Intracarotid amobarbital procedure: II. Lateralizing value in evaluation for temporal lobectomy

Presurgical Functional Cortical Mapping Using Electromagnetic Source Imaging

Preoperative localization of functionally eloquent cortex (functional cortical mapping) is common clinical practice in order to avoid or reduce postoperative morbidity. This review aims at providing a general overview of magnetoencephalography (MEG) and high-density electroencephalography (hdEEG) based methods and their clinical role as compared to common alternatives for functional cortical mapping of (1) verbal language function, (2) sensorimotor cortex, (3) memory, (4) visual, and (5) auditory cortex. We highlight strengths, weaknesses and limitations of these functional cortical mapping modalities based on findings in the recent literature. We also compare their performance relative to other non-invasive functional cortical mapping methods, such as functional Magnetic Resonance Imaging (fMRI), Transcranial Magnetic Stimulation (TMS), and to invasive methods like the intracarotid Amobarbital Test (WADA-Test) or intracranial investigations.

Anterior temporal lobectomy with amygdalohippocampectomy for mesial temporal sclerosis: predictors of long-term seizure control

Object

In this paper the authors' goal was to identify preoperative variables that predict long-term seizure freedom among patients with mesial temporal sclerosis (MTS) after single-stage anterior temporal lobectomy and amygdalohippocampectomy (ATL-AH).

Methods

The authors retrospectively reviewed 116 consecutive patients (66 females, mean age at surgery 40.7 years) with refractory seizures and pathologically confirmed MTS who underwent ATL-AH with at least 2 years of follow-up. All patients underwent preoperative MRI and video-electroencephalography (EEG); 106 patients (91.4%) underwent Wada testing and 107 patients (92.2%) had neuropsychological evaluations. The authors assessed the concordance of these 4 studies (defined as test consistent with the side of eventual surgery) and analyzed the impact of preoperative variables on seizure freedom.

Results

The median follow-up after surgery was 6.7 years (mean 6.9 years). Overall, 103 patients (89%) were seizure free, and 109 patients (94%) had Engel Class I or II outcome. Concordant findings were highest for video-EEG (100%), PET (100%), MRI (99.0%), and Wada testing (90.4%) and lowest for SPECT (84.6%) and neuropsychological testing (82.5%). Using binary logistic regression analysis (seizure free or not) and Cox proportional hazard analysis (seizure-free survival), less disparity in the Wada memory scores between the ipsilateral and contralateral sides was associated with persistent seizures.

Conclusions

Seizure freedom of nearly 90% can be achieved with ATL-AH in properly selected patients with MTS and concordant preoperative studies. The low number of poor outcomes and exclusion of multistage patients limit the statistical power to determine preoperative variables that predict failure. Strong Wada memory lateralization was associated with excellent long-term outcome and adds important localization information to structural and neurophysiological data in predicting outcome after ATL-AH for MTS.

A decisional space for fMRI pattern separation using the principal component analysis--a comparative study of language networks in pediatric epilepsy

Atypical functional magnetic resonance imaging (fMRI) language patterns may be identified by visual inspection or by region of interest (ROI)-based laterality indices (LI) but are constrained by a priori assumptions. We compared a data-driven novel application of principal component analysis (PCA) to conventional methods. We studied 122 fMRI data sets from control and localization-related epilepsy patients provided by five children's hospitals. Each subject performed an auditory description decision task. The data sets, acquired with different scanners but similar acquisition parameters, were processed through fMRIB software library to obtain 3D activation maps in standard space. A PCA analysis was applied to generate the decisional space and the data cluster into three distinct activation patterns. The classified activation maps were interpreted by (1) blinded reader rating based on predefined language patterns and (2) by language area ROI-based LI (i.e., fixed threshold vs. bootstrap approaches). The different classification results were compared through κ inter-rater agreement statistics. The unique decisional space classified activation maps into three clusters (a) lower intensity typical language representation, (b) higher intensity typical, as well as (c) higher intensity atypical representation. Inter-rater agreements among the three raters were excellent (Fleiss κ = 0.85, P = 0.05). There was substantial to excellent agreement between the conventional visual rating and LI methods (κ = 0.69-0.82, P = 0.05). The PCA-based method yielded excellent agreement with conventional methods (κ = 0.82, P = 0.05). The automated and data-driven PCA decisional space segregates language-related activation patterns in excellent agreement with current clinical rating and ROI-based methods.

Metabolic evidence for episodic memory plasticity in the nonepileptic temporal lobe of patients with mesial temporal epilepsy

PURPOSE

Metabolic changes have been described in the nonepileptic temporal lobe of patients with unilateral mesiotemporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS). To better understand the functional correlate of this metabolic finding, we have sought to characterize brain regions in patients with MTLE that show correlation between unilateral episodic memory performances, as assessed by intracarotid amobarbital test (IAT), and interictal regional cerebral metabolism measured by [(18) F]-fluorodeoxyglucose positron emission tomography (FDG-PET).

METHODS

Resting FDG-PET was performed interictally in 26 patients with unilateral MTLE caused by HS (16 female, mean age: 36 years; 16 left HS). Using statistical parametric mapping (SPM8), we performed a group comparison analysis comparing brain metabolism in the patients and in 54 adult controls (27 female, mean age: 32 years), with FDG-PET data of right HS patients being flipped. IAT scores of nonepileptic hemisphere functions (amobarbital injection ipsilateral to HS) were used as covariates of interest in a correlation analysis with regional brain metabolism.

KEY FINDINGS

The group comparison analysis revealed significant hypometabolic areas in a widespread temporofrontal network ipsilateral to HS. In addition, a significant increase in metabolism was found in mesial and lateral temporal regions contralateral to HS. Significant positive correlations were found between IAT scores of nonepileptic hemisphere functions and mesial temporal metabolism in this hemisphere.

SIGNIFICANCE

This study demonstrates the existence of significant increase in relative regional cerebral glucose metabolism in mesial and lateral temporal regions contralateral to the epileptic focus in patients with unilateral MTLE associated with HS. The positive correlation in these brain regions between IAT scores and metabolism supports the role of disease-induced plasticity mechanisms contralateral to HS in the preservation of episodic memory processes.

