Idiopathic generalised epilepsies with 3 Hz and faster spike wave discharges: a population-based study with evaluation and long-term follow-up in 71 patients.

For several years we have been following patients with intractable, childhood-onset idiopathic generalised epilepsies with > or = 3 Hz spike-wave discharges. Our need to find explanations for their intractability was the starting point for this study. We were interested in identifying characteristics, which would predict intractability; evaluating how these patients were treated and whether polytherapy was useful. We identified patients with > or = 3 Hz spike-wave discharges by reviewing EEG reports recorded between 1983 and 1992. Data were collected from medical records and through personal interviews. We identified 82 patients with tentative idiopathic generalised epilepsy. Eleven were excluded. Thirty-eight patients had childhood absence epilepsy, 18 had juvenile absence epilepsy, 13 had juvenile myoclonic epilepsy and two had eyelid myoclonia with absences: 89.5, 78, 38 and 0% of the patients in each group, respectively, had been seizure free for more than 2 years. Twenty percent of the patients had intractable seizures. All intractable patients with juvenile absence epilepsy had rhythmic, random eyelid blinking and generalised tonic-clonic seizures. A history of more than ten generalised tonic-clonic seizures was associated with intractability in juvenile myoclonic patients. Monotherapy with ethosuximide or valproate resulted in seizure control in 65% of patients. Seventeen patients (24%) were treated with polytherapy, six achieved remission. These six patients had childhood absence epilepsy and juvenile absence epilepsy. Positive outcome was found in childhood absence epilepsy and juvenile absence epilepsy. Intractable seizures were more frequent among patients with juvenile myoclonic epilepsy. None of them benefited from polytherapy with conventional anti-epileptic drugs.