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.     

Amnesia After Unilateral Temporal Lobectomy: A Case Report

Summary: We report a mixed handed (L>R) patient with exclusive right cerebral language representation who de–veloped a permanent anterograde amnestic syndrome after right anterotemporal lobectomy. Preoperative neuropsychological performance consisted of impaired verbal memory and normal nonverbal memory. Wada memory performance was asymmetrical for objects presented soon after amobarbital injection in conjunction with no memory asymmetry for items presented later in the Wada evaluation. Preand postoperative magnetic resonance imaging (MRI) scans showed no structural lesions; however, postoperative MRI hippocampal volume measurements suggested decreased hippocampal volume for the nonresected temporal lobe. These results confirm the risk of anterograde amnesia after unilateral temporal lobectomy and demonstrate that baseline neuropsychological testing may falsely literalize material-specific memory functions in patients with atypical cerebral language dominance.     

Intracarotid Amobarbital Procedure as a Predictor of Material-Specific Memory Change After Anterior Temporal Lobectomy

Summary: Memory testing during the intracarotid amobarbital procedure (IAP) is used extensively to identify temporal lobe surgery candidates "at risk" for developing severe postoperative anterograde amnesia. However, the utility of the IAP in predicting commonly observed material-specific memory deficits has not been thoroughly investigated. We examined the utility of contralateral IAP memory testing, as an index of the functional capacity of the surgical temporal lobe, to predict postoperative material-specific memory changes on the Wechsler Memory Scale-Revised (WMS-R) in patients with left hemisphere speech dominance undergoing left (n = 32) and right (n = 31) temporal lobectomy (TL). Left TL patients who "passed" contralateral IAP memory testing (368% recognition of memory items) had significantly greater verbal memory decrements than those who "failed" the IAP, presumably as a result of removal of functional tissue. A similar relationship between contralateral IAP performance and visual memory performance was not observed among right TL patients. Thus, the functional adequacy of the tissue to be resected appears to be inversely related to postoperative verbal memory decrement, at least among left TL patients. This relationship is consistent with results of recent studies demonstrating an inverse relationship between verbal memory decrements after left TL and preoperative neuropsychological verbal memory performance, magnetic resonance imaging (MRI) hippocampal volumes, and degree of mesiotemporal sclerosis (MTS).     

Wada Memory Disparities Predict Seizure Laterality and Postoperative Seizure Control

Summary: 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 ≥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 The Wada test, or intracarotid amobarbital procedure (IAP), is traditionally used to determine the laterality of language dominance and to assess the memory competence in the hemisphere contralateral to the proposed temporal lobectomy in an effort to avoid postoperative amnesia (1–6). Ipsilateral memory testing (adequacy of the hemisphere ipsilateral to anticipated resection) also is frequently examined. The validity of IAP memory testing as a measure of temporal lobe function is demonstrated by correlating IAP memory scores of the affected hemisphere with hippocampal cell counts (7,8) and with hippocampal volume assessed by magnetic resonance imaging (MRI) (9). The disparity between ipsilateral and contralateral memory scores is often predictive of seizure focus laterality (1 1–18). However, most studies have examined group means rather than the utility of the DS for predicting the seizure focus in specific patients. To date, only Loring et al. (9) have reported Presented in part at the Annual Meeting of the International Neuropsychological Society, Galveston, Texas, February 1993. 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.     

The neural substrate of memory impairment demonstrated by the intracarotid amobarbital procedure

The intracarotid amobarbital sodium (Amytal) procedure (IAP) was performed for 46 patients with temporal lobe epilepsy (21 with left seizure foci; 25 with right seizure foci). After anteromedial temporal lobectomy, neuronal densities were established for hippocampal subfields CA1, CA2, and CA3; the hilum; and the dentate granule cell layer. Intracarotid amobarbital procedure memory results were related to CA3 neuronal loss only. Patients who did not demonstrate memory after injection contralateral to the seizure focus had significantly fewer cells in CA3 than patients who did. Additionally, a significant correlation was observed between the intracarotid amobarbital procedure memory examination raw score after injection contralateral to the seizure focus and CA3 cell density. Using chi 2 analysis, significant differences were documented in the frequency with which memory was demonstrated after injection contralateral to the seizure focus for groups of patients classified by degree of CA3 neuronal loss. This finding supports prior research showing subfield specificity in some memory processes.     

