Occurrence, outcome, and prognostic factors of infantile spasms and Lennox-Gastaut syndrome

Purpose: To analyze the occurrence, outcome, and prognostic factors of infa ntile spasms (IS) and the Lennox-Gastaut syndrome (LGS) in a defined popula tion. Methods: All children treated because of IS and LGS in the Department of Pe diatrics, University of Oulu, from January 1, 1976, until December 31, 1993 , who came from the primary catchment area of the hospital were included. D etailed information concerning their individual pre-, peri-, and postnatal medical histories and medical and laboratory examinations were compiled. Results: Thirty-seven children (18 boys) had IS, and 25 (14 boys) had LGS. The occurrence of IS of 0.41/1,000 live births [95% confidence interval (CI ), 0.29-057/1,000] did not differ significantly from that of LGS, which was 0.28/1,000 live births (95% CI, 0.18-0.41/1,000). Ten (27%) of the 37 pati ents with IS evolved to LGS, which was 40% of the LGS cases. All the 10 chi ldren with both IS and LGS had symptomatic epilepsy, were mentally retarded , and had active epilepsy at the end of similar to 10 years' follow-up. Twe nty-six (87%) of the 30 symptomatic IS cases and all the 17 symptomatic LGS cases were due to either congenital or genetic etiologies. The outcome in cryptogenic IS cases was favorable; the risk for a poor neurologic and ment al outcome was extremely low; odds ratio, 0.015 (95% CI, 0.001-0.196), as i t was for therapy-resistant epilepsy; odds ratio, 0.013 (95% CI, 0.001-0.16 6). In LGS patients, cryptogenic etiology did not decrease the risk fur a p oor outcome. Conclusions: Cryptogenic etiology is associated with a very low risk for a poor outcome in IS patients, but not in LGS patients. The outcome of IS chi ldren and the relation of IS to LGS are determined by the underlying brain disease, not by the epilepsy itself.