Lack of evidence for an association between neurofibromatosis type I and intracranial aneurysms: autopsy study and review of the literature.

Neurofibromatosis type I (NF1) is an autosomal dominant, hereditary, neurocutaneous syndrome purported to be associated with intracranial aneurysms. To study the relationship between NF1 and intracranial aneurysms, we have analyzed all intracranial autopsies of NF1 patients performed at our institution from 1889 to 1999 and analyzed all intracranial aneurysm cases at our institution from 1990 to 1999 in an attempt to identify patients with NF1. In addition, we have reviewed published clinical series of NF1 patients. The autopsy database at our institution, which contains 50 000 cases from 1889 to 1999, was searched to identify NF1 patients, and the results of these autopsies were reviewed. The prevalence of intracranial aneurysms in these NF1 patients was compared with the prevalence of intracranial aneurysms in our hospital's autopsy population and with the published prevalence of intracranial aneurysms in the general population. To identify patients with intracranial aneurysms and NF1, our institution's intracranial aneurysm database was searched for patients with clinical manifestations of NF1. Published clinical series of NF1 patients were identified through searches of the literature. None of the 25 autopsy patients with NF1 had an intracranial aneurysm. None of the 925 patients treated for intracranial aneurysms were affected by NF1. A review of the literature identified 8 comprehensive clinical studies, all of which failed to document any relationship between NF1 and intracranial aneurysms. The autopsy prevalence of no NF1 patients with intracranial aneurysms out of 25 is not different from the prevalence of intracranial aneurysms in the general autopsy population. In addition, no patients treated for intracranial aneurysms at this institution had NF1. These findings are supported by the observation that an association between NF1 and intracranial aneurysms has never been identified in 8 large clinical studies of NF1 patients. We conclude that there is a lack of evidence for any association between NF1 and intracranial aneurysms.