Effects of anterior temporal lobectomy on cognitive function

Positron Emission Tomography (PET) in presurgical planning of anterior temporal lobectomy: A systematic review of efficacy and limitations

INTRODUCTION

Temporal lobe epilepsy (TLE), a debilitating neurological disorder, necessitates refined diagnostic and treatment strategies. This comprehensive review appraises the potential of positron emission tomography (PET) in enhancing the presurgical planning of Anterior Temporal Lobectomy (ATL) for patients afflicted with TLE.

METHODS

A comprehensive literature search was conducted using the PubMed, SCOPUS, and ScienceDirect databases from 1985 to 2022, following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for studies investigating PET and ATL. This review studied a range of radiotracers, including FDG, H2O, FMZ, MPPF, and FCWAY, analyzing their efficacy in detecting epileptogenic foci, establishing resection boundaries, and predicting postoperative outcomes. The study paid special attention to cases where MRI findings were inconclusive.

RESULTS

A total of 52 studies were included in the final analysis. Our analysis revealed that FDG-PET imaging was instrumental in identifying seizure foci and predicting postoperative results. It exhibited significant value in situations where structural abnormalities were absent on MRI scans. Furthermore, newer radiotracers such as 5-HT1A antagonists, FCWAY and MPPF, presented promising potential for localizing seizure foci, particularly in MRI-negative TLE, despite their comparatively limited current usage.

CONCLUSION

PET imaging, although challenged by issues such as radiation exposure, limited accessibility, and high costs, offers considerable promise. Integration with other imaging modalities, such as EEG and MRI, has contributed to improved localization of epileptogenic foci and subsequently, enhanced surgical outcomes. Further research must focus on establishing the relative efficacy and optimal combinations of these radiotracers in the orchestration of ATL surgical planning and prognostication of postoperative outcomes for TLE patients. Encouragingly, these advancements hold the potential to revolutionize the management of TLE, delivering a better quality of life for patients.

Outcomes after laser interstitial thermal ablation for temporal lobe epilepsy: a systematic review and meta-analysis

Epilepsy is a common condition that affects approximately 1% of the world's population, with about one-third being refractory epilepsy. Temporal lobe epilepsy is the most common type of drug-resistant epilepsy, and laser interstitial thermal therapy (LITT) is an innovative treatment. In this systematic review and meta-analysis, we aimed to summarize the current evidence on outcomes after LITT, including seizure freedom rate, complication rate, and neurocognitive outcome. PubMed and OVID Medline search engines were systematically searched for all indexed publications in the English language up to July15, 2023. The search was limited to human studies. Proportions and 95% confidence interval (CI) values were calculated for seizure, neurocognitive outcome, and complication rate. A total of 836 patients were included. Overall seizure outcomes, regardless of the pathology, included Engel I outcome in 56% (95% CI, 52.4-59.5%), Engel II outcome in 19.2% (95% CI, 15.4-23.6%), Engel III outcome in 17.3% (95% CI, 13.5-21.8%), and Engel IV outcome in 10.5% (95% CI 6.3-17%) of the patients. The overall decline in verbal and visual memory regardless of laterality was 24.2 (95% CI 8.6-52%) and 25.2% (8.3-55.8%). For naming, the decline was 13.4% (6.6-25.4%). The results of the pooled analysis in comparison with available data in the literature showed that seizure outcomes after LITT were slightly inferior to published data after temporal lobectomy. Data on cognitive outcomes after LITT are scarce and heterogeneous.

Lobectomy versus gross total resection for glioblastoma multiforme: A systematic review and individual-participant data meta-analysis

Overall survival (OS)for glioblastoma multiforme (GBM) has a known association with the extent of tumor resection with gross total resection (GTR) typically considered as the upper limit. In certain regions such as the anterior temporal lobe, more extensive resection by means of a lobectomy may be feasible. In our systematic review and meta-analysis, we aimed to compare the outcomes of lobectomy and GTR for GBM. PubMed and Embase were queriedfor studies that compared the outcomes after lobectomy or GTR for GBM. The primary outcomes were OS, progression-free survival (PFS), and Karnofksy Performance Status (KPS) score at the latest follow-up. The secondary outcomes were seizure control at the latest follow-up and complication rates. Meta-analysis for OS and PFS was performed using individual-participant data reconstructed from published Kaplan-Meier curves. Random-effect meta-analysis was performed for KPS. The secondary outcomes were pooled using descriptive statistics. Of the 795 records screened, 6 were included in our study. Meta-analysis revealed that anterior temporal, frontal, or occipital lobectomy was associated with significantly better OS (p < 0.001) and PFS (p < 0.001) than GTR, but not KPS (MD = 6.37; 95% CI=(-13.80, 26.54); p = 0.536). Anterior temporal lobectomy was associated with significantly better seizure control rates than GTR for temporal GBM (OR = 27; 95% CI=(1.4, 515.9); p = 0.002). There was no statistically significant difference in complication rates between anterior temporal, frontal, or occipital lobectomy and GTR. In conclusion, lobectomy was associated with significantly better OS, PFS, and seizure control than GTR for GBM.

Nonverbal memory tests revisited: Neuroanatomical correlates and differential influence of biasing cognitive functions

The detection of right temporal lobe dysfunction with nonverbal memory tests has remained difficult in the past. Reasons for this might be the potential influence of other biasing cognitive functions such as executive functions or the verbalisability of nonverbal material. The aim of this study was to investigate three classic nonverbal memory tests by identifying their neuroanatomical correlates with lesion-symptom mapping (LSM) and by probing their independence from verbal encoding abilities and executive functions. In a cohort of 119 patients with first-time cerebrovascular accident, memory performance was assessed in the Nonverbal Learning and Memory Test for Routes (NLMTR), the Rey Complex Figure Test (RCFT), and the Visual Design Learning Test (VDLT). Calculating multivariate LSM, we identified crucial brain structures for these three nonverbal memory tests. Behavioural analyses were performed to assess the impact of executive functions and verbal encoding abilities with regression analyses and likelihood-ratio tests. LSM revealed for the RCFT mainly right-hemispheric frontal, insular, subcortical, and white matter structures and for the NLMTR right-hemispheric temporal (hippocampus), insular, subcortical, and white matter structures. The VDLT did not reach significance in LSM analyses. Behavioural results showed that amongst the three nonverbal memory tests the impact of executive functions was most pronounced for RCFT, and the impact of verbal encoding abilities was most important in VDLT. Likelihood-ratio tests confirmed that only for NLMTR did the goodness of fit not significantly improve by adding executive functions or verbal encoding abilities. These results suggest that amongst the three nonverbal memory tests the NLMTR, as a spatial navigation test, could serve as the most suitable marker of right-hemispheric temporal lobe functioning, with the right hippocampus being involved only in this test. In addition, the behavioural results propose that only NLMTR seems mostly unaffected by executive functions and verbal encoding abilities.

