Memory functions following surgery for temporal lobe epilepsy in children

Long-term neuropsychological trajectories in children with epilepsy: does surgery halt decline?

Neuropsychological impairments are common in children with drug-resistant epilepsy. It has been proposed that epilepsy surgery might alleviate these impairments by providing seizure freedom; however, findings from prior studies have been inconsistent. We mapped long-term neuropsychological trajectories in children before and after undergoing epilepsy surgery, to measure the impact of disease course and surgery on functioning. We performed a retrospective cohort study of 882 children who had undergone epilepsy surgery at Great Ormond Street Hospital (1990-2018). We extracted patient information and neuropsychological functioning [obtained from IQ tests (domains: full-scale IQ, verbal IQ, performance IQ, working memory and processing speed) and tests of academic attainment (reading, spelling and numeracy)] and investigated changes in functioning using regression analyses. We identified 500 children (248 females) who had undergone epilepsy surgery [median age at surgery = 11.9 years, interquartile range = (7.8, 15.0)] and neuropsychological assessment. These children showed declines in all domains of neuropsychological functioning in the time leading up to surgery (all P-values ≤0.001; e.g. βFSIQ = -1.9, SEFSIQ = 0.3, PFSIQ < 0.001). Children lost on average one to four points per year, depending on the domain considered; 27%-43% declined by ≥10 points from their first to their last preoperative assessment. At the time of presurgical evaluation, most children (46%-60%) scored one or more standard deviations below the mean (<85) on the different neuropsychological domains; 37% of these met the threshold for intellectual disability (full-scale IQ < 70). On a group level, there was no change in performance from pre- to postoperative assessment on any of the domains (all P-values ≥0.128). However, children who became seizure free through surgery showed higher postoperative neuropsychological performance (e.g. rrb-FSIQ = 0.37, P < 0.001). These children continued to demonstrate improvements in neuropsychological functioning over the course of their long-term follow-up (e.g. βFSIQ = 0.9, SEFSIQ = 0.3, PFSIQ = 0.004). Children who had discontinued antiseizure medication treatment at 1-year follow-up showed an 8- to 13-point advantage in postoperative working memory, processing speed and numeracy, and greater improvements in verbal IQ, working memory, reading and spelling (all P-values ≤0.034) over the postoperative period compared with children who were seizure free and still receiving antiseizure medication. In conclusion, by providing seizure freedom and the opportunity for antiseizure medication cessation, epilepsy surgery might not only halt but reverse the downward trajectory that children with drug-resistant epilepsy display in neuropsychological functioning. To halt this decline as soon as possible or, potentially, to prevent it from occurring in the first place, children with focal epilepsy should be considered for epilepsy surgery as early as possible after diagnosis.

Clinical recommendations for conducting pediatric functional language and memory mapping during the phase I epilepsy presurgical workup

Objective: Pediatric epilepsy surgery effectively controls seizures but may risk cognitive, language, or memory decline. Historically, the intra-carotid anesthetic procedure (IAP or Wada Test) was pivotal for language and memory function. However, advancements in noninvasive mapping, notably functional magnetic resonance imaging (fMRI), have transformed clinical practice, reducing IAP's role in presurgical evaluations. Method: We conducted a critical narrative review on mapping technologies, including factors to consider for discordance. Results: Neuropsychological findings suggest that if pre-surgery function remains intact and the surgery targets the eloquent cortex, there is a high chance for decline. Memory and language decline are particularly pronounced post-left anterior temporal lobe resection (ATL), making presurgical cognitive assessment crucial for predicting postoperative outcomes. However, the risk of functional decline is not always clear - particularly with higher rates of atypical organization in pediatric epilepsy patients and discordant findings from cognitive mapping. We found little research to date on the use of IAP and other newer technologies for lateralization/localization in pediatric epilepsy. Based on this review, we introduce an IAP decision tree to systematically navigate discordance in IAP decisions for epilepsy presurgical workup. Conclusions: Future research should be aimed at pediatric populations to improve the precision of functional mapping, determine which methods predict post-surgical deficits and then create evidence-based practice guidelines to standardize mapping procedures. Explicit directives are needed for resolving conflicts between developing mapping procedures and established clinical measures. The proposed decision tree is the first step to standardize when to consider IAP or invasive mapping, in coordination with the multidisciplinary epilepsy surgical team.

Neuropsychological assessment in pediatric epilepsy surgery: A French procedure consensus

Neuropsychological assessment is a mandatory part of the pre- and post-operative evaluation in pediatric epilepsy surgery. The neuropsychology task force of the ILAE - French Chapter aims to define a neuropsychological procedure consensus based on literature review and adapted for French practice. They performed a systematic review of the literature published between 1950 and 2023 on cognitive evaluation of individuals undergoing presurgical work-up and post-surgery follow-up and focused on the pediatric population aged 6-16. They classified publications listed in the PubMed database according to their level of scientific evidence. The systematic literature review revealed no study with high statistical power and only four studies using neuropsychological scales in their French version. Afterwards, the experts defined a neuropsychological consensus strategy in pediatric epilepsy surgery according to the psychometric determinants of cognitive tests, specificity of epilepsy, surgery context, French culture and literature reports. A common French neuropsychological procedure dedicated to pediatric epilepsy surgery is now available. This procedure could serve as a guide for the pre- and post-surgical work-up in French centers with pediatric epilepsy surgery programs. The main goal is to anticipate the functional risks of surgery, to support the postoperative outcome beyond the seizure-related one, while taking into consideration the plasticity and vulnerability of the immature brain and allowing the possibility of collaborative studies.

The hidden face of hemispherectomy: Visuo-spatial and visuo-perceptive processing after left or right functional hemispherectomy in 40 children

Functional hemispherectomy results in good outcomes in cases of refractory epilepsy and constitutes a unique situation in which to study cerebral plasticity and the reorganization of lateralized functions of the brain, especially in cases of infancy or childhood surgery. Previous studies have highlighted the remarkable ability of the brain to recover language after left hemispherectomy. This leads to a reorganization of language networks toward right hemisphere, causing limitation in the development of visuo-spatial abilities, known as a crowding effect in the right hemisphere. Deficits in nonverbal functions have also been described as a more direct consequence of right hemipherectomy, but the results from case studies have sometimes been contradictory. We conducted a group study which may effectively compare patients with left and right hemispherectomy and address the effects of the age of seizure onset and surgery. We analyzed the general visuo-spatial and visuo-perceptive abilities, including face and emotional facial expression processing, in a group of 40 patients aged 7-16 years with left (n = 24) or right (n = 16) functional hemispherectomy. Although the groups did not differ, on average, in general visuo-spatial and visuo-perceptive skills, patients with right hemispherectomy were more impaired in the processing of faces and emotional facial expressions compared with patients with left hemispherectomy. This may reflect a specific deficit in the perceptual processing of faces after right hemispherectomy. Results are discussed in terms of limited plasticity of the left hemisphere for facial and configural processing.

Academic attainment following pediatric epilepsy surgery: A systematic review

Academic skills, such as reading, spelling and arithmetic, are central to meaningful engagement with society throughout adolescence and into adulthood. The disruption caused by on-going seizure activity places children with drug-resistant epilepsy at a particularly high risk of poor academic attainment. Though epilepsy surgery during childhood has long-been associated with various cognitive changes, less is known of the extent to which pediatric epilepsy surgery impacts academic attainment. The aim of the present systematic review was to identify the nature of the effect of pediatric epilepsy surgery on the core academic skills of reading, writing, and arithmetic. The electronic databases Embase, Medline, PubMed, PsychInfo, OpenAire, and the ISRCTN registry were searched for studies examining academic attainment following epilepsy surgery in childhood, over the last three decades. Two thousand three-hundred and sixty-eight articles were screened for relevance. Thirteen studies met the inclusion criteria. Study quality and reliability were independently assessed by two reviewers. Results indicate that academic attainment primarily stabilizes in the first year following epilepsy surgery. Though changes to learning ability would not be expected in this early recovery phase, this review indicates that children do not, at least, lose the academic skills they have acquired before surgery. Postoperative declines in performance were most notably recorded in assessments of arithmetic, suggesting an area of potential vulnerability in this cohort. These declines were noted in cohorts with the longest periods between seizure onset and surgery. While older age at onset and seizure freedom correlated with improved academic attainment, further research is necessary to fully understand the specific effect of epilepsy surgery on academic attainment. Still, the present review provides valuable information regarding the likely academic outcomes in the early years following surgical treatment for drug-resistant epilepsy.

