Electrical status epilepticus in sleep: The role of thalamus in etiopathogenesis

The thalamus: Structure, function, and neurotherapeutics

The complexity and expansive nature of thalamic research has led to numerous interventions for varied disease states. At the same time, this complexity along with siloed areas of study can hinder a comprehensive understanding. The goal of this paper is to give the reader a broader and more detailed perspective on the thalamus. In order to accomplish this goal, the paper begins with a summary of the function, electrophysiology, and anatomy of the normal thalamus. With this foundation, thalamic involvement in neurological diseases is discussed with a focus on epilepsy. Therapeutic interventions in the thalamus for epilepsy as well as movement disorders, psychiatric conditions and disorders of consciousness are described. Lastly limitations in the field and future models of data sharing and cooperation are explored.

Modulation index predicts the effect of ethosuximide on developmental and epileptic encephalopathy with spike-and-wave activation in sleep

PURPOSE

In developmental and epileptic encephalopathy with spike-and-wave activation in sleep (DEE-SWAS), the thalamocortical network is suggested to play an important role in the pathophysiology of the progression from focal epilepsy to DEE-SWAS. Ethosuximide (ESM) exerts effects by blocking T-type calcium channels in thalamic neurons. With the thalamocortical network in mind, we studied the prediction of ESM effectiveness in DEE-SWAS treatment using phase-amplitude coupling (PAC) analysis.

METHODS

We retrospectively enrolled children with DEE-SWAS who had an electroencephalogram (EEG) recorded between January 2009 and September 2022 and were prescribed ESM at Okayama University Hospital. Only patients whose EEG showed continuous spike-and-wave during sleep were included. We extracted 5-min non-rapid eye movement sleep stage N2 segments from EEG recorded before starting ESM. We calculated the modulation index (MI) as the measure of PAC in pair combination comprising one of two fast oscillation types (gamma, 40-80 Hz; ripples, 80-150 Hz) and one of five slow-wave bands (delta, 0.5-1, 1-2, 2-3, and 3-4 Hz; theta, 4-8 Hz), and compared it between ESM responders and non-responders.

RESULTS

We identified 20 children with a diagnosis of DEE-SWAS who took ESM. Fifteen were ESM responders. Regarding gamma oscillations, significant differences were seen only in MI with 0.5-1 Hz slow waves in the frontal pole and occipital regions. Regarding ripples, ESM responders had significantly higher MI in coupling with all slow waves in the frontal pole region, 0.5-1, 3-4, and 4-8 Hz slow waves in the frontal region, 3-4 Hz slow waves in the parietal region, 0.5-1, 2-3, 3-4, and 4-8 Hz slow waves in the occipital region, and 3-4 Hz slow waves in the anterior-temporal region.

SIGNIFICANCE

High MI in a wider area of the brain may represent the epileptic network mediated by the thalamus in DEE-SWAS and may be a predictor of ESM effectiveness.

Continuous Spike-Waves during Slow Sleep Today: An Update

In the context of childhood epilepsy, the concept of continuous spike-waves during slow sleep (CSWS) includes several childhood-onset heterogeneous conditions that share electroencephalograms (EEGs) characterized by a high frequency of paroxysmal abnormalities during sleep, which have negative effects on the cognitive development and behavior of the child. These negative effects may have the characteristics of a clear regression or of a slowdown in development. Seizures are very often present, but not constantly. The above makes it clear why CSWS have been included in epileptic encephalopathies, in which, by definition, frequent EEG paroxysmal abnormalities have an unfavorable impact on cognitive functions, including socio-communicative skills, causing autistic features, even regardless of the presence of clinically overt seizures. Although several decades have passed since the original descriptions of the electroclinical condition of CSWS, there are still many areas that are little-known and deserve to be further studied, including the EEG diagnostic criteria, the most effective electrophysiological parameter for monitoring the role of the thalamus in CSWS pathogenesis, its long-term evolution, the nosographic location of Landau-Kleffner syndrome, standardized neuropsychological and behavioral assessments, and pharmacological and non-pharmacological therapies.

Microstructural evaluation of the brain with advanced magnetic resonance imaging techniques in cases of electrical status epilepticus during sleep (ESES)

Background/aim

The cause and treatment of electrical status epilepticus during sleep (ESES), one of the epileptic encephalopathies of childhood, is unclear. The aim of this study was to evaluate possible microstructural abnormalities in the brain using advanced magnetic resonance imaging (MRI) techniques in ESES patients with and without genetic mutations.

