Left Anterior Temporal Lobectomy Research Articles

Temporal Lobe Epilepsy and Surgery Selectively Alter the Dorsal, Not the Ventral, Default-Mode Network

The default-mode network (DMN) is a major resting-state network. It can be divided in two distinct networks: one is composed of dorsal and anterior regions [referred to as the dorsal DMN (dDMN)], while the other involves the more posterior regions [referred to as the ventral DMN (vDMN)]. To date, no studies have investigated the potentially distinct impact of temporal lobe epilepsy (TLE) on these networks. In this context, we explored the effect of TLE and anterior temporal lobectomy (ATL) on the dDMN and vDMN. We utilized two resting-state fMRI sessions from left, right TLE patients (pre-/post-surgery) and normal controls (sessions 1/2). Using independent component analysis, we identified the two networks. We then evaluated for differences in spatial extent for each network between the groups, and across the scanning sessions. The results revealed that, pre-surgery, the dDMN showed larger differences between the three groups than the vDMN, and more particularly between right and left TLE than between the TLE patients and controls. In terms of change post-surgery, in both TLE groups, the dDMN also demonstrated larger changes than the vDMN. For the vDMN, the only changes involved the resected temporal lobe for each ATL group. For the dDMN, the left ATL group showed post-surgical increases in several regions outside the ictal temporal lobe. In contrast, the right ATL group displayed a large reduction in the frontal cortex. The results highlight that the two DMNs are not impacted by TLE and ATL in an equivalent fashion. Importantly, the dDMN was the more affected, with right ATL having a more deleterious effects than left ATL. We are the first to highlight that the dDMN more strongly bears the negative impact of TLE than the vDMN, suggesting there is an interaction between the side of pathology and DM sub-network activity. Our findings have implications for understanding the impact TLE and subsequent ATL on the functions implemented by the distinct DMNs.

Effects of dual pathology on cognitive outcome following left anterior temporal lobectomy for treatment of epilepsy

The objective of this retrospective study was to determine if dual pathology [DUAL — focal cortical dysplasia (FCD) and mesial temporal sclerosis (MTS)] in patients with left temporal lobe epilepsy is associated with greater risk for cognitive decline following temporal lobectomy than single pathology (MTS only). Sixty-three adults (Mage=36.5years, female: 52.4%) who underwent left anterior temporal lobectomy for treatment of epilepsy (MTS=28; DUAL=35) completed preoperative and postoperative neuropsychological evaluations. The base rate of dual pathology was 55.5%. Repeated measures ANOVAs yielded significant 2-way interactions (group×time) on most measures of language and memory with generally moderate effect sizes. Specifically, patients with MTS only demonstrated postoperative declines, while those with dual pathology remained unchanged or improved. Results suggest that dual pathology may be associated with better cognitive outcome following epilepsy surgery than MTS alone, possibly reflecting limited functionality of the resected tissue or intrahemispheric reorganization of function in the context of a developmental lesion.

Naming outcome after left or right temporal lobectomy in patients with bilateral language representation by Wada testing

ObjectiveThis study aimed to examine language outcome after left or right anterior temporal lobectomy (ATL) in patients with epilepsy with bilateral language representation on intracarotid sodium amobarbital (Wada) testing. MethodsTwenty-two patients with epilepsy with bilateral language (Wada laterality index between −50 and 50) underwent right ATL (RATL, n=10) or left ATL (LATL, n=12). All the patients were administered the Boston Naming Test preoperatively and six months postoperatively. ResultsLeft anterior temporal lobectomy patients showed greater postoperative naming decline than RATL patients. Group differences were also observed on subtests of the Wada test. Performance on the Wada naming and comprehension subtests was better in the nonsurgical hemisphere than in the surgical hemisphere in the RATL group, but there was no difference between the nonsurgical and the surgical hemisphere naming and comprehension performance in the LATL group. ConclusionsLeft anterior temporal lobectomy patients with bilateral language are at greater risk for naming decline than RATL patients with bilateral language. This difference may be due to relatively better naming and comprehension abilities in the nonsurgical hemisphere in the RATL group.

