Fast sleep spindles as a potential prognostic marker of developmental outcome in infantile epileptic spasms syndrome

OBJECTIVE: The presence or absence of sleep spindles in patients with infantile epileptic spasms syndrome (IESS) has been proposed as a potential predictor of cognitive outcome; however, the validity of this predictor remains uncertain. This study aimed to establish the utility of sleep spindle characteristics as prognostic markers of developmental outcomes in patients with IESS. METHODS: We retrospectively analyzed 26 patients with IESS who underwent longitudinal electroencephalography (465 recordings) to assess the presence, frequency, duration, and location of spindles. Patients were divided into two groups based on their developmental outcomes. The good outcome group consisted of patients with a developmental quotient (DQ) of ≥50, whereas the poor outcome group comprised patients with a DQ of <50. We compared the clinical and spindle characteristics between these two groups. RESULTS: The good and poor outcome groups comprised 11 and 15 patients, respectively. In the univariate analysis, known etiology, developmental delay (DQ < 70) at spasm onset, and the absence of fast spindles (≥13 Hz) within 3 months after spasm onset were significantly more common in the poor outcome group than in the good outcome group. Multivariate Firth logistic regression analysis showed that only the absence of fast spindles within 3 months after spasm onset was significantly associated with poor developmental outcomes. SIGNIFICANCE: The absence of fast sleep spindles may be a valuable predictor of developmental outcomes in IESS compared with the established developmental prognostic factors reported by previous studies. Our results show the importance of the early organization of fast spindles to obtain favorable developmental outcomes in patients with IESS. PLAIN LANGUAGE SUMMARY: We studied electroencephalography during sleep in 26 children with infantile epileptic spasms syndrome (IESS) to see if certain patterns, called sleep spindles, relate to later development. Children who did not show fast sleep spindles (≥13 Hz) within 3 months after spasm onset were more likely to have poor developmental outcomes. This finding suggests that the early appearance of fast sleep spindles may be an important marker of better brain development in children with IESS.