The impact of epilepsy surgery on cognition and behavior

Clinical, imaging, and biomarker evidence of amyloid- and tau-related neurodegeneration in late-onset epilepsy of unknown etiology

Accumulating evidence suggests amyloid and tau-related neurodegeneration may play a role in development of late-onset epilepsy of unknown etiology (LOEU). In this article, we review recent evidence that epilepsy may be an initial manifestation of an amyloidopathy or tauopathy that precedes development of Alzheimer's disease (AD). Patients with LOEU demonstrate an increased risk of cognitive decline, and patients with AD have increased prevalence of preceding epilepsy. Moreover, investigations of LOEU that use CSF biomarkers and imaging techniques have identified preclinical neurodegeneration with evidence of amyloid and tau deposition. Overall, findings to date suggest a relationship between acquired, non-lesional late-onset epilepsy and amyloid and tau-related neurodegeneration, which supports that preclinical or prodromal AD is a distinct etiology of late-onset epilepsy. We propose criteria for assessing elevated risk of developing dementia in patients with late-onset epilepsy utilizing clinical features, available imaging techniques, and biomarker measurements. Further research is needed to validate these criteria and assess optimal treatment strategies for patients with probable epileptic preclinical AD and epileptic prodromal AD.

Thalamostriatal disconnection underpins long-term seizure freedom in frontal lobe epilepsy surgery

Around 50% of patients undergoing frontal lobe surgery for focal drug-resistant epilepsy become seizure free post-operatively; however, only about 30% of patients remain seizure free in the long-term. Early seizure recurrence is likely to be caused by partial resection of the epileptogenic lesion, whilst delayed seizure recurrence can occur even if the epileptogenic lesion has been completely excised. This suggests a coexistent epileptogenic network facilitating ictogenesis in close or distant dormant epileptic foci. As thalamic and striatal dysregulation can support epileptogenesis and disconnection of cortico-thalamostriatal pathways through hemispherotomy or neuromodulation can improve seizure outcome regardless of focality, we hypothesize that projections from the striatum and the thalamus to the cortex may contribute to this common epileptogenic network. To this end, we retrospectively reviewed a series of 47 consecutive individuals who underwent surgery for drug-resistant frontal lobe epilepsy. We performed voxel-based and tractography disconnectome analyses to investigate shared patterns of disconnection associated with long-term seizure freedom. Seizure freedom after 3 and 5 years was independently associated with disconnection of the anterior thalamic radiation and anterior cortico-striatal projections. This was also confirmed in a subgroup of 29 patients with complete resections, suggesting these pathways may play a critical role in supporting the development of novel epileptic networks. Our study indicates that network dysfunction in frontal lobe epilepsy may extend beyond the resection and putative epileptogenic zone. This may be critical in the pathogenesis of delayed seizure recurrence as thalamic and striatal networks may promote epileptogenesis and disconnection may underpin long-term seizure freedom.

New insights for predicting surgery outcome in patients with temporal lobe epilepsy. A systematic review

Resective surgery is the treatment of choice for one-third of adult patients with focal, drug-resistant epilepsy. This procedure is associated with substantial clinical and cognitive risks. In clinical practice, there is no validated model for epilepsy surgery outcome prediction (ESOP). Meta-analyses on ESOP studies assessing prognostic factors report discrepancies in terms of study design. Our review aims to systematically investigate methodological and analytical aspects of studies predicting clinical and cognitive outcomes after temporal lobe epilepsy surgery. A systematic review of ESOP studies published between 2000 and 2022 from three databases (MEDLINE, Web of Science, and PsycINFO) was completed by following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. It yielded 4867 articles. Among them, 21 corresponded to our inclusion criteria and were therefore retained in the final review. The risk of bias was assessed using A Tool to Assess Risk of Bias and Applicability of Prediction Model Studies (PROBAST). Data extracted from the 21 studies were analyzed using narrative synthesis and descriptive statistics. Our findings show an increase in the use of multimodal datasets and machine learning analyses in recent ESOP studies, although regression remained the most frequently used approach. We also identified a more frequent use of network notions in recent ESOP studies. Nevertheless, several methodological issues were noted, such as small sample sizes, lack of information on the follow-up period, variability in seizure outcome, and the definition of neuropsychological postoperative change. Of 21 studies, only one provided a clinical tool to anticipate the cognitive outcome after epilepsy surgery. We conclude that methodological issues should be overcome before we move towards more complete models to better predict clinical and cognitive outcomes after epilepsy surgery. Recommendations for future studies to harness the possibilities of multimodal datasets and data fusion, are provided. A stronger bridge between fundamental and clinical research may result in developing accessible clinical tools.

Cortico-limbic disruption, material-specificity, and deficits in cognitive-affective theory of mind

The Theory of Mind deficit due to cognitive-affective disintegration is a poorly understood cognitive consequence of cortical and subcortical disruption in right temporal lobe epilepsy. Following Marr's trilevel approach, we used the material-specific processing model to understand the Theory of Mind deficit in drug-resistant epilepsy (N = 30). We examined pre- and post-surgery changes in first-order (somatic-affective, non-verbal component) and second-order Theory of Mind (cognitive-verbal component) in three groups formed using: (i) seizure side (right versus left), (ii) right temporal epilepsy (right temporal lobe epilepsy versus non-right temporal lobe epilepsy), and (iii) right temporal lobe epilepsy with amygdalohippocampectomy (right temporal lobe epilepsy versus left temporal lobe epilepsy amygdalohippocampectomy versus non-amygdalohippocampectomy). We observed a marked deficit in the first-order Theory of Mind in the right temporal lobe amygdalohippocampectomy group; we mapped this deficit to decline in the non-verbal component of Theory of Mind (somatic-affective component). Preliminary results support using a material-specific processing model to understand the Theory of Mind deficits in right temporal lobe epilepsy amygdalohippocampectomy. Malleability of verbal processing in presence of deterioration of non-verbal processing might have clinical relevance for post-surgery recovery in right temporal lobe epilepsy amygdalohippocampectomy. Documenting the material-specific nature of deficits (verbal versus non-verbal) in non-western, linguistically, and socioeconomically diverse country enables us to understand the problem of heterogeneity in post-surgery cognitive consequences in the right amygdalohippocampectomy.

