AbstractObjectiveThis study was undertaken to evaluate our treatment algorithm for infantile epileptic spasms syndrome (IESS) used between 2000 and 2018. We initiated vigabatrin (VGB), and steroids were added if the electroclinical response (spasms and electroencephalogram [EEG]) to VGB was not obtained or incomplete.MethodsIndividuals with IESS treated with VGB were recruited from our hospital clinical data warehouse based on electronic health records (EHRs) generated since 2009 and containing relevant keywords. We confirmed the diagnosis of IESS. Clinical, EEG, imaging, and biological data were extracted from the EHRs. We analyzed factors associated with short‐term response, time to response, relapse, time to relapse of spasms, and the presence of spasms at last follow‐up.ResultsWe collected data from 198 individuals (female: 46.5%, IESS onset: 6 [4.5–10.3] months, follow‐up: 4.6 [2.5–7.6] years, median [Q1–Q3]) including 129 (65.2%) with identifiable etiology. VGB was started 17 (5–57.5) days after IESS diagnosis. A total of 113 individuals were responders (57.1% of the cohort), 64 with VGB alone and 38 with VGB further combined with steroids (56.6% and 33.6% of responders, respectively). Among responders, 33 (29%) experienced relapses of spasms, mostly those with later onset of spasms (p = .002) and those who received VGB for <24 months after spasms cessation compared to a longer duration on VGB (45% vs. 12.8%, p = .003). At follow‐up, 92 individuals were seizure‐free (46.5% of the whole cohort), including 26 free of therapy (13.1%). One hundred twelve individuals (56.6%) were still receiving VGB, with a duration of 3.2 (1.75–5.7) years.SignificanceOur sequential protocol introducing VGB then adding steroids is an effective alternative to a combined VGB–steroids approach in IESS. It avoids steroid‐related adverse events, as well as those from VGB–steroid combination. According to our data, a period of 7 days seems sufficient to assess VGB response and enables the addition of steroids rapidly if needed. Continuing VGB for 2 years may balance the risk of relapse and treatment‐induced adverse events.