Abstracts

Rationale: As many as 45% of patients with infantile spasms reportedly experience relapse after successful treatment. The importance of obtaining follow up EEG to confirm short-term treatment response has widely accepted, but their value of long-term prognosis including relapse is unclear. The goal of this study was to describe clinical characteristics associated with relapse, with special attention on EEG characteristics done at the time of successful treatment.   Methods: The patients with newly diagnosed infantile spasms were prospectively enrolled for observational study since July 2013 at the Children's Hospital of Pittsburgh of UPMC. All subjects had prolonged video EEG prior to the treatment with either hormonal (ACTH at 150u/m2/d or Prednisolone at 4-6mg/kg/d) or Vigabatrin 150mg/kg/d. The follow up EEG was done within 4 weeks of treatment initiation and included sufficient duration of sleep portion. Full responder was defined as individuals with spasms freedom for at least 48 hours before their follow up EEG, which demonstrated resolution of hypsarrhythmia. This follow up EEG on full responder was coded as "success EEG" and dichotomized between non-epileptiform EEG and epileptiform EEG. Non-responder for the initial treatment was switched to another agent and follow up EEG was repeated within 4 weeks. If the patient responded to the second agent, this EEG was coded as "success EEG". Relapse was defined as spasms free for at least 4 weeks after full response, followed by recurrence of spasms and EEG consistent with hypsarrhythmia.  Results: There were 61 patients enrolled in the study. 42 patients (69%) were full responder to either first or second agent and analyzed for this study. 27/42(64%) were male, 32/42 (76%) had known etiology.  Median diagnostic lag was 2 weeks (1 week-6 months). Median age at the last clinical follow up was 28 months (13 months-42 months). The initial treatment was ACTH in 27 patients ( 64%), PSL in 4 (10%) and VGB in 13(26%). The full response to the initial treatment was 86% (38/44) and hormonal agent was more effective than Vigabatrin (94%, 29/31 in hormonal vs. 69%, 9/13 in VGB. P=0.04). Relapse was seen in 9/42 patients (21%), 7 of them had known etiology. One patient, who was initially classified as unknown etiology, was found to have cortical dysplasia on repeated MRI after relapse and subsequently had resective surgery. Relapsed patients all had abnormal "success EEG"; 2 with non-epileptiform abnormalities, 7 with epileptiform activities. Relapse was associated with epileptiform activity on "success EEG" (9% in non-epileptiform EEG group vs. 37% in epileptiform EEG group, p=0.02), but not with etiology (22% in known etiology vs. 20% in unknown etiology, p=0.83) or initial treatment choice (28% in Hormonal vs. 8% in VGB, p=0.14). Relapse was successfully treated in 7/9 patients (6/8 by hormonal agents, 1/1 by VGB). Conclusions: Relapse was associated with epileptiform activity on the follow up EEG done at the time of successful treatment, but not with etiology or initial treatment choice. This finding may help identifying high risk patients for relapse.    Funding: None