The challenge of neuropsychological assessment of visual/visuo-spatial memory: A critical, historical review, and lessons for the present and future

A proliferation of tests exists for the assessment of auditory-verbal memory processes. However, from a clinical practice perspective, the situation is less clear when it comes to the ready availability of reliable and valid tests for the evaluation of visual/visuo-spatial memory processes. While, at face value, there appear to be a wide range of available tests of visual/visuo-spatial memory, utilizing different types of materials and assessment strategies, a number of criticisms have been, and arguably should be, leveled at the majority of these tests. The criticisms that have been directed toward what are typically considered to be visual/visuo-spatial memory tests, such as (1) the potential for verbal mediation, (2) over-abstraction of stimuli, (3) the requirement of a drawing response, and (4) the lack of sensitivity to unilateral brain lesions, mean that, in reality, the number of readily available valid tests of visual/visuo-spatial memory is, at best, limited. This article offers a critical, historical review on the existing measures and resources for the neuropsychological assessment of visual/visuo-spatial memory, and it showcases some examples of newer tests that have aimed to overcome the challenges of assessing these important aspects of memory. The article also identifies new trends and examples of how technological advances such as virtual reality may add value to overcome previous obstacles to assessment, thereby offering professionals more reliable, accurate means to evaluate visual/visuo-spatial memory in clinical practice.

One-year neuropsychological outcome after temporal lobe epilepsy surgery in large Czech sample: Search for factors contributing to memory decline

Background:

Assessment of cognitive functions is an integral part of the evaluation the efficacy of temporal resections. We studied postoperative neuropsychological changes and factors contributing to worse memory outcomes in patients who experienced a significant decline using reliable change indices.

Methods:

We prospectively studied 110 patients in whom we indicated anteromesial temporal resection (AMTR) and 46 patients who underwent selective amygdalohippocampectomy (SAHE). We administrated Wechsler Adult Intelligence Scale-Revised, Wechsler Memory Scale-Revised, and the Verbal Fluency Test before and 1 year after the operation.

Results:

At a group level, we did not observe any statistically significant changes in global, verbal, and visual MQ in either the AMTR or the SAHE group. At an individual level, we found a mean decrease of verbal MQ after left-sided AMTR by −4.43 points (P = 0.01). We detected no significant differences between the left and right side of surgery in the SAHE group. In patients with significant postoperative memory decline, we found either pre-existing extrahippocampal deficits/postoperative complications or incomplete hippocampal resection or a combination of these factors.

Conclusion:

In addition to the side of surgery, structural integrity and functional adequacy of resected hippocampus and volume of resected tissue and preoperative extrahippocampal lesions/postoperative complications also contribute to postoperative memory decline after temporal lobe epilepsy surgery.

Associations between cognition and employment outcomes after epilepsy surgery

OBJECTIVES

Previous studies have shown that younger age, higher education, and seizure freedom after epilepsy surgery are associated with employment. However, very few studies have investigated associations with cognition and employment status in epilepsy surgery patients.

METHODS

This retrospective study consists of 46 adult patients, who underwent resective epilepsy surgery in the Helsinki University Hospital between 2010 and 2018 and who had been assessed by a neuropsychologist prior to surgery and 6 months after surgery using a systematic test battery. In addition to neuropsychological evaluation, neurologists assessed the patients prior to surgery and followed up the patients up to 24 months after the surgery and evaluated work status of the patients. Logistic regression models were used to assess the effects of cognition on changes in employment status, while controlling for age and education.

RESULTS

Out of the 46 patients 38 (82.6%) were seizure free and 7 (15.2%) had their seizures reduced 2 years postsurgically. From prior to surgery to 2 years postsurgery, use of antiseizure medication was reduced in most of the patients, mean reduction of the dosage being 26.9%. Employment status improved in 10 (21.7%) patients, remained unchanged in 27 (58.7%) and worsened in 3 (6.5%). An additional 6 patients were already not working prior to surgery. Subsequent analyses are based on the subsample of 37 patients whose employment status improved or remained unchanged. Mistakes in executive function tasks (p = 0.048) and working memory performance (p = 0.020) differentiated between the group whose employment status remained similar and those who were able to improve their employment status. Epilepsy surgery outcome or changes in antiseizure medication (ASM) use were not associated with changes in employment status.

CONCLUSIONS

In the subsample of 37 patients, errors in executive function tasks and poorer working memory differentiated patients whose employment status did not change from those patients who could improve their employment status. Problems in executive function and working memory tasks might hinder performance in a complex work environment. When assessing the risks and opportunities in returning to work after surgery, difficulties in working memory and executive function performance should be taken into consideration as they may predispose the patient to challenges at work.

Single-subject gray matter networks in temporal lobe epilepsy patients with hippocampal sclerosis

OBJECTIVE

Previous studies have demonstrated structural brain network abnormalities in patients with temporal lobe epilepsy (TLE) using cortical thickness or gray matter (GM) volume. However, no studies have applied single-subject GM network analysis. Here, we first applied an analysis of similarity-based single-subject GM networks to individual patients with TLE.

MATERIALS AND METHODS

We recruited 51 patients with TLE and unilateral hippocampal sclerosis (22 left, 29 right TLE) and 51 age- and gender- matched healthy controls. Single-subject structural networks were extracted from three-dimensional T1-weighted magnetic resonance images for each subject. In this method, nodes were defined as small cortical regions and edges representing connecting regions that have high statistical similarity. The constructed graphs were analyzed using the graph theoretical approach. The following global and local network properties were calculated: betweenness centrality, clustering coefficient, and characteristic path length. In addition, small world properties (normalized path length λ, normalized clustering coefficient γ, and small-world network value σ) were obtained and compared with those for the controls.

RESULTS

Although the small-world configurations were retained, impaired global clustering coefficient was observed in left and right TLE. At a regional level, patients with left TLE showed a widespread decrease of the clustering coefficient beyond the ipsilateral temporal lobe and a decreased characteristic path length in the ipsilateral temporal pole. On the other hand, patients with right TLE showed a localized decrease of the clustering coefficient in the ipsilateral temporal lobe.

CONCLUSIONS

Our findings suggest that global and local network properties disrupted and moved toward randomized networks in TLE patients in comparison to controls. This network alteration was more extensive in left TLE than in right TLE patients. Single-subject GM networks may contribute to a better understanding of the pathophysiology of TLE.