Naming outcome prediction in patients with discordant Wada and fMRI language lateralization

ObjectiveInvestigations of the validity of fMRI as an alternative to Wada language testing have yielded Wada/fMRI discordance rates of approximately 15%, but almost nothing is known regarding the relative accuracy of Wada and fMRI in discordant cases. The objective of this study was to determine which of the two (the Wada test or the language fMRI) is more predictive of postoperative naming outcome following left anterior temporal lobectomy in discordant cases. MethodsAmong 229 patients with epilepsy who prospectively underwent Wada and fMRI language testing, ten had discordant language lateralization results, underwent left anterior temporal lobectomy, and returned for postoperative language testing. The relative accuracy of Wada and fMRI for predicting language outcome was examined in these cases. ResultsFunctional magnetic resonance imaging provided a more accurate prediction of language outcome in seven patients, Wada was more accurate in two patients, and the two tests were equally accurate in one patient. ConclusionsIn cases of discordance, fMRI predicted postsurgical naming outcome with relatively better accuracy compared to the Wada test.

Surgically proven coexistence of focal and generalized epilepsy: A case report

The coexistence of focal and idiopathic generalized epilepsy (IGE) is rarely observed, and the mechanism underlying this situation remains unknown. We report a 13-year-old girl with well-controlled generalized epilepsy and medically-refractory left temporal lobe epilepsy.She underwent intracranial EEG recording, which demonstrated two characteristic seizure patterns of generalized ictal onset and left mesial temporal onset. In addition, two types of interictal spike distribution, including the left mesial temporal region and generalized spikes, were also supportive of the coexistence of left mesial temporal lobe epilepsy and IGE. Thereafter, a left anterior temporal lobectomy and post-surgical medication significantly improved her seizure outcome. This case illustrates the importance of considering surgical management for patients with medically-intractable focal epilepsy coexisting with generalized epilepsy.

The functional anatomy of non-verbal (pitch memory) function in left and right anterior temporal lobectomy patients

An fMRI pitch memory task was administered to left and right anterior temporal lobectomy (ATL) patients. The goal was to verify the neuroanatomical correlates of non-verbal memory, and to determine if pitch memory tasks can identify cognitive risk prior to ATL. The data showed that the bilateral posterior superior temporal lobes implement pitch memory in both ATL patients and NCs (normal controls), indicating that the task can be accomplished with either anterior temporal lobe resected. NCs activate the posterior temporal lobes more strongly than ATL patients during highly accurate performance. In contrast, both ATL groups activate the anterior cingulate in association with accuracy. While our data clarifies the functional neuroanatomy of pitch memory, it also indicates that such tasks do not serve well to lateralize and functionally map potentially “at risk” non-verbal memory skills prior to ATL.

An investigation of implicit memory through left temporal lobectomy for epilepsy

Temporal lobe epilepsy patients have demonstrated a relative preservation in the integrity of implicit memory procedures. We examined performance in a verbal implicit and explicit memory task in left anterior temporal lobectomy patients (LATL) and healthy normal controls (NCs) while undergoing fMRI. We hypothesized that despite the relative integrity of implicit memory in both the LATL patients and normal controls, the two groups would show distinct functional neuroanatomic profiles during implicit memory. LATLs and NCs performed Jacoby’s Process Dissociation Process (PDP) procedure during fMRI, requiring completion of word stems based on the previously studied words or new/unseen words. Measures of automaticity and recollection provided uncontaminated indices of implicit and explicit memory, respectively. The behavioral data showed that in the face of temporal lobe pathology implicit memory can be carried out, suggesting implicit verbal memory retrieval is non-mesial temporal in nature. Compared to NCs, the LATL patients showed reliable activation, not deactivation, during implicit (automatic) responding. The regions mediating this response were cortical (left medial frontal and precuneus) and striatal. The active regions in LATL patients have the capacity to implement associative, conditioned responses that might otherwise be carried out by a healthy temporal lobe, suggesting this represented a compensatory activity. Because the precuneus has also been implicated in explicit memory, the data suggests this structure may have a highly flexible functionality, capable of supporting implementation of either explicit memory, or automatic processes such as implicit memory retrieval. Our data suggest that a healthy mesial/anterior temporal lobe may be needed for generating the posterior deactivation perceptual priming response seen in normals.