Materials and methods

This research comprised 12 ESES patients without structural thalamic lesions (6 with genetic abnormalities and 6 without) and 12 healthy children. Whole-exome sequencing was used for the genetic mutation analysis. Brain MRI data were evaluated using tractus-based spatial statistics, voxel-based morphometry, a local gyrification index, subcortical shape analysis, FreeSurfer volume, and cortical thickness. The data of the groups were compared.

Results

The mean age in the control group was 9.05 ± 1.85 years, whereas that in the ESES group was 9.45 ± 2.72 years. Compared to the control group, the ESES patients showed higher mean thalamus diffusivity (p < 0.05). ESES patients with genetic mutations had lower axial diffusivity in the superior longitudinal fasciculus and gray matter volume in the entorhinal region, accumbens area, caudate, putamen, cerebral white matter, and outer cerebellar areas. The superior and middle temporal cortical thickness increased in the ESES patients.

Conclusion

This study is important in terms of presenting the microstructural evaluation of the brain in ESES patients with advanced MRI analysis methods as well as comparing patients with and without genetic mutations. These findings may be associated with corticostriatal transmission, ictogenesis, epileptogenesis, neuropsychiatric symptoms, cognitive impairment, and cerebellar involvement in ESES. Expanded case-group studies may help to understand the physiology of the corticothalamic circuitry in its etiopathogenesis and develop secondary therapeutic targets for ESES.

The thalamic clustering coefficient moderates the vigor-sleep quality relationship

Sleep disorders affect more than one-quarter of the world's population, resulting in reduced daytime productivity, impaired immune function, and an increased risk of cardiovascular disease. It is important to identify the physiological and psychological factors related to sleep for the prevention and treatment of sleep disorders. In this study, we correlated measurements of emotional state, sleep quality, and some brain neural activity parameters to better understand the brain and psychological factors related to sleep. Resting-state functional magnetic resonance imaging (rs-fMRI) of 116 healthy undergraduates were analyzed using graph theory to assess regional topological characteristics. Among these, the left thalamic cluster coefficient proved to be the ablest to reflect the characteristics of the sleep neural graph index. The Profile of Mood States (POMS) was used to measure vigor, and the Pittsburgh Sleep Quality Index (PSQI) to assess sleep quality. The results showed that the left thalamic clustering coefficient was negatively correlated with sleep quality and vigor. Further, the left thalamic clustering coefficient moderated the relationship between vigor and sleep quality. When the left thalamic clustering coefficient was very low, there was a significant positive correlation between vigor and sleep quality. However, when the left thalamic clustering coefficient was high, the correlation between vigor and sleep quality became insignificant. The relationship between vigor and sleep quality is heterogeneous. Analyzing the function of the left thalamic neural network could help understand the variation in the relationship between vigor and sleep quality in different populations. Such observations may help in the development of personalized interventions for sleep disorders.

Is sleep captured during a standard daytime EEG sufficient to diagnose Electrical Status Epilepticus in Sleep

Electrical Status epilepticus of sleep (SES) is an EEG pattern where there is significant activation of epileptiform activity in NREM sleep. A spike wave index (SWI) of > 80-85% is often labelled as typical SES. We aimed to explore if sleep during a standard daytime-EEG, as compared an overnight-EEG, was adequate to diagnose ESES. Ten children with daytime and overnight studies suggestive of SES were audited. SWI and Spike Wave Density (SWD) were calculated for 5-minute epochs of wake in the daytime and overnight study, as well daytime-EEG sleep and first and last NREM cycle in the overnight-EEG. SWI in daytime NREM was not significantly different from SWI in the first sleep cycle of the overnight study. SWI in the last sleep cycle was significantly lower than the first sleep cycle in the overnight-EEG. SWD was significantly higher in the first sleep cycle in the overnight-EEG than the daytime sleep and the last NREM cycle. SES may be diagnosed in NREM sleep from a daytime-EEG study. Larger studies are needed to explore the significance of the disparity between SWI and SWD in the first and last NREM cycles in the overnight study.

