Epilepsy in neurofibromatosis type 1: Diffuse cerebral dysfunction?

Neurofibromatosis type 1 (NF1) is accompanied by epileptic seizures in 4-7% of patients. We examined clinical, electrophysiological, and radiological features associated with epilepsy in our NF1 series in order to identify risk factors.

We reviewed data of 641 pediatric patients with NF1 diagnosis according to National Institutes of Health (NIH) criteria in Hacettepe University records from January 2008-August 2018. Demographic features, NF1-related clinical and imaging characteristics, age at onset of epilepsy, seizure semiology, and frequency, electroencephalogram (EEG) findings, and response to treatment were noted.

Twenty-six patients with NF1, 15 male, 11 female, had epilepsy. Age at seizure onset was 6 months to 13 years. Seizure semiology was focal with impaired awareness (n = 9, 34%), focal aware motor (n = 2, 8%), focal to bilateral tonic-clonic (n = 3, 12%), generalized tonic-clonic (n = 7, 28%), absence (n = 3, 12%), infantile spasms (n = 1), and unclassified type (n = 1). None had a history of status epilepticus. The EEG findings were normal for age in ten patients (38%). Others had focal (n = 8, 30%), generalized (n = 7, 27%), or multifocal (n = 1, 4%) discharges. On brain magnetic resonance imaging (MRI) signal intensity changes typical for NF1 (neurofibromatosis bright objects, NBOs) were the most common finding (80%), followed by normal MRI (20%). There was no relation between the localization of NBOs and discharges on EEG. Seventeen patients (65%) were seizure-free at the time of the study; 11 of them still under medication including four on multiple antiepileptic drugs. The rate of learning problems and NBO were significantly higher in patients with NF1 with epilepsy compared to those without.

Epilepsy in NF1 is associated with relatively infrequent seizures and good response to treatment. Learning disorders are markedly frequent in this group, irrespective of the severity of epilepsy. The absence of correlation between the localizations of epileptiform discharges and lesions on MRI support the role of cellular or synaptic mechanisms rather than structural causes in the pathogenesis of epilepsy.