Histopathological validation and clinical correlates of hippocampal subfield volumetry based on T2-weighted MRI in temporal lobe epilepsy with hippocampal sclerosis

The objectives of this study were 1) to histologically validate the hippocampal subfield volumetry based on T2-weighted MRI, and 2) to explore its clinical impact on postsurgical memory function and seizure outcome in temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS). We analyzed the cases of 24 patients with medial TLE (12 left, 12 right) and HS who were preoperatively examined with T2-weighted high-resolution MRI. The volume of each hippocampal subfield was calculated with an automatic segmentation of hippocampal subfields (ASHS) program. Hippocampal sclerosis patterns were determined pathologically, and the cross-sectional area and neuronal cell density of the CA1 and CA4 subfields were calculated using tissue specimens. Pre- and postoperative memory evaluations based on the Wechsler Memory Scale-Revised (WMS-R) were performed. We compared the presurgical MRI-based volumes with the pathological measurements in each subfield and then compared them with the change in the patients' neurocognitive function. As a result, there was a significant relationship between the presurgical MRI-based volume of CA4/dentate gyrus (DG) and the cross-sectional area of CA4 calculated with tissue specimens (Spearman's rs = 0.482, p = 0.023), and a similar trend-level correlation was observed in CA1 (rs = 0.455, p = 0.058). Some of MRI-based or pathology-based parameters in the subfields preliminarily showed relationships with the postsurgical memory changes. In conclusion, automated subfield volumetry for patients with hippocampal sclerosis moderately reflects their subfield atrophy and might be useful to predict the postsurgical change of memory function in these patients.

Memory outcomes of temporal lobe surgery in adults aged over 45 years

OBJECTIVE

It is assumed that temporal lobe resection in older people is associated with worse seizure outcomes and potential postsurgical memory decline. We studied postsurgical memory development and surgical efficacy in patients over 45 years of age compared with younger patients.

METHODS

We studied 88 patients (51 male and 37 female) after temporal lobe surgery, which involved hippocampal resection. The patients were evaluated before surgery and in the first (72 patients) and/or third (57 patients) postsurgical year. The Wechsler Memory Scale III test was performed to evaluate the MQ postsurgical development. Engel's classification was used to evaluate the postsurgical seizure outcome.

RESULTS

The presurgical MQ (median 88) in ≥45 years age group was significantly lower than in both younger groups (median MQ = 100 for ≤30 years age group, p = 0.002; median MQ = 107 for 31-44 years age group, p = 0.002). Three years after the surgery, the MQ decreased significantly in ≤30 years age group (p = 0.012), while only non-significant MQ decline was observed in both older groups. We found no significant impact of age on the surgical outcome.

CONCLUSION

Higher age at the time of surgery does not significantly increase the risk for postsurgical memory decline; however, older patients are more likely to have lowered presurgical MQ. We did not find significant differences in the impact of surgery on seizure outcome among the age groups. Epilepsy surgery appears to be a safe and effective method in the age over 45 years even though an earlier surgery should be preferred.

Wada test results contribute to the prediction of change in verbal learning and verbal memory function after temporal lobe epilepsy surgery

In recent years, the clinical usefulness of the Wada test (WT) has been debated among researchers in the field. Therefore, we aimed to assess its contribution to the prediction of change in verbal learning and verbal memory function after epilepsy surgery. Data from 56 patients with temporal lobe epilepsy who underwent WT and subsequent surgery were analyzed retrospectively. Additionally, a standard neuropsychological assessment evaluating attentional, learning and memory, visuospatial, language, and executive function was performed both before and 12 months after surgery. Hierarchical linear regression analyses were used to determine the incremental value of WT results over socio-demographic, clinical, and neuropsychological characteristics in predicting postsurgical change in patients' verbal learning and verbal memory function. The incorporation of WT results significantly improved the prediction models of postsurgical change in verbal learning (∆R² = 0.233, p = .032) and verbal memory function (∆R² = 0.386, p = .005). Presurgical performance and WT scores accounted for 41.8% of the variance in postsurgical change in verbal learning function, and 51.1% of the variance in postsurgical change in verbal memory function. Our findings confirm that WT results are of significant incremental value for the prediction of postsurgical change in verbal learning and verbal memory function. Thus, the WT contributes to determining the risks of epilepsy surgery and, therefore, remains an important part of the presurgical work-up of selected patients with clear clinical indications.

Psychiatric symptoms are the strongest predictors of quality of life in patients with drug-resistant epilepsy or psychogenic nonepileptic seizures

OBJECTIVE

This cross-sectional study aimed to determine the effect of psychiatric comorbidity and neurocognitive deficits on the quality of life in a cohort of patients admitted for Video-EEG Monitoring (VEM) for investigation into a presumed seizure disorder.

METHODS

Patients were recruited from an inpatient VEM unit between January 2009 and December 2016. All patients had formal neuropsychiatric assessment. All patients completed questionnaires assessing psychiatric symptomatology (SCL-90-R), Anxiety and Depression (HADS), quality of life (QOLIE-89), and cognition (NUCOG).

RESULTS

A total of 451 patients were enrolled. Upon discharge, 204 patients were diagnosed to have epilepsy, 118 psychogenic nonepileptic seizures (PNES), and 29 both epilepsy and PNES, while the diagnosis was uncertain diagnosis in 100. Diagnosis (p = .002), HADS Depression score (p < .001), SCL-90-R positive symptoms total (p < .001), and NUCOG total score (p < .001) were found to be significant predictors of QOLIE-89 total scores, together explaining 65.4% of variance in quality of life. Seizure frequency was not a significant predictor of quality of life (p = .082). Patients with PNES had significantly worse quality of life, and scored higher on measures of psychiatricsymptomatology, compared to patients with epilepsy alone. The prevalence of psychiatric comorbidity was significantly higher in patients with PNES (70.3%) or both PNES and epilepsy (62.1%) compared to patients with epilepsy alone (41.2%) (p < .001).

SIGNIFICANCE

Psychiatric symptomatology, depression, and cognition were stronger determinants of quality of life than seizure frequency in this study population of patients with drug-resistant epilepsy and PNES. Patients with PNES with or without comorbid epilepsy had similar neuropsychiatric profiles.

Assessing Cognitive Change and Quality of Life 12 Months After Epilepsy Surgery-Development and Application of Reliable Change Indices and Standardized Regression-Based Change Norms for a Neuropsychological Test Battery in the German Language

Objective

The establishment of patient-centered measures capable of empirically determining meaningful cognitive change after surgery can significantly improve the medical care of epilepsy patients. Thus, this study aimed to develop reliable change indices (RCIs) and standardized regression-based (SRB) change norms for a comprehensive neuropsychological test battery in the German language.

Methods

Forty-seven consecutive patients with temporal lobe epilepsy underwent neuropsychological assessments, both before and 12 months after surgery. Practice-effect-adjusted RCIs and SRB change norms for each test score were computed. To assess their usefulness, the presented methods were applied to a clinical sample, and binary logistic regression analyses were conducted to model the odds of achieving improvement in quality of life (QOL) after surgery.