Sub-patterns of language network reorganization in pediatric localization related epilepsy: a multisite study

To study the neural networks reorganization in pediatric epilepsy, a consortium of imaging centers was established to collect functional imaging data. Common paradigms and similar acquisition parameters were used. We studied 122 children (64 control and 58 LRE patients) across five sites using EPI BOLD fMRI and an auditory description decision task. After normalization to the MNI atlas, activation maps generated by FSL were separated into three sub-groups using a distance method in the principal component analysis (PCA)-based decisional space. Three activation patterns were identified: (1) the typical distributed network expected for task in left inferior frontal gyrus (Broca's) and along left superior temporal gyrus (Wernicke's) (60 controls, 35 patients); (2) a variant left dominant pattern with greater activation in IFG, mesial left frontal lobe, and right cerebellum (three controls, 15 patients); and (3) activation in the right counterparts of the first pattern in Broca's area (one control, eight patients). Patients were over represented in Groups 2 and 3 (P < 0.0004). There were no scanner (P = 0.4) or site effects (P = 0.6). Our data-driven method for fMRI activation pattern separation is independent of a priori notions and bias inherent in region of interest and visual analyses. In addition to the anticipated atypical right dominant activation pattern, a sub-pattern was identified that involved intensity and extent differences of activation within the distributed left hemisphere language processing network. These findings suggest a different, perhaps less efficient, cognitive strategy for LRE group to perform the task.

Intracarotid amobarbital procedure for epilepsy surgery

The intracarotid amobarbital procedure (IAP) has been used for more than half a century to determine language dominance and to assess risk for amnesia after anterior temporal lobectomy. However, because of the risk associated with angiography and the development of noninvasive techniques, the need for the IAP when evaluating patients for epilepsy surgery can now be questioned. The purpose of this review is to examine the clinical indications and efficacy of the Wada test in the preoperative evaluation of epilepsy surgery candidates. This article summarizes a debate that took place during the 2009 American Epilepsy Society (AES) annual course.

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.

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.

Selective Posterior Cerebral Artery Amobarbital Test: Its Role in Presurgical Memory Assessment in Temporal Lobe Epilepsy

PURPOSE

To evaluate the efficacy and risk of complications of selective posterior cerebral artery (PCA) amobarbital anesthesia in memory assessment of patients with epilepsy under consideration for temporal lobe resection.

METHODS

Thirty-two candidates for temporal lobectomy in whom conclusive memory assessment could not be obtained by the standard intracarotid amobarbital procedure were submitted to a selective PCA amobarbital test. A mean dose of 75 mg amobarbital was injected via microcatheter into the P2 segment of the PCA. Ten common objects were presented for naming and remembering while the anesthesia was judged efficient. After return to neurologic baseline, recall and recognition memory were assessed.

RESULTS

In all of the 32 patients, angiography and PCA anesthesia were successfully accomplished without serious adverse events. All but one of the patients remained alert and cooperative for memory testing under the anesthesia, and 28 of these patients showed adequate memory capacity of the hemisphere contralateral to the side targeted for surgery. So far, 19 patients have proceeded to surgery, and no case of global amnesia or serious, material-specific memory impairment has resulted. Three patients failed the PCA test (fewer than 67% items correctly recognized) and were excluded from surgery, partly on the basis of the PCA test results, but also supported by an overall evaluation of all the diagnostic procedures used.

CONCLUSIONS

The selective PCA amobarbital test appears justifiable when performed by interventional neuroradiologists and may significantly reduce the risk of erroneously excluding patients with epilepsy from temporal resection. Further corroboration of the safety of the procedure seems warranted.

Presurgical assessment of memory-related brain structures: the Wada test and functional neuroimaging

Medial temporal lobe structures are known to play a major role in memory processing. Recent work has revealed that extratemporal structures (e.g. the frontal lobe and thalamus) may also be important in memory function. In candidates for epilepsy surgery, particularly in those with temporal lobe seizures, presurgical evaluation of memory function is essential, since seizures may originate in the neural substrate that is critical for memory. In this article, we review the tools used for presurgical evaluation and their contribution to the understanding of memory function, focusing on the Wada test, [18F]fluorodeoxy-glucose positron emission tomography ([18F]FDG-PET) and functional magnetic resonance imaging (fMRI). We also explore perspectives on future studies that may elucidate the role of the temporal and extratemporal structures in memory function and the mechanisms of cerebral plasticity.

Wada memory performance predicts seizure outcome after epilepsy surgery in children

PURPOSE

Wada memory asymmetries were examined in children from four comprehensive epilepsy surgery centers who subsequently underwent epilepsy surgery to determine whether Wada memory performance could predict degree of seizure relief in children.

METHODS

One hundred fifty-six children (between ages 5 and 16 years) with intractable epilepsy underwent Wada testing before resective epilepsy surgery (93 within the left hemisphere, and 63 within the right hemisphere). Memory stimuli were presented soon after intracarotid amobarbital injection, and recognition memory for the items was assessed after return to neurologic baseline. Eighty-eight children underwent unilateral temporal lobe resection, and 68 had extratemporal lobe resections. One hundred four (67%) children were seizure free (Engel class I), and 52 (33%) were not seizure free (Engel classes II-IV) at follow-up (mean follow-up interval, 2.3 years).

RESULTS

Seizure-free children recalled 19.3% more Wada memory items after ipsilateral injection than did non-seizure-free children (p = 0.008). If analysis was restricted to youngsters with temporal lobectomies (TLs), seizure-free children recalled 27.7% more items after ipsilateral injection than did non-seizure-free TL children (p = 0.004). With regard to individual patient prediction, 75% of children who had memory score asymmetries consistent with the seizure focus were seizure free. In contrast, only 56% of children whose memory score asymmetries were inconsistent with the seizure focus were seizure free (p = 0.01).

CONCLUSIONS

Results suggest that Wada memory performance asymmetries are related to the degree of seizure relief after epilepsy surgery in children and adolescents.

Neuropsychiatric and memory issues in epilepsy

Epilepsy is an extremely complex disorder characterized by marked variability in clinical presentation, etiology, diagnostic certainty, and therapeutic options. Neuropsychiatric and cognitive concomitant disorders are equally diverse and complex. Depression and anxiety, for example, may be preexisting conditions, occur only in peri-ictal or ictal states, or persist as constant interictal phenomena; both place additional burden on memory functions, which are further taxed by the effects of recurrent seizures, temporal lobe insult, and antiseizure medications. Such factors present considerable clinical challenges, particularly in outpatient settings. This article provides an overview of major psychiatric features of epilepsy and of issues regarding the nature of memory deficits in this neurologic population. The importance of identifying and treating potentially reversible causes of memory impairment and related forms of cognitive impairment is emphasized.

Lateralising value of neuropsychological protocols for presurgical assessment of temporal lobe epilepsy

PURPOSE

To estimate the value of neuropsychological measurements in determining the side of seizure onset for presurgical assessment in patients with temporal lobe epilepsy. The lateralising value of neuropsychological protocols was evaluated for all patients and in subpopulations depending on surgical outcome with regard to seizure control, speech dominance, neuropathology, and need for intracranial EEG recordings.

