Measuring expertise in identifying interictal epileptiform discharges.

OBJECTIVE: Interictal epileptiform discharges on EEG are integral to diagnosing epilepsy. However, EEGs are interpreted by readers with and without specialty training, and there is no accepted method to assess skill in interpretation. We aimed to develop a test to quantify IED recognition skills. METHODS: A total of 13,262 candidate IEDs were selected from EEGs and scored by eight fellowship-trained reviewers to establish a gold standard. An online test was developed to assess how well readers with different training levels could distinguish candidate waveforms. Sensitivity, false positive rate and calibration were calculated for each reader. A simple mathematical model was developed to estimate each reader's skill and threshold in identifying an IED, and to develop receiver operating characteristics curves for each reader. We investigated the number of IEDs needed to measure skill level with acceptable precision. RESULTS: Twenty-nine raters completed the test; nine experts, seven experienced non-experts and thirteen novices. Median calibration errors for experts, experienced non-experts and novices were -0.056, 0.012, 0.046; median sensitivities were 0.800, 0.811, 0.715; and median false positive rates were 0.177, 0.272, 0.396, respectively. The number of test questions needed to measure those scores was 549. Our analysis identified that novices had a higher noise level (uncertainty) compared to experienced non-experts and experts. Using calculated noise and threshold levels, receiver operating curves were created, showing increasing median area under the curve from novices (0.735), to experienced non-experts (0.852) and experts (0.891). SIGNIFICANCE: Expert and non-expert readers can be distinguished based on ability to identify IEDs. This type of assessment could also be used to identify and correct differences in thresholds in identifying IEDs.

Minimum clinically important difference (MCID) of the personal impact of epilepsy scale (PIES).

INTRODUCTION: The Personal Impact of Epilepsy Scale (PIES) assesses patient functional status in subscales of (1) seizure impact, (2) medication effects, (3) mood & social status, and (4) overall quality of life. This study was designed to determine the Minimal Clinically Important Change (MCID) in PIES subscale and total scores that demonstrate improvement. METHODS: To ascertain the correspondence of PIES score change and clinical status change (improved, same, worse) in each PIES subscale and total score, we used two distinct retrospective anchor-based assessments of clinical status (patient self-assessment and trained rater assessment) across two clinic visits. Mean PIES scores were compared between clinical status groups, controlling for days between visits and initial clinical status. Personal Impact of Epilepsy Scale score change was quantified for each group to determine MCID. A small prospective proof-of-concept study was conducted in a separate subject group. RESULTS: Patient self-report anchor analysis demonstrated lower (better) PIES scores in the "improved" group vs the "worse" group on the mood & social subscale (p < .001) and total score (p = .002), with a similar trend on the seizure subscale (p = 0.056). Clinical rater anchor analysis demonstrated lower PIES scores in the "improved" vs "worse" group in the mood & social subscale (p = .029) and a trend in total score (p = .082). For the "improved" group, the reduction in PIES scores between visits averaged across both anchor analyses was 8.14% for subscales and 8.67% for total score. DISCUSSION/CONCLUSION: Reduction of 8% on a PIES subscale or total score indicates meaningful improvement in patient clinical status, and is designated the MCID for this instrument. Personal Impact of Epilepsy Scale can be useful in day-to-day clinical care and as an outcome metric in clinical research.

Interictal Epileptiform Discharge Detection in EEG in Different Practice Settings.