Physical, Emotional/Behavioral, and Neurocognitive Developmental Outcomes From 2 to 4 Years After PICU Admission: A Secondary Analysis of the Early Versus Late Parenteral Nutrition Randomized Controlled Trial Cohort

OBJECTIVES

PICU patients face long-term developmental impairments, partially attributable to early parenteral nutrition (PN) versus late-PN. We investigated how this legacy and harm by early-PN evolve over time.

DESIGN

Preplanned secondary analysis of the multicenter PEPaNIC-RCT (ClinicalTrials.gov, NCT01536275) that enrolled 1,440 critically ill children from 2012 to 2015 and its 2- (2014-2018) and 4-year (2016-2019) cross-sectional follow-up studies.

SETTING

PICUs of Leuven (Belgium), Rotterdam (The Netherlands), and Edmonton (Canada).

PATIENTS

Patients and demographically matched healthy control children that underwent longitudinal assessment for physical/emotional/behavioral/neurocognitive functions at both follow-up time points.

INTERVENTIONS

In the PEPaNIC-RCT, patients were randomly allocated to early-PN versus late-PN.

MEASUREMENTS AND MAIN RESULTS

This within-individual longitudinal study investigated changes in physical/emotional/behavioral/neurocognitive functions from 2 to 4 years after PICU admission for 614 patients (297 early-PN and 317 late-PN, tested at mean ± sd age 5.4 ± 4.2 and 7.3 ± 4.3 yr) and for 357 demographically matched healthy children tested at age 5.6 ± 4.3 and 7.5 ± 4.3 years. We determined within-group time-courses, interaction between time and group, and independent impact of critical illness and early-PN on these time-courses. Most deficits in patients versus healthy children remained prominent over the 2 years ( p ≤ 0.01). Deficits further aggravated for height, body mass index, the executive function metacognition, intelligence, motor coordination (alternating/synchronous tapping), and memory learning-index, whereas verbal memory deficits became smaller (working/immediate/delayed memory) ( p ≤ 0.05). Adjustment for risk factors confirmed most findings and revealed that patients "grew-into-deficit" for additional executive functions (flexibility/emotional control/total executive functioning) and "grew-out-of-deficit" for additional memory functions (recognition/pictures) ( p ≤ 0.05). Time-courses were largely unaffected by early-PN versus late-PN, except for weight loss and limited catch-up for visual-motor integration and alertness in early-PN patients ( p ≤ 0.05).

CONCLUSIONS

From 2- to 4-year post-PICU admission, developmental impairments remained prominent. Within that time-window, impaired growth in height, executive functioning and intelligence aggravated, and impaired memory and harm by early-PN only partially recovered. Impact on development into adulthood requires further investigation.

Connectomic Profiles and Cognitive Trajectories After Epilepsy Surgery in Children

OBJECTIVE

Neurocognitive outcomes following surgery for temporal lobe epilepsy in childhood are variable. Postoperative changes are not directly predicted by seizure-freedom and associations between epilepsy, neuropsychological function, and developing neural networks are poorly understood. Here, we leveraged whole-brain connectomic profiling in magnetoencephalography (MEG) to retrospectively study associations between brain connectivity and neuropsychological function in children with temporal lobe epilepsy undergoing resective surgery.

METHODS

Clinical and MEG data were retrospectively analyzed for children who underwent temporal lobe epilepsy surgery at the Hospital for Sick Children from 2000 to 2021. Resting-state connectomes were constructed from neuromagnetic oscillations via the weighted phase lag index. Using a partial least-squares (PLS) approach, multidimensional associations between patient connectomes, neuropsychological scores, and clinical covariates were assessed. Bootstrap resampling statistics were performed to assess statistical significance.

RESULTS

A total of 133 medical records were reviewed, and 5 PLS analyses were performed. Each PLS analysis probed a particular neuropsychological domain and the associations between its baseline and post-operative scores and the connectomic data. In each PLS analysis, a significant latent variable was identified, representing a specific percentage of the variance in the data, and relating neural networks to clinical covariates, which included changes in rote verbal memory (N=41, p = 0.01, σ² = 0.38), narrative/verbal memory (N=57, p = 0.00, σ² = 0.52), visual memory (N=51, p = 0.00, σ² = 0.43), working memory (N=44, p = 0.00, σ² = 0.52), and overall intellectual function (N=59, p = 0.00, σ² = 0.55). Children with more diffuse, bilateral intrinsic connectivity across several frequency bands showed lower scores on all neuropsychological assessments but demonstrated a greater propensity for gains following resective surgery.

CONCLUSION

Here, we report that connectomes characterized by diffuse connectivity, reminiscent of developmentally immature networks, are associated with lower pre-operative cognition and post-operative cognitive improvement. These findings provide a potential means to understand neurocognitive function in children with temporal lobe epilepsy and expected changes post-operatively.

Cognitive outcomes following pediatric epilepsy surgery

OBJECTIVES

To characterize outcomes following pediatric epilepsy surgery across a broad range of cognitive domains using empirical methods (i.e., reliable change indices: RCIs), compare these outcomes with those based on traditional methods (i.e., standard deviation: SD), and identify factors associated with postoperative cognitive declines and/or improvements.

METHODS

This retrospective cohort study included 186 children who underwent surgical resection for treatment of pharmacoresistant epilepsy and who completed pre- and postoperative neuropsychological assessments. Postoperative testing occurred approximately 6.5 months after surgery and included measures of intelligence, attention/working memory, processing speed, language, executive functioning, visuospatial skills, memory, and academic achievement. Change scores for each patient were classified as decline, no change, or improvement using epilepsy-specific RCIs. Chi-square goodness of fit tests were used to compare the distribution of outcomes as classified with RCIs to those obtained using a traditional one SD cutoff. Multinomial regression analyses were conducted to identify factors associated with cognitive decline and/or improvement.

RESULTS

While 18% of children demonstrated no postoperative declines or improvements in any cognitive domain, the majority demonstrated relatively focal changes (declines and/or improvements in 1-2 cognitive domains). Rates of postoperative decline and improvement across individual cognitive domains were variable and ranged from 4-35% and 2-31%, respectively. Compared to RCIs, SD methodology often overestimated postoperative improvements and varied with respect to declines. Factors associated with RCI decline or improvement included preoperative performance, age at surgery, surgery site, and postoperative seizures.

SIGNIFICANCE

Results suggest substantial variability in individual cognitive outcomes approximately 6.5 months following pediatric epilepsy surgery. The differences in change distributions obtained using epilepsy-specific RCIs versus SDs highlight the need for studies using empiric methodology to study postoperative cognitive change. Variables associated with postoperative cognitive change may be used to develop multivariable prediction models in future studies to aid clinical decision-making and patient counseling.

Surgery for Intractable Epilepsy in Pediatrics, a Systematic Review of Outcomes other than Seizure Freedom

To perform a systematic review evaluating reported outcomes for epilepsy surgery in pediatric patients with pharmacoresistant epilepsy beyond seizure control, including impact on quality of life, behavioral, neurocognitive outcomes as well as complications, and death. We reviewed articles from both EMBASE and MEDLINE/PubMed articles that met formal criteria (patients ≤18 years, those with intractable epilepsy, at least 5 patients in the case series, published in peer-reviewed journal). Each reviewer independently reviewed the articles and those with discrepancies were discussed and consensus was reached. Out of a total of 536 abstracts obtained from EMBASE and MEDLINE/PubMed searches combined with additional cross-referencing, a total of 98 manuscripts ultimately met all inclusion criteria. The manuscripts were divided into 3 outcomes categories: Quality of Life (16), Cognitive Outcomes (60), and Deficits and Complications (50). Several papers fell into more than 1 category. These were separated by surgical types and evaluated. We found that overall reporting in all domains was variable and inconsistent amongst the different studies. This systematic review highlights the lack of completeness in reporting outcomes and complications involving pediatric epilepsy surgery and discordant results. This underscores the importance of multicenter systematic prospective data collection in pediatric patients who undergo pediatric epilepsy surgery.

