The effect of lead time to treatment and of age of onset on developmental outcome at 4 years in infantile spasms: evidence from the United Kingdom Infantile Spasms Study

Purpose: Infantile spasms is a severe infantile seizure disorder. Several factors affect developmental outcome, especially the underlying etiology of the spasms. Treatment also affects outcome. Both age at onset of spasms and lead time to treatment (the time from onset of spasms to start of treatment) may be important. We investigated these factors. Methods: Developmental assessment using Vineland Adaptive Behaviour Scales (VABS) at 4 years of age in infants enrolled in the United Kingdom Infantile Spasms Study. Date of or age at onset of spasms was obtained prospectively. Lead time to treatment was then categorized into five categories. The effects of lead time to treatment, age of onset of spasms, etiology, and treatment on developmental outcome were investigated using multiple linear regression. Key Findings: Age of onset ranged (77 infants) from <1 to 10 months (mean 5.2, standard deviation 2.1). Lead time to treatment was 7 days or less in 11, 8–14 days in 16, 15 days to 1 month in 8, 1–2 months in 15, >2 months in 21 and not known in 6. Each month of reduction in age at onset of spasms was associated with a 3.1 [95% confidence interval (CI) 0.64–5.5, p = 0.03] decrease, and each increase in category of lead time duration associated with a 3.9 (95% CI 7.3–0.4, p = 0.014) decrease in VABS, respectively. There was a significant interaction between treatment allocation and etiology with the benefit in VABS in those allocated steroid therapy being in children with no identified etiology (coefficient 29.9, p = 0.004). Significance: Both prompt diagnosis and prompt treatment of infantile spasms may help prevent subsequent developmental delay. Younger infants may be more at risk from the epileptic encephalopathy than older infants.