Abstracts

Rationale: The prognosis is unclear for children with non-syndromic focal epilepsy with no known cause ("cryptogenic") even if intelligence and neurological function are normal. We compared the outcome of this group to otherwise normal children with focal epilepsy and cause known ("symptomatic"). Methods: Cases were selected from the population-based Nova Scotia Childhood Epilepsy cohort. All had epilepsy onset between1977-85 at age 1 month - 16 years and were followed up for a minimum of 10 years in 2009-2012. Inclusion criteria were normal intelligence and neurological examination and only focal seizures ± secondary generalization throughout their entire clinical course. "Benign" childhood epilepsy syndromes were excluded. Patients were divided into 2 groups. 1. Cause unknown with no recognized etiology identified from history, physical examination, neuroimaging and other investigations. 2. Cause known with a recognized cause identified any time during the clinical course. Statistical significance was p< 0.05. Results: Of 692 children in the cohort, entry criteria were met by 117 with focal epilepsy cause unknown (17% of all epilepsy) and 52 with cause known (7.5%). The two groups did not differ significantly for average age of onset (overall 7.2±4.6 yrs), length of follow up (27.8±5.2 yrs) and final age (34.9±12 yrs). There was no difference in the proportion with complex partial seizures, focal seizures with secondary generalization, numbers of seizures throughout follow up and febrile status epilepticus. Those with unknown cause were seizure free for a significantly longer mean time (20 vs 14 years) and significantly less likely to have markers of severe epilepsy - continuing AED treatment at the end of follow up (25% vs 40%), unprovoked status epilepticus (16% vs 30%), use of >2 AEDs (28% vs 65%), intractability (10% vs 21%), or epilepsy surgery (3% vs 17%). Educational success did not differ between groups but measures of social outcome favored those with cause unknown: married or living common law (67% vs 42%), having close friends (93% vs 83%) and employed (84% vs 54%). All patients with intractable epilepsy were then removed from both groups leaving 105 with unknown cause and 42 with cause known. The differences between groups were less striking. Patients with unknown cause now had significantly fewer secondary generalized seizures (>100 in 10% vs 24%), were still less likely to use >2 AEDs (20% vs 36%) and still had a longer mean time seizure free (22 vs 18 yrs). Socially the unknown group still had significantly higher rates of employment (85% vs 52%) and a greater chance of living with a spouse (67% vs 45%) and not with parents or sibs (11% vs 26%). Conclusions: About 75% of normal children with non-syndromic, focal epilepsy and no known cause have a favorable seizure and social outcome, significantly better than those with a known cause. Much (but not all) of this difference is related to the reduced chance of developing intractable epilepsy compared to those with a known cause.