Crossed aphasia in a patient with complex partial seizures: evidence from intracarotid amobarbital testing, functional cortical mapping, and neuropsychological assessment.

We report a right-handed patient who became transiently aphasic following a right temporal lobectomy for control of intractable complex partial seizures. Preoperative intracarotid amobarbital testing revealed right-hemisphere language dominance, although bilateral language representation was present. Memory testing during unilateral electrical hippocampal simulation with depth electrodes indicated reliance on left-hemisphere mesial temporal lobe structures for verbal memory. Functional mapping for language during surgery established several right perisylvian regions that, when stimulated, produced speech arrest and/or paraphasic substitution. One-year follow-up neuropsychological assessment demonstrated an increase in verbal learning and decrease in visual memory, a pattern associated with patients who have undergone right temporal lobectomy. These data demonstrate that (1) right cerebral language dominance can be observed when ipsilateral seizure onset is present (2) verbal memory and language dominance are not necessarily linked, and (3) some reported cases of crossed aphasia may in fact have bilateral language representation.     

Memory following intracarotid amobarbital injection contralateral to hippocampal damage

We examined the relationship between memory performance and hippocampal damage in temporal lobe epileptics undergoing the intracarotid amobarbital sodium procedure (IAP). Overall memory performance in the course of IAP was correlated with seizure lateralization. The hemisphere of seizure focus had impaired IAP memory in 63% (19/30) of the patients. The IAP memory performance following perfusion of the hemisphere contralateral to severe hippocampal lesions was impaired in five of six patients. These patients also exhibited hypometabolism of the impaired temporal lobe as determined independently by positron emission tomography. The single patient with a severely damaged hippocampus who did not demonstrate IAP memory impairment with contralateral hemisphere injection did not exhibit perfusion of the ipsilateral posterior cerebral artery with amobarbital. Memory performance following intracarotid amobarbital injection contralateral to a less severely damaged hippocampus was impaired in 14 of 24 patients and was not related to extent of hippocampal damage, temporal lobe hypometabolism of labeled glucose, perfusion of the ipsilateral posterior cerebral artery, hemispheric language dominance, or order of injection. These results indicate that impaired memory performance during IAP may reflect severe hippocampal damage and/or epileptogenic abnormality.     

Crossed aphasia in a patient with complex partial seizures: Evidence from intracarotid amobarbital testing,functional cortical mapping,and neuropsychological assessment

Abstract

We report a right-handed patient who became transiently aphasic following a right temporal lobectomy for control of intractable complex partial seizures. Pre-operative intracarotid amobarbital testing revealed right-hemisphere language dominance, although bilateral language representation was present. Memory testing during unilateral electrical hippocampal simulation with depth electrodes indicated reliance on left-hemisphere mesial temporal lobe structures for verbal memory. Functional mapping for language during surgery established several right perisylvian regions that, when stimulated, produced speech arrest and/or paraphasic substitution. One-year follow-up neuropsychological assessment demonstrated an increase in verbal learning and decrease in visual memory, a pattern associated with patients who have undergone right temporal lobectomy. These data demonstrate that (1) right cerebral language dominance can be observed when ipsilateral seizure onset is present (2) verbal memory and language dominance are not necessarily linked, and (3) some reported cases of crossed aphasia may in fact have bilateral language representation.     

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.     