OBJECTIVE: The goal of the study was to measure the performance of academic and private practice (PP) neurologists in detecting interictal epileptiform discharges in routine scalp EEG recordings. METHODS: Thirty-five EEG scorers (EEGers) participated (19 academic and 16 PP) and marked the location of ETs in 200 30-second EEG segments using a web-based EEG annotation system. All participants provided board certification status, years of Epilepsy Fellowship Training (EFT), and years in practice. The Persyst P13 automated IED detection algorithm was also run on the EEG segments for comparison. RESULTS: Academic EEGers had an average of 1.66 years of EFT versus 0.50 years of EFT for PP EEGers (P < 0.0001) and had higher rates of board certification. Inter-rater agreement for the 35 EEGers was fair. There was higher performance for EEGers in academics, with at least 1.5 years of EFT, and with American Board of Clinical Neurophysiology and American Board of Psychiatry and Neurology-E specialty board certification. The Persyst P13 algorithm at its default setting (perception value = 0.4) did not perform as well at the EEGers, but at substantially higher perception value settings, the algorithm performed almost as well human experts. CONCLUSIONS: Inter-rater agreement among EEGers in both academic and PP settings varies considerably. Practice location, years of EFT, and board certification are associated with significantly higher performance for IED detection in routine scalp EEG. Continued medical education of PP neurologists and neurologists without EFT is needed to improve routine scalp EEG interpretation skills. The performance of automated detection algorithms is approaching that of human experts.

Characteristics of EEG Interpreters Associated With Higher Interrater Agreement.

PURPOSE: The goal of the project is to determine characteristics of academic neurophysiologist EEG interpreters (EEGers), which predict good interrater agreement (IRA) and to determine the number of EEGers needed to develop an ideal standardized testing and training data set for epileptiform transient (ET) detection algorithms. METHODS: A three-phase scoring method was used. In phase 1, 19 EEGers marked the location of ETs in two hundred 30-second segments of EEG from 200 different patients. In phase 2, EEG events marked by at least 2 EEGers were annotated by 18 EEGers on a 5-point scale to indicate whether they were ETs. In phase 3, a third opinion was obtained from EEGers on any inconsistencies between phase 1 and phase 2 scoring. RESULTS: The IRA for the 18 EEGers was only fair. A select group of the EEGers had good IRA and the other EEGers had low IRA. Board certification by the American Board of Clinical Neurophysiology was associated with better IRA performance but other board certifications, years of fellowship training, and years of practice were not. As the number of EEGers used for scoring is increased, the amount of change in the consensus opinion decreases steadily and is quite low as the group size approaches 10. CONCLUSIONS: The IRA among EEGers varies considerably. The EEGers must be tested before use as scorers for ET annotation research projects. The American Board of Clinical Neurophysiology certification is associated with improved performance. The optimal size for a group of experts scoring ETs in EEG is probably in the 6 to 10 range.

Mortality following status epilepticus in persons with and without epilepsy.

PURPOSE: Incidence of status epilepticus (SE) ranges from 6.8 to 41.0 per 100,000 population. Although SE is associated with significant morbidity and mortality, the temporal relationship between SE, epilepsy, and mortality is less clear. The risk of all-cause mortality following SE with and without prior epilepsy was investigated. METHOD: This study identified hospitalizations and emergency department visits for persons with SE and persons with epilepsy between 2000 and 2013. Excluded were those with epilepsy subsequent to SE, epilepsia partialis continua, less than 90days follow-up, and less than 2 years of data prior to first diagnosis. The cohort was grouped into: 1) SE only, 2) post-epilepsy SE (PES), and 3) epilepsy only. The risk of mortality was estimated using Cox proportional hazard models adjusting for potential confounders. RESULTS: The cohort (N=82,331) consisted of 1296 SE only cases (1.6%); 2136 PES cases (2.6%); and 78,899 epilepsy only controls (95.8%) with 24.9%, 29.2% and 20.0% mortality, respectively. Compared with controls, the hazard of mortality was increased for those with SE only (hazard ratio [HR]=1.61, 95% CI=1.41-1.82) and PES (HR=1.16, 95% CI=1.07-1.25) after adjustment for demographic and clinical factors. Prior stroke, central nervous system infection, and brain tumor increased the mortality hazard. CONCLUSION: There is a statistically significant increased risk of all-cause mortality with SE. The risk is stronger in those with no prior epilepsy. Specific etiologies increase mortality risk in those with SE warranting further investigation of the complex associations between these etiologies and SE.

