After the Spasms: Long-Term Outcomes Following Pulsatile Dexamethasone Therapy for Infantile Epileptic Spasms Syndrome: A Retrospective Observational Study

INTRODUCTION: Dexamethasone pulse therapy is a novel, individualizable treatment option for infantile epileptic spasms syndrome (IESS). Whereas its safety and efficacy was demonstrated in the short term, follow-up data beyond the first months post-therapy remains limited. We present a comprehensive long-term outcome analysis of the cohort of 66 infants with IESS treated with pulsatile dexamethasone. METHODS: Clinical, demographic and electroencephalogram (EEG) data of the 66 infants included in the original publication was assessed retrospectively. Time period between last dexamethasone pulse and last follow-up until March 2026 was included. Mortality data, developmental status, seizure control and relapse characteristics, and use of pharmacologic and non-pharmacologic epilepsy treatment modalities were extracted from the medical records. RESULTS: Sixty-three infants with a 60% male prevalence, all treated with pulsatile dexamethasone for IESS, were followed up for an average of 6.3 years. Seizure relapse occurred in 54% of patients 1.7 years post-therapy on average, with 50% of relapses within 2.7 months after last dexamethasone pulse. Number of pulses and interval between them showed no association with seizure relapse timing or semiology; sustained seizure freedom was achieved among infants receiving 4-7 pulses. Structural and unknown IESS etiology was associated with highest (76%) and lowest (30%) relapse rate, respectively. Among children with structural etiologies, early seizure relapse was associated with subsequent epilepsy surgery. Developmental abnormalities affected 75% of subjects at last follow-up. Only patients with unknown IESS etiology presenting with developmental delay at diagnosis regained normal neurocognitive status. CONCLUSIONS: Pulsatile dexamethasone for IESS treatment shows long-term outcomes comparable with other corticosteroids; patients achieving seizure freedom in the examined population received 4-7 pulses. Majority of seizure relapses occur within the first year after therapy, highlighting the importance of close follow-up, and early relapse in structural IESS may warrant prompt referral for epilepsy surgery evaluation.