Abstracts

Rationale: Infantile spasms is a severe infantile seizure disorder which is difficult to treat and has a high morbidity. Several factors affect developmental outcome the most important of which are the underlying aetiology of the spasms. Treatment affects outcome and both the age at onset of spasms and the time between onset of spasms and treatment, that we call lead time to treatment, have also been suggested as important. We examined this in the United Kingdom Infantile Spasms Study. Methods: Developmental follow up of infants in UKISS was performed using the Vineland Adaptive Behaviour Scales at 4 years of age. Information on date of onset or age of onset of spasms was obtained prospectively and lead-time to treatment was categorised post hoc into groups: 7 days or less; 8 - 14 days; 15 days - 1 month; 1 - 2 months, greater than 2 months or not known. No hypothesis was investigated for any specific lead time or age of onset. Results: 77 infants were assessed at 4 years. Age of onset of spasms in this group ranged from less than one month to 10 months (mean 5.2 months, standard deviation 2.1 months) and lead time to treatment was 7 days or less for 11, 8 - 14 days for 16; 15 days - 1 month for 8; 1 - 2 months for 15, greater than 2 months for 21 and not known for 6. The effects of lead-time to treatment, age of onset of spasms, aetiology and treatment on developmental outcome were investigated using multiple linear regression. Age of onset of spasms (regression coefficient 3.1, p=0.014) and lead-time to treatment (regression coefficient -3.9, p=0.03) were both significantly associated with development. There was also a significant interaction between treatment and aetiology with regards to developmental outcome (regression coefficient 29.9, p=0.004). Conclusions: In infantile spasms, later age at onset of spasms is associated with better developmental outcome suggesting that younger infants may be more susceptible to damage from the presence of an epileptic encephalopathy. Increasing lead time to treatment is associated with worse developmental progress suggesting that prompt diagnosis and treatment of infantile spasms may help prevent developmental delay.