to protocol adjusted volumes of interest and lateralization indices resulted in complete congruence and therefore redundance of fMRI and IAP in 16 of 45 patients. Extrapolating lateralization index thresholds for unilateral language dominance defined in this highly selected group of patients to all epilepsy surgery patients who received language fMRI in Bonn between 2000 and 2002 (n=203) indicates that about two-thirds of IAPs are redundant. Discussion: Without exclusion of interfering factors, fMRI-based language lateralization is error-prone and replacement of IAP by fMRI not recommendable. With the proposed algorithm, however, fMRI is a valuable tool in routine presurgical language lateralization.

Can the Wada test evaluate mesial temporal function? A SPECT study.

To assess the value of SPECT during intracarotid amobarbital procedure (IAP) to discriminate which patients performed the test with the hippocampus inactivated and correlate it with the risk of amnesia after anterior temporal lobectomy (ATL). The authors studied 40 consecutive patients undergoing ATL for refractory epilepsy. SPECT was performed after IV injection of 99mTc-HMPAO during the IAP (IAP-SPECT). Interictal SPECT and IAP-SPECT were realigned to obtain the perfusion change percentage (PCP), allowing a quantitative measurement. Wechsler Memory Scale Revised (WMS-R) before and during the first year of follow-up was used to assess memory impairment after surgery. A decrease between 10 and 12% of the mean PCP values was observed in the frontal, parietal, and lateral temporal lobes of the injected side and in the contralateral cerebellum. However, no significant PCP changes were observed in the occipital or mesial temporal lobes. Thirty-eight passed the memory evaluation of the IAP and in 6 of those 38 patients a decline in memory was demonstrated 1 year after ATL. However, high preoperative neuropsychological score (in two patients) and IAP asymmetry scores (in other three patients) predicted postoperative memory risk in five of these six patients. Fourteen of the 38 patients (40%) had hypoperfusion of the hippocampus during the IAP-SPECT (i.e., the hippocampus was inactivated) and only 1 of these 14 patients (2.5%) developed memory impairment after temporal lobectomy. On the other hand, 5 of the 24 patients (13%) who had a functional hippocampus on IAP-SPECT developed memory impairment. The results suggest that the combination of SPECT, intracarotid amobarbital procedure, and neuropsychological testing predicted risk for all patients who had postoperative memory decline, indicating that risk prediction should be based on multiple factors. IAP-SPECT results demonstrated that the hippocampus is not inactivated in over 60% of patients and that the lack of accuracy of the IAP alone in predicting the risk of amnesia is probably related to an insufficient inactivation of the ipsilateral hippocampus during the test.

Determination of language dominance with near-infrared spectroscopy: comparison with the intracarotid amobarbital procedure

Purpose: To determine the efficacy of near-infrared spectroscopy (NIRS) in identifying the hemisphere associated with language by measuring changes in bilateral lateral inferior frontal blood flow during a word generation task in epilepsy surgery patients and healthy volunteers. Methods: Sixteen patients who underwent the intracarotid amobarbital procedure (IAP) and eight healthy right-handed/right-footed individuals were tested with NIRS during a word generation paradigm. Results: Increases in lateral inferior frontal total hemoglobin concentrations agreed with the IAP in 11 of 16 patients, including 2 of 3 with right hemisphere (atypical) speech dominance ( P=0.13). NIRS revealed increases in lateral inferior frontal total hemoglobin concentrations congruent with language dominance predicted by handedness/footedness in 18 of 24 subjects, including 100% of healthy right-handed subjects ( P=0.02). Conclusion: NIRS is a simple, non-invasive, safe modality for measuring cerebral blood flow. Further research and development of testing procedures and instrumentation are needed before routine implementation in pre-surgical testing.

Clinical and neuropsychological characteristics of pediatric epilepsy patients with atypical language dominance

Studies on intracarotid amobarbital procedures (IAP) in pediatric patients are rare and mainly focus on practicability aspects. Very few studies have reported characteristics of children with atypical language dominance. We compared children with left-sided focal epilepsy and atypical (i.e., right or bilateral) versus left-sided language representation ( n=12 versus 17). Our results indicate a higher incidence of left handedness, extratemporal lesions, an earlier onset of epilepsy, and a neuropsychological “crowding effect” with distinct nonverbal memory deficits in the atypical group. We conclude that atypical language representation in children with left-sided epilepsy is associated with similar characteristics as in adults. It is recommended that the possibility of a language shift in the presurgical workup of pediatric patients be considered, particularly if a left-hemispheric epileptic focus is suspected.

Temporal lobe epilepsy: analysis of patients with dual pathology.

To determine the frequency and types of dual pathology in patients with temporal lobe epilepsy (TLE) and to analyze the clinical manifestations and surgical outcome. A total of 240 patients with TLE underwent temporal resections following a comprehensive pre-surgical evaluation. Thirty-seven (15.4%) of these had hippocampal sclerosis (HS) or temporal lobe gliosis in association with another lesion (dual pathology). Eighteen of 37 patients with dual pathology had heterotopia of the temporal lobe, nine had cortical dysplasia, four had cavernous angiomas or arteriovenous malformations, one had a dysembryoplastic neuroepithelial tumor, one had a contusion and four patients had cerebral infarctions in childhood. 68.5% had abnormal head magnetic resonance imagings, 91.3% had abnormal positron emission tomography scans, and 96% had abnormal ictal SPECT. The intracarotid amobarbital procedure (IAP) showed impaired memory of the epileptogenic side in 72% of the patients. Twenty patients had left and 17 had right-sided en bloc temporal resections, including the lesion and mesial temporal structures. Twenty-six (70.2%) became seizure-free, eight (21.6%) had rare seizures, two (5.4%) had worthwhile seizure reduction and one (2.7%) had no improvement (range of follow-up 1-16 years, mean = 7.4 years). 15.4% had dual pathology. The dual pathology was almost exclusively seen in patients whose lesions were congenital, or occurred early in life, suggesting that the hippocampus is more vulnerable and more readily develops HS in early childhood. Resections, including the lateral and mesial temporal structures led to a favorable outcome with no mortality and little morbidity.

Predicting verbal memory decline following anterior temporal lobectomy (ATL).

To develop a multivariate risk factor model for predicting postoperative verbal memory decline in an individual patient following dominant or nondominant anterior temporal lobectomy (ATL). The authors studied 132 consecutive ATL patients who 1). were older than 16 years at surgery, 2). had estimated preoperative Full Scale IQ score of >69, 3) had unilateral language dominance based on the intracarotid amobarbital procedure (IAP), and 4) underwent neuropsychological testing at baseline and >or=6 months postoperatively (mean 1.2 years). Five potential risk factors for postoperative verbal memory decline were selected a priori that reflect the functional adequacy of the to-be-resected temporal lobe. These were 1). resection in the dominant hemisphere, 2). MRI findings other than exclusively unilateral mesial temporal sclerosis, intact preoperative 3). immediate and 4). delayed verbal memory function, and 5). intact IAP memory performance following injection contralateral to the seizure focus. Verbal memory decline was defined using two verbal memory tests and published reliable change indices. Thirty-eight percent of the sample declined reliably on one or both verbal memory measures. Logistic regression analysis demonstrated that all five risk factors were significantly and independently associated with outcome, with side of surgery having the strongest association (p < 0.0001) and preoperative immediate verbal memory the weakest (p < 0.05). An individual patient's risk for postoperative verbal memory decline following dominant or nondominant ATL can be predicted using clinical data routinely available preoperatively (side of surgery, qualitative MRI, baseline memory testing, IAP performance). This information may be useful for preoperative patient counseling.