Memory Outcomes Following Selective Versus Nonselective Temporal Lobe Removal: A Systematic Review

The surgical removal of brain tissue for the treatment of temporal lobe epilepsy can be either nonselective, as with an anterior temporal lobectomy (ATL), or selective, as with a selective amygdalohippocampectomy (SAH). Although seizure outcomes are similar with both procedures, cognitive and memory outcomes remain a matter of debate. This study aims to evaluate current evidence with regard to memory outcomes in ATL and SAH. A systematic literature review was conducted combining the search term “memory” with each of the search terms “temporal lobe epilepsy surgery,”“anterior temporal lobectomy,” and “amygdalohippocampectomy,” with articles from 1995 to November 2011 included. A total of 27 articles met the inclusion criteria. These were compared using statistically significant outcomes from validated neuropsychological tests assessing verbal and visual memory. Analysis revealed that verbal memory decline is significantly associated with left ATL, while visual memory decline is significantly associated with right ATL. Evidence for memory outcomes in SAH, however, was inconclusive, as studies failed to show a consistent pattern with regard to type of memory decline and side of surgery. Surgery of the left temporal lobe relates to verbal memory decline, while surgery of the right temporal lobe relates to visual memory decline. Despite this generality, however, further research is necessary to determine the superiority of selective versus nonselective temporal surgical methods in regard to these memory outcomes and their effects on learning.

Discordance on FMRI and Wada Tests of Language Dominance in a Large Epilepsy Cohort (IN5-1.007)

Objective: To quantify discordance between fMRI and Wada language tests, identify factors associated with discordance, and compare the predictive value of each test in discordant cases. Background FMRI assessment of language dominance has begun to replace the traditional Wada test, but the incidence of discordance and factors underlying discordance between these tests have not been well defined. Design/Methods: Participants were 229 epilepsy patients who underwent both fMRI and Wada language testing. The fMRI protocol used a semantic decision task contrasted with a tone decision task. Patients were classified as left dominant, right dominant, or symmetric based on cutoff values applied to the lateralization index (LI, range -100 to +100) from each test. Results were discordant if the two tests failed to classify the patient in the same dominance category AND the LIs from the two tests differed by more than 50 units. A variety of Wada and fMRI quality measures were assessed for association with discordance. Regression formulas for predicting postoperative naming outcome were computed for each test based on data from the 56 left anterior temporal lobectomy patients in whom the tests were concordant, and these formulas were used to compare predicted and observed outcomes in patients with discordant fMRI and Wada. Results: Discordant results occurred in 30/229 patients (13.1%). The main predictor of discordance was the fMRI LI (p Conclusions: FMRI and Wada language dominance tests are generally concordant, though fMRI appears to be more sensitive for detecting atypical dominance. Overall, fMRI may provide a more accurate prediction of postoperative language outcome. Supported by: NIH grant R01 NS035929. Disclosure: Dr. Binder has nothing to disclose. Dr. Janecek has nothing to disclose. Dr. Swanson has nothing to disclose. Dr. Sabsevitz has nothing to disclose. Dr. Hammeke has nothing to disclose.

Hallucinations and Reversed Cerebral Dominance in Mesial Temporal Sclerosis

The localizing value of experiential phenomena in temporal and occipital lobe epilepsy has become increasingly elucidated. We describe complex visual and auditory hallucinations in a right-handed adolescent and review the localization value of ictal visual and auditory auras in partial epilepsy. A 15-year-old right-handed girl with 2 previous secondarily generalized seizures manifested a new semiology of complex visual and auditory hallucinations, characterized by seeing a school bus full of children and then hearing a male voice tell her to "feed the children." Feeling compelled, she "fed" the children, and they reboarded the bus and the bus drove away. Video electroencephalogram monitoring demonstrated fluent language during her seizures. Magnetic resonance imaging was compatible with left mesial temporal sclerosis. Fluorodeoxyglucose positron emission tomography demonstrated left temporal hypometabolism. An ictal single-photon emission computed tomography study demonstrated left anterior temporal hyperperfusion; Wada testing revealed reversed cerebral dominance. The patient underwent left anterior temporal lobectomy without complication and remains seizure-free. Complex auditory and visual hallucinations can occur in occipitotemporal and anteromedial temporal epilepsy. Reversed cerebral dominance is more common in children than adults and should be considered in any dextral person with fluent ictal speech with a left-sided epileptogenic lesion.

