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 may 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 neuropsychology 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., ßFSIQ = -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 or more 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., ßFSIQ = 0.9, SEFSIQ = 0.3, pFSIQ = 0.004). Children who had discontinued antiseizure medication (ASM) treatment at one-year follow-up showed an eight-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 to children who were seizure-free and still receiving ASMs. In conclusion, by providing seizure freedom and the opportunity for ASM cessation, epilepsy surgery may 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 prevent it from occurring in the first place, children with focal epilepsy should be considered for epilepsy surgery as early as possible after diagnosis.

Pediatric epilepsy surgery from 2000 to 2018: Changes in referral and surgical volumes, patient characteristics, genetic testing, and postsurgical outcomes.

OBJECTIVE: Neurosurgery is a safe and effective form of treatment for select children with drug-resistant epilepsy. Still, there is concern that it remains underutilized, and that seizure freedom rates have not improved over time. We investigated referral and surgical practices, patient characteristics, and postoperative outcomes over the past two decades. METHODS: We performed a retrospective cohort study of children referred for epilepsy surgery at a tertiary center between 2000 and 2018. We extracted information from medical records and analyzed temporal trends using regression analyses. RESULTS: A total of 1443 children were evaluated for surgery. Of these, 859 (402 females) underwent surgical resection or disconnection at a median age of 8.5 years (interquartile range [IQR] = 4.6-13.4). Excluding palliative procedures, 67% of patients were seizure-free and 15% were on no antiseizure medication (ASM) at 1-year follow-up. There was an annual increase in the number of referrals (7%, 95% confidence interval [CI] = 5.3-8.6; p < .001) and surgeries (4% [95% CI = 2.9-5.6], p < .001) over time. Duration of epilepsy and total number of different ASMs trialed from epilepsy onset to surgery were, however, unchanged, and continued to exceed guidelines. Seizure freedom rates were also unchanged overall but showed improvement (odds ratio [OR] 1.09, 95% CI = 1.01-1.18; p = .027) after adjustment for an observed increase in complex cases. Children who underwent surgery more recently were more likely to be off ASMs postoperatively (OR 1.04, 95% CI = 1.01-1.08; p = .013). There was a 17% annual increase (95% CI = 8.4-28.4, p < .001) in children identified to have a genetic cause of epilepsy, which was associated with poor outcome. SIGNIFICANCE: Children with drug-resistant epilepsy continue to be put forward for surgery late, despite national and international guidelines urging prompt referral. Seizure freedom rates have improved over the past decades, but only after adjustment for a concurrent increase in complex cases. Finally, genetic testing in epilepsy surgery patients has expanded considerably over time and shows promise in identifying patients in whom surgery is less likely to be successful.

Predicting seizure outcome after epilepsy surgery: Do we need more complex models, larger samples, or better data?

OBJECTIVE: The accurate prediction of seizure freedom after epilepsy surgery remains challenging. We investigated if (1) training more complex models, (2) recruiting larger sample sizes, or (3) using data-driven selection of clinical predictors would improve our ability to predict postoperative seizure outcome using clinical features. We also conducted the first substantial external validation of a machine learning model trained to predict postoperative seizure outcome. METHODS: We performed a retrospective cohort study of 797 children who had undergone resective or disconnective epilepsy surgery at a tertiary center. We extracted patient information from medical records and trained three models-a logistic regression, a multilayer perceptron, and an XGBoost model-to predict 1-year postoperative seizure outcome on our data set. We evaluated the performance of a recently published XGBoost model on the same patients. We further investigated the impact of sample size on model performance, using learning curve analysis to estimate performance at samples up to N = 2000. Finally, we examined the impact of predictor selection on model performance. RESULTS: Our logistic regression achieved an accuracy of 72% (95% confidence interval [CI] = 68%-75%, area under the curve [AUC] = .72), whereas our multilayer perceptron and XGBoost both achieved accuracies of 71% (95% CIMLP = 67%-74%, AUCMLP = .70; 95% CIXGBoost own = 68%-75%, AUCXGBoost own = .70). There was no significant difference in performance between our three models (all p > .4) and they all performed better than the external XGBoost, which achieved an accuracy of 63% (95% CI = 59%-67%, AUC = .62; pLR = .005, pMLP = .01, pXGBoost own = .01) on our data. All models showed improved performance with increasing sample size, but limited improvements beyond our current sample. The best model performance was achieved with data-driven feature selection. SIGNIFICANCE: We show that neither the deployment of complex machine learning models nor the assembly of thousands of patients alone is likely to generate significant improvements in our ability to predict postoperative seizure freedom. We instead propose that improved feature selection alongside collaboration, data standardization, and model sharing is required to advance the field.