Results

The determined RCIs at 90% confidence intervals and the SRB equations for each test score included in the test battery are provided. Cohen’s kappa analyses revealed a moderate mean agreement between the two measures, varying from slight to almost perfect agreement across test scores. Using these measures, a negative association between improvement in QOL and decline in verbal memory functions after surgery was detected (adjusted odds ratio = 0.09, p = 0.006).

Significance

To the best of our knowledge, this study is the first to develop RCIs and SRB change norms necessary for the objective determination of neuropsychological change in a comprehensive test battery in the German language, facilitating the individual monitoring of improvement and decline in each patients’ cognitive functioning and psychosocial situations after epilepsy surgery. The application of the described measures revealed a strong negative association between improvement in QOL and decline in verbal memory functions after surgery.

Temporal lobe surgery and memory: Lessons, risks, and opportunities

Careful study of the clinical outcomes of temporal lobe epilepsy (TLE) surgery has greatly advanced our knowledge of the neuroanatomy of human memory. After early cases resulted in profound amnesia, the critical role of the hippocampus and associated medial temporal lobe (MTL) structures to declarative memory became evident. Surgical approaches quickly changed to become unilateral and later, to be more precise, potentially reducing cognitive morbidity. Neuropsychological studies following unilateral temporal lobe resection (TLR) have challenged early models, which simplified the lateralization of verbal and visual memory function. Diagnostic tests, including intracarotid sodium amobarbital procedure (WADA), structural magnetic resonance imaging (MRI), and functional neuroimaging (functional MRI (fMRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT)), can more accurately lateralize and localize epileptogenic cortex and predict memory outcomes from surgery. Longitudinal studies have shown that memory may even improve in seizure-free patients. From 70 years of experience with epilepsy surgery, we now have a richer understanding of the clinical, neuroimaging, and surgical predictors of memory decline-and improvement-after TLR. "Special Issue: Epilepsy & Behavior's 20th Anniversary".

Factorial validity of a neuropsychological test battery and its ability to discern temporal lobe epilepsy from frontal lobe epilepsy - A retrospective study

PURPOSE

Firstly, to evaluate the validity of a neuropsychological test battery in epilepsy patients, i.e. whether its tests sufficiently allow the assessment of the required cognitive domains in this specific group. Secondly, to examine its ability to differentiate between cognitive profiles of different subgroups of focal epilepsy.

METHODS

The test battery suggested by the German ILAE Chapter was performed on 207 epilepsy patients, and its factor structure was investigated by principal component analysis (PCA). To further examine its accuracy in two matched subgroups of patients with temporal lobe epilepsy (TLE, n = 35) and frontal lobe epilepsy (FLE, n = 35), a discriminant function analysis (DFA) was used.

RESULTS

PCA revealed eleven interpretable factors, accounting for 69.1% of total variance: Divided Attention, Reaction Time, Verbal Learning, Verbal Memory, Contextual Memory, Short-term- and Working Memory, Visuospatial Functioning, Space Perception, Verbal Fluency, Response Monitoring and Cognitive Flexibility. DFA identified six test to be most appropriate to discern TLE from FLE: WMS-IV Logical Memory, recognition; WMS-R Digit Span, backwards; VLMT, repetitions; VOSP Silhouettes; VLMT, delayed recall; and RWT Phonemic verbal fluency. Group membership was correctly predicted for 78.6% of patients using cross-validation.

CONCLUSIONS

As neuropsychological assessments are central in clinical decision-making in presurgical work-up of epilepsy patients, the appropriateness of the test battery in use is essential. The majority of cognitive domains are sufficiently measurable by the test battery and it is highly sensitive to differentiate between the cognitive profiles of TLE and FLE. However, the selection of tests assessing nonverbal memory functions requires further improvement.

Predicting verbal memory decline following temporal lobe resection for epilepsy

OBJECTIVES

The aim of the study was to develop a prediction model for verbal memory decline after temporal lobe resection (TLR) for epilepsy. The model will be used in the preoperative counselling of patients to give individualized information about risk for verbal memory decline.

MATERIALS AND METHODS

A sample of 110 consecutive patients who underwent TLR for epilepsy at Sahlgrenska University Hospital between 1987 and 2011 constituted the basis for the prediction model. They had all gone through a formal neuropsychological assessment before surgery and 2 years after. Penalized regression and 20 × 10-fold cross-validation were used in order to build a reliable model for predicting individual risks.

RESULTS

The final model included four predictors: side of surgery; inclusion or not of the hippocampus in the resection; preoperative verbal memory function; and presence/absence of focal to bilateral tonic-clonic seizures (TCS) the last year prior to the presurgical investigation. The impact of a history of TCS is a new finding which we interpret as a sign of a more widespread network disease which influences neuropsychological function and the cognitive reserve. The model correctly identified 82% of patients with post-operative decline in verbal memory, and the overall accuracy was 70%-85% depending on choice of risk thresholds.

CONCLUSIONS

The model makes it possible to provide patients with individualized prediction regarding the risk of verbal memory decline following TLR. This will help them make more informed decisions regarding treatment, and it will also enable the epilepsy surgery team to prepare them better for the rehabilitation process.

Ability to knit may be impaired following right temporal lobe resection for drug-resistant epilepsy

•

The ability to knit may be compromised following a right or non-dominant temporal lobe resection.

•

Non-lesional patients may be at particular risk.

•

It is important to disseminate knowledge of impact of epilepsy surgery on specialist skills, via case studies.

Test-specific differences in verbal memory assessments used prior to surgery in temporal lobe epilepsy

OBJECTIVE

To study the relationship between two commonly used verbal memory tests in presurgical evaluation for temporal lobe epilepsy (TLE) in Sweden, the Claeson-Dahl Test for verbal learning and retention (CDT) and the Swedish version of the Rey Auditory Verbal Learning Test (RAVLT).

METHODS

Fifty-nine patients with TLE (male: 41%, mean: age 41.7 ± 12.3 years; epilepsy onset at mean age: 18.3 ± 13.1 years) previously tested with the CDT, the RAVLT, and three nonverbal memory tests on the same occasion were included. We performed (1) a principal component analysis (PCA) on test performances in the CDT and the RAVLT as well as in nonverbal memory tests; (2) a Pearson's correlation analysis for memory components, biological age, education, age at epilepsy onset, and self-rating scores for depression and anxiety; and (3) an estimation of clinically significant verbal memory impairment in patients with left TLE and left-sided hippocampal sclerosis.