Working Memory in Pediatric Epilepsy: A Systematic Review and Meta-Analysis

Working memory is a multicomponent system that is supported by overlapping specialized networks in the brain. Baddeley's working memory model includes four components: the phonological loop, visuo-spatial sketchpad, the central executive, and episodic buffer. The aim of this review was to establish the gravity and pattern of working memory deficits in pediatric epilepsy. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guided electronic searches. Sixty-five studies were included in the review. Meta-analyses revealed significant impairments across each working memory component: phonological loop (g = 0.739), visuo-spatial sketchpad (g = 0.521), and central executive (g = 0.560) in children with epilepsy compared to controls. The episodic buffer was not examined. The pattern of impairments, however, differed according to the site and side of seizure focus. This suggests that working memory components are differentially vulnerable to the location of seizure focus in the developing brain.

Quantitative Meta-Analyses: Lateralization of Memory Functions Before and After Surgery in Children with Temporal Lobe Epilepsy

RATIONALE

Memory deficits in children with epilepsy have been reported in some but not all studies assessing the effects of side of seizures and resection from the temporal lobe on cognitive performance. This meta-analysis provides a quantitative systematic review of previous studies on this issue.

METHOD

A critical review and meta-analysis of the literature on memory performance in children with Temporal Lobe Epilepsy (TLE) was conducted. Search identified 25 studies, 13 of which compared children with TLE to healthy age-matched controls and 12 of which compared children with TLE before and after surgery.

RESULTS

Heterogeneity of the comparisons of children with TLE to healthy controls impeded drawing definitive conclusions. However, in 55% of the studies, verbal memory in children with left TLE (LTLE) was impaired as compared to healthy controls. Verbal memory performance slightly declines after pediatric LTLE surgery, but nonverbal memory tasks are not affected. By contrast, verbal memory performance is not affected by pediatric right TLE (RTLE) surgery.

CONCLUSIONS

The findings suggest that side of the epileptogenic zone and resection from the temporal lobe affect verbal memory in children with LTLE. Right resection seems to be safe with respect to verbal memory performance.

Memory dysfunctions

Since the seminal work on the patient HM, who in his adulthood presented an acquired amnesic syndrome following the resection of the bilateral temporal lobe, other research has described several cases of isolated memory dysfunction in children. This chapter presents developmental and long-lasting memory disorders emerging from an organic or neurologic cause at birth or in infancy. More notably, we focus on developmental amnesic syndrome caused by neonatal bihippocampal damage and memory dysfunction caused by medial temporal developmental epilepsy. We describe these two pediatric populations and present the consequences of hippocampal/medial temporal lobe damage in the development of memory systems. We review episodic memory deficits in children with developmental amnesia and temporal lobe epilepsy and highlight their impact on new learning, personal memories, and independent life. Finally, we provide a brief overview of some of the insights and debates emerging from classic work and recent advances in the context of episodic memory dysfunction displayed by children with hippocampal/medial temporal lobe amnesia and propose new perspectives in child neuropsychology of memory, suggesting new avenues for more ecologic memory assessment and rehabilitation.

Neuropsychological outcomes after pediatric epilepsy surgery: Role of electrical stimulation language mapping

PURPOSE

We studied the association between electrical stimulation mapping (ESM) with a visual naming task and post-operative neuropsychological outcomes after pediatric epilepsy surgery.

METHODS

Children who underwent epilepsy surgery, having pre- and 1-year post-surgery neuropsychological evaluation (NPE) available, were included. NPE scores were transformed using principal components (PC) analysis. The relationship between post-surgical PC scores, adjusted for pre-surgery PC scores, and ESM was analyzed. Clinical variables influencing this relationship were also sought.

RESULTS

One hundred and four children (89 patients >5 years-old, and 15 patients 3-5 years-old) were included. Among children >5 years-of-age, a significant effect of language ESM was observed on all 3 post-surgery PC scores adjusted for respective pre-surgery PC scores. Specifically, only 30 % patients who underwent language ESM had a decrease in PC1 scores ≥1-year after epilepsy surgery, compared to 68 % those who did not undergo language ESM (p = 0.001). Seizure outcomes, age at the time of surgery, predominant seizure type, and family history of epilepsy were other significant determinants of post-surgical PC scores including a change in PC scores from pre-surgery baseline. Combinations of pre-surgical variables were able to predict post-surgical PC scores with high specificity. In children aged 3-5 years, no significant effect of language ESM was seen on post-surgery PC scores adjusted for respective pre-surgery PC scores.

CONCLUSIONS

Speech/language ESM should be performed more widely in patients >5 years-of-age undergoing epilepsy surgery. Also, more efficient brain mapping techniques and language paradigms are needed for younger children.

Verbal associative memory outcomes in pediatric surgical temporal lobe epilepsy: Exploring the impact of mesial structures

OBJECTIVE

We examined verbal associative memory outcomes in children with left- or right-sided temporal lobe epilepsy (TLE) who received combined lateral and mesial resections versus lateral resections sparing mesial structures. We hypothesized that children who underwent left-sided resections including mesial structures would show the greatest verbal associative memory declines following surgery.

METHOD

We retrospectively analyzed neuropsychology assessment results from a sample of 65 children with TLE who completed pre- and postoperative evaluation at the Hospital for Sick Children in Toronto, Canada. We examined verbal associative memory score changes between groups by laterality (left versus right) and resection type (lateral only versus lateral and mesial resection). We also explored potential associations between certain epilepsy-related characteristics and verbal associative memory changes.

RESULTS

Postoperative decline was found in children with left-sided resections, but not those with right-sided resections. In children who received left-sided resections, there was some suggestion of verbal associative memory decline in those who had both lateral and mesial tissues excised, but not in those with lateral resections only. Notably, there was also a language dominance (typical versus atypical) by resection type interaction. Specifically, for the typical language group, children with left lateral plus mesial resections (but not mesial sparing resections) showed postoperative verbal associative memory declines, whereas the opposite was true for the atypical language group.

SIGNIFICANCE

These data contribute to our growing understanding of verbal memory outcomes following TLE in childhood, with consideration of the extent of resection to mesial structures. Our findings also highlight the importance of language laterality when interpreting neuropsychological assessment findings and making predictions regarding risk of functional loss following surgery.

Story Learning Test: Decelerated Learning and Accelerated Forgetting in Children with Epilepsy

Introduction

Increasing interest is seen for early and late memory consolidation and accelerated forgetting, but little is known about these phenomena in children with epilepsy. The present study analysed the trajectory of learning and retention in typically developing children and children with epilepsy on a story learning test.

Methods

285 children, 126 typically developing children and 159 children with epilepsy, in ages between 4 and 10 years and Full-Scale IQs ≥ 75, were given a specifically designed story learning test (iter-sein). The learning phase included Initial reading and a Free Recall trial with 10 Questions, and up to three repetition trials with Questions. Trials of Delayed Free Recall and Questions followed after half an hour, the next day and 1 week later. With several repeated measures analyses of variance, level of performance and gains or losses over time were analysed.

Results

Age-dependent learning was seen after repetitions. On the Questions, typically developing children outperformed children with epilepsy increasingly, due to smaller gains after the second trial. Learned information was similarly preserved. Free Recall showed similar performance for both groups up to day 2. A week later, a conspicuous loss of information was observed in the children with epilepsy, whilst typically developing children retained the information. On index scores, reliable cognitive loss of information was seen in epilepsy in 24.5% of the children. Semantic neuropsychological tasks and severity measures of epilepsy were associated with level of performance.

Discussion

The results provided evidence for early decelerated learning and late accelerated forgetting in children with epilepsy.

Are frontal and temporal lobe epilepsy dissociable in their memory functioning?

There is controversy in the literature as to how dissociable frontal lobe epilepsy (FLE) and temporal lobe epilepsy (TLE) are in terms of memory deficits. Some researchers have demonstrated that FLE is associated with greater executive dysfunction including working memory, whereas TLE is associated with greater memory impairment. Others have found the two groups to be comparable in memory functioning. Hence, we examined this question in children with FLE and TLE versus typically developing controls. We found most of the expected effects when the groups with focal onset epilepsy were compared to controls. Specifically, children with left TLE performed worse on verbal short-term memory/learning and long-term memory measures. In contrast, children with right TLE exhibited a more global pattern of difficulty on short-term memory/learning measures but performed worse than controls on long-term memory for faces. Children with FLE performed worse than controls on verbal working memory. Nevertheless, laterality effects were mild, as children with right and left TLE did not differ significantly from each other. Further, children with FLE did not differ from those with TLE on most measures except delayed facial recognition, where children with right TLE performed worse. In addition, attention problems and poor behavioral regulation were related to encoding problems in both the total epilepsy sample and in children with TLE specifically. Hence, our findings overall are consistent with prior studies indicating that children with TLE and FLE are commensurate in most aspects of memory impairment when compared to each other, likely related to rapid propagation between the frontal and temporal lobes, as would be expected with an excitatory lesion.