METHODS

A battery of neuropsychological procedures was carried out preoperatively in 125 patients who underwent left (n = 66) or right (n = 59) temporal lobectomies. Binary logistic regression analysis was performed to find sets of variables that allowed the best prediction of the side of seizure onset (assumed to be the operated-on side).

RESULTS

Combinations of noninvasive neuropsychological tests and Wada subscores showed the highest lateralising values: 80.8% for all patients, 79.4% in seizure-free patients, 86.0% in patients not rendered seizure free, 85.7% in left speech patients, 77.8% in non-left speech patients, 89.3% in patients with mesial temporal sclerosis (MTS), 78.1% in non-MTS patients, 80.3% in patients who underwent intracranial EEG recordings, and 77.3% in those who did not.

CONCLUSIONS

The lateralising value (80-90%) of neuropsychological protocols appears similar to that of other tests widely accepted for lateralisation (ictal and interictal scalp EEG and neuroimaging). Attention should be paid to neuropsychological results, particularly from the Wada test, during presurgical assessment of temporal lobe epilepsy, as they can provide strong support for findings from other lateralising tests, particularly in patients with presumed MTS or in left-speech patients.

Effect of Wada methodology in predicting lateralized memory impairment in pediatric epilepsy surgery candidates

Because Wada evaluations are not standardized, it is impossible to know to what degree method variance accounts for reported differences in results. To examine this problem, three comprehensive epilepsy surgery centers compared the efficacy of two Wada memory methods to predict seizure onset laterality in 152 children being considered for epilepsy surgery. Wada memory asymmetries were evaluated using either real objects with no verbal response required or more mixed stimuli requiring a verbal response. When using real objects, Wada memory performance was significantly worse when relying on the side of seizure onset in both left and right seizure onset children. In contrast, Wada memory performance using mixed stimuli was worse on the side of seizure onset only among patients with seizures originating in the left-hemisphere. The superiority of real objects was most apparent in younger children with left side seizure onset. Results suggest the use of mixed stimuli is less sensitive to the effects of unilateral seizure onset, and thus, diminishes the capacity of the Wada test to predict lateralized seizure onset in children.

Prediction of seizure-onset laterality by using Wada memory asymmetries in pediatric epilepsy surgery candidates

PURPOSE

Because the capacity of intracarotid amobarbital (Wada) memory assessment to predict seizure-onset laterality in children has not been thoroughly investigated, three comprehensive epilepsy surgery centers pooled their data and examined Wada memory asymmetries to predict side of seizure onset in children being considered for epilepsy surgery.

METHODS

One hundred fifty-two children with intractable epilepsy underwent Wada testing. Although the type and number of memory stimuli and methods varied at each institution, all children were presented with six to 10 items soon after amobarbital injection. After return to neurologic baseline, recognition memory for the stimuli was assessed. Seizure onset was determined by simultaneous video-EEG recordings of multiple seizures.

RESULTS

In children with unilateral temporal lobe seizures (n = 87), Wada memory asymmetries accurately predicted seizure laterality to a statistically significant degree. Wada memory asymmetries also correctly predicted side of seizure onset in children with extra-temporal lobe seizures (n = 65). Although individual patient prediction accuracy was statistically significant in temporal lobe cases, onset laterality was incorrectly predicted in < or =52% of children with left temporal lobe seizure onset, depending on the methods and asymmetry criterion used. There also were significant differences between Wada prediction accuracy across the three epilepsy centers.

CONCLUSIONS

Results suggest that Wada memory assessment is useful in predicting side of seizure onset in many children. However, Wada memory asymmetries should be interpreted more cautiously in children than in adults.

Bilateral Memory Dysfunction in Epilepsy Surgery Candidates Detected by the Intracarotid Amobarbital Procedure (Wada Memory Test)

The intracarotid amobarbital procedure (IAP) is widely used in the evaluation of candidates for resective epilepsy surgery, in part to identify patients at risk for postoperative amnesia. Yet there is no widely accepted standardized protocol, and there is a paucity of quantitative data to assess the factors associated with poor IAP performance. This report summarizes our findings on 110 patients with intractable focal epilepsy who underwent IAP testing at our center. Ipsilateral IAP scores for patients with left-sided seizure foci were significantly lower than those for patients with right-sided seizure foci. Falsely and poorly lateralizing scores were also significantly more common in subjects with left-sided seizure onsets. Twenty-four percent of subjects failed the IAP bilaterally, and patients who failed the IAP bilaterally had significantly lower scores on neuropsychologic measures. There was no difference between patients who passed and failed in the location, etiology, duration, or age of onset of epilepsy. We conclude that bilateral memory dysfunction is common in patients with intractable partial epilepsy. Whether memory dysfunction detected by IAP testing as performed at our center is predictive of functionally limiting postoperative amnesia remains to be determined.

Focal functional deficits in temporal lobe epilepsy on PET scans and the intracarotid amobarbital procedure: comparison of patients with unitemporal epilepsy with those requiring intracranial recordings

PURPOSE

To analyze the relationship between the intracarotid amobarbital procedure (IAP) and positron emission tomography (PET) and study the lateralizing value of these tests in patients with unitemporal epilepsy and those requiring intracranial recordings.

METHODS

We compared 51 patients with unitemporal epilepsy (group1) with 26 patients in whom surface recordings failed to reveal a distinct unitemporal focus, necessitating invasive recordings (group 2).

RESULTS

The brain magnetic resonance imaging (MRI) scans for group 1 showed mesial temporal sclerosis in 70.5% of the patients. PET showed unilateral temporal hypometabolism in 88%. In addition, 74.5% of the patients in group 1 had impaired memory on the epileptogenic side on the IAP, and 89.4% of those patients also had ipsilateral temporal hypometabolism on PET scans. All the group 1 patients underwent temporal resections. The pathologic examination showed hippocampal sclerosis in 72% of the patients. Eighty percent of group 1 patients became seizure free, and 16% had rare seizures (follow-up, 2-7 years). MRIs for group 2 showed mesial temporal sclerosis in 31% of the patients; PET scans showed temporal hypometabolism in 39%. The IAP was lateralized in 47.8%. Sixty-nine percent had temporal lobe resections. The pathologic examination showed hippocampal sclerosis in 44% of the patients. Forty-four percent of group 2 patients became seizure free, and 27.7% had rare seizures (follow-up, 2-8 years).

CONCLUSIONS

Ninety-six percent of the patients with unitemporal foci had focal functional deficits on the epileptogenic side on 18-fluorodeoxyglucose-(FDG) PET scans, the IAP, or both. The results of the FDG-PET were predictive of impaired memory on the IAP. Memory impairment contralateral to the temporal hypometabolism found on the PET scans was never seen. These patients had an excellent outcome. In contrast, <50% of the patients requiring intracranial recordings had focal functional deficits, suggesting that more a diffuse pathology may account for their less favorable outcome.

