Focal interictal epileptiform discharges in idiopathic generalized epilepsy

Long-term prognosis of patients with photosensitive idiopathic generalized epilepsy

OBJECTIVE

The long-term prognosis of photosensitive idiopathic generalized epilepsy (p-IGE) is generally considered favorable; however, its specific characteristics remain unclear. Our objective was to investigate the extended prognosis of p-IGE.

METHODS

We analyzed the demographics, clinical, and electroencephalographic (EEG) data of consecutive patients who were diagnosed as having p-IGE, who were under follow-up for a minimum of 10 years and exhibited a photoparoxysmal response (PPR) in their EEGs. Prognostic data, epilepsy course types, and electroclinical variables were compared using appropriate statistical methods.

RESULTS

The mean follow-up duration for 108 consecutive patients with p-IGE (74.1 % female) was 16.8 ± 6.5 years. The main syndromes within this cohort included juvenile myoclonic epilepsy (37 %), juvenile absence epilepsy (15.7 %), and epilepsy with eyelid myoclonia (EEM) (14.8 %). In terms of epilepsy course types, 27.8 % were in the relapse-remission group, and 13.9 % had never experienced remission. A low early remission rate (5.6 %) was evident, with the remaining half of the cohort categorized as the late remission group. Several significant poor prognostic factors were identified including self-induction, clinical symptoms accompanying PPR, asynchrony and focal findings in EEG discharges, a wide frequency range of PPR, the coexistence of three seizure types, the presence of accompanying focal seizure features, and a history of convulsive status epilepticus.

CONCLUSIONS

Our long-term follow-up study, conducted within a substantial p-IGE group, unveiled newly proposed course types within this epilepsy category and highlighted significant poor prognostic factors related to photosensitivity. These findings furnish valuable insights for precise prognosis counselling and effective management strategies for patients with p-IGE.

Focal electroclinical features in generalized tonic-clonic seizures: Decision flowchart for a diagnostic challenge

OBJECTIVE

Bilateral tonic-clonic seizures with focal semiology or focal interictal electroencephalography (EEG) can occur in both focal and generalized epilepsy types, leading to diagnostic errors and inappropriate therapy. We investigated the prevalence and prognostic values of focal features in patients with idiopathic generalized epilepsy (IGE), and we propose a decision flowchart to distinguish between focal and generalized epilepsy in patients with bilateral tonic-clonic seizures and focal EEG or semiology.

METHODS

We retrospectively analyzed video-EEG recordings of 101 bilateral tonic-clonic seizures from 60 patients (18 with IGE, 42 with focal epilepsy). Diagnosis and therapeutic response were extracted after ≥1-year follow-up. The decision flowchart was based on previous observations and assessed concordance between interictal and ictal EEG.

RESULTS

Focal semiology in IGE was observed in 75% of seizures and 77.8% of patients, most often corresponding to forced head version (66.7%). In patients with multiple seizures, direction of head version was consistent across seizures. Focal interictal epileptiform discharges (IEDs) were observed in 61.1% of patients with IGE, whereas focal ictal EEG onset only occurred in 13% of seizures and 16.7% of patients. However, later during the seizures, a reproducible pattern of 7-Hz lateralized ictal rhythm was observed in 56% of seizures, associated with contralateral head version. We did not find correlation between presence of focal features and therapeutic response in IGE patients. Our decision flowchart distinguished between focal and generalized epilepsy in patients with bilateral tonic-clonic seizures and focal features with an accuracy of 96.6%.

SIGNIFICANCE

Focal semiology associated with bilateral tonic-clonic seizures and focal IEDs are common features in patients with IGE, but focal ictal EEG onset is rare. None of these focal findings appears to influence therapeutic response. By assessing the concordance between interictal and ictal EEG findings, one can accurately distinguish between focal and generalized epilepsies.

EEG Markers of Treatment Resistance in Idiopathic Generalized Epilepsy: From Standard EEG Findings to Advanced Signal Analysis