Visuospatial learning and memory in children pre- and posttemporal lobe resection: Patterns of localization and lateralization

In children with epilepsy, the impact of surgery including or sparing the mesial temporal lobes (TLs) on visuospatial memory has not been thoroughly investigated, and a clear pattern of hemispheric lateralization has not been observed. The primary aim of this study was to examine visuospatial learning and memory outcomes in children with epilepsy prior to and one year after surgical excision, to determine whether outcomes differed as a function of the localization and lateralization of surgical excisions. Forty-six children who underwent unilateral TL surgery with sparing of the mesial structures (TL group, N = 21, 16 left) or including mesial structures (TL + M group, N = 25 children, 12 left) were retrospectively recruited. Outcomes on the Children's Memory Scale (CMS) Dot Locations subtest (learning, immediate, and delayed recall scores) were examined prior to and following epilepsy surgery. Results revealed significantly reduced visuospatial memory (delayed recall) in the TL + M compared with the TL group after surgery. Despite this significant postoperative difference, there was no significant change in learning, immediate, or delayed recall scores in either group. However, inspection of individual change scores showed that fewer children in the TL + M group improved in delayed recall after surgery (7.2%) compared with children in the TL group (30%) whereas a similar proportion of children in the TL + M (30.4%) and TL (23.3%) groups showed a decline. There were no significant differences in learning or memory scores as a function of seizure laterality before or after surgery and no differences in change over time. Seizure outcome, age at surgery, age at seizure onset, and percentage life with epilepsy were not related to visuospatial learning or memory outcomes; however, greater number of antiepileptic drugs (AEDs) following surgery was related to poorer visuospatial memory (delayed recall) in the TL + M group. In summary, the results show that visuospatial learning and memory performance do not seem to show a significant decline following TL resections in childhood, regardless of whether or not surgery includes the mesial TL and involves the left or right hemisphere. However, although mesial TL excisions might not result in a deficit in visuospatial memory, they may hinder progressions made after surgery. Further research is needed to examine how resection of the mesial TL (alone or in combination with lateral TL structures) affects visuospatial memory outcomes in children, as well as to investigate the degree to which other treatment factors, such as medication, may affect visual memory outcomes.

Unique and shared areas of cognitive function in children with intractable frontal or temporal lobe epilepsy

OBJECTIVE

Previous findings have been mixed in terms of identifying a distinct pattern of neuropsychological deficits in children with frontal lobe epilepsy (FLE) and in those with temporal lobe epilepsy (TLE). The current study investigated the neuropsychological similarities and differences across these two pediatric medically intractable localization-related epilepsies.

METHOD

Thirty-eight children with FLE, 20 children with TLE, and 40 healthy children (HC) participated in this study. A comprehensive battery of standardized tests assessed five neuropsychological domains including intelligence, language, memory, executive function, and motor function. A principal component analysis (PCA) was used to distill our neuropsychological measures into latent components to compare between groups.

RESULTS

Principal component analysis extracted 5 latent components: executive function (F1), verbal semantics (F2), motor (F3), nonverbal cognition/impulsivity (F4), and verbal cognition/attention (F5). The group with FLE differed from the HC group on F1, F2, F4, and F5, and had worse performance than the group with TLE on F1; the group with TLE had lower performance relative to the HC group on F2.

CONCLUSION

Our findings suggest that, in comparison with neurotypically developing children, children with medically intractable FLE have more widespread neuropsychological impairments than do children with TLE. The differences between the two patient groups were greatest for the factor score most clearly related to executive function. The results provide mixed support for the concept of specificity in neuropsychological dysfunction among different subtypes of localization-related medically intractable childhood epilepsies.

Development of verbal short-term memory and working memory in children with epilepsy: Developmental delay and impact of time-related variables. A cross-sectional study

While short-term memory (STM) and working memory (WM) are understood as being crucial for learning, and children with epilepsy often experience learning difficulties, little is known about the age-related development of memory span tasks in children with epilepsy. Short-term memory and WM, operationalized as digit span forwards (DSF) or digit span backwards (DSB), respectively, were studied. Participants were 314 children with epilepsy and 327 typically developing children in ages between 5 and 15years and full scale intelligence quotient (FS-IQ)≥75. Cross-sectional analyses of the data were done with analyses of variance and analyses of covariance ((M)ANCOVAs) and generalized linear analyses. The analyses revealed that STM problems in epilepsy were mediated by age-related gains in WM as well as by differences in IQ. Working memory developed at a quick pace in the younger children, the pace slowed down to some extent in the later primary school years and resumed again later on. Working memory problems prevailed in epilepsy, independent of IQ and development of STM. Timing of the epilepsy in terms of age at onset and duration determined memory development. The youngest children with epilepsy showed age-appropriate development in STM but were the most vulnerable in terms of WM development. Later in the course of the epilepsy, the WM problems of the young children attenuated. In later onset epilepsy, WM problems were smaller but persisted over time.

Cognitive Outcome After Epilepsy Surgery in Children

Cognitive dysfunction in children with epilepsy is primarily contributed by etiology, seizures, frequency of interictal epileptiform discharges, and adverse effects of antiepileptic drugs. The direct effect of epilepsy surgery on cognitive outcome depends on two key factors: the function that is present in the epileptogenic zone to be removed, and the dysfunction outside the epileptogenic zone caused by epilepsy. Studies on cognitive outcome in children after various types of epilepsy surgery estimate "no significant change" in about 70% of children, improvement in cognition in 10%-15%, and decline in 10%-15%. In young children with epileptic encephalopathy, the reversible dysfunction outside the epileptogenic zone is larger and hence carry better chances of improved outcome after successful surgery. If the epileptogenic zone harbors significant cognitive function (memory, language, or other function), then a decline in function may occur with its resection. Understanding the pathophysiological basis for the cognitive changes after epilepsy surgery assists in counseling patients and families before surgery.

Neuropsychological outcomes following paediatric temporal lobe surgery for epilepsies: Evidence from a systematic review

OBJECTIVE

The systematic review aimed to assess the neuropsychological outcomes of temporal lobe resections for epilepsy in children. Additional objectives included determining whether earlier age at surgery leads to better neuropsychological outcomes; the relationships between and predictors of these outcomes.

METHODS

Using advanced search terms, a systematic review of electronic databases was conducted, comprising MEDLINE, Embase, PsycINFO, Global Health, Web of Science and CINAHL. Included studies reported on outcome following neurosurgical treatment for epilepsy. Specifically, studies were included if they reported neuropsychological outcomes and were concerned only with temporal lobe resection.

RESULTS

73 studies met inclusion criteria. For reported neuropsychological outcomes, the majority of participants remained stable after surgery; some declined and some improved. There was some evidence for increased material-specific memory deficits after temporal lobe surgery based on resection side, and more positive cognitive outcome for those with lower pre-surgical ability level.

SIGNIFICANCE

Retrieved evidence highlights the need for improvements to quality of methodology and reporting. Appropriately designed prospective multicentre trials should be conducted with adequate follow-up for long-term outcomes to be measured. Core outcome measures should be agreed between centres. This would permit higher quality evidence so that clinicians, young people and their families may make better informed decisions about whether or not to proceed with surgery and likely post-operative profile.

Cognitive outcome after epilepsy surgery in children: A controlled longitudinal study

OBJECTIVE

To analyze the determinants of cognitive outcome two years after surgery for drug-resistant epilepsy in a cohort of 31 children when compared to a control group of 14 surgical candidates who had yet to undergo surgery two years after the first neuropsychological assessment.

METHODS

Controlled longitudinal study including three evaluations of IQ (Intelligence Quotient) scores or GDQ (General Developmental Quotient) for each group depending on the patient's age: prior to surgery (T0), one year (T1) and two years (T2) after surgery for the surgical group; baseline (T0) and one year (T1) and 2years (T2) after the first evaluation for the control-group. At follow-up, 25 children (80%) of the surgical group were seizure free, while seizure outcome was unsatisfactory in the remaining six (20%). To analyze language, visuomotor skills, memory, reading, visual attention, and behavior, we selected 11 school age children in the surgical group and nine controls. We reported performance prior to (T0) and one year after surgery (T1).