Does the intracarotid amobarbital procedure predict global amnesia after temporal lobectomy?

PURPOSE

The intracarotid amobarbital procedure (IAP) is widely used to help predict who might be at risk for postoperative amnesia after unilateral temporal lobectomy for intractable seizures. We describe the memory outcome in 10 patients who underwent standard temporal lobectomy, including mesial temporal structures, despite failing the memory portion of the IAP after injections both ipsilateral and contralateral to the resected seizure focus.

METHODS

Data for seven of the study subjects were obtained through a retrospective review of patients assessed on a surgical epilepsy unit during a 15-year period who failed the Montreal Neurological Institute IAP memory protocol after both ipsilateral and contralateral injections and subsequently underwent unilateral temporal lobectomy. More recently, we have studied temporal lobectomy patients who failed the Medical College of Georgia memory protocol after both ipsilateral and contralateral injections (n = 3). Preoperative and postoperative memory test scores were compared, and data regarding seizure outcome and self-perception of postoperative memory were collected.

RESULTS

At follow-up, none of the patients presented with a pattern indicative of a global amnesia, and 80% demonstrated >90% improvement in their seizure disorder or were seizure-free.

CONCLUSIONS

These findings indicate that bilateral memory failure on the IAP does not preclude the removal of an epileptogenic temporal lobe or a successful surgical outcome. In addition, the findings raise questions regarding the validity of the IAP and the possibility that memory may be reorganized in patients with a long history of temporal lobe epilepsy.

The wada test: prediction of focus lateralization by asymmetric and symmetric recall

PURPOSE

The intracarotid amytal test is commonly used as a predictor of memory dysfunctioning after anterior temporal lobe resection (ATL) for intractable epilepsy. Asymmetry in memory scores can provide focus lateralizing information. In this study the predictive value of a set of Wada test parameters was analyzed, including patients with symmetrical memory scores.

METHODS

The Wada test was carried out in 226 patients undergoing ATL (94 L, 132 R). Data were collected on item recognition (five items), story recall, amytal dose, presentation time, EEG and arterial filling of amytal. A logistic regression analysis was performed on these data in order to find a set of variables which could best predict the side of seizure onset.

RESULTS

The analysis yielded four variables, i.e. both memory scores, story recall after right-sided injection and presentation time of stimuli after left-sided injection which could correctly predict seizure lateralization in 85% of the cases. Misclassification was lower for right foci than for left foci. Seizure outcome was four times more favourable in the correctly classified patients.

CONCLUSIONS

The results suggest that prediction of focus lateralization in temporal lobe epilepsy can be fairly exact even if left/right memory scores are equal. Performing the Wada test with only five memory items keeps the time window of active amytal short enough and gives accurate information about contralateral temporal lobe functioning. The classification scheme can be useful in predicting a lowered chance of seizure freedom.

Risk factors for unsuccessful testing during the intracarotid amobarbital procedure in preadolescent children

PURPOSE

Identification of risk factors for unsuccessful testing during intracarotid amobarbital procedure (IAP) in preadolescent children.

METHODS

A pediatric IAP protocol was attempted in 42 candidates for epilepsy surgery (5-12 years old; mean, 10 years) based on the ability to pass a practice test. Language dominance was defined by marked asymmetry until first verbal response and paraphasic errors. Intact hemispheric memory was defined by recall of >/=60% of test items. The odds ratios of baseline variables (age at IAP, Full-Scale IQ, side of disease, age at seizure onset, amobarbital dose) were calculated for various IAP outcomes.

RESULTS

IAPs were accomplished in 40 children. Language dominance was established in 25 (62.5%) of 40 patients: all 21 focal resection candidates were left language dominant; four hemispherectomy candidates had intact language after injection of the damaged hemisphere. In 12 (30%) of 40 patients, language testing failed because of agitation or obtundation. Compared with the 21 children with language dominance established by bilateral IAP, these 12 children had lower mean Full-Scale IQ (66.4 vs. 87.9; p = 0.014), and more frequently, the epileptogenic lesion in the left hemisphere (presumed dominant by right-handedness; 78 vs. 33%; p = 0.04). Excluding hemispherectomy candidates (intentionally only one injection), memory testing could not be completed in 13 (36%) of 36 children because of obtundation or agitation. These children were significantly younger than the 23 (64%) of 36 with successful bilateral memory testing (mean age, 107.6 vs. 128.7 months; p = 0. 006). The eight (25%) of 32 children with failing retention scores after ipsilateral injection had lower Full-Scale IQ than did the 24 (75%) patients who passed (mean, 59.6 vs. 81.7 months; p = 0.03).

CONCLUSIONS

The IAP successfully established hemispheric language dominance and memory representation for just under two thirds of the preselected preadolescent children. Risk factors for unsuccessful testing included low Full-Scale IQ (especially <80), young age (especially <10 years), and seizures arising from the left hemisphere presumed dominant by right-handedness.

Beyond speech lateralization: a review of the variability, reliability, and validity of the intracarotid amobarbital procedure and its nonlanguage uses in epilepsy surgery candidates

While the intracarotid amobarbital procedure (IAP) was originally utilized to lateralize speech functions as an aid in the surgical treatment of epilepsy, additional uses for the IAP have emerged including: (1) the use of the IAP to predict post-surgical memory changes, including both global amnesia and smaller, yet significant, material-specific memory deficits; (2) the use of the IAP to provide confirmatory evidence of lateralization of seizure focus; and (3) the use of the IAP to predict post-surgical relief from seizures. While the literature on the IAP is extensive and growing, its utility is marred by the wide variability associated with the procedure itself from epilepsy center to center. This variability renders comparisons among IAP studies problematic and conclusions about IAP efficacy difficult. The variability associated with the amobarbital procedures, as well as the reliability and the validity of the IAP in its nonlanguage uses is reviewed here. A special emphasis is devoted to research conducted in the last decade. Also discussed is the future of the IAP including anticipated research directions.

Interpretation of Wada memory test for lateralization of seizure focus by use of (99m)technetium-HMPAO SPECT

PURPOSE

Although the intracarotid amobarbital procedure (IAP) or Wada test is useful in lateralizing seizure focus in patients with temporal lobe epilepsy (TLE), the results of the IAP memory test are frequently nonlateralizing. An insufficient suppression of the medial temporal region contralateral to the seizure focus may contribute to the failure of lateralization. We tried to correlate IAP memory results with the functional changes in the contralateral medial temporal region as measured by single photon emission computed tomography (SPECT) during IAP.

METHODS

We performed a (99m)technetium-(Tc) hexamethylene-propylene-amine-oxime (HMPAO) brain SPECT in 19 medial TLE patients during a contralateral IAP (sodium amobarbital injected contralateral to the seizure focus). Regional cerebral blood flow (rCBF) was measured in the contralateral medial temporal region. The amount of decrease in the rCBF was calculated by subtracting the previous measurement from the one obtained with the interictal SPECT.

