Long-term prognosis of typical childhood absence epilepsy: remission or progression to juvenile myoclonic epilepsy.

OBJECTIVE: To determine the proportion and characteristics of children presenting with childhood absence epilepsy (CAE) who were not taking anti-epileptic drugs (AEDs) and were seizure-free over the last year of long-term follow-up.
METHODS: For case finding, centralized EEG records for the province of Nova Scotia allowed identification of all children with typical CAE diagnosed between 1977 and 1985. Follow-up was done in 1994 to 1995.
RESULTS: Of 81 children with CAE, 72 (89%) were contacted for follow-up. Mean age at seizure onset was 5.7 years (range, 1 to 14 years) and at follow-up was 20.4 years (range, 12 to 31 years). Forty-seven (65%) were in remission. Twelve others (17%) were not taking AEDs but continued to have seizures. Thirteen (18%) were taking AEDs; five were seizure-free over the last year (in four of these a trial without AEDs had previously failed). Fifteen percent of the total cohort had progressed to juvenile myoclonic epilepsy (JME). Multiple clinical and EEG factors were examined as predictors of outcome. Factors predicting no remission (p < 0.05) included cognitive difficulties at diagnosis, absence status prior to or during AED treatment, development of generalized tonic clonic or myoclonic seizures after onset of AEDs, abnormal background on initial EEG, and family history of generalized seizures in first-degree relatives.
CONCLUSIONS: Only 65% of children presenting with CAE had remission of their epilepsy. Forty-four percent of those without remission had developed JME. At the time of diagnosis, remission is difficult to predict accurately in most patients. However, development of generalized tonic-clonic seizures or myoclonic seizures during AED treatment is ominous, predicting both lack of remission of CAE and progression to JME.