Epilepsy in neurofibromatosis type 1: Prevalence, phenotype, and genotype in adults.

Purpose: Studies have shown an increased risk of epilepsy in patients with neurofibromatosis type 1 (NF1). However, most reports focus on the pediatric population. In this study, we describe the trajectory of patients with NF1 and epilepsy beyond childhood.

Methods: Patients with NF1 ≥18 years-old consecutively seen at a multidisciplinary neurofibromatosis clinic during a four-year period were prospectively enrolled and offered routine EEG, MRI, and genetic testing. The lifelong and point prevalence of epilepsy in patients with NF1 were calculated. Demographic, genetic, radiological, and clinical features found to be statistically associated with having received a diagnosis of epilepsy were incorporated into a logistic regression model.

Results: Among 113 patients with NF1 included in this study (median age at study inclusion: 33 years), the lifelong prevalence of epilepsy was 11% (CI=6-18%) and point prevalence 7% (CI= 3-13%). Most patients (73%) were diagnosed with epilepsy before the age of 18 and achieved seizure-freedom by adulthood. At study inclusion, three-quarters of patients with a diagnosis of epilepsy had been seizure-free for more than one year and a third had resolved epilepsy. A routine EEG with epileptiform discharges had a sensitivity of 25% (CI=3-65) and specificity of 99% (CI=93-100) for identifying adult patients with NF1 and unresolved epilepsy. A history of epilepsy was associated with having a low-grade glioma (OR: 38.2; CI=2.2-674.7; p<0.01), learning disability (OR: 5.7; CI=1.0-31.5; p<0.05), and no plexiform neurofibroma (OR: 0.05; CI=0.0-0.8; p=0.04). No single mutation type was associated with the development of epilepsy.

Conclusions: In patients with NF1, although resolution of epilepsy over time was observed in many cases, the prevalence of epilepsy was higher among adults with NF1 than that reported in the general population. Epileptogenesis in NF1 likely requires the combination of multiple genetic and environmental factors and suggests involvement of a network that spreads beyond the borders of a well-defined parenchymal lesion.