Determinants of IQ outcome after focal epilepsy surgery in childhood: A longitudinal case-control neuroimaging study.

OBJECTIVE: Intelligence quotient (IQ) outcomes after pediatric epilepsy surgery show significant individual variation. Clinical factors such as seizure cessation or antiepileptic medication discontinuation have been implicated, but do not fully account for the heterogeneity seen. Less is known about the impact of neurobiological factors, such as brain development and resection location. This study examines clinical and neuroimaging factors associated with cognitive outcome after epilepsy surgery in childhood. METHODS: Fifty-two children (28 boys, 24 girls) were evaluated for epilepsy surgery and reassessed on average 7.7 years later. In the intervening time, 13 were treated pharmacologically and 39 underwent focal surgery (17 temporal, 16 extratemporal, six multilobar; mean age at surgery = 14.0 years). Pre- and postsurgical assessments included IQ tests and T1-weighted brain images. Predictors of IQ change were investigated, including voxel-based analyses of resection location, and gray and white matter volume change. RESULTS: Overall modest IQ improvement was seen in children treated surgically, but not in those treated pharmacologically only. Applying a ≥10-point change threshold, 39% of the surgically treated children improved, whereas 10% declined. Clinical factors associated with IQ increases were lower preoperative IQ and longer follow-up duration, whereas seizure and antiepileptic medication cessation were not predictive. Among neuroimaging factors, we observed that left anterior temporal resections impacted negatively on verbal reasoning, linked to full-scale IQ decline. In contrast, gray matter volume change in ipsi- and contralesional hemispheres was positively correlated with IQ change. Voxel-based morphometry identified the gray matter volume change in the contralesional dorsolateral frontal cortex as most strongly associated with IQ improvement. SIGNIFICANCE: We show that a variety of factors are likely to contribute to patterns of postsurgical change in IQ. Neuroimaging results indicate that left anterior temporal resections constrain development of verbal cognition, whereas simultaneously cortical growth after surgical treatment can support improvements in IQ.

Current standards of neuropsychological assessment in epilepsy surgery centers across Europe.

We explored the current practice with respect to the neuropsychological assessment of surgical epilepsy patients in European epilepsy centers, with the aim of harmonizing and establishing common standards. Twenty-six epilepsy centers and members of "E-PILEPSY" (a European pilot network of reference centers in refractory epilepsy and epilepsy surgery), were asked to report the status of neuropsychological assessment in adults and children via two different surveys. There was a consensus among these centers regarding the role of neuropsychology in the presurgical workup. Strong agreement was found on indications (localization, epileptic dysfunctions, adverse drugs effects, and postoperative monitoring) and the domains to be evaluated (memory, attention, executive functions, language, visuospatial skills, intelligence, depression, anxiety, and quality of life). Although 186 different tests are in use throughout these European centers, a core group of tests reflecting a moderate level of agreement could be discerned. Variability exists with regard to indications, protocols, and paradigms for the assessment of hemispheric language dominance. For the tests in use, little published evidence of clinical validity in epilepsy was provided. Participants in the survey reported a need for improvement concerning the validity of the tests, tools for the assessment of everyday functioning and accelerated forgetting, national norms, and test co-normalization. Based on the present survey, we documented a consensus regarding the indications and principles of neuropsychological testing. Despite the variety of tests in use, the survey indicated that there may be a core set of tests chosen based on experience, as well as on published evidence. By combining these findings with the results of an ongoing systematic literature review, we aim for a battery that can be recommended for the use across epilepsy surgical centers in Europe.