Idiopathic generalized epilepsy (IGE) represents a common form of epilepsy in both adult and pediatric epilepsy units. Although IGE has been long considered a relatively benign epilepsy syndrome, a remarkable proportion of patients could be refractory to treatment. While some clinical prognostic factors have been largely validated among IGE patients, the impact of routine electroencephalography (EEG) findings in predicting drug resistance is still controversial and a growing number of authors highlighted the potential importance of capturing the sleep state in this setting. In addition, the development of advanced computational techniques to analyze EEG data has opened new opportunities in the identification of reliable and reproducible biomarkers of drug resistance in IGE patients. In this manuscript, we summarize the EEG findings associated with treatment resistance in IGE by reviewing the results of studies considering standard EEGs, 24-h EEG recordings, and resting-state protocols. We discuss the role of 24-h EEG recordings in assessing seizure recurrence in light of the potential prognostic relevance of generalized fast discharges occurring during sleep. In addition, we highlight new and promising biomarkers as identified by advanced EEG analysis, including hypothesis-driven functional connectivity measures of background activity and data-driven quantitative findings revealed by machine learning approaches. Finally, we thoroughly discuss the methodological limitations observed in existing studies and briefly outline future directions to identify reliable and replicable EEG biomarkers in IGE patients.

GRIN2A Variants Associated With Idiopathic Generalized Epilepsies

Objective: The objective of this study is to explore the role of GRIN2A gene in idiopathic generalized epilepsies and the potential underlying mechanism for phenotypic variation.

Methods: Whole-exome sequencing was performed in a cohort of 88 patients with idiopathic generalized epilepsies. Electro-physiological alterations of the recombinant N-methyl-D-aspartate receptors (NMDARs) containing GluN2A mutants were examined using two-electrode voltage-clamp recordings. The alterations of protein expression were detected by immunofluorescence staining and biotinylation. Previous studies reported that epilepsy related GRIN2A missense mutations were reviewed. The correlation among phenotypes, functional alterations, and molecular locations was analyzed.

Results: Three novel heterozygous missense GRIN2A mutations (c.1770A > C/p.K590N, c.2636A > G/p.K879R, and c.3199C > T/p.R1067W) were identified in three unrelated cases. Electrophysiological analysis demonstrated R1067W significantly increased the current density of GluN1/GluN2A NMDARs. Immunofluorescence staining indicated GluN2A mutants had abundant distribution in the membrane and cytoplasm. Western blotting showed the ratios of surface and total expression of the three GluN2A-mutants were significantly increased comparing to the wild type. Further analysis on the reported missense mutations demonstrated that mutations with severe gain-of-function were associated with epileptic encephalopathy, while mutations with mild gain of function were associated with mild phenotypes, suggesting a quantitative correlation between gain-of-function and phenotypic severity. The mutations located around transmembrane domains were more frequently associated with severe phenotypes and absence seizure-related mutations were mostly located in carboxyl-terminal domain, suggesting molecular sub-regional effects.

Significance: This study revealed GRIN2A gene was potentially a candidate pathogenic gene of idiopathic generalized epilepsies. The functional quantitative correlation and the molecular sub-regional implication of mutations helped in explaining the relatively mild clinical phenotypes and incomplete penetrance associated with GRIN2A variants.

Seizure frequency discrepancy between subjective and objective ictal electroencephalography data in dogs

Background

Many studies of epilepsy in veterinary medicine use subjective data (eg, caregiver‐derived histories) to determine seizure frequency. Conversely, in people, objective data from electroencephalography (EEG) are mainly used to diagnose epilepsy, measure seizure frequency and evaluate efficacy of antiseizure drugs. These EEG data minimize the possibility of the underreporting of seizures, a known phenomenon in human epileptology.

Objective

To evaluate the correlation between reported seizure frequency and EEG frequency of ictal paroxysmal discharges (PDs) and to determine whether seizure underreporting phenomenon exists in veterinary epileptology.

Animals

Thirty‐three ambulatory video‐EEG recordings in dogs showing ≥1 ictal PD, excluding dogs with status epilepticus.

Methods

Retrospective observational study. Ictal PDs were counted manually over the entire recording to obtain the frequency of EEG seizures. Caregiver‐reported seizure frequency from the medical record was categorized into weekly, daily, hourly, and per minute seizure groupings. The Spearman rank test was used for correlation analysis.

Results

The coefficient value (r_s) comparing reported seizure to EEG‐confirmed ictal PD frequencies was 0.39 (95% confidence interval [CI] = 0.048‐0.64, P = .03). Other r_s values comparing history against various seizure types were: 0.36 for motor seizures and 0.37 for nonmotor (absence) seizures.

Conclusions and Clinical Importance

A weak correlation was found between the frequency of reported seizures from caregivers (subjective data) and ictal PDs on EEG (objective data). Subjective data may not be reliable enough to determine true seizure frequency given the discrepancy with EEG‐confirmed seizure frequency. Confirmation of the seizure underreporting phenomenon in dogs by prospective study should be carried out.