The effects of anterior temporal lobectomy on semantic network

This study examined the effects of anterior temporal lobectomy on semantic network. 22 patients who underwent left (LATL, n = 11) or right (RATL, n = 11) anterior temporal lobectomy were administered test of verbal fluency test, preoperatively and 3 weeks, 1 year postoperatively. The semantic network was derived by multidimensional scaling analysis based on data from the animal category fluency test. In the preoperative period LATL group showed the breakdown of semantic network, but the semantic network was conceptually organized in the postoperative period. The results indicated the reduction of seizure frequency improved the semantic network of LATL. On the other hand, RATL group showed persistent breakdown of semantic network after surgery. This suggested that the right anterior temporal lobe might be involved in semantic network.

Postoperative interictal epileptiform discharge within 1 month is associated with seizure recurrence after anterior temporal lobectomy

To investigate the relationship of interictal epileptiform discharges (IEDs) within 1 month of anterior temporal lobectomy (ATL) to seizure outcome, we reviewed data for 202 (107 left ATL, 95 right ATL) patients who had undergone ATL for mesial temporal epilepsy. Postoperative EEGs within 30 days and other preoperative variables were analyzed to examine the significant factors that determine freedom from disabling seizures. IEDs were noted in 29 (22.3%) of the 130 patients without seizures for 2 years after ATL compared with 31 (43.1%) of the 72 patients with recurrent seizures ( P = 0.002). Postoperative IEDs remained an independent predictive factor for seizure outcome by logistic regression (adjusted OR = 2.38, 95% CI = 1.18–4.81, P = 0.016, 2 years postoperatively; adjusted OR = 2.22, 95% CI = 1.03–4.82, P = 0.043, 5 years postoperatively) and Cox hazard regression analysis (adjusted HR = 1.76, 95% CI = 1.18–2.62, P = 0.006) after controlling for other predicting factors (unilateral hippocampal atrophy, history of febrile seizures, and IQ scores). In this study, IEDs on the EEG obtained soon after surgery were associated with postoperative seizure recurrence. These results can be used in the assessment of risk of seizure recurrence after ATL.

Neurocutaneous melanosis: surgical pathological features of an apparently hamartomatous lesion in the amygdala

Neurocutaneous melanosis (NCM) is a rare, congenital phakomatosis characterized by the presence of congenital melanocytic nevi and a benign or malignant pigmented cell tumor of the leptomeninges of the CNS. Here the authors report the surgical pathological features of a lesion in the left amygdala in a 10-year-old girl with giant congenital pigmented nevi and mesial temporal lobe epilepsy. The lesion exhibited high intensity on T1-weighted MR images and low intensity to isointensity on T2-weighted images. A left anterior temporal lobectomy and hippocampectomy were performed. Histologically, the lesion was composed of melanin-containing polygonal cells arranged in solid alveolar or multiple lobular patterns. Immunohistochemically, the cells were immunoreactive for HMB45, S100 protein, and vimentin, the profiles being consistent with those of melanocytes. Bundles of astrocytic processes surrounded the nests of melanocytes. Melanin-containing and dysmorphic neurons were also scattered near the nests. In the temporal neocortex adjacent to the amygdaloid melanocytic lesion, cortical dysplasia with cortical laminar disorganization was evident. Based on the histopathological features, the parenchymal lesion appeared to be hamartomatous in nature rather than a neoplasm, involving aberrant migration of melanocytes into the developing neuroepithelial tissue. This case appears to represent an unusual CNS manifestation of NCM.

Visual naming performance after ATL resection: Impact of atypical language dominance

Purpose To characterize the interaction between language dominance and lateralization of the epileptic focus for pre- and postoperative Boston Naming Test (BNT) performance in patients undergoing anterior temporal lobectomy (ATL). Methods Analysis of pre- and postoperative BNT scores depending on lateralization of language as measured by the intracarotid amobarbital procedure (IAP) versus lateralization of the temporal lobe epileptic focus. Results Changes between pre- and postoperative BNT performance depended on epilepsy lateralization (effect size = 0.189) with significant decrease in patients undergoing left ATL. Subgroup analysis in these showed that postoperative decline in BNT scores was significant in patients with atypical ( n = 14; p < 0.05), but did not reach statistical significance in patients with left language dominance ( n = 36; p = 0.09). Chi-square test revealed a trend of higher proportions of patients experiencing significant postsurgical deterioration in naming performance in atypical (57.1%) as compared to left language dominance (30.6%; p = 0.082). Surgical failure was also associated with greater decline of BNT scores and was more common in atypical than in left language dominant patients ( χ 2 (1, n = 98) = 4.62, p = 0.032). Age of onset, duration of epilepsy, and seizure frequency had no impact on changes in BNT performance. Conclusion Atypical language dominance is a predictor of change in visual naming performance after left ATL and may also impact postsurgical seizure control. This should be considered when counseling surgical candidates.

