Relationship between initial electroencephalographic characteristics and seizure outcomes in children with non-lesional West syndrome

Does the absence or presence of sleep spindles on EEG have prognostic value for cognitive outcome in children with infantile epileptic spasms syndrome? A systematic literature review

Infantile Epileptic Spasms Syndrome (IESS) is an epileptic encephalopathy in childhood that affects infants under the age of two years. When spasm series occur, prognosis for cognitive outcome is poor in the majority of cases. The encephalopathy in IESS includes delayed maturation of normal sleep phenomena in the EEG, such as sleep spindles. Children with intellectual disabilities often have abnormal sleep, and children with sleep problems have difficulties learning at school. We examined whether there is evidence of prognostic value of detection of sleep spindles in the EEG of children with IESS on their future cognitive development. A systematic literature search yielded five studies touching this question. They were evaluated by two scorers independently. The lack of normal sleep patterns including lack of sleep spindles was used as a biomarker of poor cognitive outcome. Positive (PPV) and Negative (NPV) prognostic values were calculated. A summary of all five studies indicates a PPV of 82% and an NPV of 45%. Given the small amount of data, the retrospective quality of most studies, and the differences in the outcome parameters reported, it is prudent to say that currently available data do not allow us to conclude whether spindles have a specific and independent role in the cognitive prognosis of affected children. Since sleep spindles are needed for memory consolidation and demonstrate the active role of sleep for learning and memory, the hypothesis remains that their absence in the EEG may indicate an increased risk of cognitive delay, but more supporting data are needed to reach such a firm conclusion.

Sleep architecture in neonatal and infantile onset epilepsies in the first six months of life: A scoping review

AIM

Epilepsy occurs in approximately 80 per 100,000 infants in the first year of life, ranging in severity from self-limited and likely to spontaneously resolve, to severe developmental and epileptic encephalopathies. Sleep plays a key role in early brain development and the reciprocal relationship between sleep and seizures is not yet fully understood, particularly in young children. We conducted a Scoping Review to synthesise current knowledge of sleep architecture in neonates and infants with epilepsy.

METHOD

Peer-reviewed publications from 2005 to 2022 describing sleep architecture in infants up to six months of age with unprovoked seizures were included. The analysis set was derived from EMBASE, Web of Science and PubMED using key terms "sleep, epilepsy and infant" and related descriptors. Inclusion criteria were prospectively described in a Scoping Review protocol. Sleep architecture was assessed as macro- and micro-structural elements.

RESULTS

21 publications were included in the qualitative analysis. In self-limited familial and genetic epilepsy, sleep macrostructure was generally preserved. In DEEs and in epileptic encephalopathies of genetic or structural aetiology, sleep architecture was significantly disrupted.

INTERPRETATION

Early identification of infants with epilepsy is important to ensure early and effective treatment. In the DEE spectrum, sleep architecture is significantly impacted, and abnormal sleep architecture may be associated with compromised developmental outcome. Further research is needed to identify the sequence of events in abnormal brain development, epilepsy and sleep disruption and potentially help to predict the course of epilepsy towards a self-limited epilepsy versus a DEE.

Scoring Systems for the Evaluation of Hypsarrhythmia

SUMMARY

Hypsarrhythmia is a well-recognized EEG pattern and it has been long known as a feature of one of the more severe forms of epilepsy early in life with adverse consequences if not recognized and treated promptly. Yet, it has been difficult to objectively quantify its varied manifestations and link them to the clinical severity of epilepsy, implications for treatment, or the overall seizure and developmental outcome of young patients. This is not for want of effort, for there have been several approaches to score hypsarrhythmia ever since its initial recognition as a unique EEG pattern. In this article, we review the different methods proposed to score hypsarrhythmia and highlight the challenges inherent to each one of them.

The prognostic value of sleep spindles in long-term outcome of West Syndrome

OBJECTIVE

There is a high risk for a profound developmental disorder in West Syndrome. However, a prognostic biomarker for neurodevelopmental outcome does not exist. Hypsarrhythmia disturbs normal EEG sleep patterns and hence sleep spindles, which are thought to be important for memory consolidation and learning. We postulated that the early recurrence of sleep spindles as well as an early resolution of hypsarrhythmic patterns after onset of West Syndrome lead to a favourable long-term outcome.

METHOD

448 sleep EEGs recorded during the first two years of life in 44 patients with newly diagnosed West Syndrome between 1980 and 1989 were reviewed retrospectively. Long-term outcome was assessed in 2015-2016 by the Functional Independence Measurement Score as an indicator for coping with everyday situations. EEG-data were correlated with long-term outcome by Fisher's Exact Probability Test or Kruskal-Wallis H test.

RESULTS

There were no statistically noticeable differences between time to cessation of hypsarrhythmia and long-term outcome. In a subgroup analysis of patients with cryptogenic etiology only (n = 13) recurrence of sleep spindles correlated with better long-term outcome (p = 0.038). In this subgroup 11/13 showed recurrence of sleep spindles in childhood, 10 of which had a good or intermediate outcome. Considering the whole patient cohort, recurrence of sleep spindles showed a statistically non-significant better long-term outcome.

CONCLUSION

Recurrence of sleep spindles and cessation of hypsarrhythmia cannot be used as a valid prognostic biomarker of neurodevelopmental outcome in non-cryptogenic West Syndrome.