Lateralized differences for verbal learning across trials in temporal lobe epilepsy are not affected by surgical intervention

This research aimed to broaden understanding of learning verbal material in participants with left- and right-sided mesial temporal lobe epilepsy (MTLE). We modeled word list-learning to determine how anterior temporal lobe resection affects verbal learning. Verbal learning (across trials) was assessed using the first five trials of the Rey Auditory Verbal Learning Test (RAVLT) in 128 participants with MTLE. Mixedeffects modeling was used to determine whether learning curves differed between participants with left- and right-sided MTLE pre- and post- anterior temporal lobe resection. Laterality of MTLE had a significant effect on both the model intercept and the linear slope, whereby participants with left-sided MTLE retained fewer words on both the first trial and on each subsequent trial than participants with right-sided MTLE; and this held regardless of anterior temporal lobe resection status (t(117) = -3.516, p < .001; t(120.50) = -2.049, p = .042, for intercept and linear slope, respectively). There were no significant differences in the learning curves after anterior temporal lobe resection surgery in either left- or right-sided MTLE. Our findings suggest that acquisition of verbal information may be especially impaired in patients with left-sided MTLE. Further, we show that verbal learning across trials was not affected by surgical intervention. This finding contributes to the broader understanding of the impacts of anterior temporal lobe resection on verbal memory function, and has important implications for the clinical management and surgical planning for patients with temporal lobe epilepsy.

A Connectomic Atlas of the Human Cerebrum-Chapter 6: The Temporal Lobe

In this supplement, we build on work previously published under the Human Connectome Project. Specifically, we show a comprehensive anatomic atlas of the human cerebrum demonstrating all 180 distinct regions comprising the cerebral cortex. The location, functional connectivity, and structural connectivity of these regions are outlined, and where possible a discussion is included of the functional significance of these areas. In part 6, we specifically address regions relevant to the temporal lobe.

Standardization of an Arabic-Language Neuropsychological Battery for Epilepsy Surgical Evaluations

OBJECTIVES

This study provides a standardized Arabic language neuropsychological test battery and tests its ability to distinguish patients with left and right hemisphere epileptic foci who are candidates for surgical resection.

METHODS

An Arabic language battery of 15 tests was developed based on the neuropsychological test battery used at the Johns Hopkins Hospital for surgical evaluation of patients undergoing temporal lobe resection. With modifications where culturally required, 11 tests were translated to Arabic by the principal investigator and back-translated by two bilingual health professionals; four tests were available in Arabic and added to the battery. The battery was administered to 21 Arabic-speaking patients with left temporal epileptic foci, 21 with right temporal epileptic foci, and 46 neurologically and psychiatrically healthy adults.

RESULTS

Nearly all the Arabic test versions were capable of differentiating healthy controls and the temporal lobe epilepsy (TLE) groups. Tests known to distinguish left and right temporal lobectomy candidates, such as wordlist memory and prose recall, were able to do so as accurately as the English versions. Also, a roughly "culturally free" task (the Baltimore Board) and a newly developed version of the Boston Naming Test demonstrated some sensitivity to left temporal lobe involvement.

CONCLUSIONS

Arabic-language neuropsychological tests for epilepsy surgical evaluations are made available, demonstrate cultural sensitivity and clinical validity, and require further psychometric property and normative research. (JINS, 2019, 25, 761-771).

Improvement in cognitive function after surgery for low-grade glioma

OBJECTIVE

Cognition is a key component in health-related quality of life (HRQoL) and is currently incorporated as a major parameter of outcome assessment in patients treated for brain tumors. The effect of surgery on cognition and HRQoL remains debatable. The authors investigated the impact of resection of low-grade gliomas (LGGs) on cognition and the correlation with various histopathological markers.

METHODS

A retrospective analysis of patients with LGG who underwent craniotomy for tumor resection at a single institution between 2010 and 2014 was conducted. Of 192 who underwent resective surgery for LGG during this period, 49 had complete pre- and postoperative neurocognitive evaluations and were included in the analysis. These patients completed a full battery of neurocognitive tests (memory, language, attention and working memory, visuomotor organization, and executive functions) pre- and postoperatively. Tumor and surgical characteristics were analyzed, including volumetric measurements and histopathological markers (IDH, p53, GFAP).

RESULTS

Postoperatively, significant improvement was found in memory and executive functions. A subgroup analysis of patients with dominant-side tumors, most of whom underwent intraoperative awake mapping, revealed significant improvement in the same domains. Patients whose tumors were on the nondominant side displayed significant improvement only in memory functions. Positive staining for p53 testing was associated with improved language function and greater extent of resection in dominant-side tumors. GFAP positivity was associated with improved memory in patients whose tumors were on the nondominant side. No correlation was found between cognitive outcome and preoperative tumor volume, residual volume, extent of resection, or IDH1 status.

CONCLUSIONS

Resection of LGG significantly improves memory and executive function and thus is likely to improve functional outcome in addition to providing oncological benefit. GFAP and pP53 positivity could possibly be associated with improved cognitive outcome. These data support early, aggressive, surgical treatment of LGG.

The association between childhood trauma and memory functioning in schizophrenia

OBJECTIVE

Both neurocognitive impairments and a history of childhood abuse are highly prevalent in patients with schizophrenia. Childhood trauma has been associated with memory impairment as well as hippocampal volume reduction in adult survivors. The aim of the following study was to examine the contribution of childhood adversity to verbal memory functioning in people with schizophrenia.

METHODS

Eighty-five outpatients with a Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) diagnosis of chronic schizophrenia were separated into 2 groups on the basis of self-reports of childhood trauma. Performance on measures of episodic narrative memory, list learning, and working memory was then compared using multivariate analysis of covariance.

RESULTS

Thirty-eight (45%) participants reported moderate to severe levels of childhood adversity, while 47 (55%) reported no or low levels of childhood adversity. After controlling for premorbid IQ and current depressive symptoms, the childhood trauma group had significantly poorer working memory and episodic narrative memory. However, list learning was similar between groups.

CONCLUSION

Childhood trauma is an important variable that can contribute to specific ongoing memory impairments in schizophrenia.

Presurgical epilepsy localization with interictal cerebral dysfunction

Localization of interictal cerebral dysfunction with 2-[(18)F]fluoro-2-D-deoxyglucose (FDG) positron emission tomography (PET) and neuropsychological examination usefully supplements electroencephalography (EEG) and brain magnetic resonance imaging (MRI) in planning epilepsy surgery. In MRI-negative mesial temporal lobe epilepsy, correlation of temporal lobe hypometabolism with extracranial ictal EEG can support resection without prior intracranial EEG monitoring. In refractory localization-related epilepsies, hypometabolic sites may supplement other data in hypothesizing likely ictal onset zones in order to intracranial electrodes for ictal recording. Prognostication of postoperative seizure freedom with FDG PET appears to have greater positive than negative predictive value. Neuropsychological evaluation is critical to evaluating the potential benefit of epilepsy surgery. Cortical deficits measured with neuropsychometry are limited in lateralizing and localizing value for determination of ictal onset sites, however. Left temporal resection risks iatrogenic verbal memory deficits and dysnomia, and neuropsychological findings are useful in predicting those at greatest risk. Prognostication of cognitive risks with resection at other sites is less satisfactory.