RESULTS

Ten (53%) patients passed and nine (47%) failed the contralateral IAP. The mean percentage decrease in rCBF was 5.3+/-5.3%. There was a significant negative correlation between a decrease in the rCBF and the IAP memory-retention score by Spearman correlation (p = -0.53: p<0.021). Patients with smaller decreases in rCBF (<5%) more frequently passed the contralateral IAP memory test than did those with larger decreases (80 vs. 22%; p<0.023).

CONCLUSIONS

We suggest that an insufficient suppression of the contralateral medial temporal function is partly responsible for nonlateralizing IAP memory tests. An IAP-SPECT may be useful in interpreting IAP memory tests for the lateralization of seizure focus in TLE patients.

Lateralized memory deficits on the Wada test correlate with the side of lobectomy only for patients with unilateral medial temporal lobe epilepsy

The aim of this study was to determine whether the predictive value of the intracarotid amobarbital test (IAT) for the side to be resected is applicable only to medial temporal lobe epilepsy and to investigate whether there are different patterns of memory performances on the IAT between patients with unilateral mesial temporal sclerosis (UMT group) and those without (non-UMT group). We studied 30 patients in the UMT group and 10 in the non-UMT group, who underwent pre-surgical evaluation for intractable temporal lobe epilepsy. Memory performances on the IAT was defined as the percentage of memory items presented during unilateral hemispheric anesthesia that was recognized after recovery. More than a 20% decline of the memory performance on the IAT compared with the memory performance on the pre-test was regarded as a memory deficit. Age at onset of epilepsy was significantly younger in the UMT than in the non-UMT group. Surgical outcome was significantly better in the UMT than in the non-UMT group. The lateralizing value of unilateral memory deficits on the IAT was statistically confirmed. There was a significant association between falsely lateralizing memory performances and the non-UMT group. Excluding the exceptional cases with right-sided language dominance in spite of right-sided lesions, the high incidence of the unilateral right-sided memory deficits in the non-UMT group was statistically significant. This study suggested that the excellent lateralizing value of the memory performances on the IAT is limited to patients with mesial temporal lobe epilepsy. IAT memory performances in patients without such lesions can be misleading, even if lateralized, because their memory status presumably reflects a natural lateralization of the memory organization which is independent of the epileptogenic focus.

Effects of incorporating memory confidence ratings and language handicap modifications on intracarotid amobarbital procedure (Wada test) memory asymmetry scores

PURPOSE

Intracarotid amobarbital procedure (IAP) memory asymmetry scores are often considered in determining lateralization of temporal lobe seizure foci. Additionally, these scores sometimes influence treatment plans for epilepsy surgery candidates. We examined the effects of two scoring modifications on IAP asymmetry scores: incorporating memory confidence ratings (MC), and use of a language handicap (LH) (i.e., adding a point to the memory score with anesthetization of the language-dominant hemisphere), both of which could be applied to most IAP protocols despite variations in testing methods among epilepsy surgery programs.

METHODS

Sixty-nine consecutive unilateral temporal lobe epilepsy (TLE) patients with subsequent good surgical outcomes (Engel I or II) underwent bilateral IAP testing. Confidence ratings were obtained for all memory responses. The incorporation of confidence ratings and the application of a language handicap for dominant-hemisphere injections were applied to memory asymmetry scores in all combinations, resulting in four scoring methods. Results of the four methods were compared with respect to the proportion of patients lateralized accurately by each method.

RESULTS

No patients were falsely lateralized with any method. Percentage of patients correctly lateralized with each scoring method is shown in Table 2. The results obtained with MC and with MC + LH (67% and 64% of patients accurately lateralized, respectively) were significantly better than results obtained with LH (55%, p<0.05). No other differences were significant.

CONCLUSIONS

Although not statistically superior to standard methods, these results suggest that incorporating memory confidence ratings into IAP protocols may increase the likelihood of obtaining asymmetry scores that accurately lateralize to the hemisphere of seizure onset. In contrast, inclusion of a language handicap for scores obtained with the language-dominant ICA injection were not helpful and may even decrease the probability of obtaining clinically useful lateralizing data. These scoring modifications can be applied to most IAP protocols.

Wada difference a day makes: interpretive cautions regarding same-day injections

OBJECTIVE

To determine whether memory scores after second intracarotid amobarbital procedure (IAP) injections are affected by the time between the first and second injections.

METHODS

Sixty-two patients received their second IAP injection on the day after the first injection. Forty-three other patients received the second injection on the same day as the first injection. Both groups underwent similar IAP protocols and memory assessments, except for the timing of the second injection.

RESULTS

The second IAP memory scores in the two-day group were significantly higher (p < 0.05) than those in the one-day group. Timing of second injection was a significant correlate of second memory scores, but amobarbital dosage, first IAP memory score, and pre-IAP measures of memory and intelligence were not significant correlates.

CONCLUSION

One-day and two-day IAP protocols do not result in similar memory scores after the second injection. Nineteen percent of a subset of patients in the one-day protocol were misclassified, in terms of IAP memory ratings, because of the deleterious effect of having both injections on the same day. It is recommended that correction scores be considered, for some patients who receive two IAP injections on one day, to approximate what the second IAP memory score would have been had the second injection occurred on a second day.

Hemispheric asymmetries in arousal affect outcome of the intracarotid amobarbital test

Objective: To evaluate changes in arousal and their impact on memory performance during the intracarotid amobarbital test (IAT).

Methods: Along with memory measures, level of arousal was evaluated through clinical ratings and nonverbal self-ratings in epilepsy patients undergoing IAT before anterior temporal lobectomy.

Results: Irrespective of seizure focus, left-sided amobarbital injection resulted in decreased objective and subjective arousal more often than right-side injection. Impaired objective arousal was greater when the left hemisphere was injected second, because of the presumed additive effects of systemic amobarbital residual from the first injection. Decreased objective arousal was related to poorer performance on memory testing following left-hemisphere injection.

Conclusions: The IAT, as practiced in most centers, is biased, so patients with right temporal lobe seizure focus are more likely to “pass” the test, whereas patients with left seizure focus are more likely to “fail” the test. The significant impact of changes in arousal on memory testing needs to be considered when using IAT results to select patients for temporal lobectomy.