RESULTS

The PCAs showed coherence between the learning variables of the CDT and the RAVLT and divergence between the recall variables of the two tests. The RAVLT delayed recall variable was correlated to four out of five nonverbal memory measures. Both tests showed 70-80% clinically significant impairment of verbal memory in patients with left TLE, with or without hippocampal sclerosis, similar to other cohorts with resistant TLE.

CONCLUSIONS

The construct structure of the two verbal memory differs. It was shown that the RAVLT correlated with visuospatial memory, whereas the CDT did not. The study highlights that there are important nonoverlapping features regarding verbal recall of the two tests, indicating that these tests cannot fully replace one another.

The impact of brain-derived neurotrophic factor Val66Met polymorphism on cognition and functional brain networks in patients with intractable partial epilepsy

INTRODUCTION

Medial temporal lobe epilepsy (mTLE) is the most common refractory focal epilepsy in adults. Around 30%-40% of patients have prominent memory impairment and experience significant postoperative memory and language decline after surgical treatment. BDNF Val66Met polymorphism has also been associated with cognition and variability in structural and functional hippocampal indices in healthy controls and some patient groups.

AIMS

We examined whether BDNF Val66Met variation was associated with cognitive impairment in mTLE.

METHODS

In this study, we investigated the association of Val66Met polymorphism with cognitive performance (n = 276), postoperative cognitive change (n = 126) and fMRI activation patterns during memory encoding and language paradigms in 2 groups of patients with mTLE (n = 37 and 34).

RESULTS

mTLE patients carrying the Met allele performed more poorly on memory tasks and showed reduced medial temporal lobe activation and reduced task-related deactivations within the default mode networks in both the fMRI memory and language tasks than Val/Val patients.

CONCLUSIONS

Although cognitive impairment in epilepsy is the result of a complex interaction of factors, our results suggest a role of genetic factors on cognitive impairment in mTLE.

Neurocognitive problems in epilepsy

Cognitive dysfunction is one of the major contributors to the burden of epilepsy. It can significantly disrupt intellectual development in children and functional status and quality of life in adults. Epilepsy affects cognition through a number of mechanisms in complex interrelationship. Cognitive deficits in epilepsy may be treated indirectly through aggressive seizure control using anti-epileptic drugs or surgery, and by treating comorbid conditions such as depression. The beneficial effects of reducing seizures may offset the adverse cognitive side-effects of these therapies. Direct treatment of cognitive impairment in epilepsy mainly involves memory rehabilitation. Other direct treatments are mostly experimental and their evidence base is currently poor.

Stable psychological functioning after surgery for epilepsy: An informant-based perspective

OBJECTIVE

Psychological adjustment following surgery for epilepsy has been assessed primarily with self-report measures. In the current work, we investigated pre- to postoperative changes in various dimensions of personality and behavior from the perspective of a well-known family member or friend for 27 patients operated on for medically intractable epilepsy.

METHODS

For each patient, a close family member or friend ("informant") provided pre- and postoperative ratings on five dimensions of personality and behavior. All ratings were collected during the chronic epoch of recovery, when personality and behavior of the patients are relatively stable. Self-report measures were also used to examine the relation between self-report and informant-report assessment of psychological adjustment. Lastly, the relation between seizure outcomes and psychological adjustment was investigated.

RESULTS

Personality and behavior characteristics, as rated by an informant, remained stable and within a normal range of functioning following surgery for epilepsy. There were no significant differences between pre- and postoperative levels of executive functioning, social behavior, hypo-emotionality, irascibility, or distress. Informant-ratings on levels of current depression and overall current psychological functioning were significantly related to patient reports of current depression and global personality characteristics derived from the MMPI-2 (e.g., psychasthenia, schizophrenia, hypomania, psychopathic deviation, social introversion). There was no significant relationship between seizure outcome and psychological adjustment.

SIGNIFICANCE

Informant-based reports on psychological adjustment following surgery for epilepsy provide a unique perspective on important aspects of the success of the intervention. Assessing outcomes beyond seizure status is important for developing a comprehensive understanding of the potential consequences of surgery for epilepsy. Based on the current work, personality and behavior seem to be stable following surgery for epilepsy, and our study provides a unique informant-based perspective on this encouraging result.

A Functional MRI-Based Model for Individual Memory Assessment in Patients Eligible for Anterior Temporal Lobe Resection

Title:

A functional (f) MRI-based model for individual memory assessment in patients eligible for temporal lobe resection.

Aim:

To investigate if pre-operative fMRI memory paradigms, add predictive information with regard to post-surgical memory deficits.

Methods:

Fourteen pharmacoresistant Temporal Lobe Epilepsy (TLE) patients accepted for Anterior Temporal Lobe Resection (ATLR) were included. A clinical risk assessment score (RAS 0-3) was constructed from structural MRI, neuropsychological testing and hemisphere dominance. fMRI lateralization indices (LIs) over frontal language and medial temporal regions were calculated. Predictive value from clinical risk scoring and added value from fMRI LIs were correlated to post-surgical memory change scores (significant decline -1 SD). Verbal memory outcome was classified either as expected (RAS 2-3 and post-operative decline; RAS 0-1 and intact post-operative verbal memory) or as unexpected (RAS 2-3 and intact post-operative verbal memory post-surgery; RAS 0-1 and post-operative decline).

Results:

RAS for verbal memory decline exhibited a specificity of 67% and a sensitivity of 75%. Significant correlations were found between frontal language LIs and post-operative verbal memory (r = -0.802; p = 0.017) for left (L) TLE and between medial temporal lobe LIs and visuospatial memory (r = 0.829; p = 0.021), as well as verbal memory (r = 0.714; p = 0.055) for right (R) TLE. Ten patients had expected outcome and four patients had an unexpected outcome. In two MRI-negative RTLE patients that suffered significant verbal memory decline post-operatively, fMRI identified bilateral language and right lateralized medial temporal verbal encoding. In two LTLE patients with MRI pathology and verbal memory dysfunction, neither RAS nor fMRI identified the risk for aggravated verbal memory decline following ATLR.

Conclusion:

fMRI visualization of temporal-frontal network activation may add value to the pre-surgical work-up in epilepsy patients eligible for ATLR. Frontal language patterns are important for prediction in both L and RTLE. Strong left lateralized language in LTLE, as well as bilateral language combined with right lateralized encoding in RTLE, seems to indicate an increased risk for post-operative verbal memory decline.