[Memory improvement in patients with temporal lobe epilepsy at one-year postoperative]

INTRODUCTION

Several studies have assessed the impact of surgery on both anterograde and remote memory in patients with temporal lobe epilepsy (TLE). The majority of results have shown an extensive memory deficit in patients after temporal resection (TL). However, few protocols have used a prospective longitudinal design. Moreover, the postoperative delays were variable from one study to the next, instead of regular monitoring to identify the potential effect of time elapsed after surgery on memory performance. In addition, some studies have not used strict inclusion criteria to establish homogeneous patient groups. Finally, the impact of surgery on memory has been often assessed by comparing memory skills between epileptic patients and healthy controls. Our aim was to examine the impact of TL on memory in patients with TLE, recruited according to clear-cut clinical criteria. Moreover, we focused on memory performance progression per se in epileptic patients pre- and postoperatively, rather than on memory performance analysis expressed as "deficient" or "normal".

METHODS

We assessed 30 patients with unilateral TLE (17 right TLE and 13 left TLE) on four anterograde memory tests and six remote memory tasks. Patients completed all tests preoperatively, and 5 and 12 months after TL.

RESULTS

Five months after surgery, performance was equivalent to the preoperative scores for both groups in anterograde memory tasks and remote memory tests. One year after TL, patients with right TLE showed enhanced performance in the verbal anterograde memory tests and in retrieving recent autobiographical memories. Results for left TL showed improved scores only in a recognition memory test of faces.

CONCLUSIONS

In the present study, surgical patients were "double winners" gaining seizure freedom and potential of memory stability or recovery. The gain was observed only 12 months after surgery and following temporal resection lateralisation. Our data showed postoperative memory improvement in patients with temporal lobe epilepsy presenting with specific clinical characteristics.

Different spatial memory systems are involved in small- and large-scale environments: evidence from patients with temporal lobe epilepsy

Recent reports show that humans and animals do not acquire information about routes and object locations in the same way. In spatial memory, a specific sub-system is hypothesized to be involved in encoding, storing and recalling navigational information, and it is segregated from the sub-system devoted to small-scale environment. We assessed this hypothesis in a sample of patients treated surgically for intractable temporal lobe epilepsy. We found double dissociations between learning and recall of spatial positions in large space versus small space. These results strongly support the hypothesis that two segregate systems process navigational memory for large-scale environments and spatial memory in small-scale environments.

Trans-Sylvian selective amygdalohippocampectomy for medically intractable temporal lobe epilepsy: a single-centre experience

Selective amygdalohippocampectomy (SelAH) is now widely used in the surgical treatment of patients with medically intractable medial temporal lobe epilepsy (MTLE). We present our single-centre experience of a uniform series of drug-resistant MTLE patients treated exclusively with SelAH. A retrospective study of 50 adult patients (25 males, 25 females, mean age 34 years) suffering from medically intractable MTLE was conducted. All patients has been investigated under the same protocol and operated by SelAH performed by one surgeon. Immediate and long-term follow-up was also available and is presented. Forty-two patients (84%) became seizure free (Engel's I); eight of them (16%) were classified as Engel's II; four (8%) as Engel's III; and one as Engel's IV (2%). In 42 of them the final result has been achieved after a single operation, while in the rest eight after a second or third surgical procedure. The mean follow-up period was 6.2 years. Two permanent complications (4%) with no treatment-related mortality have been detected. SelAH performed in well selected cases, where concordance between electrophysiological and MR findings exists, can be a safe and effective surgical treatment method for medically intractable MTLE.

Structural and functional correlates of unilateral mesial temporal lobe spatial memory impairment

The aim of this study was to explore the effects of preoperative and postoperative lateralized mesial temporal damage on three measures of spatial learning: navigation, object location and plan drawing, and to determine the relationship between volumetry of the hippocampus and memory performance. Fifteen patients with well-characterized unilateral hippocampal sclerosis, 15 patients who had undergone unilateral anterior temporal lobectomy (ATL), and a comparison group consisting of 15 patients with idiopathic generalized epilepsy and 25 neurologically healthy participants explored a novel virtual environment. Volumetric analyses of both hippocampi were conducted on unilateral hippocampal sclerosis and idiopathic generalized epilepsy patients' T(1)-weighted magnetic resonance imaging scans. Performance of temporal lobe epilepsy (TLE) patients (either unilateral hippocampal sclerosis or anterior temporal lobectomy) on the different spatial memory variables, namely navigation, object location and plan drawing, was significantly worse relative to the comparison groups (either idiopathic generalized epilepsy or controls). Patients with right TLE did not differ from patients with left TLE on any of the spatial memory measures. An index of absolute hippocampal asymmetry did not correlate with any of the spatial memory measures. Together, our lesion and volumetry findings suggest that the domain of spatial memory is systematically related to the integrity of both right and left mesial temporal lobe, and is unlikely to be a strongly lateralized function. From the standpoint of cerebral organization (lateralization), the notion of material-specificity, which postulates that all components of verbal and spatial memory are lateralized in their entirety to the left and right hemispheres, respectively, requires modification. Instead it would appear that the notion of task-specificity is a more accurate description of patterns of lateralization of spatial memory.

Changes in individual and group spatial and verbal learning characteristics after anterior temporal lobectomy

PURPOSE

To evaluate the effects of anterior temporal lobectomy (ATL) on individual and group spatial and verbal learning and memory abilities as a function of side of surgery and seizure control outcome.

METHODS

We evaluated pre- and postsurgical learning and memory abilities of 75 left-hemisphere language dominant individuals who underwent ATL (33 left, 42 right) using the 8-trial Nonverbal Selective Reminding test and the 12-trial Verbal Selective Reminding test.

RESULTS

Reliable change index methods indicated that 40.5% of individuals who underwent right-ATL had a clinically significant decline in spatial memory, and 62.5% of individuals who underwent left-ATL had a significant reduction in verbal memory. Growth curve analyses indicated that both side of surgery and poor seizure outcome independently affected the learning slope in the best fitting models. Left-ATL reduced the slope, but did not affect the overall shape, of verbal learning across trials. On the other hand, poor seizure control outcome affected the slope of spatial learning regardless of the side of surgery.

DISCUSSION

Results demonstrate both individual and group declines in spatial memory and learning after ATL. Results suggest that individuals who undergo right-ATL should be counseled regarding the likelihood of a decline in spatial memory and learning abilities after ATL. Results also suggest that individuals with poor seizure control after ATL should be referred for rehabilitation services given the significant declines in spatial and verbal memory that occurred in our sample regardless of side of surgery.

Preoperative fMRI predicts memory decline following anterior temporal lobe resection

BACKGROUND

Anterior temporal lobe resection (ATLR) benefits many patients with refractory temporal lobe epilepsy (TLE) but may be complicated by material specific memory impairments, typically of verbal memory following left ATLR, and non-verbal memory following right ATLR. Preoperative memory functional MRI (fMRI) may help in the prediction of these deficits.

OBJECTIVE

To assess the value of preoperative fMRI in the prediction of material specific memory deficits following both left- and right-sided ATLR.