Lateralizing value of the Wada memory test in non-Western patients with temporal lobe epilepsy

The Wada memory test measures a psychological construct (i.e. memory), which is widely acknowledged to be under the influence of a vast array of moderating variables including culture. Thus, the lateralizing value of the Wada memory test for epileptogenic foci may potentially differ for Western versus non-Western patients with temporal lobe epilepsy (TLE). In the present study, the lateralizing value of the Wada memory test was investigated in 17 Korean patients with medically intractable TLE who were post-operatively seizure-free. The Wada memory stimuli were composed of eight drawings of common objects, animals, and fruits. A clinical criterion of at least 2 points difference between left and right injections correctly classified 14 patients (82%) into left and right TLE groups, with only one patient (6%) falsely classified. This diagnostic accuracy is at least as high as that reported for Western TLE patients. These results indicate that whatever culture-specific factors Korean TLE patients may bring to the Wada memory test, they do not significantly reduce the lateralizing value of the test.

Absence of correlation between amobarbital distribution as assessed with SPECT brain perfusion imaging and behavioral manifestations during the intracarotid amobarbital procedure (Wada test)

1. The IAP is used presurgically in patients with temporal lobe epilepsy to predict the effects on LTM and language of the planned temporal lobectomy. This prognosis presumes that a similar pattern of perfusion will result in anesthesia of the same cerebral regions in most patients. 2. Coinjection of Tc-99m HMPAO with the barbiturate during the IAP has been used to ascertain whether this actually is true, with variable results. Moreover, most studies document only unilateral IAPs and do not report on behavioral performance. 3. The authors coinjected Tc-99m HMPAO and amobarbital in 33 IAPs from 18 patients (15 injected bilaterally, 3 unilaterally) to clarify this and to evaluate the relationship of the perfusion pattern to behavioral performance; SPECT results were also compared to angiographic evaluation obtained at the time of catheter placement. 4. SPECT perfusion data was rated for presence/absence and intensity of perfusion to the ACA, MCA, PCA territories and to H, i or c to the injection site. V, STM and LTM were graded according to a standardized protocol. 5. MCAi was perfused in 100% of cases, ACAi in 91%, PCAi in 21% and Hi in only 6%. Cross-over flow was shown in 9 studies; 50% of the patients in whom both sides were injected (on different days) had crossover, involving the ACAc territory in 80% of cases. As expected, injection on the non-ES was associated with a significantly worse LTM performance than on the ES (p = 0.006). There was no relationship between the perfusion pattern and the V level of the patients (a potential confounding variable in memory/language evaluation) during IAP, nor between perfusion pattern and LTM. STM was significantly adversely affected by the presence of crossover perfusion. Angiography in general overestimated the extent of cerebral perfusion demonstrated by SPECT, most probably because of the markedly different injection conditions. 6. Despite the best efforts to standardize injections, the perfusion pattern has been mostly unpredictable in the patients. Moreover, it has little bearing on their behavioral performance, except for the prediction of poor STM performance (the clinical implications of this remaining dubious). Marked LTM alterations after non-ES injections confirm remote hippocampal effects in the presence of only rare direct perfusion of that region. Tc-99m HMPAO/Amobarbital coinjection was unhelpful from a clinical perspective, most probably because a large part of the effects of amobarbital arise from deafferentation of regions not directly perfused by the anesthetic agent.

Prediction of presence of hippocampal sclerosis from intracarotid amobarbital procedure memory asymmetry scores and epilepsy on set age

Identification of the pathological status of the hippocampus prior to surgery is important since the absence of hippocampal sclerosis (HS) carries risks to memory function following anterior temporal lobectomy (ATL). We studied 62 patients undergoing ATL (31 L, 31 R) for intractable epilepsy of temporal lobe origin in whom no pathology was identified apart from HS. An intracarotid amobarbital procedure (IAP) was performed as part of the preoperative evaluation. All patients were left hemisphere dominant for language. IAP memory testing was according to the protocol of Loring. We examined IAP memory asymmetry scores at four levels of difference (<2, > or =2, > or =4, > or =6) as a function of the presence (HS+) or absence (HS-) of HS. A logistic regression analysis was performed with HS+ as the dependent variable, and age at onset of epilepsy, age at time of surgery, gender, side of surgery and significant IAP memory asymmetry as independent variables. At each level of memory asymmetry, onset age and memory asymmetry were the only predictors of HS+. Younger age at onset was associated with HS+. Curves were constructed showing probability of HS+ for age at onset for each level of asymmetry. These can be used to predict the likelihood of presence of HS based on age at onset of epilepsy and the IAP memory asymmetry score. It is concluded that IAP memory asymmetry scores reflect the functional and pathological status of the hippocampus, and greater asymmetry increases the probability of finding HS in the resected hippocampus.

Asymmetries in the effect of side of seizure onset on recognition memory following intracarotid amobarbital injection

PURPOSE

To assess interhemispheric differences in recognition memory for objects during the intracarotid amobarbital sodium procedure (IAP).

METHODS

The recognition memory for real objects of patients with either right (RTLE; n = 28) or left (LTLE; n = 22) temporal lobe epilepsy was assessed at baseline, and after left and right intracarotid amobarbital sodium injection.

RESULTS

There were no differences between groups on baseline performance. Performance following injection ipsilateral to the side of seizure focus was relatively lower for the LTLE as compared with the RTLE group, but this difference did not reach statistical significance. However, performance following injection contralateral to the side of seizure focus was significantly lower for the RTLE as compared with the LTLE group. Within-group differences in performance after ipsilateral as compared with contralateral injection were significant for the RTLE but not the LTLE group. The difference in interhemispheric asymmetry in IAP memory performance between RTLE and LTLE groups was reflected in decreased ability to classify LTLE patients as compared with RTLE patients about side of seizure onset, using a clinically applicable decision rule.

CONCLUSIONS

Recognition memory during the IAP for real objects, simultaneously named and presented visually during encoding, is mediated effectively by both the left and right hemisphere when there is no seizure focus present. However, memory appears to be more vulnerable to the presence of a seizure focus in the right as compared with the left hemisphere.

Use of the intracarotid amobarbital procedure in the evaluation of memory

The intracarotid amobarbital procedure (IAP) involves the temporary inactivation of one cerebral hemisphere by the injection of sodium amobarbital, which allows independent testing of the contralateral hemisphere. Initially used for lateralization of language, IAP later found a role in the evaluation of memory function in patients with intractable temporal lobe epilepsy being considered for resective surgery. IAP technique varies widely across centers, but, in general, memory is assessed by presenting the patient with a number of items during the period of hemispheric inactivation and testing recall or recognition of these items after the effect of the drug has worn off. Because the medial temporal lobe is not directly perfused by the internal carotid artery, concerns have been raised about the ability of the IAP to test hippocampal memory function. Consequently, a variety of selective procedures have been devised. Findings on both intracranial EEG recordings and pathologic and neuroimaging studies support the association of IAP memory results with hippocampal function. The IAP memory test was originally designed to predict the risk for development of global amnesia following unilateral temporal lobectomy. More recently, it also has been used as an adjunct in lateralizing the seizure focus and for predicting postoperative selective memory deficits and seizure outcome.