Psychosocial factors associated with in postsurgical prognosis of temporal lobe epilepsy related to hippocampal sclerosis

We examined the long-term psychosocial trajectory in a consecutive and homogeneous series of 120 patients followed up for five years after corticoamygdalohippocampectomy (CAH). Evaluation of psychosocial variables at baseline and at five-year follow-up were compared. After five years of CAH, a significant improvement in educational level (p=0.004) and employment status (p<0.001) was observed, although retirement (p<0.001) and divorce (p=0.021) rates increased. In a long-term follow-up, a tendency to have similar QOL profile was observed between Engel classes IA and IB (p>0.05). A more favorable surgical outcome (Engel IA) was related to better psychiatric status (p=0.012). Poor psychosocial adjustment before surgery was the most important predictor of QOL outcome (p<0.05). Patients' trajectory after surgical treatment showed positive effects mainly in those with better seizure outcome. Our results emphasized the influence regarding baseline psychosocial functioning on postoperative psychosocial adjustment. Furthermore, many psychosocial gains and difficulties after surgery may be similar in developing and developed countries.

Factors affecting reorganisation of memory encoding networks in temporal lobe epilepsy

AIMS

In temporal lobe epilepsy (TLE) due to hippocampal sclerosis reorganisation in the memory encoding network has been consistently described. Distinct areas of reorganisation have been shown to be efficient when associated with successful subsequent memory formation or inefficient when not associated with successful subsequent memory. We investigated the effect of clinical parameters that modulate memory functions: age at onset of epilepsy, epilepsy duration and seizure frequency in a large cohort of patients.

METHODS

We studied 53 patients with unilateral TLE and hippocampal sclerosis (29 left). All participants performed a functional magnetic resonance imaging memory encoding paradigm of faces and words. A continuous regression analysis was used to investigate the effects of age at onset of epilepsy, epilepsy duration and seizure frequency on the activation patterns in the memory encoding network.

RESULTS

Earlier age at onset of epilepsy was associated with left posterior hippocampus activations that were involved in successful subsequent memory formation in left hippocampal sclerosis patients. No association of age at onset of epilepsy was seen with face encoding in right hippocampal sclerosis patients. In both left hippocampal sclerosis patients during word encoding and right hippocampal sclerosis patients during face encoding, shorter duration of epilepsy and lower seizure frequency were associated with medial temporal lobe activations that were involved in successful memory formation. Longer epilepsy duration and higher seizure frequency were associated with contralateral extra-temporal activations that were not associated with successful memory formation.

CONCLUSION

Age at onset of epilepsy influenced verbal memory encoding in patients with TLE due to hippocampal sclerosis in the speech-dominant hemisphere. Shorter duration of epilepsy and lower seizure frequency were associated with less disruption of the efficient memory encoding network whilst longer duration and higher seizure frequency were associated with greater, inefficient, extra-temporal reorganisation.

Rehabilitation of verbal memory by means of preserved nonverbal memory abilities after epilepsy surgery

We present a patient with epilepsy who underwent left anterior temporal cortex resection, sparing the hippocampus, to stop drug-refractory seizures. Given that one year after surgery the patient showed verbal memory difficulties, we proposed a short (twelve weeks) and intensive (two times a week) training based on visual imagery strategies as the nonverbal memory abilities were preserved. Neuropsychological and fMRI assessments were performed before and after rehabilitation to evaluate the cognitive progress and cerebral modifications induced by this rehabilitation program. Our results showed that the rehabilitation program improved both scores for verbal memory and the everyday quality of life. Changes in cerebral activity highlighted by fMRI suggest that the program might have facilitated the development of compensatory strategies, as reflected by the shift of activation from the anterior to the posterior cerebral network during a verbal memory task. One year after the rehabilitation program, the patient reported using mental imagery in everyday life for routine and professional activities. Although supplementary evidence is necessary to increase the robustness of these findings, this case report suggests that an efficient rehabilitation program is feasible and (a) should be based on the individual cognitive profile and on the preserved cognitive abilities, (b) can be short but intensive, (c) can be applied even months after the lesion occurrence, and (d) can induce a positive effect which may be sustainable over time.

Long-term postoperative atrophy of contralateral hippocampus and cognitive function in unilateral refractory MTLE with unilateral hippocampal sclerosis

OBJECTIVE

This study aimed to evaluate long-term atrophy in contralateral hippocampal volume after surgery for unilateral MTLE, as well as the cognitive outcome for patients submitted to either selective transsylvian amygdalohippocampectomy (SelAH) or anterior temporal lobe resection (ATL).

METHODS

We performed a longitudinal study of 47 patients with MRI signs of unilateral hippocampal sclerosis (23 patients with right-sided hippocampal sclerosis) who underwent surgical treatment for MTLE. They underwent preoperative/postoperative high-resolution MRI as well as neuropsychological assessment for memory and estimated IQ. To investigate possible changes in the contralateral hippocampus of patients, we included 28 controls who underwent two MRIs at long-term intervals.

RESULTS

The volumetry using preoperative MRI showed significant hippocampal atrophy ipsilateral to the side of surgery when compared with controls (p<0.0001) but no differences in contralateral hippocampal volumes. The mean postoperative follow-up was 8.7 years (± 2.5 SD; median=8.0). Our patients were classified as Engel I (80%), Engel II (18.2%), and Engel III (1.8%). We observed a small but significant reduction in the contralateral hippocampus of patients but no volume changes in controls. Most of the patients presented small declines in both estimated IQ and memory, which were more pronounced in patients with left TLE and in those with persistent seizures. Different surgical approaches did not impose differences in seizure control or in cognitive outcome.

CONCLUSIONS

We observed small declines in cognitive scores with most of these patients, which were worse in patients with left-sided resection and in those who continued to suffer from postoperative seizures. We also demonstrated that manual volumetry can reveal a reduction in volume in the contralateral hippocampus, although this change was mild and could not be detected by visual analysis. These new findings suggest that dynamic processes continue to act after the removal of the hippocampus, and further studies with larger groups may help in understanding the underlying mechanisms.

An evidence-based checklist to assess neuropsychological outcomes of epilepsy surgery: how good is the evidence?

PURPOSE

We aimed to assess the quality of evidence on neuropsychological outcomes after epilepsy surgery (ES). Accordingly, we created an evidence-based neuropsychology (EBNP) checklist to assess neuropsychological outcomes and applied this tool to studies from a systematic review.