METHODS

We report 15 patients with unilateral TLE undergoing ATLR; eight underwent dominant hemisphere ATLR and seven non-dominant ATLR. Patients performed an fMRI memory paradigm which examined the encoding of words, pictures and faces.

RESULTS

Individual patients with relatively greater ipsilateral compared with contralateral medial temporal lobe activation had greater memory decline following ATLR. This was the case for both verbal memory decline following dominant ATLR and for non-verbal memory decline following non-dominant ATLR. For verbal memory decline, activation within the dominant hippocampus was predictive of postoperative memory change whereas activation in the non-dominant hippocampus was not.

CONCLUSION

These findings suggest that preoperative memory fMRI may be a useful non-invasive predictor of postoperative memory change following ATLR and provide support for the functional adequacy theory of hippocampal function. They also suggest that fMRI may provide additional information, over that provided by neuropsychology, for use in the prediction of postoperative memory decline.

Diffusion-based magnetic resonance imaging and tractography in epilepsy

Diffusion-based imaging is an advanced MRI technique that is sensitive to the movement of water molecules, providing additional information on the micro-structural arrangement of tissue. Qualitative and quantitative analysis of peri, post and interictal diffusion images can aid the localization of seizure foci. Diffusion tensor tractography is an extension of diffusion-based imaging, and can provide additional information about white matter pathways. Both techniques are able to increase understanding of the effects of epilepsy on the structural organization of the brain, and can be used to optimize presurgical planning of patients with epilepsy. This review focuses on the basis, applications, limitations, and future directions of diffusion imaging in epilepsy. Literature search strategy: We searched Pubmed using the terms "diffusion MRI or diffusion tensor MRI or tractography and epilepsy."

Tractography of the parahippocampal gyrus and material specific memory impairment in unilateral temporal lobe epilepsy

INTRODUCTION

Temporal lobe epilepsy (TLE) is associated with disrupted memory function. The structural changes underlying this memory impairment have not been demonstrated previously with tractography.

METHODS

We performed a tractography analysis of diffusion magnetic resonance imaging scans in 18 patients with unilateral TLE undergoing presurgical evaluation, and in 10 healthy controls. A seed region in the anterior parahippocampal gyrus was selected from which to trace the white matter connections of the medial temporal lobe. A correlation analysis was carried out between volume and mean fractional anisotropy (FA) of the connections, and pre-operative material specific memory performance.

RESULTS

There was no significant difference between the left and right sided connections in controls. In the left TLE patients, the connected regions ipsilateral to the epileptogenic region were found to be significantly reduced in volume and mean FA compared with the contralateral region, and left-sided connections in control subjects. Significant correlations were found in left TLE patients between left and right FA, and verbal and non-verbal memory respectively.

CONCLUSION

Tractography demonstrated the alteration of white matter pathways that may underlie impaired memory function in TLE. A detailed knowledge of the integrity of these connections may be useful in predicting memory decline in chronic temporal lobe epilepsy.

Update on epilepsy and cerebral localization

The field of epilepsy has contributed significantly to localization of neurologic function, particularly in the neocortex. Methodologies such as cortical stimulation, positron emission tomography, functional MRI, trans-cranial magnetic stimulation, surgical resection, and magnetoencephalography have been used successfully in patients with epilepsy to locate specific functions, primarily for the purpose of defining eloquent cortex before surgical resections. The left hemisphere serves language-related functions and verbal memory in most people, whereas the right hemisphere serves some language function in addition to perceiving most components of music and other forms of nonverbal material. Both hemispheres cooperate in understanding spatial relationships. Studies in patients with developmental abnormalities have enriched our understanding of localization of function within the cortex. Future studies may help us understand the sequence in which specific regions are activated during specific tasks and determine which regions are necessary for tasks and which are supplementary. The ability to predict preoperatively the effect of removal of specific tissues would benefit surgical planning for all patients who undergo cortical resections, including those with epilepsy.

Memory and the medial temporal lobe: hemispheric specialization reconsidered

The role of the medial temporal lobe in learning and memory has been well established in research on humans and other animals. In humans, clinical and neuroimaging studies typically suggest material-specific lateralization in which the left and right temporal lobes are associated with verbal and nonverbal memory, respectively. It is often assumed that the temporal lobes are functionally alike, differing only in terms of the content to be learned. Here we present data that challenge this notion, showing that the type of material used during a memory task can influence fMRI activation patterns beyond the expected left-verbal/right-nonverbal dichotomy. Our results also suggest some degree of functional asymmetry in the medial temporal lobe that is independent of material type, pointing to underlying processing differences between the left and right temporal lobes.

Reorganization of verbal and nonverbal memory in temporal lobe epilepsy due to unilateral hippocampal sclerosis

Purpose: Patients with temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) often suffer from material-specific memory impairments. The purpose of this study was to use functional magnetic resonance imaging (fMRI) to study the organization of specific memory functions in these patients.

Methods: We report 14 patients with unilateral TLE and HS, and 10 controls, performing an fMRI memory paradigm of word, picture, and face encoding.

Results: Compared with controls, patients with left TLE demonstrated less left MTL and greater right MTL activation and patients with right TLE demonstrated less right MTL and greater left MTL activation. Correlations between fMRI activation and memory performance revealed greater activation in the damaged left hippocampus to be correlated with better verbal memory performance in left TLE patients and greater right hippocampal activation to be correlated with better nonverbal memory in right TLE patients. Conversely, greater fMRI activation in the contralateral hippocampus correlated with worse memory performance.

Conclusions: Our findings suggest that memory function in unilateral TLE is better when it is sustained by activation within the damaged hippocampus and that reorganization to the undamaged MTL is an inefficient process, incapable of preserving memory function.

Evaluating the contributions of state-of-the-art assessment techniques to predicting memory outcome after unilateral anterior temporal lobectomy

PURPOSE

Although anterior temporal lobectomy (ATL) is an effective treatment for many patients with medically refractory temporal lobe epilepsy (TLE), one risk associated with this procedure is postsurgical decline in memory. A substantial number of past studies examined factors that predict memory decline after surgery, but few have investigated multiple predictors simultaneously or considered measures that are currently in use.

METHODS

This study compared the relative contributions made by presurgical neuropsychological test scores, MRI-based hippocampal volumetric analysis, and Wada test results to predicting memory outcome after ATL in a group of 87 patients.

RESULTS

Logistic regression analyses indicated that noninvasive procedures (neuropsychological testing and MRI) made significant contributions to improving the prediction of memory outcome in this sample. The results from the Wada procedure did not significantly improve prediction once these other factors were considered. The only exception was in predicting memory for visual information after a delay, in which Wada results improved prediction accuracy from 78% to 81%.

CONCLUSIONS

Current neuropsychological tests and MRI volumetric measures predict changes in verbal and visual memory after ATL. The relatively small change in correct classification rates when Wada memory scores are considered calls into question the benefits of using Wada test results to predict memory outcome when the results of noninvasive procedures are available.

Memory, emotional and vocational impairments before and after anterior temporal lobectomy for complex partial seizures

PURPOSE

To assess the pre- and postsurgical frequency of memory, emotional, and vocational impairments in patients who underwent anterior temporal lobectomy (ATL), and to assess the relationship between emotional disturbance and memory abilities after ATL.