Severe amnesia following bilateral medial temporal lobe damage occurring on two distinct occasions

Abstract A comprehensive neuropsychological assessment was performed on a 38-year-old woman with drug-resistant right temporal lobe epilepsy before temporal lobectomy, during a 2-year follow-up period, and approximately 3 years after surgery when she developed a malignant glioma in the left medial temporal lobe (MTL). Both before and after epilepsy surgery, memory function was normal. When the tumour was discovered, the patient suffered from severe retrograde and anterograde amnesia, whereas working memory and the other cognitive abilities were preserved. Compared with other cases of bilateral temporal lesion, this case is peculiar because the damage occurred on two distinct occasions. It suggests that only one MTL can allow normal memory function, or can take over the function normally subserved by a dysfunctional contralateral MTL when the dysfunction is marked and prolonged, such as in chronic epilepsy.     

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.     

Comparison of Mesial Versus Neocortical Onset Temporal Lobe Seizures: Neurodiagnostic Findings and Surgical Outcome

Summary: We compared historical features, surface EEG findings, results of intracarotid sodium amobarbital memory testing (IAT), and outcome after anterotemporal lobectomy (ATL) in patients with mesiotemporal lobe seizure onset with those with more diffuse temporal lobe seizure onset (intracranial EEG). Forty-eight patients evaluated consecutively between July 1985 and October 1991 with both scalp/sphenoidal and intracranial EEG were shown to have seizures originating in one temporal lobe. No patients had temporal lobe tumor or vascular malformation. Thirty-seven of the 48 patients had seizure onset in the amygdale/hippocampus (amyg/hipp). Eleven of the 48 had either temporal neocortical onset or simultaneous amydhipp and neocortical onset. Patients with mesial onset seizures were more likely to have lateralized memory impairment on I AT (p = 0.05). We noted a trend toward a difference in age of first risk for epilepsy between the two groups (p = 0.09) but not for a difference in any specific risk factor. There were no significant differences in surface EEG interictal findings. Unlike in previous studies, comparison of outcome between the two groups showed no difference in seizure-free outcome. Sudden unexpected death (SUD) was more frequent in neocortical seizure patients who were not seizure-free (p < 0.05).     

Memory performance following unilateral electrical stimulation of the hippocampus in a child with right temporal lobe epilepsy

Verbal and visual memory performance was evaluated during unilateral stimulation of the hippocampus in an 11-year-old child with complex partial epilepsy associated with a right mesial temporal lobe focus. Memory was assessed during left and right hippocampal stimulation as well as preoperatively and 6-months postoperatively following anterior temporal lobe resection including removal of the anterior portion of the hippocampus. Stimulation of the left hippocampus resulted in a mild to moderate decrement in both verbal and visual memory performance as compared with a right hippocampal stimulation. In addition, stable or improved performance on memory assessment as well as general neuropsychological evaluation was noted 6 months postoperatively. Taken together, these data suggest that, in this child with early seizure onset (8 months of age), visual learning/memory functions shifted to the contralateral hippocampus and associated structures following damage to the right mesial temporal lobe structures. In addition, verbal learning/memory continues to be mediated by the left hippocampus, as expected. Thus, it appears that, as in the case of language lateralization, there may be a distinct subset of temporal lobe seizure patients (i.e., early seizure onset, high seizure frequency, chronic duration) in whom the brain has the capacity to shift material-specific memory functions to the contralateral mesial temporal lobe structures.     

Temporal lobectomy in patients with bitemporal epilepsy defined by depth electroencephalography

Patient selection for temporal lobectomy was reviewed for 23 patients with seizures that arose independently from each temporal lobe as detected by depth electroencephalography (EEG). Although neuropsychological testing, interictal EEG findings, imaging studies, and subclinical seizures were also considered, all patients offered temporal lobectomy had (1) at least 50% of the clinical seizures originating from the lobe to be resected, (2) adequate contralateral memory on testing with amobarbital, and (3) no clear evidence of an extratemporal focus. Eleven patients underwent temporal lobectomy. Pathological findings were considered positive in all nine specimens reviewed. Nine patients had no seizures, one had greater than 75% reduction in seizure frequency, and 1 had 50 to 75% reduction. Pathological features and clinical outcome were similar in the 6 patients with fewer than 80% and the 5 patients with at least 80% of seizures originating from the resected lobe. Thus, having fewer than 80% of seizures originate from one temporal lobe should not be an absolute contraindication for temporal lobectomy.     

