Do sleep-deprived EEG recordings reflect spike index as found in full-night EEG recordings?

The Spike-Wave Index of the First 100 Seconds of Sleep Can Be a Reliable Scoring Method for Electrographic Status Epilepticus in Sleep

INTRODUCTION

Electrical status epilepticus in sleep (ESES) is an electrographic pattern in which interictal epileptiform activity is augmented by the transition to sleep, with non-rapid eye movement sleep state characterized by near-continuous lateralized or bilateral epileptiform discharges. The aim of this study was to measure the reliability of the spike-wave index (SWI) of the first 100 seconds of sleep as a tool for the diagnosis of ESES.

METHODS

One hundred forty studies from 60 unique patients met the inclusion. Two neurophysiologists calculated the SWI of the first 100 seconds of spontaneous stage II non-rapid eye movement sleep. This was compared with the SWI of the first 5 minutes of non-rapid eye movement sleep and the cumulative SWI of three 5-minute bins of sleep. Agreement between the three SWI methods were analyzed using several statistical tools and methods.

RESULTS

Using an SWI of 50% as a diagnostic cutoff, 57% of records had a diagnosis of ESES based on the first 100 seconds of sleep. Fifty-four percent of records had a diagnosis of ESES based on the method of using the SWI of three bins. This resulted in a diagnostic accuracy of 92%, sensitivity of 96%, and specificity of 88%. Positive predictive values of children diagnosed with ESES using the first 100 seconds of sleep, compared with 3 combined bins, was determined to be 90% and a negative predictive value was determined to be 95%.

CONCLUSIONS

This analysis confirmed the diagnostic accuracy of using the SWI of the first 100 seconds of sleep and the cumulative total of three 5-minute bins.

Is epileptiform activity related to developmental language disorder? Findings from the HelSLI study

Objective

To study if interictal epileptiform discharges (IEDs) are associated with language performance or pre-/perinatal factors in children with developmental language disorder (DLD).

Methods

We recorded routine EEG in wake and sleep in 205 children aged 2.9-7.1 years with DLD, without neurologic diseases or intellectual disability. We examined the language performance of the children and collected data on pre-/perinatal factors.

Results

Interictal epileptiform discharges were not associated with lower language performance. Children with so-called "rolandic", i.e. centrotemporoparietal, IEDs had better language skills, but age explained this association. Most pre-/perinatal factors evaluated did not increase the risk of rolandic IEDs, except for maternal smoking (OR 4.4, 95% CI 1.4-14). We did not find electrical status epilepticus during slow-wave sleep (ESES)/spike-and-wave activation in sleep (SWAS) in any children.

Conclusions

Interictal epileptiform discharges are not associated with lower language performance, and ESES/SWAS is not common in children with DLD.

Significance

Routine EEGs do not bring additional information about language performance in children with DLD who do not have any neurologic diseases, seizures, intellectual disability, or regression of language development.

[Epileptiform activity index for the evaluation of treatment efficacy in patients with epileptic encephalopathy]

Continuous spike and waves during sleep (CSWS) may lead to different cognitive, motor and behavioral symptoms. CSWS is characterized by an electroencephalography (EEG) pattern of electrical status epilepticus during sleep (ESES). The article reviews the main criteria of ESES, localization of EEG-changes and main EEG-patterns. An analysis of abnormal neuroimaging findings in patients with ESES was performed. The main pathophysiologic theories of ESES pattern formation are reviewed. ESES diagnosis is usually based on rough visual assessment of the number of spikes and waves, but other methods of assessment are also utilized, including spike-wave index (SWI), which is widely used in clinical practice. SWI reflects the percentage of sleep covered with spikes and waves. Two different strategies of SWI calculation are used, but none of them is officially validated. Moreover, there is no consensus on the period of sleep to be used for the calculation of SWI. The article presents a detailed review of calculation and utilization of SWI. It is concluded that further research is needed to develop an optimal algorithm of SWI calculation.