Comparison of a Novel Dry Electrode Headset to Standard Routine EEG in Veterans.

OBJECTIVE: This purpose of this study was to evaluate the usefulness of a prototype battery-powered dry electrode system (DES) EEG recording headset in Veteran patients by comparing it with standard EEG. METHODS: Twenty-one Veterans had both a standard electrode system recording and DES recording in nine different patient states at the same encounter. Setup time, patient comfort, and subject preference were measured. Three experts performed technical quality rating of each EEG recording in a blinded fashion using the web-based EEGnet system. Power spectra were compared between DES and standard electrode system recordings. RESULTS: The average time for DES setup was 5.7 minutes versus 21.1 minutes for standard electrode system. Subjects reported that the DES was more comfortable during setup. Most subjects (15 of 21) preferred the DES. On a five-point scale (1-best quality to 5-worst quality), the technical quality of the standard electrode system recordings was significantly better than for the DES recordings, at 1.25 versus 2.41 (P < 0.0001). But experts found that 87% of the DES EEG segments were of sufficient technical quality to be interpretable. CONCLUSIONS: This DES offers quick and easy setup and is well tolerated by subjects. Although the technical quality of DES recordings was less than standard EEG, most of the DES recordings were rated as interpretable by experts. SIGNIFICANCE: This DES, if improved, could be useful for a telemedicine approach to outpatient routine EEG recording within the Veterans Administration or other health system.

Premature deaths among children with epilepsy - South Carolina, 2000-2011.

Epilepsy is a common childhood neurologic disorder. In 2007, epilepsy affected an estimated 450,000 children aged 0-17 years in the United States. Approximately 53% of children with epilepsy and special health care needs have co-occurring conditions, and only about one third have access to comprehensive care. The few studies of mortality risk among children with epilepsy as compared with the general population generally find a higher risk for death among children with epilepsy with co-occurring conditions but a similar risk for death among children with epilepsy with no co-occurring conditions. However, samples from these mortality studies are often small, limiting comparisons, and are not representative. This highlights the need for expanded mortality surveillance among children with epilepsy to better understand their excess mortality. This report describes mortality among children with epilepsy in South Carolina during 2000-2011 by demographic characteristics and underlying causes of death. The overall mortality rate among children with epilepsy was 8.8 deaths per 1,000 person-years, and the annual risk for death was 0.84%. Developmental conditions, cardiovascular disorders, and injuries were the most common causes of death among children with epilepsy. Team-based care coordination across medical and nonmedical systems can improve outcomes and reduce health care costs for children with special health care needs, but they require more study among children with epilepsy. Ensuring appropriate and timely health care and social services for children with epilepsy, especially those with complications, might reduce the risk for premature death. Health care providers, social service providers, advocacy groups and others can work together to assess whether coordinated care can improve outcomes for children with epilepsy.

Risk of venous thromboembolism in people with epilepsy.

OBJECTIVE: Risk of venous thromboembolism (VTE) among people with epilepsy (PWEs) has not been previously reported. Standard VTE prevention methods may increase the risk of complications in this population. This statewide study assessed the risk of VTE in PWEs. METHODS: Main risk categories were grouped into definite epilepsy (DE), probable epilepsy (PE), and migraine, a comparable neurologic condition. All inpatient, emergency department, and hospital-based outpatient encounters in South Carolina from January 1, 2000 through December 31, 2011, were evaluated for the primary outcome variable of VTE, defined as having a diagnosis of VTE at or after the diagnosis of epilepsy or migraine. Coagulopathies and common comorbidities of epilepsy were enumerated. Differences in VTE proportions were assessed using 95% confidence intervals (CIs). Association of VTE with epilepsy and migraine was evaluated with Cox proportional hazard modeling. RESULTS: A total of 138,497 people with migraine (PWMs) and 67,900 PWEs (32,186 DE, 35,714 PE) were included. VTE occurred in 2.7% of PWEs (4.2% among DE), and 0.6% of PWMs. The hazard ratio for VTE in DE compared with PWMs was 3.08 (95% CI 2.76-3.42), adjusted for all covariables. Higher numbers of comorbidities were strongly associated with VTE. PWE had higher numbers of comorbidities (52% with 2+ comorbidities versus 23% of PWM), but the impact of comorbidities on VTE risk was larger in PWM. SIGNIFICANCE: Higher VTE risk in PWE than PWM suggests risk factors associated with epilepsy, independent of chronic neurologic illness. VTE occurrence in PWE is comparable to published rates among people with cancer.