Effect of focus lateralization on memory assessment during the intracarotid amobarbital procedure

Despite the use of stimuli that can be processed by both hemispheres, a number of studies have reported lower memory scores after the left intracarotid amobarbital procedure (IAP) than after the right IAP. Because of that, failure after ipsilateral IAP is observed more often in patients with a left temporal seizure focus (LT) than in right temporal patients (RT), possibly needlessly excluding some LT patients from surgery. In order to overcome the deleterious effects of anesthetizing the dominant hemisphere, we designed an IAP protocol that did not promote verbal encoding of the stimuli. For this purpose, a large number of visual and tactile stimuli (colored pictures and real objects) were presented to be recognized later. The effect of seizure focus lateralization was examined in 82 temporal lobe epileptic patients who underwent IAP as part of their presurgical evaluation. As expected, for both RT and LT patients, long-term recognition of pictures presented under the effect of amobarbital was highly sensitive to the presence of a contralateral epileptic focus. However, contrary to what is generally reported, LT patients performed better than RT patients when their left (ipsilateral) hemisphere was anesthetized. In RT patients, although memory scores were lower after the left contralateral injection, the disparity in memory scores between the right and left injection was not as marked as in LT patients. These results are discussed in terms of the influence of type of processing required during the initial encoding on later recognition during IAP.

Effects of hemisphere speech dominance and seizure focus on patterns of behavioral response errors for three types of stimuli

We used a protocol consisting of a continuous presentation of stimuli with associated response requests during an intracarotid sodium amobarbital procedure (IAP) to study the effects of hemisphere injected (speech dominant vs. nondominant) and seizure focus (left temporal lobe vs. right temporal lobe) on the pattern of behavioral response errors for three types of visual stimuli (pictures of common objects, words, and abstract forms). Injection of the left speech dominant hemisphere compared to the right nondominant hemisphere increased overall errors and affected the pattern of behavioral errors. The presence of a seizure focus in the contralateral hemisphere increased overall errors, particularly for the right temporal lobe seizure patients, but did not affect the pattern of behavioral errors. Left hemisphere injections disrupted both naming and reading responses at a rate similar to that of matching-to-sample performance. Also, a short-term memory deficit was observed with all three stimuli. Long-term memory testing following the left hemisphere injection indicated that only for pictures of common objects were there fewer errors during the early postinjection period than for the later long-term memory testing. Therefore, despite the inability to respond to picture stimuli, picture items, but not words or forms, could be sufficiently encoded for later recall. In contrast, right hemisphere injections resulted in few errors, with a pattern suggesting a mild general cognitive decrease. A selective weakness in learning unfamiliar forms was found. Our findings indicate that different patterns of behavioral deficits occur following the left vs. right hemisphere injections, with selective patterns specific to stimulus type.

Effect of Wada memory stimulus type in discriminating lateralized temporal lobe impairment

PURPOSE

To examine the effects of memory stimulus type on Wada memory performance.

METHOD

Ninety-six patients (left, 47; right, 49) from four epilepsy centers who were candidates for anterior temporal lobectomy (ATL) and who have subsequently undergone surgery were studied. Patients with atypical cerebral language lateralization or with evidence on magnetic resonance imaging (MRI) to suggest a lesion other than hippocampal sclerosis were excluded. Wada memory performance was obtained by using both real objects and line drawings as memory stimuli.

RESULTS

Wada memory laterality scores with either real objects or line drawings as memory stimuli discriminated left from right-ATL groups. However, objects were superior to line drawings in making this differentiation. Further, objects were superior to line drawings in individual patient classification of candidates for left ATL, with no difference in the classification rates using either objects or line drawings in candidates for right ATL.

CONCLUSIONS

Type of memory stimuli is an important factor affecting memory results during the Wada test.

Treatment of temporal lobe epilepsy

Initial management of patients with temporal lobe epilepsy is with antiepileptic drugs, but these control seizures in only half the patients. Patients refractory to drugs should be evaluated for resective surgery. That evaluation requires identification of a focus of onset of seizures, as well as establishing that the focus is in an area of the brain that can be removed with a low risk of new neurologic deficits. Techniques used in that evaluation, including electroencephalography, imaging, recording form intracranial electrodes, use of the intracarotid amobarbitol perfusion test, and the role of specialized studies such as positron emission tomography, are reviewed, along with the correlation of the findings on that evaluation to the control of seizures after surgery. The different surgical techniques for temporal lobe resections are also reviewed, along with the risks of surgery, particularly to recent memory, and the changes in quality of life following surgery.

Neuropsychological evaluation in epilepsy surgery

Neuropsychology has played a prominent role throughout the modern era of epilepsy surgery. Neuropsychology, including the Wada test, has been of benefit in documenting dysfunction associated with a lateralized temporal lobe seizure onset. In addition, neuropsychological results have some predicative power regarding seizure outcome following anterior temporal lobectomy. The current status of neuropsychology in patient evaluation and outcome prediction will be presented. Differences between the Wada test, an inactivation procedure, and functional magnetic resonance imaging, which is an activation procedure, will be discussed. This paper will also present preliminary information about the Wechsler Adult Intelligence Scale-III, the recent revision of the most commonly used test of intellectual function, and its effects on neuropsychological performance results.

Neuropsychologic assessment in surgical treatment of epilepsy

Neuropsychologic assessment has long been an integral part of evaluation for surgical treatment of epilepsy. Neuropsychologic evaluation and consultation continue to be an important part of the assessment for operative intervention for epilepsy, but the role of neuropsychology has changed over time. At one time, neuropsychologic assessment assumed a diagnostic role in preoperative evaluation for epilepsy and also contributed to the lateralization and localization of the seizure focus. Sophisticated electroencephalographic techniques and especially neuroimaging have revolutionized the diagnosis and management in epilepsy surgical treatment centers. Although still helpful, neuropsychology no longer has a major role in lateralization or localization of seizure onset. This report describes neuropsychologic evaluation and its current role in surgical treatment of epilepsy. The characteristics and purposes of neuropsychologic assessment and Wada testing (intracarotid injection of amobarbital) are described. Current research on assessment of emotional adjustment and on its predictors before and after surgical therapy for epilepsy is reviewed. Finally, the risk for neuropsychologic decline after temporal lobectomy is discussed in light of recent research on preoperative memory, hippocampal pathologic lesions, and quantitative neuroimaging data.

Intracartotid amobarbital procedure memory performance and age at first risk for seizures distinguish between lateral neocortical and mesial temporal lobe epilepsy

PURPOSE

To determine whether intracarotid amobarbital procedure (IAP) memory-performance asymmetries and early risk factors for epilepsy distinguish between lateral neocortical temporal lobe epilepsy (LNTLE) and mesiobasal temporal lobe epilepsy (MBTLE).