Long-term follow-up of cognitive functions in patients with continuous spike-waves during sleep (CSWS)

Continuous spike-waves during sleep (CSWS) are associated with several cognitive, neurological, and psychiatric disorders, which sometimes persist after CSWS disappearance. The purpose of this retrospective study was to investigate the correlation between general (clinical and instrumental) and neuropsychological findings in CSWS, to identify variables that predispose patients to a poorer long-term neuropsychological outcome. Patients with spikes and waves during sleep with a frequency ≥25/min (spikes and waves frequency index - SWFI) were enrolled. There were patients presenting abnormal EEG activity corresponding to the classic CSWS and patients with paroxysmal abnormalities during sleep <85% with SWFI ≥25/min that was defined as excessive spike-waves during sleep (ESWS). Clinical and instrumental features and neuropsychological findings during and after the spike and wave active phase period were considered. A statistical analysis was performed utilizing the Spearman correlation test and multivariate analysis. The study included 61 patients; the mean follow-up (i.e., the period between SWFI ≥25 first recording and last observation) was 7years and 4months. The SWFI correlated inversely with full and performance IQ during CSWS/ESWS. Longer-lasting SWFI ≥25 was related to worse results in verbal IQ and performance IQ after CSWS/ESWS disappearance. Other variables may influence the neuropsychological outcome, like age at SWFI ≥25 first recording, perinatal distress, pathologic neurologic examination, and antiepileptic drug resistance. This confirms that CSWS/ESWS are a complex pathology and that many variables contribute to its outcome. The SWFI value above all during CSWS/ESWS and long-lasting SWFI ≥25 after CSWS/ESWS disappearance are the most significant indexes that appear mostly to determine cognitive evolution. This finding underscores the importance of EEG recordings during sleep in children with a developmental disorder, even if seizures are not reported, as well as the importance of using therapy with an early efficacy.

Longitudinal stability of interictal spikes in benign epilepsy with centrotemporal spikes

OBJECTIVE

To describe the natural history of electroencephalography (EEG) changes in patients with benign epilepsy with centrotemporal spikes (BECTS) over 1 year.

METHODS

Centrotemporal spikes were visually evaluated based on 24-h ambulatory EEG studies to determine the total, left, right, and bilateral centrotemporal spikes patients were awake and asleep. These spike rates were then used to compare the entire night of sleep to the first 2 h of sleep, the repeatability of spike frequency over two recordings (done within days to weeks), and longitudinal changes in spike rate over 6 and 12 months.

RESULTS

Nineteen children with newly diagnosed and untreated BECTS were included in this analysis. An excellent correlation was found between the centrotemporal spike rate during the entire duration of sleep and the first 2 h of sleep (intraclass correlation [ICC] 0.87, 95% confidence interval [CI] 0.67-0.95). In addition, an excellent correlation was found between two recordings completed an average of 23 days apart while patients were asleep (ICC 0.92, 95% CI 0.80-0.97) and good correlation while patients were awake (ICC 0.70, 95% CI 0.39-0.87). The average change in spike rate between recordings at baseline and at 6 months was a decrease of 64.7% (range -100% to +51.5%, p = 0.01) and the average change in rate between recordings at baseline and at 12 months was a decrease of 57.7% (range -100% to +29.1%, p = 0.01). In addition, within 6 months, most children had decreased centrotemporal rates, with 30% of children being spike-free. This absence of spikes did not continue in all children, since the majority (60%) had some spikes at 1 year following diagnosis.

SIGNIFICANCE

Centrotemporal spike rates during sleep are stable when compared over days to weeks; however, when comparing spike rates over months there is a larger degree of variability.