RESULTS

There was a significant correlation between earlier age at seizure onset and lower IQ/GDQ at T0 (r=0.39; p=0.03) in the overall cohort. IQ/GDQ scores did not significantly differ between the surgical and control groups when analyzed at T0 and T2. However, they evolved differently with an improved developmental trajectory becoming identifiable only in the surgical group (F_1,31=5.33 p=0.028; η²=0.15). There was also a significant increase of forward digit span (Z=2.33; p=0.02) and Rey recall scores (Z=1.97; p=0.049) in the surgical school age subgroup at T1 versus T0.

SIGNIFICANCE

We identified significantly different developmental trajectories in operated versus non- operated children with improved IQ/GDQ scores in operated children only. We also observed a significant increase of digit span scores and Rey recall scores a year after surgery. Further studies including larger samples with longer follow-ups are needed to confirm these preliminary findings.

Seizure-related variables are predictive of attention and memory in children with epilepsy

Children with epilepsy (CWE) are at greater risk for cognitive deficits and behavioral difficulties than are typically developing healthy children, and particular epileptic symptoms and treatments may contribute to this risk. The current study examined the relationships between four seizure-related variables and attention and memory functioning in a sample of 207 CWE (ages 6-16) using both neurocognitive and parent/teacher-report measures. Sociodemographic, medical, and neuropsychological data were collected from patients' medical charts in a retrospective fashion. Hierarchical multiple regressions were performed with sociodemographic variables (age, gender, race) entered as step one and seizure-related variables (number of anti-epileptic drugs [AEDs], EEG laterality, EEG lobe of focus, lifetime seizure duration) entered as step two. Results indicated that seizure-related variables were consistently predictive of poor cognitive performances above and beyond sociodemographic variables, although only minimally predictive of parent/teacher-reports. A longer duration of seizure burden and greater number of AEDs were robust predictors of performances on most cognitive measures. These findings indicate that CWE with long lifetime seizure durations and multiple AEDs are at risk for inefficiencies in attention and memory. Knowledge of this risk will allow treating providers greater accuracy and precision when planning medical treatment and making recommendations to families.

The executive profile of children with Benign Epilepsy of Childhood with Centrotemporal Spikes and Temporal Lobe Epilepsy

RATIONALE

Benign Epilepsy of Childhood with Centrotemporal Spikes (BECTS) and temporal lobe epilepsy (TLE) represent two distinct models of focal epilepsy of childhood. In both, there is evidence of executive dysfunction. The purpose of the present study was to identify particular deficits in the executive function that would distinguish children with BECTS from children with TLE.

METHODS

We prospectively evaluated 19 consecutive children and adolescents with TLE with hippocampal sclerosis (HS) (57.9% male; mean 11.74years [SD 2.05]; mean IQ 95.21 [SD 15.09]), 19 with BECTS (36.8% male; mean 10.95years [SD 2.33]; mean IQ 107.40 [SD 16.01]), and 21 age and gender-matched controls (33.3% male; mean 11.86years [SD 2.25]; mean IQ 108.67 [15.05]). All participants underwent a neuropsychological assessment with a comprehensive battery for executive and attentional functions. We used ANOVA and chi-square to evaluate differences on demographic aspects among groups (BECTS, TLE-HS, and control groups). Group comparisons on continuous variables were complemented by MANOVA and Bonferroni posthoc comparisons.

RESULTS

Patients with BECTS had worse performance than controls in: Matching Familiar Figures Test, time (p=0.001); Matching Familiar Figures Test, time×errors index (p<0.001); Verbal Fluency for foods (p=0.038); Trail Making Test, part B time (p=0.030); Trail Making Test, part B number of errors (p=0.030); and WCST, number of categories achieved (p=0.043). Patients with BECTS had worse performance than patients with TLE-HS on Matching Familiar Figures Test, time (p=0.004), and Matching Familiar Figures Test, time×errors index (p<0.001). Patients with TLE-HS had worse performance than controls on the following tests: Verbal Fluency for foods (p=0.004); Wisconsin Card Sorting Test, the number of categories achieved (p<0.001); and Wisconsin Card Sorting Test, the number of perseverative errors (p=0.028). Patients with TLE-HS had worse performance than patients with BECTS on Digit Backward (p=0.002); and the Wisconsin Card Sorting Test, the number of perseverative errors (p<0.001).

CONCLUSIONS

Patients with TLE and BECTS present distinct cognitive profiles. Patients with TLE-HS had worse performance in mental flexibility, concept formation, and working memory compared to BECTS. Patients with BECTS had worse inhibitory control compared to children with TLE-HS. Both TLE-HS and BECTS had a higher number of errors on an inhibitory control test. However, patients with BECTS had a slower mental processing even when compared to patients with TLE-HS. Rehabilitation programs for children with epilepsy must include children with benign epilepsies and must take into account the epileptic syndrome and its particular neurocognitive phenotype.

The impact of intelligence on memory and executive functions of children with temporal lobe epilepsy: Methodological concerns with clinical relevance

PURPOSE

Patients with TLE are prone to have lower IQ scores than healthy controls. Nevertheless, the impact of IQ differences is not usually considered in studies that compared the cognitive functioning of children with and without epilepsy. This study aimed to determine the effect of using IQ as a covariate on memory and attentional/executive functions of children with TLE.

METHODS

Thirty-eight children and adolescents with TLE and 28 healthy controls paired as to age, gender, and sociodemographic factors were evaluated with a comprehensive neuropsychological battery for memory and executive functions. The authors conducted three analyses to verify the impact of IQ scores on the other cognitive domains. First, we compared performance on cognitive tests without controlling for IQ differences between groups. Second, we performed the same analyses, but we included IQ as a confounding factor. Finally, we evaluated the predictive value of IQ on cognitive functioning.

RESULTS

Although patients had IQ score in the normal range, they showed lower IQ scores than controls (p = 0.001). When we did not consider IQ in the analyses, patients had worse performance in verbal and visual memory (short and long-term), semantic memory, sustained, divided and selective attention, mental flexibility and mental tracking for semantic information. By using IQ as a covariate, patients showed worse performance only in verbal memory (long-term), semantic memory, sustained and divided attention and in mental flexibility. IQ was a predictor factor of verbal and visual memory (immediate and delayed), working memory, mental flexibility and mental tracking for semantic information.

CONCLUSION

Intelligence level had a significant impact on memory and executive functioning of children and adolescents with TLE without intellectual disability. This finding opens the discussion of whether IQ scores should be considered when interpreting the results of differences in cognitive performance of patients with epilepsy compared to healthy volunteers.

Everyday memory impairment in patients with temporal lobe epilepsy caused by hippocampal sclerosis

OBJECTIVE

Patients with temporal lobe epilepsy caused by hippocampal sclerosis (TLE-HS) have episodic memory impairment. Memory has rarely been evaluated using an ecologic measure, even though performance on these tests is more related to patients' memory complaints. We aimed to measure everyday memory of patients with TLE-HS to age- and gender-matched controls.

METHODS

We evaluated 31 patients with TLE-HS and 34 healthy controls, without epilepsy and psychiatric disorders, using the Rivermead Behavioral Memory Test (RBMT), Visual Reproduction (WMS-III) and Logical Memory (WMS-III). We evaluated the impact of clinical variables such as the age of onset, epilepsy duration, AED use, history of status epilepticus, and seizure frequency on everyday memory. Statistical analyses were performed using MANCOVA with years of education as a confounding factor.

RESULTS

Patients showed worse performance than controls on traditional memory tests and in the overall score of RBMT. Patients had more difficulties to recall names, a hidden belonging, to deliver a message, object recognition, to remember a story full of details, a previously presented short route, and in time and space orientation. Clinical epilepsy variables were not associated with RBMT performance. Memory span and working memory were correlated with worse performance on RBMT.

SIGNIFICANCE

Patients with TLE-HS demonstrated deficits in everyday memory functions. A standard neuropsychological battery, designed to assess episodic memory, would not evaluate these impairments. Impairment in recalling names, routes, stories, messages, and space/time disorientation can adversely impact social adaptation, and we must consider these ecologic measures with greater attention in the neuropsychological evaluation of patients with memory complaints.

Reading in children with temporal lobe epilepsy: A systematic review

OBJECTIVE

Children with epilepsy have higher rates of reading difficulties compared to the general population. Reading difficulties are associated with lower academic attainments, higher school drop-out rates, greater risk of unemployment, lower income, and poorer adjustment. We examined the literature dealing with reading in children with the most common type of focal epilepsy, temporal lobe epilepsy (TLE), in relation to: presence of reading difficulties, contributing factors, and efficacy of treatments for reading difficulties.