Epilepsy beyond seizure: a population-based study of comorbidities.

Comorbid conditions may affect the quality of life in persons with epilepsy (PWE) more than seizures. Using legally mandated healthcare encounter data, somatic, psychiatric, and neurodevelopmental comorbidities in a large population-based cohort of PWE, were compared to persons with migraine (PWM), a similar neurologic condition, and lower extremity fracture (PWLF), otherwise healthy controls. 64,188 PWE, 121,990 PWM, and 89,808 PWLF were identified from inpatient, outpatient, and emergency department from 2000 to 2011. Epilepsy was ascertained with ICD-9-CM code 345; migraine with 346; fracture of the tibia, fibula, and ankle with 823 and 824. Common comorbidities of epilepsy were identified from the literature. Differences in prevalence among PWE, PWM, and PWLF were assessed by comparison of 95% confidence intervals (CI) constructed under the assumption of independence and normal approximation. The association of the comorbid conditions with epilepsy and migraine, compared to lower extremity fracture, were evaluated with polytomous logistic regression controlling for demographic and mortality covariables. PWE had significantly elevated prevalence of comorbidities compared with PWM and PWLF. Compared with PWLF, the adjusted odds ratios (OR) of having both somatic and psychiatric/neurodevelopmental comorbidities were 5.44 (95% CI=5.25-5.63) and 2.49 (95% CI=2.42-2.55) in PWE and PWM, respectively. The association with epilepsy was the strongest for cognitive dysfunction (OR=28.1; 95% CI=23.3-33.8); autism spectrum disorders (OR=22.2; 95% CI=16.8-29.3); intellectual disability (OR=12.9; 95% CI=11.6-14.3); and stroke (OR=4.2; 95% CI=4.1-4.4). The absolute risk increase in PWE compared with PWM for any somatic or psychiatric/neurodevelopmental comorbidity was 58.8% and 94.3%, respectively. Identifying comorbidities that are strongly and consistently associated with seizures, particularly disorders with shared underlying pathophysiology, is critical in identifying specific research and practice goals that may ultimately improve the quality of life for PWE. This study contributes to that effort by providing population-based comorbidity data for PWE compared with PWM and PWLF.

Standardized database development for EEG epileptiform transient detection: EEGnet scoring system and machine learning analysis.

The routine scalp electroencephalogram (rsEEG) is the most common clinical neurophysiology procedure. The most important role of rsEEG is to detect evidence of epilepsy, in the form of epileptiform transients (ETs), also known as spike or sharp wave discharges. Due to the wide variety of morphologies of ETs and their similarity to artifacts and waves that are part of the normal background activity, the task of ET detection is difficult and mistakes are frequently made. The development of reliable computerized detection of ETs in the EEG could assist physicians in interpreting rsEEGs. We report progress in developing a standardized database for testing and training ET detection algorithms. We describe a new version of our EEGnet software system for collecting expert opinion on EEG datasets, a completely web-browser based system. We report results of EEG scoring from a group of 11 board-certified academic clinical neurophysiologists who annotated 30-s excepts from rsEEG recordings from 100 different patients. The scorers had moderate inter-scorer reliability and low to moderate intra-scorer reliability. In order to measure the optimal size of this standardized rsEEG database, we used machine learning models to classify paroxysmal EEG activity in our database into ET and non-ET classes. Based on our results, it appears that our database will need to be larger than its current size. Also, our non-parametric classifier, an artificial neural network, performed better than our parametric Bayesian classifier. Of our feature sets, the wavelet feature set proved most useful for classification.