METHODS

Retrospective analysis of data was performed on 90 patients with medically intractable complex partial seizures who underwent ATL between 1981 and 2003. Patients were evaluated an average of 5 months before surgery and 11.3 months after surgery.

RESULTS

A moderate to high frequency of memory impairment (44.4%; verbal or nonverbal), emotional disturbance (38.9%) and unemployment (27.8%) existed in the same individuals both before and after surgery. There were small to moderate rates of new onset memory (18.9%), emotional (11.1%), and vocational (7.8%) difficulties after surgery often regardless of seizure control outcome. Patients who underwent left-ATL and had emotional disturbance after surgery had the lowest verbal memory test scores.

CONCLUSIONS

Results highlight the importance of taking into account emotional status when assessing memory abilities after ATL. Results replicate the finding of moderate to high frequencies of memory impairment, emotional disturbance, and unemployment both before and after ATL. Results provide support for the rationale that cognitive, psychiatric and vocational interventions are indicated to mitigate the problems that exist before and persist after ATL.

Surgical outcome and prognostic factors of pediatric epilepsy caused by cortical dysplasia

OBJECTS

We analyzed 30 patients with cortical dysplasia (CD) and epilepsy to evaluate the clinical characteristics and surgical outcome of both epilepsy control and neurocognition.

MATERIALS AND METHODS

The mean ages at seizure onset and at the time of the operation were 3.6 years (range, 1 month-12.6 years) and 10.3 years (range, 1.5-18.3 years), respectively. The mean follow-up period was 3.2 years (range, 1-5.3 years). (18)FDG-positron emission tomography was the most sensitive and magnetic resonance imaging was the most specific in localizing the lesion. Developmental/intellectual delay was predominant in the early-onset group (n=18, seizure onset <3 years), with intelligence tending to be normal in the late-onset group (n=12, seizure onset >or=3 years). Mild CD predominated in the late-onset epilepsy group and moderate or severe CD in the early-onset group (p=0.005). The surgical success rate of epilepsy control was 87%. A better outcome was obtained if the lesion was confined to the temporal lobe. School performance was favorable in 43%. The age at seizure onset and preoperative developmental/intellectual delay were the important prognostic factors in school performance as well as the epilepsy control. A total of 77% of patients had relatively good social adaptation. Successful epilepsy control and good school performance were affirmative conditions precedent to social adaptation.

CONCLUSIONS

Due to the favorable control of epilepsy and its effect on school performance and social adaptation, surgical treatment is strongly recommended for cortical dysplasia and intractable epilepsy.

Neuropsychological tests with lateralizing value in patients with temporal lobe epilepsy: reconsidering material-specific theory

PURPOSE

To assess the ability of neuropsychological tests to determine the side of seizure onset for preoperative assessment in patients with drug-resistant temporal lobe epilepsy.

METHODS

Twenty-nine consecutive patients diagnosed with temporal lobe epilepsy (TLE), in whom the epileptogenic focus was clearly identified and localized to either the right or left hemisphere. Patients underwent a full neuropsychological assessment as part of their pre-surgical investigation, including the Boston Naming Test (BNT) and a variety of Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) and Wechsler Memory Scale-Third Edition (WMS-III) subtests. Two multivariate analyses of variance were carried out to assess differences on memory and language measures between groups according to side of epileptogenic focus. Binary logistic regression analysis was performed to find the sets of tests that best predicted the side of seizure onset (determined by EEG and MRI).

RESULTS

Memory multivariate analysis of variance failed to show significant differences between the right- and left-sided groups. Among language measures, only the BNT revealed significant differences between the groups. The neuropsychological measures that best predicted the side of seizure onset were the BNT and Visual Reproduction II.

CONCLUSIONS

Language measures predict the side of seizure focus better than memory measures. The results of this study in a sample of drug-resistant temporal lobe epilepsy patients challenge the memory material-specific theory for the side of seizure focus.

Material-specific lateralization of memory encoding in the medial temporal lobe: Blocked versus event-related design

Lesion-deficit studies have provided evidence for a functional dissociation between the left medial temporal lobe (MTL) mediating verbal memory encoding and right MTL mediating non-verbal memory encoding. While a small number of functional MRI studies have demonstrated similar findings, none has looked specifically for material-specific lateralization using subsequent memory effects. In addition, in many fMRI studies, encoding activity has been located in posterior MTL structures, at odds with lesion-deficit and positron emission tomography (PET) evidence. In this study, we used an event-related fMRI memory encoding paradigm to demonstrate a material-specific lateralization of encoding in the medial temporal lobes of ten healthy control subjects. Activation was left-lateralized for word encoding, bilateral for picture encoding, and right-lateralized for face encoding. Secondly, we demonstrated the locations of activations revealed using an event-related analysis to be more anterior than those revealed using a blocked analysis of the same data. This suggests that anterior MTL structures underlie memory encoding as judged by subsequent memory effects, and that more posterior activity detected in other fMRI studies is related to deficiencies of blocked designs in the analysis of memory encoding.

Non-parametric evaluation of memory changes at group and individual level following temporal lobe resection for pharmaco-resistant partial epilepsy

Group versus individual verbal and visuospatial memory outcome following epilepsy surgery was evaluated by a non-parametric method in 25 left and 29 right temporal lobectomy patients. Twenty-five controls were assessed twice. Analyses of change at an individual level evaluated by this statistical approach based on paired-ranks were compared to results with a method based on distances (Reliable Change). The left temporal lobectomy group deteriorated in the two verbal memory variables (p < 0.01 and 0.05). High levels of individual changes unexplained by group patterns were disclosed in the three memory variables analyzed in the patients. Significant individual change, although less pronounced, also occurred in the controls. Group versus individual outcome was adequately distinguished by the non-parametric method. To properly analyze memory change after epilepsy surgery, evaluation at group and individual level ought to combined.

Memory and intelligence outcome following surgery for intractable temporal lobe epilepsy: relationship to seizure outcome and evaluation using a customized neuropsychological battery

The main objectives of this prospective study were to (1) assess memory and intelligence outcome following surgery for intractable temporal lobe epilepsy, (2) correlate this with seizure outcome and side of surgery, and (3) perform (1) and (2) using an indigenously developed battery customized to the Indian population. Prior to use in our epilepsy surgery program, the test-retest and interexaminer variance reliability of this battery had been established in both normal and cognitively compromised populations. The memory scores were overall rather than material-specific. The battery was administered to right-handed adults undergoing surgery for intractable temporal lobe epilepsy without any evidence of opposite temporal lobe abnormality, both presurgery and postsurgery at a mean follow-up of 8 months. Twenty-five consecutive patients were included; 13 underwent right and 12 underwent left temporal surgery. Seizure outcome was assessed using Engel's classification. Among 13 patients who underwent right temporal surgery, although 4 patients with poor seizure outcome had insignificant changes in scores, 7 of 9 patients with good seizure outcome exhibited considerable (> 20% over preoperative) improvement in their memory and intelligence scores. Statistical analysis using Student's t test and the Mann-Whitney test revealed that the patients who underwent right temporal surgery with good seizure outcome had significant improvement in both memory (P = 0.007) and intelligence (P = 0.043) scores compared with those with poor seizure outcome. In contrast, patients who underwent left temporal surgery had no significant change in cognitive scores irrespective of seizure outcome. Cognitive improvement seems to occur in patients with good seizure outcome following nondominant temporal lobe surgery for intractable epilepsy with no evidence of pathology in the opposite temporal lobe. The same finding was not observed in patients undergoing left temporal surgery.