METHODS

The EBNP checklist was created using clinical expert input, scale development methodology for item generation and reduction and inter-rater reliability, and critical appraisal guidelines for studies about treatment. The checklist was applied to articles obtained through a systematic review of resective ES neuropsychological outcomes. The proportion of studies fulfilling the quality criteria and the total quality score were used to assess the quality of the evidence.

RESULTS

An initial 45-item checklist was applied to 147 articles, with excellent inter-rater agreement (kappa=0.80). The mean quality score was 23 (SD: 4, range: 12-33). There was substantial variability in the percentage of studies meeting the criteria for specific items (0-99%). The median proportion of papers fulfilling various quality criteria was 1.4% for items related to group comparisons, 37% for clinical applicability, 67% for patient description, 78% for outcome assessment, and 91% for interventions. Higher quality correlated with longitudinal design, reporting presurgical IQ, seizure frequency and antiepileptic drugs, and using validated measures of change in individual patients. The final EBNP checklist consisted of 19 items.

DISCUSSION

The EBNP checklist reliably identified quality strengths and threats to validity of neuropsychological outcome studies in ES. Studies would be most improved by the inclusion of random allocation to interventions or at minimum blinded outcome assessment, empirically based measures of reliable change and completeness of reporting of follow-up.

Dysembryoplastic neuroepithelial tumors: a model for examining the effects of pathology versus seizures on cognitive dysfunction in epilepsy

PURPOSE

Dysembryoplastic neuroepithelial tumors (DNTs) provide a unique model for studying the effects of seizures on cognitive development. Epilepsy and antiepileptic medications are prominent features in the lives and schooling of people who develop seizures in childhood. People with an adult onset share the same underlying brain pathology, but their childhood development is unaffected by seizures. Therefore, DNTs provide a model to examine the specific influence of seizures and their treatment on cognitive development, over and above the effects of the underlying pathology in epilepsy.

METHODS

We examined the neuropsychological characteristics of 56 adults with DNT and medically intractable epilepsy (mean age 32.7 years). Twenty-two adults (39%) had an age of onset of epilepsy before the age of 12 years (childhood-onset group). Scores on tests of intelligence (Verbal IQ and Performance IQ), reading, working memory, verbal learning, verbal recall, visual learning, and expressive and receptive language ability were analyzed.

KEY FINDINGS

There were no significant localization effects (right vs. left vs. extratemporal) on any of the neuropsychological test scores. In the group as a whole, the neuropsychological test scores were significantly lower than healthy, age-matched controls on measures of Verbal IQ (p < 0.01), naming p < 0.01, verbal learning (p < 0.01), and working memory (p < 0.05). The childhood-onset group had significantly lower scores on the measures of Verbal IQ (p < 0.01), Performance IQ (p < 0.05), reading (p < 0.05), naming (p = 0.05), and verbal retention (p < 0.05) than those with an onset of seizures at the age of 12 or older.

SIGNIFICANCE

The traditional pattern of lateralized memory deficits seen in people with hippocampal sclerosis may not be present in people with temporal lobe epilepsy associated with a DNT. The presence of seizures and their treatment in early childhood may adversely influence the development of these core cognitive abilities, resulting in patterns of cognitive deficits that remain apparent in adulthood.

Hemispheric lateralization interrupted: material-specific memory deficits in temporal lobe epilepsy

The hemispheric lateralization of memory has largely been informed through the study of patients with temporal lobe epilepsy originating from medial temporal sources (mTLE). The material-specific model of memory relies on the basic framework that the left temporal lobe mediates verbal memories, while the right temporal lobe mediates non-verbal memories. Over the years, this model has been refined, and even challenged, as our understanding of the material-specific memory deficits in mTLE has been further elaborated in the neuropsychological and neuroimaging literature. The first goal of this mini-review is to highlight the major findings in the mTLE literature that have advanced and expanded our understanding of material-specific memory deficits in mTLE. Second, we will review how functional neuroimaging patterns of material-specific hemispheric lateralization in mTLE are being translated into the innovative clinical application of preoperative fMRI memory mapping.

Psychosocial status 10 years after temporal lobe resection for epilepsy, a longitudinal controlled study

Knowledge about long-term psychosocial outcome of temporal lobe resection (TLR) for epilepsy is limited. The aims of this study were to describe vocational outcome 10 years after TLR and to analyze the effect on the vocational situation by seizures, laterality of resection, verbal memory, and mood. Fifty-one patients were prospectively followed 10 years after TLR. Psychosocial and neuropsychological data were ascertained at baseline and 10 years after surgery and at corresponding time points for 23 controls. Fewer patients worked 10 years post-operatively compared with controls (TLR patients: 61% and controls: 96%). However, seizure-free patients were more likely to retain employment (71%) than patients who had seizures (41%). The odds of working full-time were 9.5 times higher for patients with seizure freedom than for those with continuing seizures. There were no associations between working at 10 years and side of resection or mood, and impairment of verbal memory did not have an influence on vocational outcome.

Computerized cognitive testing in epilepsy (CCTE): a new method for cognitive screening

PURPOSE

Optimized therapy in epilepsy should include individual care for cognitive functions. Here we introduce a computerized screening instrument, called "Computerized Cognitive Testing in Epilepsy" (CCTE), which allows for time-efficient repetitive assessment of the patient's cognitive profile regarding the domains of memory and attention, which are frequently impaired due to side effects of antiepileptic medication.

METHODS

The CCTE battery takes 30min and covers tasks of verbal and figural memory, cognitive speed, attention and working memory. The patient's results are displayed immediately in comparison to age-related normative data. For evaluation of psychometrics and clinical correlations, data from patients of a tertiary referral epilepsy center (n=240) and healthy subjects (n=83) were explored.

RESULTS

CCTE subtests show good reliability and concurrent validity compared to standard neuropsychological tests (p<0.01). Adverse cognitive effects of antiepileptic medication can be detected (p<0.05), e.g. significant negative effects of increasing drug load. Specific epilepsy subgroups, e.g. focal versus primary generalized epilepsy or right versus left mesial temporal lobe epilepsy, showed different CCTE profiles.

CONCLUSION

CCTE appears valuable for early detection of individual cognitive alterations related to medication. In addition, it displays interesting differences between epilepsy syndromes. The CCTE battery provides a standardized, time- and personnel-efficient assessment of cognitive functions open to a large number of patients and applicable for clinical and scientific use in epilepsy.

