Abstracts

Rationale: To determine long-term seizure outcome in children who developed early-onset medically intractable epilepsy.Methods: All children with newly-diagnosed epilepsy, diagnosed while resident in Olmsted County, MN between January 1, 1980 and December 31, 2009, and who were followed for a minimum of 2 years were identified through the Rochester Epidemiology Project database. Those with early-onset, medically intractable epilepsy (defined as seizure frequency >q6 months and failing >2 antiepileptic agents for lack of efficacy within two years of initial diagnosis of epilepsy) were identified and long-term seizure outcome assessed for this group.Results: Early-onset medically intractable epilepsy was present in 84/414 (20.3%) of cases, with median follow-up of 10.6 years (range 2.0-28.2). Mode of onset was focal in 48 (57%), generalized in 26 (31%), spasms in 6 (7%), unknown in 1 (1%) and both generalized and focal in 3 (4%). Etiology was structural/metabolic in 41 (49%), genetic in 19 (23%) and unknown in 24 (29%). Neurological examination and developmental abnormalities were each found in 48%. At final follow-up, 35/84 (42%) had been seizure-free for the preceding year, and 18 (21%) of these were off antiepileptic medication. Of those with a generalized mode of onset, 16 (62%) were seizure-free. Nine of these had a defined primary generalized epilepsy syndrome, 2 had genetic mutations (1 Trisomy 21, 1 XYY), 1 had a neurotransmitter disorder, and 4 were of unknown etiology. In these patients, seizure freedom was attained with increased dose or addition of another medication in 9, after discontinuation of carbamazepine in 2, with a ketogenic diet in 1, and with no change in therapy in 4 cases. Significantly fewer cases with a focal mode of onset achieved seizure freedom (13/48 27%, p=0.004). Of those with focal mode of onset, 7 achieved seizure-freedom following epilepsy surgery, 3 with increased dose or addition of another medication, 1 with improved compliance, and 2 with no change in therapy. Three of the 6 cases of spasms achieved seizure-freedom at follow-up, 1 after epilepsy surgery, 1 with addition of another medication and one despite no change in therapy. Conclusions: Approximately one in five children with new-onset epilepsy will meet criteria for early-onset medical intractability. After long-term follow-up, 42% of these children achieve seizure-freedom. Our results suggest that long-term outcome in early-onset medically intractable patients is much more favorable if seizures have a generalized as opposed to a focal mode of onset.