Interictal epileptiform activity and autism

Many individuals with autism have epileptiform discharges on their EEG without having definite clinical seizures. The clinical significance of epileptiform activity in patients with autism is controversial. Some consider it an epiphenomenon of the underlying condition that should be ignored, and others believe that frequent spikes may contribute to the cognitive impairment and advocate treatment. Several studies have reported variable rates of epileptiform activity and variable response to treatment. There is an urgent need to conduct controlled clinical trials to assess the true incidence of epileptiform activity in children with autism, develop a risk assessment model, and study the effectiveness of treatment. This article is part of a Special Issue entitled "Autism and Epilepsy".

[French guidelines on electroencephalogram]

Electroencephalography allows the functional analysis of electrical brain cortical activity and is the gold standard for analyzing electrophysiological processes involved in epilepsy but also in several other dysfunctions of the central nervous system. Morphological imaging yields complementary data, yet it cannot replace the essential functional analysis tool that is EEG. Furthermore, EEG has the great advantage of being non-invasive, easy to perform and allows control tests when follow-up is necessary, even at the patient's bedside. Faced with the advances in knowledge, techniques and indications, the Société de Neurophysiologie Clinique de Langue Française (SNCLF) and the Ligue Française Contre l'Épilepsie (LFCE) found it necessary to provide an update on EEG recommendations. This article will review the methodology applied to this work, refine the various topics detailed in the following chapters. It will go over the summary of recommendations for each of these chapters and underline proposals for writing an EEG report. Some questions could not be answered by the review of the literature; in those cases, an expert advice was given by the working and reading groups in addition to the guidelines.

Measuring spike strength in patients with continuous spikes and waves during sleep: comparison of methods for prospective use as a clinical index

OBJECTIVE

To compare methods of estimating spike strength as a potential index in the assessment of continuous spikes and waves during sleep (CSWS).

METHODS

Spikes were searched and averaged automatically from pre- and postoperative EEGs of ten patients with CSWS who underwent corpus callosotomy (eight) or resective epilepsy surgery (two). From the most prominent spike, we measured peak amplitude and root mean square (RMS) over ±150ms window around the peak. In order to compensate for spatiotemporal instability of spikes, the cumulative amplitude and RMS were computed from the highest quartile of electrodes (Ampl-Q and RMS-Q, respectively). The stability of parameters was studied by comparing two ten minute epochs during the first hour of NREM sleep, as well as by analyzing overnight variation of indices in further ten patients with CSWS. The Ampl-Q and RMS-Q were compared between pre- and postoperative recordings.

RESULTS

All four measures, amplitude, RMS, Ampl-Q and RMS-Q, were correlated with each other and highly dependent on NREM/REM-sleep stage and arousals. Expectedly, Ampl-Q and RMS-Q had the greatest intra-individual stability. The amplitude had up to 71% intra-individual variation making it unhelpful for clinical use. Ampl-Q and RMS-Q were comparable in assessing change following surgical treatment.

CONCLUSIONS

Computing an integrated RMS over multiple electrodes during steady NREM sleep offers a stable and reliable parameter for evaluating the strength of spikes in CSWS.

SIGNIFICANCE

Analyzing spike strength with RMS-Q may offer a clinically useful, supplementary index for EEG monitoring of CSWS where spike index has been of limited value.

Subclinical epileptiform activity in children with electrical status epilepticus during sleep: effects on cognition and behavior before and after treatment with levetiracetam

We performed a double-blind placebo-controlled crossover study of the effects of spike activity during sleep and when awake on learning, long-term memory, vigilance and behavior before and after treatment with levetiracetam in children with electrical status epilepticus during sleep. At baseline, verbal learning declined with increasing spike activity, but there were no relations between spike activity and memory, vigilance or behavior. Levetiracetam was effective in reducing sleep-related spike activity, but on a group level, this had no clear effects on behavior, vigilance or learning and memory. Our results do not allow firm conclusions whether to treat nocturnal epileptiform activity or not; larger samples and longer follow-up may be needed.