METHODS

We searched databases (MEDLINE, EMBASE, PsycINFO and PubMed) for studies published before September 2016. Included studies (i) reported on a group of children with TLE, (ii) used a standardized reading test or included a control group, (iii) involved original research published in peer reviewed journals in the English language.

RESULTS

Of 2018 citations obtained through literature searches, six met inclusion criteria. Reading accuracy and/or reading comprehension were assessed using different tests. All but one study found statistical evidence of reading difficulties in children with TLE. Only two studies examined relations between cognitive deficits and reading. One found that memory contributed to reading accuracy and comprehension. Another found evidence of a small decline in reading accuracy, which was not associated with a decline in memory post-surgery. Several studies were underpowered, giving false negative findings and not allowing relations between epilepsy factors, underlying cognitive deficits, and reading to be adequately examined. No study examined efficacy of reading intervention in this patient population.

SIGNIFICANCE

We showed that reading difficulties that are present in children with TLE are under researched, yet they have significant functional consequences through childhood and into adulthood. There is an urgent need to identify risk factors and investigate efficacy of treatments for reading difficulties in children with TLE, as this will enable early identification and evidence-based treatment to be delivered in clinical practice.

Verbal memory after temporal lobe epilepsy surgery in children: Do only mesial structures matter?

OBJECTIVE

Previous findings have been mixed regarding verbal memory outcome after left temporal lobectomy in children, and there are few studies comparing verbal memory change after lateral versus mesial temporal lobe resections. We compared verbal memory outcome associated with sparing or including the mesial structures in children who underwent left or right temporal lobe resection. We also investigated predictors of postsurgical verbal memory change.

METHODS

We retrospectively assessed verbal memory change approximately 1 year after unilateral temporal lobe epilepsy surgery using a list learning task. Participants included 23 children who underwent temporal lobe surgery with sparing of the mesial structures (13 left), and 40 children who had a temporal lobectomy that included resection of mesial structures (22 left).

RESULTS

Children who underwent resection from the left lateral and mesial temporal lobe were the only group to show decline in verbal memory. Furthermore, when we considered language representation in the left temporal resection group, patients with left language representation and spared mesial structures showed essentially no change in verbal memory from preoperative to follow-up, whereas those with left language representation and excised mesial structures showed a decline. Postoperative seizure status had no effect on verbal memory change in children after left temporal lobe surgery. Finally, we found that patients with intact preoperative verbal memory experienced a significant decline compared to those with below average preoperative verbal memory.

SIGNIFICANCE

Our findings provide evidence of significant risk factors for verbal memory decline in children, specific to left mesial temporal lobe epilepsy. Children who undergo left temporal lobe surgery that includes mesial structures may be most vulnerable for verbal memory decline, especially when language representation is localized to the left hemisphere and when preoperative verbal memory is intact.

Predictors of language skills in the long term after pediatric epilepsy surgery

OBJECTIVE

The objective of this study was to evaluate language skills in a heterogeneous cohort of patients who underwent or were considered for epilepsy surgery in childhood 4-11years earlier. The few existing studies that have evaluated cognitive function in the long term after surgery have examined intelligence and memory.

METHOD

Participants were 97 patients, of whom 61 underwent surgery. They completed standardized tests of picture naming, vocabulary, letter fluency, semantic fluency and intelligence at baseline and, on average, 7years later.

RESULTS

Among all patient groups, scores across language tasks were similar at baseline and follow-up. Language skills were largely independent of surgical status but were associated with seizure control. Seizure freedom and/or a longer proportion of life without seizures were associated with higher scores across all language tasks at follow-up. However, few patients showed meaningful improvements or deterioration at the individual level. Older age at epilepsy onset, higher IQ, and higher baseline scores were associated with higher follow-up scores on all language tasks. Localization and lateralization of epileptogenic foci and language lateralization were associated with higher scores on some language tasks at follow-up. Most of these variables were also predictive of change in scores over time on some of the language tasks.

SIGNIFICANCE

Language skills largely remained similar at baseline and follow-up. Seizure freedom was associated with a modest advantage at the group level, and no significant change at the individual level, suggesting an abnormal neural substrate or epileptic activity prior to seizure control may hinder the long-term capacity for improvement, even in the absence of seizure activity.

Risks and benefits of epilepsy surgery in a pediatric population: Consequences for memory and academic skills

We examined benefits and risks for memory and academic functioning associated with epilepsy surgery in a pediatric population. A total of 46 patients with intractable seizures and a single seizure focus were divided into four groups according to focus localization: right temporal, left temporal, frontal, and parietal/occipital region. Pre- and postsurgery performance measures were compared across groups and with a fifth group of patients that had intractable seizures but did not undergo surgery. Both groups with temporal lobe epilepsy showed significant declines in memory test scores, while performance of the group with frontal lobe epilepsy improved. These changes were mirrored in parental reports of everyday memory. Consistent with other pediatric studies, no lateralized material-specific declines in the groups with temporal lobe epilepsy were found. When memory improved, the improvement was associated with decreases in seizure frequency and the number of anticonvulsant medications. Presurgical performance was the best predictor of declines in memory test performance. Deterioration of academic test scores in the group that did not have surgery exemplified a potential risk of living with seizures and antiepilepsy medication.

Object naming in epilepsy and epilepsy surgery

The ability to express oneself verbally is critical for success in academic, occupational, and social domains. Unfortunately, word-finding or "naming" difficulty is the most common cognitive complaint among individuals with temporal lobe epilepsy (TLE), and a substantial body of work over the past several decades has documented naming impairment in left (language-dominant) TLE, with further risk to naming ability following left temporal lobe resection for seizure control. With these findings well established, this paper reviews more recent work that has aimed to identify the neuroanatomical substrates of naming, understand how adverse structural and functional effects of TLE might impinge upon these brain regions, predict and potentially reduce the risk of postoperative naming decline, and begin to understand naming difficulty in TLE from a developmental perspective. Factors that have confounded interpretation and hindrances to progress are discussed, and suggestions are provided for improved empirical investigation and directions for future research.

Temporal lobe epilepsy in infants and children

Clinical expression of temporal lobe seizures is different with a more diverse and more extensive etiology in infants and children than it is in adults. It is dominated by cortical dysplasia, low-grade tumors and perinatal damage. Hippocampal sclerosis, although less frequent, exists in children usually as a dual pathology associated with ipsilateral neocortical lesions. The clinical semiology of temporal seizures is more varied, and sometimes misleading. Motor features including tonic, clonic or myoclonic behaviors, and infantile spasms predominate in infants. Classical complex partial seizures with behavioral arrest and automatisms, as well as lateralizing signs are rare and occur mostly with onset after the age of two years. Interestingly, aura, emotional, and autonomic signs seem to be independent on the brain maturation process. Moreover, the neuropsychological profile varies according to age of onset and duration, lateralization of the focus and etiology. Quality of care benefits from individual cognitive assessment for memory and emotional processes.

Associative episodic memory and recollective processes in childhood temporal lobe epilepsy

While the current literature on children suffering from temporal lobe epilepsy (CTLE) mostly focuses on material-related episodic memory deficits according to seizure-onset lateralization, the present study examined associative episodic memory according to the type of information to memorize (e.g., factual, spatial, and sequential) and further investigated subjective and objective recollection. Eleven children with left temporal lobe epilepsy (LTLE), 10 children with right temporal lobe epilepsy (RTLE), among whom 9 displayed hippocampal sclerosis (HS), and 42 healthy controls completed the WHAT-WHEN-WHERE protocol (Guillery-Girard et al., 2013). Group comparisons were first conducted according to the affected side and second according to the underlying pathology. Results showed associative memory impairments in patients irrespective of the affected side. Moreover, this study revealed that HS is particularly deleterious to associative and subjective recollection in CTLE. In addition, this study emphasizes the need for assessing episodic memory in childhood TLE beyond material specificity.

Verbal memory and literacy outcomes one year after pediatric temporal lobectomy: a retrospective cohort study

OBJECTIVE

In children with temporal lobe epilepsy (TLE), temporal lobectomy (TL) is a treatment of choice for those children with seizure that are difficult to control with medication. Semantic memory is dependent on functional integrity of the temporal lobes and is thought to be critical for development of literacy skills. However, little is known about semantic memory and literacy outcomes post-TL in children.