Evaluation of patients with epileptiform activities in the posterior temporal-parietal-occipital regions

OBJECTIVE

The aim of this study was to determine the type, etiology and the rates of epilepsy and to identify accompanying cognitive and behavioral problems in patients with epileptiform abnormalities in the posterior cerebral localization.

METHODS

In this study, 3500 patients with at least one EEG record at the EEG Laboratory of Clinical Child Neurology Department of Cerrahpaşa Medical Faculty of Istanbul University were evaluated in 2014-2015. Three hundred forty-six patients were included in the study.

RESULTS

Of the 346 patients included in the study, 42.4% were female and 57.5% were male. The age range of the cases was 1-21 (mean: 8.7) years. Epileptiform activities were observed in post TPO region isolatedly in 58,95% (n = 204), post-TPO epileptiform focus with focal epileptiform focus in different localizations in 31.21% (n = 108), generalized epileptiform activity with more than one epileptiform focus in 9.8% (n= 34). In the period of EEG examinations 250 (72.25%) patients had a history of epileptic seizures and / or epilepsy, while 96 (27.74%) had non-epileptic clinical conditions such as behavioral disorder and autism.

CONCLUSION

In the EEG recordings we examined, sharp and spike wave activities were frequently observed in the post TPO region isolatedly. We believe that this study, which investigated the relationship between focal epilptiform activity in post TPO region and different clinical conditions, will serve as an example for other studies.

Generalized polyspike train: An EEG biomarker of drug-resistant idiopathic generalized epilepsy

OBJECTIVE

To identify clinical and EEG biomarkers of drug resistance in adults with idiopathic generalized epilepsy.

METHODS

We conducted a case-control study consisting of a discovery cohort and a replication cohort independently assessed at 2 different centers. In each center, patients with the idiopathic generalized epilepsy phenotype and generalized spike-wave discharges on EEG were classified as drug-resistant or drug-responsive. EEG changes were classified into predefined patterns and compared between the 2 groups in the discovery cohort. Factors associated with drug resistance in multivariable analysis were tested in the replication cohort.

RESULTS

The discovery cohort included 85 patients (29% drug-resistant and 71% drug-responsive). Their median age at assessment was 32 years and 50.6% were female. Multivariable analysis showed that higher number of seizure types ever experienced (3 vs 1: odds ratio [OR] = 31.1, 95% confidence interval [CI]: 4.5-214, p < 0.001; 3 vs 2: OR = 14.6, 95% CI: 2.3-93.1, p = 0.004) and generalized polyspike train (burst of generalized rhythmic spikes lasting less than 1 second) during sleep were associated with drug resistance (OR = 10.8, 95% CI: 2.4-49.4, p = 0.002). When these factors were tested in the replication cohort of 80 patients (27.5% drug-resistant and 72.5% drug-responsive; 71.3% female; median age 27.5 years), the proportion of patients with generalized polyspike train during sleep was also higher in the drug-resistant group (OR = 4.0, 95% CI: 1.35-11.8, p = 0.012).

CONCLUSION

Generalized polyspike train during sleep may be an EEG biomarker for drug resistance in adults with idiopathic generalized epilepsy.

Predictive factors of higher drug load for seizure freedom in idiopathic generalized epilepsy: Comparison between juvenile myoclonic epilepsy and other types

PURPOSE

Predictive factors of higher drug load for seizure freedom were investigated in idiopathic generalized epilepsy (IGE), focusing on the difference between juvenile myoclonic epilepsy (JME) and other types of IGE (non-JME IGE).

METHODS

Twelve patients with JME and 12 patients with non-JME IGE, who achieved seizure freedom for 1 year or longer with appropriate antiepileptic drugs (AEDs) after video electroencephalography monitoring, were reviewed retrospectively. The sum of prescribed daily dose/defined daily dose ratio of all prescribed AEDs at the final visit was defined as total AED load. Patients requiring total AED load >1 were classified into the higher AED load group. Clinical background and the presence of interictal focal epileptiform abnormalities (FEAs) were compared between the higher and lower AED load groups.

RESULTS

Higher AED load group of patients with JME had interictal FEAs and family history of epilepsy more frequently than the lower AED load group (p = 0.03 and p = 0.03). Similar comparison of patients with non-JME IGE showed no significant differences.

CONCLUSIONS

The presence of interictal FEAs and a family history of epilepsy are significantly associated variables for higher AED load for seizure freedom in patients with JME, but not in patients with non-JME IGE.