Relationship of number of seizures recorded on video-EEG to surgical outcome in refractory medial temporal lobe epilepsy.

INTRODUCTION: Surgical planning for refractory medial temporal lobe epilepsy (rMTLE) relies on seizure localization by ictal electroencephalography (EEG). Multiple factors impact the number of seizures recorded. We evaluated whether seizure freedom correlated to the number of seizures recorded, and the related factors. METHODS: We collected data for 32 patients with rMTLE who underwent anterior temporal lobectomy. Primary analysis evaluated number of seizures captured as a predictor of surgical outcome. Subsequent analyses explored factors that may seizure number. RESULTS: Number of seizures recorded did not predict seizure freedom. More seizures were recorded with more days of seizure occurrence (p<0.001), seizure clusters (p≤0.011) and poorly localized seizures (PLSz) (p=0.004). Regression modeling showed a trend for subjects with fewer recorded poorly localized seizures to have better surgical outcome (p=0.052). CONCLUSIONS: Total number of recorded seizures does not predict surgical outcome. Patients with more PLSz may have worse outcome.

Relationship of number of seizures recorded on video-EEG to surgical outcome in refractory medial temporal lobe epilepsy / Relação entre o número de crises epilépticas registradas em vídeo-EEG e o resultado cirúrgico na epilepsia refratária do lobo temporal

INTRODUCTION: Surgical planning for refractory medial temporal lobe epilepsy (rMTLE) relies on seizure localization by ictal electroencephalography (EEG). Multiple factors impact the number of seizures recorded. We evaluated whether seizure freedom correlated to the number of seizures recorded, and the related factors. METHODS: We collected data for 32 patients with rMTLE who underwent anterior temporal lobectomy. Primary analysis evaluated number of seizures captured as a predictor of surgical outcome. Subsequent analyses explored factors that may seizure number. RESULTS: Number of seizures recorded did not predict seizure freedom. More seizures were recorded with more days of seizure occurrence (p<0.001), seizure clusters (p<0.011) and poorly localized seizures (PLSz) (p=0.004). Regression modeling showed a trend for subjects with fewer recorded poorly localized seizures to have better surgical outcome (p=0.052). CONCLUSIONS: Total number of recorded seizures does not predict surgical outcome. Patients with more PLSz may have worse outcome.

INTRODUÇÃO: O planejamento cirúrgico para epilepsia refratária do lobo medial temporal (rMTLE) depende da localização da região de origem das convulsões por meio do eletroencefalografia (EEG) ictal. Múltiplos fatores podem influenciar o número de crises registradas. Neste artigo, avaliamos se a obtenção de liberdade de crises epilépticas no pós-operatório se relaciona com o número de crises epilépticas registradas durante a avaliação pré-operatória e os fatores que afetam tal resultado. MÉTODOS: Foram coletados dados de 32 pacientes com rMTLE que foram submetidos à lobectomia temporal anterior. A análise principal avaliou o número de convulsões captadas como fator preditivo do resultado cirúrgico, e as análises subsequentes exploraram outros fatores que podem ter afetado o resultado cirúrgico. RESULTADOS: O número de convulsões registradas não mostrou valor preditivo para resultados livres de crises. Foi registrado maior número de convulsões quando houve: maior número de dias em que ocorreram crises (p<0,001); salvas de convulsões (p<0,011); e localização subótima da origem das crises (PLSz) (p=0,004). O modelo de regressão mostrou tendência para os indivíduos com um menor número de crises pobremente localizadas terem um melhor desfecho cirúrgico (p=0,052). CONCLUSÕES: O número total de crises registrado não afeta o desfecho cirúrgico, que possivelmente é influenciado por múltiplos fatores. Pacientes com mais PLSz têm maior possibilidade de pior resultado cirúrgico.