Electrical status epilepticus in sleep: clinical presentation and pathophysiology

Electrical status epilepticus in sleep involves an electroencephalographic pattern where interictal epileptiform activity is potentiated in the transition from wakefulness to sleep. Near-continuous spikes and waves that occupy a significant proportion of nonrapid eye movement sleep appear as a result of sleep-potentiated epileptiform activity. This electroencephalographic pattern appears in different electroclinical syndromes that present three common characteristics with different degrees of severity: seizures, sleep-potentiated epileptiform activity, and neuropsychologic regression. Continuous spikes and waves during sleep comprise the severest epileptic encephalopathy in the electroclinical spectrum. Landau-Kleffner syndrome presents with intermediate severity. Some "benign" pediatric focal epileptic syndromes represent the mildest end of this continuum. Based on published data, we provide a framework for clinical and electrical events. The underlying mechanisms leading to sleep potentiation of epileptiform activity in electrical status epilepticus in sleep are incompletely understood. A genetic basis or acquired early developmental insult may disrupt the normal maturation of neuronal networks. These factors may dynamically alter normal processes of brain development, leading to an age-related pattern of electroclinical expression of electrical status epilepticus in sleep.

Clinical staging and electroencephalographic evolution of continuous spikes and waves during sleep

PURPOSE

Currently, in continuous spikes and waves during sleep (CSWS) there is a lack of systematic assessments of the clinically relevant stages and the evolution of the electroencephalographic features. The aim of this study is to describe the evolution over time of clinical and electroencephalographic features in CSWS.

METHODS

We enrolled patients from our video-electroencephalography (EEG) monitoring unit with CSWS and with overnight EEG studies with at least one overnight assessment per year over a minimum period of 3 years. We studied clinical presentation and electroencephalographic features. We calculated the (1) spike-wave percentage (SWP) as the percentage of 1-s bins containing at least one spike-wave complex and (2) spike frequency (SF) as the number of spikes per 100 s.

KEY FINDINGS

Nine children (six boys) met the inclusion criteria during a 15-year period. Seven (78%) had an abnormal development prior to the epilepsy onset, and in two (22%) seizures were the only presenting symptom. Median age at epilepsy onset was 2 years (range 2 days to 4 years), at neuropsychological regression 5.1 years (4-7.7 years), and at seizure freedom 8.6 years (6.5-11.4 years). Median duration and range of clinically relevant stages were as follows: dormant stage (birth-epilepsy onset median 2 years, range 2 days-4 years), prodromal stage (epilepsy onset-neuropsychological regression 3.9 years, range 0.9-7.7 years), acute stage (neuropsychological regression-seizure freedom 2.9 years, range 2.1-6.6 years), and residual stage (after seizure freedom). Seven patients (78%) had a structural lesion on neuroimaging. At last follow-up (median 11.4 years, range 7.2-20.3 years), eight patients (89%) were receiving antiepileptic treatment, and all patients had residual neurocognitive deficits. During the acute stage, SWP was <85% in 13 (42%) of 31 assessments, and after seizure freedom, 3 of 5 patients (60%) had SWP >85%. Evolution of electroencephalographic patterns included increasing-decreasing, continuously elevated, and fluctuating patterns (33.3% each). There was good correlation between SWP and SF (Spearman correlation-coefficient = 0.942; p < 0.0001). SF, which can exceed 100%, reflected changes in electroencephalography pattern in more detail than SWP, which cannot exceed 100% and therefore has a ceiling effect.

SIGNIFICANCE

Our series systematically studied the age of occurrence of the significant clinical events. These may assist in defining clinical stages, which can provide a useful framework for future clinical trials in patients with CSWS. The severity of the epileptiform discharges on EEG did not always correlate with seizure frequency and severity; epileptiform discharges could be prominent after seizure freedom and fluctuated along the course of the disease. The values of SWP and SF correlated well, but SWP based on 1-s bins has the potential disadvantage of a ceiling effect.