Patients' Perceptions of Memory Functioning Before and After Surgical Intervention to Treat Medically Refractory Epilepsy

PURPOSE

One risk associated with epilepsy surgery is memory loss, but perhaps more important is how patients perceive changes in their memories. This longitudinal study evaluated changes in memory self-reports and investigated how self-reports relate to changes on objective memory measures in temporal or extratemporal epilepsy patients who underwent surgery.

METHODS

Objective memory (Wechsler Memory Scale-Revised) and subjective memory self-reports (Memory Assessment Clinics Self-Rating Scale) were individually assessed for 136 patients approximately 6 months before and 6 months after surgery. A measure of depressive affect (Beck Depression Inventory-2nd Edition) was used to control variance attributable to emotional distress.

RESULTS

Despite a lack of significant correlational relationships between objective and subjective memory for the entire sample, significant correlations between objective memory scores and self-reports did emerge for a subset of patients who evidenced memory decline. Differences also were found in the subjective memory ratings of temporal lobe versus extratemporal patients. Temporal lobe patients rated their memories more negatively than did extratemporal patients and were more likely to report significant improvements in their memory after surgery.

CONCLUSIONS

In general, patients were not accurate when rating their memories compared to other adults. However, patients with significant declines in their memories were sensitive to actual changes in their memories over time relative to their own personal baselines.

Relationships between epilepsy-related factors and memory impairment

OBJECTIVES

In this study, we will explore the effect of epilepsy-related factors such as: 'type of epilepsy, 'site and side of focus localisation' and 'age at onset', as well as four seizure-related factors: 'years with continuing seizures', 'seizure type' and 'seizure frequency', and the treatment factor 'adverse effects of the medication', on memory impairment. Additionally, we explored whether these epilepsy factors are related to different aspects of memory, i.e. short-term recall vs long-term recall, learning, and verbal memory vs non-verbal memory.

MATERIAL AND METHODS

A total of 252 patients with epilepsy and subjective memory complaints were consecutively included from the three epilepsy centres in the Netherlands. To assess memory functions the Wechsler Memory Scale-Revised (WMS-r), and the Dutch version of the California Verbal Learning Test for verbal list learning, was administered.

RESULTS

A multivariate analysis of variance (MANOVA) did not show statistically significant effects of the epilepsy factors on memory for the total study sample. For the patients with a unilateral epileptogenic focus in the temporal lobes, MANOVA showed statistically significant effects of lateralisation, with most impairment for patients with left temporal lobe epilepsy and, independently, seizure frequency and 'years with seizures'.

CONCLUSION

We may conclude that epilepsy-related dysfunctions in the temporal lobe are the dominant risk factor for developing memory problems, specifically verbal memory problems (verbal learning and problems consolidating verbal information), with more severe impairments with continuing seizures and when seizure frequency is high.

Noninvasive in vivo demonstration of the connections of the human parahippocampal gyrus

MR tractography techniques provide a method for noninvasively studying white matter pathways in vivo. In this study we have used diffusion tensor imaging (DTI) and the fast marching tractography (FMT) algorithm to plot the structural connectivity of the human parahippocampal gyrus (PHG) in 10 healthy subjects, using seed points selected in the anterior parahippocampal gyrus. Our results demonstrate connectivity between the parahippocampal gyrus and the anterior temporal lobe, orbitofrontal areas, posterior temporal lobe and extrastriate occipital lobe via the lingual and fusiform gyri. We also demonstrate for the first time noninvasively direct connectivity between the parahippocampal gyrus and the hippocampus itself. These results agree with previous histological tract-tracing studies in animals. The connections demonstrated between neocortical areas and the hippocampus via the parahippocampal gyrus may provide the structural basis for theoretical models of memory and higher visual processing.

Differential effects of left versus right mesial temporal lobe epilepsy on Wechsler intelligence factors

This study investigates the effects of left versus right mesial temporal lobe epilepsy (MTLE) on Wechsler intelligence factors. In the left MTLE group, the Verbal Comprehension (VC) factor score was significantly lower than the Perceptual Organization (PO) factor score, whereas in the right MTLE group, the PO factor score was significantly lower than the VC factor score. The VC factor score was significantly lower for the left than the right MTLE group, whereas the PO factor score was significantly lower for the right than the left MTLE group. Thus, left versus right MTLE was associated with relative deficits in verbal versus nonverbal intelligence, respectively. These findings indicate that lateralized cognitive deficits in unilateral MTLE patients are not limited to the learning-memory domain but include more global intelligence functions.

Minimal model to document psychometric change after standard anterior temporal lobectomy for intractable seizure disorder

Neuropsychological assessment of persons with epilepsy is recommended whenever neurosurgery is considered as an alternative therapy for seizure disorders refractory to ordinary medical management. Although psychological assessment is common in centers specialized in the care of epilepsy patients, standardized protocols are not common. This study addresses the question of the optimal minimal test battery necessary to differentiate groups of right-handed patients with refractory, complex partial seizure disorder who receive either right or left anterior temporal lobectomy or no surgery. No variable differentiated the groups before surgery. Only Logical Memory-Immediate of the Wechsler Memory Scale differentiated the groups following surgery. This finding is consistent with the literature.

Seizure control and cognitive outcome after temporal lobectomy: a comparison of classic Ammon's horn sclerosis, atypical mesial temporal sclerosis, and tumoral pathologies

PURPOSE

Neuropathologic examination of resected tissue after anterior temporal lobectomy (ATL) for treatment of complex partial seizures revealed several distinct histologic substrates. Our study examined the relation between neuropathology, seizure control, and cognition in ATL patients and described preliminary profiles to aid in the prediction of outcome.

METHODS

Of the 149 patients who underwent ATL from 1980 to 1999, long-term follow-up was available for 145. Specimens from 124 of the 145 patients had histologic findings consistent with one of three diagnoses: classic Ammon's horn sclerosis (cAHS; n = 75), atypical mesial sclerosis (Atypical; n = 21), or low-grade tumor (Tumor; n = 28). The other 20 patients had diverse pathologies that were insufficient for analysis. ATL patients underwent a complete preoperative and 68 underwent a postoperative neuropsychological evaluation.

RESULTS

Of the 145 patients, 84% of cAHS, 57% of Tumor, and 29% of Atypical patients had a > or =95% reduction in seizure frequency. Neuropsychological testing suggested that cAHS patients demonstrate more generalized preoperative cognitive impairment than do the Atypical or Tumor patients. The Atypical group recalled significantly less nonverbal material after surgery than did the cAHS or Tumor groups. Stratification by both pathology and surgery side revealed that the right Atypical patients declined more on information processing and set shifting.