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.     

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.     

Decline in Verbal Memory Associated with Duration of Epilepsy: An Intracarotid Amobarbital Study

Background. Many patients with mesial temporal sclerosis (MTS) observe that their memory has declined over time, but objective evidence for this is scant.Method. Verbal memory scores were obtained during amobarbital injection of the right carotid artery in 30 right-handed patients with right mesial temporal sclerosis and unilateral right temporal lobe seizures. These were compared with duration of epilepsy and seizure frequency. An estimate of the total number of lifetime seizures was formed by multiplying epilepsy duration by seizure frequency.Results. Verbal memory function in the left temporal lobe was negatively associated with longer duration of epilepsy (P < 0.05). There was a strong negative correlation between verbal memory and increased lifetime number of seizures (P < 0.01).Conclusion. This study provides evidence that seizures arising in the right temporal lobe lead to progressive dysfunction of memory functions in the contralateral side.     

Ictal semiology in patients with medial temporal lobe epilepsy: value in lateralizing the seizure focus]

We have evaluated useful lateralizing signs in 28 patients with medial temporal lobe epilepsy who were seizure-free after anterior temporal lobectomy by reviewing videotapes during video-EEG monitoring. The most frequent types of aura were epigastric sensation and psychic symptom in 8, respectively, both of which did not predict lateralization of the focus. Of the motor signs, early head deviation and unilateral upper extremity automatism predicted an ipsilateral focus in 72 and 80%, respectively. On the other hand, late head deviation(< 15 seconds before secondarily generalized seizure) and unilateral upper extremity dystonic posturing predicted a contralateral focus in 80 and 100%, respectively. Twelve of the patients displayed oroalimentary automatism which did not predict focus lateralization. Three patients with ictal speech demonstrated a seizure focus contralateral to their language-dominant hemisphere. In medial temporal lobe epilepsy, several clinical seizure manifestations such as: early and late head deviation, unilateral upper extremity automatism and dystonic posturing were not a little noted and provided additional information as to the side of seizure origin.     

Asymmetries in the Effect of Side of Seizure Onset on Recognition Memory Following Intracarotid Amobarbital Injection

Summary: Purpose : To assess inter hemispheric 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 inter hemispheric 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.     

Prognostic implication of contralateral secondary electrographic seizures in temporal lobe epilepsy

PURPOSE: Interhemispheric propagation of seizures in temporal lobe epilepsy is frequently noted during intracranial EEG monitoring. We hypothesized that a distinct secondary electrographic seizure (DSES) in the temporal lobe contralateral to primary seizure onset may be an unfavorable prognostic indicator. METHODS: We reviewed intracranial depth electrode EEG recordings, 1-year outcome, and medical records of 51 patients (M 29, F 22: age 15-64 years) who underwent anterior temporal lobectomy during 1988-96. We defined DSES as a seizure that spread to the contralateral temporal lobe and produced distinct contralateral EEG features. The distinct feature was focal involvement of one or two electrode contacts at onset, which starts and evolves independently from the ipsilateral temporal lobe. We considered DSES as the predominant seizure pattern when it occurred in more than one half of the patients' recorded seizures. RESULTS: Only nine of 19 (47%) patients with predominant DSES had a 1-year seizure-free outcome, whereas 27 of 32 (84%) patients without predominant DSES had a 1-year seizure-free outcome (p < 0.01). Bitemporal independent seizures were more common in patients with predominant DSES (9/19 versus 0/32; p < 0.001). CONCLUSION: Our results suggest that distinct contralateral secondary electrographic seizure is a predictor of unfavorable outcome and is also more likely to be associated with bitemporal seizures.