Intractable seizures after a lengthy remission in childhood‐onset epilepsy

Summary Objectives To establish the risk of subsequent intractable epilepsy after ≥2, ≥5, and ≥10 years of remission in childhood‐onset epilepsy. Methods From the Nova Scotia childhood‐onset epilepsy population‐based cohort patients with all types of epilepsy were selected with ≥20 years follow‐up from seizure onset (incidence cases). Children with childhood absence epilepsy were excluded. The rate of subsequent intractable epilepsy was then studied for patients with ≥5 years remission on or off AED treatment and compared with the rate for those with ≥2 and ≥10 years of remission. Results Three hundred eighty‐eight eligible patients had ≥20 years follow‐up (average 27.7 ± (standard deviation) 4 years) until they were an average of 34 ± 6.5 years of age. Overall, 297 (77%) had a period of ≥5 years of seizure freedom (average 21.2 ± 8 years), with 90% of these remissions continuing to the end of follow‐up. Seizures recurred in 31 (10%) and were intractable in 7 (2%). For the 332 with a remission of ≥2 years seizure‐free, 6.9% subsequently developed intractable epilepsy (p = 0.001). For the 260 with ≥10 years remission, 0.78% subsequently developed intractable epilepsy (p = 0.25 compared with ≥5 years remission). Significance Even after ≥5 or ≥10 years of seizure freedom, childhood‐onset epilepsy may reappear and be intractable. The risk is fortunately small, but for most patients it is not possible to guarantee a permanent remission.