Medial temporal lobe epilepsy is associated with neuronal fibre loss and paradoxical increase in structural connectivity of limbic structures.

BACKGROUND: It has been hypothesised that seizure induced neuronal loss and axonal damage in medial temporal lobe epilepsy (MTLE) may lead to the development of aberrant connections between limbic structures and eventually result in the reorganisation of the limbic network. In this study, limbic structural connectivity in patients with MTLE was investigated, using diffusion tensor MRI, probabilistic tractography and graph theory based network analysis. METHODS: 12 patients with unilateral MTLE and hippocampal sclerosis (five left and seven right MTLE) and 26 healthy controls were studied. The connectivity of 10 bilateral limbic regions of interest was mapped with probabilistic tractography, and the probabilistic fibre density between each pair of regions was used as the measure of their weighted structural connectivity. Binary connectivity matrices were then obtained from the weighted connectivity matrix using a range of fixed density thresholds. Graph theory based properties of nodes (degree, local efficiency, clustering coefficient and betweenness centrality) and the network (global efficiency and average clustering coefficient) were calculated from the weight and binary connectivity matrices of each subject and compared between patients and controls. RESULTS: MTLE was associated with a regional reduction in fibre density compared with controls. Paradoxically, patients exhibited (1) increased limbic network clustering and (2) increased nodal efficiency, degree and clustering coefficient in the ipsilateral insula, superior temporal region and thalamus. There was also a significant reduction in clustering coefficient and efficiency of the ipsilateral hippocampus, accompanied by increased nodal degree. CONCLUSIONS: These results suggest that MTLE is associated with reorganisation of the limbic system. These results corroborate the concept of MTLE as a network disease, and may contribute to the understanding of network excitability dynamics in epilepsy and MTLE.

Subtypes of medial temporal lobe epilepsy: influence on temporal lobectomy outcomes?

Surgical resection of the hippocampus is the most successful treatment for medication-refractory medial temporal lobe epilepsy (MTLE) due to hippocampal sclerosis. Unfortunately, at least one of four operated patients continue to have disabling seizures after surgery, and there is no existing method to predict individual surgical outcome. Prior to surgery, patients who become seizure free appear identical to those who continue to have seizures after surgery. Interestingly, newly converging presurgical data from magnetic resonance imaging (MRI) and intracranial electroencephalography (EEG) suggest that the entorhinal and perirhinal cortices may play an important role in seizure generation. These areas are not consistently resected with surgery and it is possible that they continue to generate seizures after surgery in some patients. Therefore, subtypes of MTLE patients can be considered according to the degree of extrahippocampal damage and epileptogenicity of the medial temporal cortex. The identification of these subtypes has the potential to drastically improve surgical results via optimized presurgical planning. In this review, we discuss the current data that suggests neural network damage in MTLE, focusing on the medial temporal cortex. We explore how this evidence may be applied to presurgical planning and suggest approaches for future investigation.

Sixty day continuous use of subdermal wire electrodes for EEG monitoring during treatment of status epilepticus.

INTRODUCTION: Use of continuous EEG in the ICU setting is increasing. The EEG electrode continues to be a weak link in the chain from recording to interpretation. The technical difficulties of maintaining artifact-free, low impedance data collection are magnified by the ICU environment and prolonged duration of monitoring often required for these patients. CASE: We describe a case demonstrating the longest reported continuous use of subdermal wire electrodes. DISCUSSION: Subdermal wire electrodes offer a safe method to overcome technical challenges while maintaining high-recording quality. Their advantages and disadvantages are considered in specific circumstances and in comparison to other electrode types.