Abstracts

Rationale: Studies of phenomenology of first febrile seizure (FS) suggest that agreement is poor for the presence of focality (1). No prior study has examined agreement for duration of seizure in minutes and none has modeled the distribution of duration. Methods: We analyzed a subset from a prospective study of children with first FS ascertained as part of the Columbia University Febrile Seizure study. This subset forms the control group for the FEBSTAT study. At identification, parents were questioned about the FS phenomenology and emergency department records were reviewed. Consensus, using these sources, was performed by three epileptologists as part of the FEBSTAT study. Agreement for FS semiology was assessed by the kappa statistic and by the intraclass correlation coefficient (ICC) for FS duration. The distribution of seizure duration was further modeled. Results: Among 142 children with first FS, seizures lasted a median of 4.0 minutes (IQR=2-8). Seizures were complex in 35.0%. Among the complex FS, 20.1% were focal, 10.6% were repeated, 15.1% were 15 minutes or longer and 7.8% met criteria for status epilepticus. Agreement on features of the febrile seizure was excellent (Table) for the comparison of each epileptologist to the final consensus. The ICC was 0.86 for seizure duration in minutes, indicating excellent agreement across reviewers. The distribution of FS duration was best fit by the sum of two exponentials [F(t)= 0.78e-t/3.0 + 0.22 e-t/21.3]. This suggests that are two distinct patient populations: one accounting for 78% of FS with mean seizure duration of 3 minutes and the other accounting for 22% of FS with mean seizure duration of 21.3 minutes.Conclusions: Agreement was excellent for focality and duration and was better than when the same epileptologists rated focality and duration in febrile status epilepticus (2). The distribution of duration of FS is remarkably similar to that reported in children with first unprovoked seizures (3). This suggests that more than one-fifth of children with febrile and afebrile seizures have a predisposition to prolonged seizures. Supported by grants NS 43209 from NINDS and by HD 36867 from NICHD. REFERENCES: 1. Berg AT, Steinschneider M, Kang H, Shinnar S. Classification of complex features of febrile seizures: Inter-rater agreement. Epilepsia 1992; 33:661-666. 2. Shinnar S, Hesdorffer DC, Nordli DR, Pellock JM, O'Dell C, Lewis DV, Frank LM, Moshe SL, Marmarou A, and FEBSTAT Study Team. Phenomenology of Prolonged Febrile Seizures: Preliminary Results of the FEBSTAT Study. Epilepsia 2006;47(Suppl 4);15. 3. Shinnar S, Berg AT, Moshe SL, Shinnar R. How long do new-onset seizures in children last? Ann Neurol 2001;49:659-664.