METHODS

We studied 10 patients with LNTLE and 22 with MBTLE. All LNTLE patients showed (a) presence of temporal neocortical lesion or lateral seizure onset by intracranial recording, and (b) absence of mesial temporal sclerosis (MTS) by histopathologic analysis. All patients with MBTLE showed (a) video-scalp EEG seizures consistent with mesial TLE, and (b) presence of unilateral MTS by histopathologic analysis. All patients had good surgical outcomes (Engel I or II). Unilateral IAP memory performance was defined as percentage of memory items presented during hemispheric anesthesia that was recognized after recovery. IAP asymmetry scores were the differences in memory performance after right and left injections.

RESULTS

Mean memory-asymmetry scores were significantly lower in the LNTLE than in the MBTLE group. An IAP memory asymmetry of < 25% correctly classified seven of 10 patients with LNTLE, and an asymmetry of > or = 25% correctly classified 18 of 22 patients with MBTLE. Age at first risk for epilepsy was significantly younger in those with MBTLE than in those with nonlesional LNTLE. Results suggest that both IAP memory performance and age at first risk can help distinguish between MBTLE and LNTLE.

Relation between intracarotid amobarbital memory asymmetry scores and hippocampal sclerosis in patients undergoing anterior temporal lobe resections

The intracarotid amobarbital procedure (IAP) is used to evaluate memory function preoperatively in candidates for anterior temporal lobe resections (ATL). We examined IAP memory asymmetry scores in 30 patients undergoing ATL (17 R, 13 L), as a function of the presence (HS+) or absence (HS-) of hippocampal sclerosis. Ictal onset zones were determined by extraoperative recording with subdural strip electrodes in all but 3 patients in whom magnetic resonance imaging (MRI) scan showed HS. MRI scans were otherwise normal. All patients were left hemisphere dominant for language except 1, in whom language was represented bilaterally. IAP memory testing involved presentation of eight subjects during anesthesia of each hemisphere, followed by recognition testing after patients recovered from amobarbital effects. A score of 1 was given for each correctly recognized object, and 0.5 was deducted for each false-positive identification. There were 16 foils. A total asymmetry score was calculated, which was positive if there was agreement between the direction of the symmetry and side of operation and negative if reversed. The mean asymmetry score for HS- (n = 8) was 0.9; that for HS+ (n = 22) was 4.1 (p < 0.01). IAP memory performance provided lateralizing information (asymmetry score > or = + or -2) in 73% of cases; among these, the lateralization was correct in 91%. Our data indicate that IAP memory asymmetry predicts both laterality of ictal onset and the presence of HS.

Wada memory disparities predict seizure laterality and postoperative seizure control

We examined the efficacy of a memory difference score (DS: right minus left hemisphere memory) during the Wada test (intracarotid amobarbital procedure, IAP) for predicting seizure laterality and postoperative seizure outcome in 70 left speech dominant patients from two epilepsy centers. DS > or = 2, after addition of 1 point to the left hemisphere injection score to account for aphasia, were noted in 71.4% of patients and correctly predicted surgery side for 98.0% of these patients. The DS related significantly to seizure outcome at 1-year follow-up (p < 0.002) and correctly predicted 80% of patients who were seizure-free. Patients whose DS did not correctly predict seizure laterality more frequently required invasive studies to establish seizure onset. The relationship of the DS to laterality did not differ significantly by class of IAP memory stimuli. When seizures originate from the temporal lobe, the IAP memory DS predicts seizure laterality by assessing the functional adequacy of the involved hemisphere and is predictive of seizure control.

[Temporal lobectomy: indications and role in the surgery of epilepsy]

When a focal epilepsy proves refractory to medical therapy, surgical treatment is increasingly used. Most interventions consist in cortical resections, and by far the most common operation is a temporal lobectomy. The presurgical evaluation is a multi-disciplinary one, and includes history and examination, neuropsychological testing, neuro-imaging techniques, functional studies (functional imaging and intracarotid amobarbital procedure), and neurophysiologic data (EEG-video monitoring). When non-invasive EEG does not succeed in localizing the epileptogenic zone with sufficient accuracy, several invasive techniques are available. Each has its own advantages and disadvantages. In appropriately selected cases, postoperative outcome is excellent, especially in temporal lobe epilepsy. In general, outcome is slightly less successful in extra-temporal cases.

Future directions for functional mapping

The intracarotid amobarbital procedure and direct cortical stimulation are commonly used techniques for functional mapping in candidates for epilepsy surgery. The role of these two procedures has been challenged recently. Emerging technologies recently applied to functional mapping include optical imaging, functional positron emission tomography studies, transcranial magnetic stimulation, magnetoencephalography, and fast magnetic resonance imaging. Studies have used these new technologies and the potential for these procedures to replace the established but more invasive techniques is being considered.

Characteristics of medial temporal lobe epilepsy: II. Interictal and ictal scalp electroencephalography, neuropsychological testing, neuroimaging, surgical results, and pathology

Sixty-seven patients with temporal lobe epilepsy without circumscribed, potentially epileptogenic lesions, who were studied with intracranial electrodes and who became seizure free following temporal lobectomy were retrospectively evaluated with regard to preoperative scalp electroencephalographic (EEG) findings, neuropsychological test results, neuroimaging findings, results of surgery, and pathology of resected tissue. Interictal scalp EEG showed paroxysmal abnormalities during prolonged monitoring in 64 patients (96%). These were localized in the anterior temporal region in 60 (94%) of these 64 patients. Bilateral independent paroxysmal activity occurred in 42% of the patients and was preponderant over the side of seizure origin in half. Ictal EEG changes were rarely detected at the time of clinical seizure onset, but lateralized buildup of rhythmic seizure activity during the seizure occurred in 80% of patients. In 13%, the scalp EEG seizure buildup was, however, contralateral to the side of seizure origin as subsequently determined by depth EEG and curative surgery. Lateralized postictal slowing, when present, was a very reliable lateralizing finding. Neuropsychological testing provided lateralizing findings concordant with the side of seizure origin in 73% of patients. When neuropsychological testing produced discordant results or nonlateralizing findings, those patients were usually found to have right temporal seizure origin. Intracarotid amobarbital (Amytal) testing demonstrated absent or marginal memory functions on the side of seizure onset in 63% of patients, but 26 patients (37%) had bilaterally intact memory. In those patients who had magnetic resonance imaging, it was very sensitive in detecting subtle medial temporal abnormalities. These abnormalities were present in 23 of 28 magnetic resonance images, and corresponded with mesial temporal sclerosis on pathological examination in all but 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)