Visual memory in patients after anterior right temporal lobectomy and adult normative data for the Brown Location Test

Several large meta-analytic studies have failed to support a consistent relationship between visual or “nonverbal” memory deficits and right mesial temporal lobe changes. The Brown Location Test (BLT), a recently developed dot location learning and memory test, uses a nonsymmetrical array and provides control over many of the confounding variables (e.g., verbal influence and drawing requirements) inherent in other measures of visual memory. In the present investigation, we evaluated the clinical utility of the BLT in patients who had undergone left or right anterior mesial temporal lobectomy. We also provide normative data of 298 healthy adults for standardized scores. Results revealed significantly worse performance on the BLT in the right as compared to the left lobectomy group and the healthy adult normative sample. The present findings support a role for the right anterior mesial temporal lobe in dot location learning and memory.

Cortical reorganization following anterior temporal lobectomy in patients with temporal lobe epilepsy

Functional MRI was used to study the impact of temporal lobe epilepsy (TLE) and anterior temporal lobectomy (ATL) on the cortical language network in patients with medically refractory TLE. Nineteen patients with medically refractory TLE and 11 healthy control subjects were enrolled in this study. Ten patients underwent left ATL (mean age 35.2 +/- 3.8 years), and 9 underwent right ATL (mean age 35.9 +/- 2.6 years). The subjects silently generated verbs in response to a series of visually presented nouns inside the scanner. Correlation analysis was performed between the subjects' performance on the clinical language tests and their neural response in the a priori cortical regions. Preoperative data revealed that the patients with TLE showed increased neural activity in the right inferior frontal gyri (IFG) and middle frontal gyri (MFG). The right TLE patients demonstrated strong correlation between their language performance and the level of cortical activation within the typical language areas. However, such a correlation was absent in the left TLE patients. After the ATL surgery, the left TLE patients showed reduced activation in the left MFG and right IFG, whereas no difference was observed in the right TLE patients. In the right TLE patients, the correlation between language performance and neural response shifted from the typical language areas to the anterior cingulate cortex. This study demonstrates that the cortical language network is affected differently by the left and right temporal lobe epilepsy and is reorganized after anterior temporal lobectomy.

Pathophysiological implications of focal cortical dysplasia of end folium for hippocampal sclerosis

Dual pathology is a well-known cause of temporal lobe epilepsy (TLE), but TLE associated with dual pathology within the hippocampus has rarely been reported. We describe a patient with medically refractory TLE due to a focal cortical dysplasia of the end folium of the left hippocampus (i.e. CA4) and left hippocampal sclerosis (HS) that was successfully treated with left anterior temporal lobectomy and speculate on the interaction between end folium sclerosis and HS.

Poor presurgical performance on both verbal and visual memory measures is associated with low risk for memory decline following left temporal lobectomy for intractable epilepsy

Studies have shown a lower risk for verbal memory decline following dominant anterior temporal lobectomy (ATL) among patients with poor, presurgical verbal memory scores. It is unclear however, if the risk of decline is increased in patients who also have reduced visual memory. Objective and subjective memory outcome following left ATL was examined in twelve patients with reduced presurgical visual and verbal memory scores. Only one patient demonstrated a meaningful decline in memory scores, with a decline in visual memory following surgery. Presurgically, this patient demonstrated poor memory bilaterally on Wada testing and small discrepancy in hippocampal volumes. She was also one of two patients who continued to have seizures post-surgery. This preliminary study suggests that patients with unilateral, left TLE and poor verbal and visual memory are unlikely to show meaningful memory declines following left ATL, particularly if they demonstrate expected patterns on Wada testing, hippocampal volume discrepancy (left < right), and postsurgical seizure-freedom.