Verbal memory decline is less frequent at 10 years than at 2 years after temporal lobe surgery for epilepsy

We investigated individual short- and long-term verbal memory changes after temporal lobe resection for epilepsy. Fifty-one patients (23 operated on the speech-dominant temporal lobe, DTL and 28 on the non-dominant temporal lobe, NDTL) were tested on learning/immediate recall and delayed recall of word-list and word-pairs preoperatively, 2 years postoperatively and 10years postoperatively. Changes were defined using reliable change indices of 23 healthy controls assessed at corresponding intervals. Fewer patients had reliable declines at 10 years than at 2 years (DTL: 13-35% vs 35-44%; NDTL: 0-4% vs 7-21%). Four DTL patients (17%) had reliable declines in ≥2 tests at 10-year follow-up. More NDTL patients had improvement at 10 years than at 2 years (18-30% vs 4-22%). The only risk factor for decline both short and long term was DTL resection. In conclusion, most patients had stable verbal memory postoperatively. A few DTL patients had a lasting decline at long-term follow-up, but more patients showed partial recovery, especially in the NDTL group.

Naming outcomes of anterior temporal lobectomy in epilepsy patients: a systematic review of the literature

Anterior temporal lobectomy (ATL) is the standard surgical treatment for medically intractable temporal lobe epilepsy (TLE). While seizure outcome is favorable, cognitive outcomes are a concern, particularly in respect of memory and naming. A systematic review of the literature on the naming outcomes of ATL is presented in this article. Searches were conducted on PubMed and PsycInfo, yielding a total of 93 articles, 21 of which met inclusion criteria. Declines in visual naming are common following ATL in the dominant hemisphere, and particularly, for naming living stimuli or famous faces. The Boston Naming Test (BNT) declines by a mean of 5.8 points, exceeding the Reliable Change Index (RCI). There are no reports of deficits in auditory naming following ATL, despite the fact that auditory naming has shown to be a more sensitive measure of dysnomia than the BNT in TLE patients. The absence of structural hippocampal pathology and late-onset epilepsy are the strongest predictors of naming decline. Recommendations are made for further study.

The cognitive effects of amygdalohippocampal deep brain stimulation in patients with temporal lobe epilepsy

The aim of this study was to examine the effects of amygdalohippocampal deep brain stimulation (AH-DBS) on cognitive functioning in patients with refractory temporal lobe epilepsy. The population consisted of 10 patients (7 men) who underwent ipsilateral (n=8) or bilateral (n=2) AH-DBS. Intellectual and neuropsychological evaluation was performed before and 6 months after initiation of AH-DBS. Group analyses revealed no overall pattern of change in cognitive measures, but improvement was seen in emotional well-being. Individual results varied over a broad spectrum ranging from no cognitive effects to negative effects on intelligence capacities, divided attention, and concept formation, to positive effects on speed of information processing and speed of finger movements. AH-DBS is a valuable treatment alternative for patients with refractory epilepsy that appears to have no major adverse neuropsychological consequences and enhances emotional well-being on the group level. Individual results are too diverse at this moment to allow viable interpretation. Additional studies are needed to confirm these preliminary results.

Current challenges in the practice of epilepsy surgery

The accurate prediction of individual outcomes after epilepsy surgery represents a key challenge facing clinicians. It requires a precise understanding of surgical candidacy and the optimal timing of surgery to maximize a range of outcomes, including medical, psychosocial, cognitive, and psychiatric outcomes. We promote careful consideration of how epilepsy has affected an individual's developmental trajectory as key to constructing more differentiated profiles of postsurgical risk or resilience across multiple outcome measures. This life span approach conceives surgery as a crucial "turning point" in an individual's development from which varied outcome trajectories may follow. This helps clinicians understand the expectations patients and families bring to surgery, and emphasizes the interplay of factors that determine a patient's outcome. It also promotes comprehensive, longitudinal assessment of outcome using data analytical techniques that capture individual differences and identify subgroups with similar trajectories. An ongoing challenge facing clinicians is the development of an outcome classification system that incorporates outcomes other than seizures. We illustrate two emerging areas of research shaping how we define surgical candidacy and predict outcome: (1) using cortico-cortical evoked potentials to identify pathways of seizure propagation and cortico-cortical networks mediating cortical functions, and (2) predicting postoperative depression using a model that incorporates psychosocial and neurobiological factors. The latter research points to the importance of routine follow-up and postoperative psychosocial rehabilitation, particularly in patients deemed at "high risk" for poor outcomes so that early treatment interventions can be implemented. Significantly more research is needed to characterize those patients with poor outcomes who may require re-surgery.

Diverse perspectives on developments in epilepsy surgery

The objective of this article is to review the dramatic changes that have occurred in the field of epilepsy surgery since the founding of Epilepsy Action in 1950. We have chosen to consider these advances from the biomedical perspective (the physician and basic scientist), and the behavioral perspective (the psychologist and the patient). Both these viewpoints are equally important in understanding the evolution of epilepsy surgery over the past 60 years, but may not always be well synchronized.

The experience of seizures after epilepsy surgery

Postoperative seizures occur in 20-60% of patients who have epilepsy surgery. Despite this, there is limited understanding of a patient's experience of the recurrence of seizures after surgery. This study used a qualitative approach to identify key themes derived from content analysis of 15 in-depth patient interviews about the experience of seizure recurrence. The results showed a prominence of psychological issues over medical concerns. The four most frequently expressed themes were perceived success of surgery, medication, acceptance of seizure recurrence, and personal independence. Despite seizure recurrence, patient sentiments were not universally negative; rather there was heterogeneity of views, with some reporting ambivalence and others a sense of satisfaction with outcome. The findings provide evidence for the importance of cognitive reframing and benefit finding in the context of seizure recurrence.

Verbal memory in mesial temporal lobe epilepsy: beyond material specificity

The idea that verbal and non-verbal forms of memory are segregated in their entirety, and localized to the left and right hippocampi, is arguably the most influential concept in the neuropsychology of temporal lobe epilepsy, forming a cornerstone of pre-surgical decision making, and a frame for interpreting postoperative outcome. This critical review begins by examining some of the unexpressed but inescapable assumptions of the material-specificity model: (i) verbal and non-verbal memory are unitary and internally homogenous constructs; and (ii) left and right memory systems are assumed to be independent, self-contained modules. The next section traces the origins of an alternative view, emanating largely from three challenges to these assumptions: (i) verbal memory is systematically fractionated by left mesial temporal foci; (ii) the resulting components are differentially localized within the left temporal lobe; and (iii) verbal and non-verbal memory functions are not entirely lateralized. It is argued here that the perirhinal cortex is a key node in a more extensive network mediating protosemantic associative memory. Impairment of this fundamental memory system is a proximal neurocognitive marker of mesial temporal epileptogenesis.