Abstracts

RATIONALE: We often assume that the early course of a seizure disorder determines its long-term outcome. To test this, we studied the latency time (LT) between the initial onset of epilepsy and the appearance of intractable epilepsy (failure of 2nd drug) and examined factors associated with LT.
METHODS: As part of a multicenter study, patients with refractory partial epilepsy were evaluated for surgery. Historical information was obtained through interview and medical chart review. Onset of epilepsy was the occurrence of the first unprovoked seizure. Febrile seizures (FS) were defined as occurring before the onset of epilepsy (Epilepsia 1993;34:592-6). Information from the first 229 enrollees with complete data was analyzed.
RESULTS: Average LT=9.3yrs, median 6, range 0-53, inter-quartile range 1-14. The second drug was failed within two years in 31.5%. LT was longer in association with age at onset [lt]5 vs [gt]5 years (14.5 vs 7.8 p=0.001); history of FS (12.0 vs 8.3, p=0.02); hippocampal atrophy (HA) (10.9 vs 6.9, p=0.002). Onset [lt]5 years, HA and FS were strongly inter-correlated. In a multiple linear regression model, only age [lt]5 years was significantly associated with LT (p=0.0007). The bivariate associations for HA and FS were due to their associations with onset age [lt]5 years although an independent association with HA was not ruled. Detailed information about the early course of the seizure disorder, particularly occurrence of previous remission, was not available; however information about ever having had a driver[ssquote]s license was. This was used as a surrogate measure for remission earlier in the course of the disorder in those with onset [lt]16 years. Of the 140 individuals with onset [lt]16 years, 67 (48%) had held licenses. LT was significantly longer in those who did vs. did not have a license (13.8 vs 8.6 yr p=0.008) suggesting that this, at least in part, identified individuals with onset [lt]16 years who had experienced a period of good seizure control before becoming intractable.
CONCLUSIONS: These results suggest that a substantial proportion of intractability may not become evident until years after initial diagnosis, especially in those with early onset, the same group who have FS and HA. That 48% of individuals with onset [lt]16 years held a driver[ssquote]s license suggests some had well-controlled epilepsy before becoming intractable. If true, and if we can understand the mechanisms behind epilepsy becoming intractable after a quiescent period, this could open avenues for exploring neuro-protective measures to prevent some intractable epilepsy.
Support: NIH-NINDS RO1 NS 32375.