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.