Use of preoperative functional MRI to predict verbal memory decline after temporal lobe epilepsy surgery

Verbal memory decline is a frequent complication of left anterior temporal lobectomy (L-ATL). The goal of this study was to determine whether preoperative language mapping using functional magnetic resonance imaging (fMRI) is useful for predicting which patients are likely to experience verbal memory decline after L-ATL. Sixty L-ATL patients underwent preoperative language mapping with fMRI, preoperative intracarotid amobarbital (Wada) testing for language and memory lateralization, and pre- and postoperative neuropsychological testing. Demographic, historical, neuropsychological, and imaging variables were examined for their ability to predict pre- to postoperative memory change. Verbal memory decline occurred in over 30% of patients. Good preoperative performance, late age at onset of epilepsy, left dominance on fMRI, and left dominance on the Wada test were each predictive of memory decline. Preoperative performance and age at onset together accounted for roughly 50% of the variance in memory outcome (p < 0.001), and fMRI explained an additional 10% of this variance (p <or= 0.003). Neither Wada memory asymmetry nor Wada language asymmetry added additional predictive power beyond these noninvasive measures. Preoperative fMRI is useful for identifying patients at high risk for verbal memory decline prior to L-ATL surgery. Lateralization of language is correlated with lateralization of verbal memory, whereas Wada memory testing is either insufficiently reliable or insufficiently material-specific to accurately localize verbal memory processes.

Lexical retrieval and semantic knowledge in patients with left inferior temporal lobe lesions

Background: It has been proposed that anomia following left inferior temporal lobe lesions may have two different underlying mechanisms with distinct neural substrates. Specifically, naming impairment following damage to more posterior regions (BA 37) has been considered to result from a disconnection between preserved semantic knowledge and phonological word forms (pure anomia), whereas anomia following damage to anterior temporal regions (BAs 38, 20/21) has been attributed to the degradation of semantic representations (semantic anomia). However, the integrity of semantic knowledge in patients with pure anomia has not been demonstrated convincingly, nor were lesions in these cases necessarily confined to BA 37. Furthermore, evidence of semantic anomia often comes from individuals with bilateral temporal lobe damage, so it is unclear whether unilateral temporal lobe lesions are sufficient to produce significant semantic impairment. This research was supported by a Graduate Imaging Fellowship from the University of Arizona and by NIH grants RO1DC008286 and RO1DC07464. Scans were funded through Arizona Alzheimer's Research Consortium, Cognition and NeuroImaging Lab, Arizona Department of Health Services HB2354. Many thanks to Jen Parrott, Kristin Boruff, and Cathy West for their time and assistance. The authors thank Mark Borgstrom, statistical consultant at the University of Arizona, for his assistance with this project. We also thank Chris Rorden for advice regarding lesion analyses. Aims: The main goals of this study were to determine whether anomia following unilateral left inferior temporal lobe damage reflected a loss of semantic knowledge or a post‐semantic deficit in lexical retrieval and to identify the neuroanatomical correlates of the naming impairment. Methods & Procedures: Eight individuals who underwent left anterior temporal lobectomy (L ATL) and eight individuals who sustained left posterior cerebral artery strokes (L PCA) completed a battery of language measures that assessed lexical retrieval and semantic processing, and 16 age‐ and education‐matched controls also completed this battery. High‐resolution structural brain scans were collected to conduct lesion analyses. Outcomes & Results: Performance of L ATL and L PCA patients was strikingly similar, with both groups demonstrating naming performance ranging from moderately impaired to unimpaired. Anomia in both groups occurred in the context of mild deficits to semantic knowledge, which manifested primarily as greater difficulty in naming living things than nonliving things and greater difficulty in processing visual/perceptual as opposed to functional/associative semantic attributes. Lesion analyses indicated that both patient groups sustained damage to anterior inferior temporal lobe regions implicated in semantic processing. Conclusions: These results contribute to a better understanding of the cognitive mechanism of naming impairment in patients with temporal lobe damage and support the notion that pure anomia and semantic anomia represent two endpoints along a continuum of semantic impairment. Unilateral left temporal lobe lesions in our patients resulted in relatively mild semantic deficits that were apparent primarily in lexical production tasks, whereas severe semantic impairment likely requires bilateral temporal lobe damage.