Etiology of Infantile Epileptic Spasms Syndrome and Clinical Response With Vigabatrin as the First Treatment

Etiology is an important predictor for treatment outcomes of infantile epileptic spasms syndrome (IESS). In Thailand, vigabatrin (VGB) is the first-line treatment for all patients due to the unavailability of adrenocorticotropic hormone. We aimed to determine the etiology of IESS using the 2017 International League Against Epilepsy classification and evaluate the clinical response of VGB as a first-line treatment.

A retrospective cohort study was conducted on IESS-diagnosed patients between January 2013 and December 2022. Etiology was categorized per the 2017 International League Against Epilepsy classification. Clinical outcomes were assessed at days 14-42 and one year after treatment.

We included 191 IESS patients (57.6% males). Etiology was identified in 75.4% (structural 61.2%: 48.1% with nontuberous sclerosis complex [non-TSC] and 13.1% with TSC; genetic, 6.3%; infectious, 6.3%; and metabolic, 1.6%). Among the 163 patients who received VGB as first-line treatment, 50 (30.7%) achieved clinical cessation of epileptic spasms at days 14-42, and 44 patients (27.0%) had sustained freedom of epileptic spasms at one year. Patients with TSC etiology were more likely to achieve cessation of epileptic spasms at day 14-42 after treatment (adjusted OR 3.548, 95% confidence interval 1.193, 10.550, P = 0.023). Definite developmental delay at spasm diagnosis decreased the odds of sustained clinical freedom from epileptic spasms at one year (adjusted OR 0.26, 95% confidence interval 0.09, 0.74, P = 0.012).

The etiology of IESS was identified in 75%. VGB was most effective as first-line, short-term treatment in TSC patients, and one-year treatment in children with normal development at diagnosis of IESS.