CONCLUSIONS

Patients with cAHS or Tumor demonstrated better seizure control and fewer declines in cognitive functioning after ATL than did the Atypical patients, highlighting the need to investigate this group as a distinct entity.

Surgical versus medical treatment for severe epilepsy: consequences for intellectual functioning in children and adults. A follow-up study

We compared the effects of medical and combined surgical and medical treatment of refractory epilepsy on intellectual functioning in a group of children (n=13) and a group of adults (n=15). The patients were tested with the age-appropriate versions of Wechsler's intelligence scales twice prior to and once after epilepsy surgery. There were no significant differences between the groups in preoperative epilepsy-related variables, including age at onset. The IQ scores were submitted to two-way analyses of variance (ANOVA). We also evaluated individual changes in IQ scores. Adult patients maintained stable levels of performance after drug treatment as well as following surgery, while children declined in Full Scale IQ after both kinds of treatment. Children also declined in Performance IQ, but not in Verbal IQ after drug treatment, and in Verbal IQ, but not in Performance IQ after surgery. Three of six children who underwent a significant decline in Full Scale IQ before surgery did not show any further decline postoperatively. We have proposed a developmental model to account for the different findings in children and adults, and conclude tentatively that refractory, long-standing epilepsy may interfere with intellectual development both during drug treatment and following combined surgical and medical treatment in children, while the impact of long-standing refractory epilepsy of similar severity as in children is not strong enough to reduce intellectual performance in adults, irrespective of treatment modality.

Prognostic factors and outcome after different types of resection for temporal lobe epilepsy

OBJECT

It is unknown whether different resection strategies for temporal lobe epilepsy (TLE) produce alterations in seizure control or neuropsychological performance.

METHODS

A series of 321 patients who underwent surgery for TLE between 1989 and 1997 was submitted to a uni- and multifactorial analysis of clinical, electrophysiological, neuroimaging, neuropsychological, and surgical factors to determine independent predictors of outcome. Until 1993, most patients with TLE underwent standard anterior temporal lobectomy (ATL); beginning in 1993, surgical procedures were increasingly restricted to lesions detected on magnetic resonance (MR) imaging and the presumed epileptogenic foci: for example, amygdalohippocampectomy (AH) or lesionectomy/corticectomy began to be used more often. The mean follow-up duration in this study was 38 months. Two hundred twenty-seven patients were classified as seizure free (70.7%), and 36 patients had rare and nondisabling seizures (11.2%); these groups were summarized as having good seizure control (81.9%). Twenty-four patients attained more than 75% improvement (7.5%), and no worthwhile improvement was seen in 34 cases (10.6%); these groups were summarized as having unsatisfactory seizure control (18.1%). On unifactorial analysis the following preoperative factors were associated with good seizure control (p < 0.05): single and concordant lateralizing focus on electroencephalography studies, low seizure frequency, absence of status epilepticus, concordant lateralizing memory deficit, clear abnormality on MR images, suspected ganglioglioma or dysembryoplastic neuroepithelial tumor (DNT), and absence of dysplasia on MR images. Stepwise logistic regression revealed a model containing five factors that were predictive for good seizure control (p < 0.1): 1) clear abnormality on MR images; 2) absence of status epilepticus; 3) MR imaging-confirmed ganglioglioma or DNT; 4) concordant lateralizing memory deficit; and 5) absence of dysplasia on MR images. Seizure outcome was mainly correlated with diagnosis and clinical factors. No significant differences were found regarding different resection types performed for comparable tumors. Neuropsychological testing revealed better postoperative results after limited resections compared with standard ATL, especially with regard to attention level, verbal memory, and calculated total neuropsychological performance.

CONCLUSIONS

Different strategies for surgical approaches in TLE result in equally good outcomes. Seizure outcome is mainly dependent on the diagnosis and clinical factors, whereas the neuropsychological results are more beneficial after resections limited to an epileptogenic lesion and focus.

Epilepsy surgery within the temporal lobe and its short-term and long-term effects on memory

In patients with pharmacologically intractable, complex-partial seizures, surgical excision of the involved temporal lobe may have significant therapeutic benefit. Resection of mesial structures of the temporal lobes, however, entails a significant risk of decreased memory function. Recent advances in the assessment of memory changes following temporal lobectomy surgery emphasize the complexity of subjective ratings of memory functioning in this population. Neuroimaging tools useful in the diagnostic evaluation of epilepsy surgical candidates have now been shown to be useful in predicting memory change in the post-surgical period. Functional magnetic resonance imaging appears to provide significant information regarding hemispheric representation of language in the temporal lobe epilepsy patient, and the use of this technique to predict memory status following surgery appears promising. Clinical studies involving patients who had temporal lobectomy surgeries have also revealed changes in emotional learning related to the degree of amygdala involvement. Moreover, there is increasing evidence to suggest that differential changes in emotional learning occur among patients with right versus left temporal lobe resections.

Memory deficits after resection from left or right anterior temporal lobe in humans: a meta-analytic review

PURPOSE

Memory deficits in epileptic patients have been found in some, but not all studies assessing the effects of side of seizures and resection from a temporal lobe on cognitive performance. The purpose of this study was to provide a quantitative review of previous studies on this issue.

METHODS

Based on conventional meta-analytic procedures, we identified 33 studies that assessed verbal and nonverbal memory performance before and after anterior temporal lobectomy. The Logical Memory and Visual Reproduction subtests from the Wechsler Memory Scale were used. These studies were then subjected to two levels of analyses: (a) vote-counting procedure, and (b) effect-size calculations and comparisons.

RESULTS

Overall, the data confirmed previous findings that verbal memory tasks are sensitive to left hemisphere dysfunction. The efficacy of a "nonverbal" task for tapping function in the nondominant (right) hemisphere was not confirmed, although a trend supporting this speculation was observed. With regard to the comparison of changes in verbal and nonverbal memory before and after resection from a temporal lobe, a clear trend was observed for decline in verbal memory function after resection from the left, especially significant for immediate verbal recall. A trend for contralateral improvement on nonverbal memory also was observed. The pattern of memory change after resection from the right temporal lobe was less clear.

CONCLUSIONS

The findings of this study suggest that side of epileptic seizure and surgical resection from a temporal lobe affect verbal memory functions. The relations between the laterality of epileptic seizure, surgical resection from the temporal lobe, and nonverbal memory are to be verified by further research.

Memory outcome after selective amygdalohippocampectomy: a study in 140 patients with temporal lobe epilepsy

PURPOSE

The technique of selective amygdalohippocampectomy (SAH) was originally developed in epilepsy surgery to spare unaffected brain tissue from surgery, thus minimizing the cognitive consequences of temporal lobe surgery. The results of previous studies, however, are equivocal in this regard. This study evaluated memory after SAH in a large sample of patients with mesial temporal lobe epilepsy.

METHODS

The 140 patients received material-specific memory tests before and 3 months after unilateral SAH.

