Specialty: Pediatric Neurology

Keywords: infantile spasms, vigabatrin, relapse

Background: Vigabatrin is an effective first-line treatment for infantile spasms (IS). However, relapse after initial remission remains a significant clinical challenge, with limited data on predictors to guide risk stratification and treatment optimization.

Objective: To identify clinical and treatment-related predictors of relapse in patients with IS who achieved initial remission with VGB.

Methods: We conducted a retrospective cohort study of infants diagnosed with IS at UCLA from 2004–2024 with response to VGB within 30 days and sustained remission for > 30 days. Clinical features, treatment characteristics, and outcomes were extracted from medical records. Cox proportional hazards models and Kaplan-Meier survival analyses were used to evaluate associations between relapse and candidate predictors, including time to treatment (TTT), VGB dose and duration, etiology, dual therapy, prior seizures, and developmental status. Chi-square and t-tests were used for group comparisons.

Results: Among 164 patients with initial remission on VGB, 63 (38.4%) relapsed. A multivariable Cox regression model significantly predicted relapse (p < .001). Factors associated with an increased risk of relapse included delayed TTT (HR 1.0013 per day, p < .001), history of relapse prior to VGB treatment (HR 1.87, p = .047), and presence of non-spasm seizures at IS onset (HR 1.81, p = .037). An unknown IS etiology was significantly protective against relapse (HR: 0.33, p = .018). VGB dosing showed a non-linear relationship; relapse rates were lowest in the 100–149 mg/kg/day group (31.0%) compared to lower (53.1%) and higher (42.2%) dosing groups (p = .039). Neither dual therapy nor treatment duration significantly reduced relapse rates.

Conclusions: Earlier VGB initiation, absence of prior relapse or non-spasm seizures, and unknown etiology were associated with reduced relapse risk. Intermediate VGB dosing may offer optimal protection. These findings underscore the importance of prompt treatment, risk stratification, and the need for further research into dosing VGB dosing optimization.