METHOD

In this retrospective cohort study, 40 children with TLE were administered tests of memory and literacy pre-TL and 1year post-TL in one hospital between 1996 and 2011.

RESULTS

One year post-TL, 60% of the children became seizure-free. A significant decline was found in one aspect of semantic memory (naming) in children who underwent left TL. In addition, a significant drop was also evident in one aspect of literacy (reading accuracy), irrespective of the side of surgery. These declines were related neither to each other nor to epilepsy variables including seizure outcome.

CONCLUSIONS

This is the largest pediatric outcome study of memory and literacy skills to date and shows that TL is associated with a risk of a mild drop in specific aspects of semantic memory (naming, following left TL) and reading accuracy, while other areas of memory and literacy remain unchanged.

There are laterality effects in memory functioning in children/adolescents with focal epilepsy

In a sample of individuals with childhood focal epilepsy, children/adolescents with left hemisphere foci outperformed those with right foci on both measures of nonverbal learning. Participants with left foci performed worse than controls on paired associate delayed recall and semantic memory, and they had greater laterality effects in IQ. Participants with right foci performed worse than controls on delayed facial recognition. Both groups displayed reduced focused attention and poor passage retention over time. Although participants with bilateral foci displayed poor learning and lower IQ than controls, they did not have worse impairment than those with a unilateral focus.

Lexical retrieval pre- and posttemporal lobe epilepsy surgery in a pediatric sample

PURPOSE

This study aimed to evaluate lexical retrieval, presurgery and postsurgery, among children and adolescents who had undergone temporal lobe resection for intractable epilepsy and to compare outcomes in patients whose surgery involved the left temporal lobe or the right temporal lobe.

MATERIALS AND METHODS

A retrospective chart review identified 36 patients from a major pediatric epilepsy treatment center who had undergone temporal lobe resection (21 underwent left temporal lobe resection; 15 underwent right temporal lobe resection) for intractable epilepsy and who had completed neuropsychological testing that included a measure of confrontation naming (Boston Naming Test, BNT) and verbal fluency (Delis-Kaplan Executive Function System (D-KEFS) Fluency) prior to and after surgery. Linear mixed effects regression models were used to evaluate presurgery and postsurgery changes and to compare the left temporal lobe resection group with the right temporal lobe resection group.

PRINCIPAL RESULTS

Confrontation naming performance declined after left, but not right, temporal lobe resection (p<0.05). This effect was not documented for verbal fluency.

MAJOR CONCLUSIONS

Left temporal lobe resection for intractable epilepsy is associated with a decline in lexical retrieval. The risk of decline in specific language functions following surgery involving the left temporal lobe should be incorporated in the counseling of patients and families in decision-making with regard to surgery.

Temporal lobe surgery in childhood and neuroanatomical predictors of long-term declarative memory outcome

See Berg (doi:10.1093/brain/awu320) for a scientific commentary on this article.

In a long-term follow-up study of children who underwent temporal lobe surgery for treatment of epilepsy, Skirrow et al. identify no significant pre-to-post-surgery memory losses, but instead robust improvements in memory functions supported by the unoperated temporal lobe. The integrity of remaining temporal lobe structures places constraints on long-term memory outcomes.

The temporal lobes play a prominent role in declarative memory function, including episodic memory (memory for events) and semantic memory (memory for facts and concepts). Surgical resection for medication-resistant and well-localized temporal lobe epilepsy has good prognosis for seizure freedom, but is linked to memory difficulties in adults, especially when the removal is on the left side. Children may benefit most from surgery, because brain plasticity may facilitate post-surgical reorganization, and seizure cessation may promote cognitive development. However, the long-term impact of this intervention in children is not known. We examined memory function in 53 children (25 males, 28 females) who were evaluated for epilepsy surgery: 42 underwent unilateral temporal lobe resections (25 left, 17 right, mean age at surgery 13.8 years), 11 were treated only pharmacologically. Average follow-up was 9 years (range 5–15). Post-surgical change in visual and verbal episodic memory, and semantic memory at follow-up were examined. Pre- and post-surgical T₁-weighted MRI brain scans were analysed to extract hippocampal and resection volumes, and evaluate post-surgical temporal lobe integrity. Language lateralization indices were derived from functional magnetic resonance imaging. There were no significant pre- to postoperative decrements in memory associated with surgery. In contrast, gains in verbal episodic memory were seen after right temporal lobe surgery, and visual episodic memory improved after left temporal lobe surgery, indicating a functional release in the unoperated temporal lobe after seizure reduction or cessation. Pre- to post-surgical change in memory function was not associated with any indices of brain structure derived from MRI. However, better verbal memory at follow-up was linked to greater post-surgical residual hippocampal volumes, most robustly in left surgical participants. Better semantic memory at follow-up was associated with smaller resection volumes and greater temporal pole integrity after left temporal surgery. Results were independent of post-surgical intellectual function and language lateralization. Our findings indicate post-surgical, hemisphere-dependent material-specific improvement in memory functions in the intact temporal lobe. However, outcome was linked to the anatomical integrity of the temporal lobe memory system, indicating that compensatory mechanisms are constrained by the amount of tissue which remains in the operated temporal lobe. Careful tailoring of resections for children undergoing epilepsy surgery may enhance long-term memory outcome.

Pretherapeutic functional magnetic resonance imaging in children

In this article, some specificities of functional magnetic resonance imaging (fMRI) in children (eg, blood-oxygen-level-dependent response and brain maturation, paradigm design, technical issues, feasibility, data analysis) are reviewed, the main knowledge on presurgical cortical mapping in children (motor, language, reading, memory) is summarized, and the emergence of resting state fMRI in presurgical cortical mapping is discussed.

Memory in children with epilepsy: a systematic review

PURPOSE

Research suggests an increased risk for cognitive impairment in childhood epilepsy with memory being one area of cognition most likely to be affected. Understanding the prevalence and predictors of memory difficulties may help improve awareness of the difficulties and allow efficacious supports to be put in place.

METHOD

A systematic review was carried out using the search terms 'memory', 'children' and 'epilepsy' in the database PUBMED. Eighty-eight studies met inclusion criteria. The review focuses on comparisons of memory scores of children with epilepsy and controls, and comparison of memory scores of children with epilepsy to normative scores. Predictors of memory impairment and the effect of surgery on memory functioning are also reviewed.

RESULTS

The majority (78%) of studies reviewed revealed that children with epilepsy scored lower than controls and normative scores on measures of memory. Post-surgery, memory scores were reported to improve in 50% of studies. Predictors of memory impairment included a greater number of AEDs used, younger age of onset, increased seizure frequency and longer duration of epilepsy.

CONCLUSION

Children with epilepsy have a high frequency of memory impairments. However, the exact prevalence of difficulties is not clear due to the lack of population-based data. Most studies have not controlled for IQ and thus it is unclear if difficulties are always related to global cognitive difficulties. There is need for future population-based studies and studies focussing on the neurobiology of memory problems in children with epilepsy.

Memory functioning in children with epilepsy: frontal lobe epilepsy, childhood absence epilepsy, and benign epilepsy with centrotemporal spikes

Specific cognitive deficits have been identified in children with epilepsy irrespective of results on intelligence tests. Memory deficits are traditionally attributed to temporal lobe epilepsy, whereas the impact of frontal lobe epilepsy on memory functions has remained controversial. The aim of this study was the examination of memory abilities in other childhood common epilepsy syndromes (frontal lobe epilepsy (FLE), childhood absence epilepsy (CAE), and benign epilepsy with centrotemporal spikes (BECTS)) and the influence of epilepsy-related variables. Memory was examined in 90 children with epilepsy (each epilepsy group consisted of 30 children), aged 6–15, and compared with 30 control children. Children with FLE showed significant deficits in verbal and visual memory. In addition, type of epilepsy, earlier age at epilepsy onset, and longer active duration of epilepsy were associated with memory problems. Seizure frequency and treatment, however, did not influence memory performance. This study indicates that children with FLE show greater risk of developing memory deficits than children with CAE or BECTS, thus highlighting the importance of assessing also memory functions in frontal lobe epilepsy.