Evaluation of long-term neurocognitive functions in patients with epileptic encephalopathy with continuous spike-and-wave during sleep (CSWS)/epileptic encephalopathy with spike-and-wave activation in sleep (EE-SWAS)

OBJECTIVES

Epileptic encephalopathy with continuous spike-and-wave during sleep (CSWS) or the newly named Epileptic encephalopathy with spike-and-wave activation in sleep (EE-SWAS) is a syndrome in which epileptiform abnormalities are associated with the progressive impairment of cognitive functions. This study aimed to evaluate the neurocognitive executive functions of patients at later ages and determine the long-term prognosis of the condition, as well as the factors affecting this.

METHODS

This is a hospital-based cross-sectional study of 17 patients with a diagnosis of CSWS, and a minimum age of 7.5 years. The Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) was used for neurocognitive assessment. The use of immunotherapy (intravenous immunoglobulin and/or steroid for at least 6 months) at the time of initial diagnosis, baseline activity and spike wave index (SWI) of the last wake and sleep EEG, cranial MRI findings, active epileptic seizures since the last examination, and WISC-IV parameters were statistically compared. The results of patients with genetic etiology determined by the whole exome sequencing (WES) method are also reported.

RESULTS

A total of 17 patients were included in the study, with a mean age of 10.30 ± 3.15 years (range from 7.9 to 15.8 years). The mean full scale IQ score of the subjects was 61.41 ± 17.81 (range 39-91), classified as follows: 5.9% (n = 1), average; 23.5% (n = 4), low average; 5.9% (n = 1), very low; 35.3% (n = 6), extremely low (upper range); 29.4% (n = 5), extremely low (lower range) intelligence. Among the four domains of WISC-IV, the most affected index was the Working Memory Index (WMI). EEG parameters, cranial MRI findings and treatment with immunotherapy did not have a significant effect on neurocognitive outcomes. Thirteen patients (76%) were evaluated with WES for a genetic etiology. Pathogenic variants in 5 different genes (GRIN2A, SLC12A5, SCN1A, SCN8A, ADGRV1) associated with epilepsy were detected in 5/13 patients (38%).

CONCLUSION

These results indicated that neurocognition is highly affected in the long term in CSWS.

Clinical Spectrum and Treatment Outcomes of Patients with Developmental and/or Epileptic Encephalopathy with Spike-and-Wave Activation in Sleep

Purpose: Developmental and/or epileptic encephalopathy with spike-and-wave activation in sleep (D/EE-SWAS) is a spectrum of conditions characterized by various phenotypes of cognitive, linguistic, and behavioral regression associated with spike-and-wave activation in sleep. We aimed to investigate the phenotypic spectrum and treatment outcomes of pediatric patients with D/EE-SWAS.Methods: We retrospectively analyzed the medical records of pediatric patients diagnosed with D/EE-SWAS and treated at Severance Children’s Hospital from 2006 to 2022. We extracted information from their medical records on electroencephalography before and after treatment, types of treatment, seizure frequency, and developmental profiles. The primary outcome was reduction of the spike-wave index on electroencephalography after treatment.Results: Twenty-one patients with a median age of 5.3 years (interquartile range, 4.1 to 6.6) at diagnosis were included. Ten patients had delayed development. The patients received various anti-seizure medications. Fourteen received long-term, high-dose steroid therapy, 10 were placed on a ketogenic diet, four received intravenous steroid pulse therapy, and one each was treated with intravenous immunoglobulin and cannabidiol. The most effective treatments were steroid therapy and a ketogenic diet, which were also effective in reducing seizures and improving cognition. Side effects during treatment were transient and treatable.Conclusion: We described the clinical spectrum of pediatric patients with D/EE-SWAS. Steroid therapy and a ketogenic diet can be considered effective therapeutic options for patients with D/EE SWAS.

Electrical Status Epilepticus in Sleep (ESES) in an Elderly Adult: A Case Report

Electrical status epilepticus in sleep (ESES) is a pattern of continuous spikes seen in electroencephalography (EEG) and may be associated with neuropsychological deficits in children. This EEG pattern has not previously been reported in older adults. In this case report, a 66-year-old woman with post-traumatic epilepsy presented to the emergency department following a breakthrough seizure. Her EEG exhibited a striking pattern of continuous spikes during sleep that stopped abruptly with wakefulness, which is characteristic of the ESES phenomenon. This patient had triggers for a breakthrough seizure including subtherapeutic seizure medication levels, exposure to flashing lights, and iatrogenic hyperthyroidism, but none of these triggers have been known to cause selectively continuous spikes during sleep on EEG. This finding suggests that the phenomenon of ESES may persist into older adulthood.