Characteristics and long-term outcomes of children with confirmed focal cortical dysplasia type 1 after epilepsy surgery: A population-based study.

objectiveFocal cortical dysplasia type 1 (FCD1) is a rare and heterogeneous cause of drug-resistant epilepsy (DRE) in children. Its clinical characteristics remain poorly understood, and surgical outcomes may be less favorable than in FCD2. We conducted a population-based study to characterize the clinical presentation and long-term seizure and cognitive outcomes of pediatric patients undergoing epilepsy surgery for isolated FCD1.

methodsWe retrospectively reviewed all children ≤18 years who underwent resective epilepsy surgery at Helsinki University Hospital between 1994 and 2022. Thirty-eight patients with histopathologically confirmed isolated FCD1 and no clinical or EEG features suggesting FCD2 were included. Clinical features, presurgical evaluations, surgical variables, postoperative outcomes, and cognitive trajectories were systematically extracted. Cognitive outcomes were assessed using a trajectory-based approach at 2 years after surgery (or 2 years post-reoperation).

resultsThe median age at epilepsy onset was 1.5 years, and 63% presented with recently accelerated cognitive decline. Two years after surgery, 34% achieved Engel class 1. At a median long-term follow-up of 8.4 years, Engel class 1 remained stable at 32%. Residual MRI-visible lesion following surgery strongly predicted seizure recurrence. Frontal resections were most common (42%). Surgery diminished the recently accelerated cognitive decline in 46% of affected patients, with either stabilization or improvement in their cognitive trajectory at 2 year follow-up. Two patients required life-saving palliative procedures due to super-refractory epilepsy. SIGNIFICANCE: In this nationwide cohort, isolated FCD1 frequently presented with early-onset DRE and preoperative accelerated cognitive decline. Although complete seizure freedom was achieved in a minority, over half of the patients experienced worthwhile improvement in seizure outcomes, along with stabilization or enhancement of cognitive trajectory. As FCD1 can cause life-threatening epilepsy and contribute to cognitive regression, epilepsy surgery should be actively considered for children with FCD1-related drug-resistant epilepsy. PLAIN LANGUAGE SUMMARY: Focal cortical dysplasia type 1 is a rare brain abnormality that can cause severe epilepsy in children that does not respond to medication. In this nationwide study of 38 children who underwent brain surgery for this condition, about one-third became seizure-free, and over half experienced meaningful improvement. Nearly two-thirds of patients showed worsening thinking and learning abilities before surgery, and surgery helped slow or stop this decline in almost half of them. These findings suggest that brain surgery should be considered for children with this difficult-to-treat condition.