Visual memory after epilepsy surgery in children: a standardized regression-based analysis of group and individual outcomes

Visual memory is vulnerable to epilepsy surgery in adults, but studies in children suggest no change or small improvements. We investigated visual memory after epilepsy surgery, both group-wise and in individual children, using two techniques to assess change: 1) repeated measures analysis of variance (ANOVA) and 2) an empirically based technique for detecting cognitive change [standardized regression-based (SRB) analysis]. A prospective cohort consisting of 21 children completed comprehensive assessments of memory both before surgery (T0) and 6 (T1), 12 (T2), and 24 months (T3) after surgery. For each patient, two age- and gender-matched controls were assessed with the same tests at the same intervals. Repeated measures ANOVA replicated the results of previous studies reporting no change or minor improvements after surgery. However, group analysis of SRB results eliminated virtually all improvements, indicating that the ANOVA results were confounded by practice effects. Standardized regression-based group results showed that in fact patients scored lower after surgery than would be predicted based on their presurgical performance. Analysis of individual SRB results showed that per visual memory measure, an average of 18% of patients obtained a significantly negative SRB score, whereas, on average, only 2% obtained a significantly positive SRB score. At T3, the number of significantly negative SRB scores outweighed the number of significantly positive SRB scores in 62% of patients. There were no clear associations of clinical variables (including side and site of surgery and postsurgical seizure freedom) with memory outcome. The present analysis revealed that given their individual presurgical functioning, many children obtained disappointing results on some visual memory tests after epilepsy surgery. Comparison of the SRB analysis with ANOVA results emphasizes the importance of empirically based techniques for detecting cognitive effects of epilepsy surgery in childhood.

Advanced structural and functional MRI in childhood epilepsies

New noninvasive MR imaging techniques are currently deeply changing the exploration of epileptic and functional networks in childhood epilepsies, as well as of the normally developing brain. While DTI can be used to look at the anatomical connectivity and at the microstructural changes that reflect the organization of an epileptic network, in addition to other techniques such as SPECT and PET, functional MRI is nowadays used routinely in the presurgical planning of focal epilepsies to assess the cortical organization of motor and language networks, helping to select surgical patients and plan the resection. Precise and robust motor mapping can be obtained in children comparably to adults. The assessment of language dominance by fMRI has reduced the need for invasive techniques such as the Wada test, provided age-related paradigms are being used in cooperating children (from 5 to 6 years of developmental age, with IQs of at least 60, and without behavioral disorders). Recent data indicate that the localizing value of language fMRI might be good when compared to cortical stimulation, and memory fMRI is emerging in children. However, invasive techniques are still necessary in difficult cases with high risk of postoperative deficit.

Temporal lobe epilepsy in children: executive and mnestic impairments

The current definition of epilepsy emphasizes the importance of cognitive impairment for a complete understanding of the disorder. Cognitive deficits have distinct functional manifestations that differentially impact the daily life experiences of children and adolescents with epilepsy and are a particular concern as they frequently impair academic performance. In particular, memory impairment and executive dysfunction are common disabilities in adults with temporal lobe epilepsy but are less easily recognized and studied in the pediatric population. This review focuses on the consequences of early-onset temporal lobe epilepsy for the development of memory and executive function and discusses current theories to explain these deficits.

Reading impairment in an adolescent with temporo-occipital epilepsy. Pre- and post-surgical evaluation

We present a 16 year-old right-handed case who underwent a left temporo-occipital resection to treat intractable epilepsy. Pre- and post-surgical evaluations showed an average intellectual quotient, preserved abilities in language and visuo-spatial functions and increased reading and spelling deficits (difficulties with irregular words, homophones and phonologically valid spelling errors of irregularly spelled words, associated with preserved performances in non-words). This pattern of characteristic lexical route deficits highlights the major role of the temporo-occipital areas in reading acquisition. We discussed the consequences of temporo-occipital dysfunction on reading.

Epilepsy surgery in children with drug-resistant epilepsy, a long-term follow-up

OBJECTIVES

In this follow-up study, we wanted to present the long-term outcome (5-21 years) in terms of seizure freedom, seizure reduction, and the cognitive development in the first 47 children who underwent epilepsy surgery at the University Hospital in Lund from 1991 to 2007.

MATERIALS AND METHODS

All children who underwent epilepsy surgery in the southern region of Sweden were assessed for cognitive function before surgery and at follow-up. A review of medical documents for demographic data and seizure-related characteristics was made by retrospectively examining the clinical records.

RESULTS

Forty-seven children with a median age at surgery of 8 years (range 0.5-18.7 years) were included. Twenty-three children achieved seizure freedom, six demonstrated >75% improvement in seizure frequency, and none of the children experienced an increase in seizure frequency. Twenty-one children required a reoperation to achieve satisfactory seizure outcomes. Cognitive functional level was preserved, and the majority of patients, 34 (76%), followed their expected cognitive trajectory. The patients who became seizure free significantly improved their cognitive processing speed, even after long-term follow-up.

CONCLUSIONS

Epilepsy surgery in children offers suitable candidates a good chance of significantly improved outcome and low rates of complications. Several children, however, required a reoperation to achieve satisfactory seizure outcomes. Cognitive level was preserved, and the majority of patients followed their expected cognitive trajectory. Cognitive improvements in processing speed appear to occur in parallel with seizure control and were even more pronounced in subjects with no anti-epilepsy drugs. These improvements persisted even after long-term follow-up.

Verbal memory after epilepsy surgery in childhood

PURPOSE

To investigate verbal memory after epilepsy surgery both group-wise and at the level of individual children, and to assess associations with side of surgery and removal of the temporal lobe.

METHODS

A prospective controlled study in a consecutive sample of 21 children undergoing epilepsy surgery, with comprehensive assessments of verbal memory before surgery and six, 12 and 24 months after surgery. For each patient, two age- and gender-matched controls were tested at similar intervals. Standardized regression-based (SRB) analysis was applied to compare post-surgical change in individual patients with change in controls.

RESULTS

Group-wise, average normed scores on verbal memory tests were higher after epilepsy surgery than before, corroborating earlier reports. By dint of empirically based SRB analysis, however, considerable individual differences in post-surgical change were revealed. Children with resections that included the left temporal lobe functioned significantly poorer than predicted on the basis of their pre-surgical performance. In contrast, verbal memory performance after surgery was consistent with pre-surgical baseline in the majority of children with resections that spared the left temporal lobe.

CONCLUSIONS

Despite cessation of epileptic seizures, verbal memory remains vulnerable in children who required surgery including the left temporal lobe. In most - but not all - children with other types of surgery, post-surgical verbal memory is consistent with their individual pre-surgical base level.

Everyday memory in children after resective epilepsy surgery

This study investigated parent reports of everyday memory and performance on objective memory tests in children with intractable epilepsy. Participants were 119 children with epilepsy (75 of whom underwent surgery) and 57 healthy controls. The group with epilepsy was examined twice, approximately 2 years apart. Parents reported on their child's memory as manifested in everyday activities and situations, and children with epilepsy completed standardized objective memory tests. At baseline, the children with epilepsy had poorer everyday memory than the healthy control group. Memory did not change significantly over time in the children with epilepsy, and no changes were found related to surgery or to seizure outcome. Intractable epilepsy in childhood is associated with difficulty in using memory in everyday activities. Resective surgery does not result in changes in the parents' observations of their child's memory as manifested in their daily functioning or in the child's performance on objective measures of memory.

Temporal lobe epilepsy surgery in children versus adults: from etiologies to outcomes

Temporal lobe epilepsy (TLE) is the most common type of medically intractable epilepsy in adults and children, and mesial temporal sclerosis is the most common underlying cause of TLE. Unlike in the case of adults, TLE in infants and young children often has etiologies other than mesial temporal sclerosis, such as tumors, cortical dysplasia, trauma, and vascular malformations. Differences in seizure semiology have also been reported. Motor manifestations are prominent in infants and young children, but they become less obvious with increasing age. Further, automatisms tend to become increasingly complex with age. However, in childhood and especially in adolescence, the clinical manifestations are similar to those of the adult population. Selective amygdalohippocampectomy can lead to excellent postoperative seizure outcome in adults, but favorable results have been seen in children as well. Anterior temporal lobectomy may prove to be a more successful surgery than amygdalohippocampectomy in children with intractable TLE. The presence of a focal brain lesion on magnetic resonance imaging is one of the most reliable independent predictors of a good postoperative seizure outcome. Seizure-free status is the most important predictor of improved psychosocial outcome with advanced quality of life and a lower proportion of disability among adults and children. Since the brain is more plastic during infancy and early childhood, recovery is promoted. In contrast, long epilepsy duration is an important risk factor for surgically refractory seizures. Therefore, patients with medically intractable TLE should undergo surgery as early as possible.