RESULTS

Significant declines in all aspects of verbal learning and memory were found particularly for the left resected group. With reliability-of-change indices, a high number of patients showed postoperative verbal memory declines, < or = 51% in left SAH and < or = 32% in right SAH. For left SAH, a higher preoperative verbal memory performance, a lower preoperative nonverbal memory score, an older age at surgery, and a later onset of epilepsy predicted a stronger decline in verbal memory. After right SAH, the risk for a verbal memory decline was slightly increased when patients had surgical complications or a presurgical evaluation with bilateral intrahippocampal depth electrodes. Results concerning nonverbal memory were less clear.

CONCLUSIONS

The results clearly indicate, that particularly left SAH can lead to a significant decline in memory functions. Predictors of postoperative verbal memory were similar to those reported for temporal lobectomy. Postoperative deteriorations were broader and stronger in our study than in previous studies. We discuss methodologic differences (sample size, retest interval, extent of resection) and other factors as possible reasons.

Memory outcome after left anterior temporal lobectomy in patients with expected and reversed Wada memory asymmetry scores

PURPOSE

The ideal candidate for anterior temporal lobectomy surgery shows a Wada memory asymmetry (WMA) score characterized by better memory performance in the hemisphere contralateral to the seizure focus relative to the ipsilateral (surgical) hemisphere. However, some surgical candidates show a reversed WMA or better Wada memory performance in the hemisphere of surgical interest relative to the hemisphere contralateral to the seizure focus. To date, no data are available contrasting memory and seizure outcome for these two Wada groups. The present study compared memory and seizure outcome after left anterior temporal lobectomy (L-ATL) in patients showing expected and reversed WMA scores, and also examined the relationship of the individual hemisphere Wada memory scores for predicting verbal memory outcome after L-ATL.

METHODS

We compared 6-month postoperative verbal memory change scores and seizure outcome in L-ATL patients with either an expected (n=12) or reversed WMA (n=9) pattern on Wada memory testing.

RESULTS

L-ATL patients showing a reversed WMA score had a poorer verbal memory outcome and poorer seizure control after surgery compared with patients showing a WMA score in the expected direction.

CONCLUSIONS

L-ATL patients with a reversed WMA score have a greater risk for memory morbidity and poorer seizure outcome than do patients with a WMA score in the expected direction. The WMA score was the best predictor of memory outcome after L-ATL. When the WMA score is not considered, both individual Wada hemisphere scores (contralateral and ipsilateral) provided significant and independent contribution to predicting postoperative verbal memory functioning. These findings are discussed in the context of the functional reserve and hippocampal adequacy models of memory change after temporal lobectomy.

Pre--and postoperative general neurocognitive status and memory in 70 epilepsy surgery patients

PURPOSE

To describe cognitive function preoperatively and cognitive change 2 years postoperatively in 70 consecutive adults in the Göteborg epilepsy surgery series.

METHODS

Analysis of general neurocognitive status and memory for the total group and for three subgroups: 26 patients with seizure onset in dominant temporal lobe, 28 patients with onset in non-dominant temporal lobe and 12 with frontal lobe onset. Preoperative performance was compared with a control group (n=30).

RESULTS

Preoperatively, patients were more impaired in general neurocognitive status than controls. Patients in the temporal lobe subgroups performed worse than controls in two memory variables. No postoperative negative change was found at group level. There was a small increase in Full Scale IQ and Performance IQ for the total patient group, and in Performance IQ for the frontal lobe subgroup. At individual level, many patients suffered losses or obtained gains in a number of memory variables without any consistent intra-pattern.

CONCLUSIONS

Cognitive stability was the main postoperative result. The importance of considering inter- and intra-individual variability of negative as well as positive change is emphasized.

Subnecrotic stereotactic radiosurgery controlling epilepsy produced by kainic acid injection in rats

OBJECT

Any analysis of the potential role of stereotactic radiosurgery for epilepsy requires the experimental study of its potential antiepileptogenic, behavioral, and histological effects. The authors hypothesized that radiosurgery performed using subnecrotic tissue doses would reduce or abolish epilepsy without causing demonstrable behavioral side effects. The kainic acid model in rats was chosen to test this hypothesis.

METHODS

Chronic epilepsy was successfully created by stereotactic injection of kainic acid (8 microg) into the rat hippocampus. Epileptic rats were divided into three groups: high-dose radiosurgery (60 Gy, 16 animals), low-dose (30 Gy, 15 animals), and controls. After chronic epilepsy was confirmed by observation of the seizure pattern and by using electroencephalography (EEG), radiosurgery was performed on Day 10 postinjection. Serial seizure and behavior observation was supplemented by weekly EEG sessions performed for the next 11 weeks. To detect behavioral deficits, the Morris water maze test was performed during Week 12 to study spatial learning and memory. Tasks involved a hidden platform, a visible platform, and a probe trial. After radiosurgery, the incidence of observed and EEG-defined seizures was markedly reduced in rats from either radiosurgically treated group. A significant reduction was noted after high-dose (60 Gy) radiosurgery in Weeks 5 to 9 (p < 0.003). After low-dose (30 Gy) radiosurgery, a significant reduction was found after 7 to 9 weeks (p < 0.04). During the task involving the hidden platform, kainic acid-injected rats displayed significantly prolonged latencies compared with those of control animals (p < 0.05). Hippocampal radiosurgery did not worsen this performance. The probe trial showed that kainic acid-injected rats that did not undergo radiosurgery spent significantly less time than control rats in the target quadrant (p = 0.03). Rats that had undergone radiosurgery displayed no difference compared with control rats and demonstrated better performance than rats that received kainic acid alone (p = 0.04). Radiosurgery caused no adverse histological effects.

CONCLUSIONS

In a rat model, radiosurgery performed with subnecrotic tissue doses controlled epilepsy without causing subsequent behavioral impairment.

Confrontation naming after anterior temporal lobectomy is related to age of acquisition of the object names

Decline in visual confrontation naming ability may occur as a postacute complication of left anterior temporal lobectomy (ATL) for the treatment of intractable mesial temporal lobe epilepsy. In this study of 26 left ATL patients who demonstrated postsurgery decline on a standardized naming measure, it was hypothesized that naming performance would be significantly associated with specific attributes of the object names. We investigated the relation between performance on the Boston Naming Test (BNT) and the following attributes of the test items: living versus nonliving category (L/NL), word length (WL), written word frequency (WF), and age of acquisition (AoA). Regression analyses revealed that AoA and WF were significant predictors of preoperative group performance. AoA was the only significant predictor of performance after left ATL. For the 17 individuals who demonstrated a statistically meaningful decline on the BNT, as indicated by a Reliable Change Index, individual logistic regressions demonstrated that AoA was the strongest and most consistent predictor of postoperative success/failure for items that had been named correctly preoperatively. Consistent with the literature on naming errors in elderly normals and patients with aphasia or semantic dementia, the results provide evidence that object names learned in late childhood are among the most vulnerable when there is a decline in object naming ability. Investigation of additional attributes and semantic knowledge for the concepts represented by the pictured objects will be necessary to determine whether the naming deficit associated with TLE and ATL reflects an impairment of phonological word-form retrieval, semantics, or both.