Spenner B, et al. - Because hypsarrhythmia disturbs normal EEG sleep patterns and hence sleep spindles, which are thought to be important for memory consolidation and learning, researchers tested the assumption that the early recurrence of sleep spindles and an early resolution of hypsarrhythmic patterns following the onset of West Syndrome resulted in a favourable long-term outcome. Between 1980 and 1989, 448 sleep EEGs recorded during the first 2 years of life in 44 patients with newly diagnosed West Syndrome were reviewed retrospectively. Through Fisher’s Exact Probability Test or Kruskal-Wallis H test, EEG-data were correlated with long-term outcome. Between time to hypsarrhythmia cessation and long-term outcome, there were no statistically notable differences. The recurrence of sleep spindles displayed a statistically non-significant better long-term outcome, taking into account the entire patient cohort. According to findings, recurrence of sleep spindles and hypsarrhythmia cessation can not be used in non-cryptogenic West Syndrome as a valid prognostic biomarker of the neurodevelopmental outcome.