Epileptic seizures in neurofibromatosis type 1 are related to intracranial tumors but not to neurofibromatosis bright objects

Objective: To investigate the relationship between intracranial lesions and epileptic seizures in neurofibromatosis type 1 (NF1) patients.

Background: NF1 is one of the most common autosomal dominant neurocutaneous disorders, and epilepsy is more prevalent in NF1 patients than in the general population. Epileptic seizures were found to be related to various types of intracranial lesions in NF1 patients.

Methods: The clinical characteristics of NF1 (1986-2006 in Chung-Gung Memorial Hospital), diagnosed on the basis of the criteria of the National Institutes of Health Consensus Conference (1988), were reviewed by 2 neurologists. We diagnosed epileptic seizures of NF1 patients on the basis of clinical appearances and a history of antiepileptic drugs. Magnetic resonance images were also evaluated by 2 neuroradiologists to confirm the locations of brain tumors or neurofibromatosis bright objects (NBOs). The locations of NBOs were classified into 4 categories: cortex and hippocampus, subcortical white matter, basal ganglia, and infratentorial area. The association between the location of the lesions and the occurrence of seizure in NF1 patients was analyzed statistically.

Results: The medical records of 630 NF1 patients were reviewed. In this cohort, 37 (5.87%) NF1 patients had epileptic seizures. The patients include 22 males (59.5%) and 15 females (40.5%). The mean seizure onset age was 14.8 years (2 months to 72 years). The most common seizure pattern was partial onset seizures, 3 simple partial seizures, and 14 complex partial seizures. Other seizure types found include 15 primary generalized seizures (2 absence seizures and 13 generalized tonic-clonic seizures), 2 infantile spasms, and 3 unclassified. A total of 172 (23 with epilepsy and 149 without epilepsy) NF1 patients underwent MRI examinations. NBOs were identified in 16 (69.6%) epilepsy patients and in 108 (72.5%) patients without epilepsy. The location or the number of these intracranial lesions does not show significant correlation with the occurrence of epilepsy in our cohort. Among 11 NF1 patients with intracranial tumors, 4 patients had seizures (36.36%), vs. 19 out of 161 NF1 patients (11.80%) without tumors.

Conclusion: The occurrence of epileptic seizures in NF1 patients is related to intracranial tumors but not to NBOs.