BACKGROUND von Recklinghausen's neurofibromatosis is a hereditary disease that may affect any organ or system of the body primarily or secondarily, including the vascular system. Among the rare cerebrovascular abnormalities, the most common is stenosis or occlusion of the cerebral artery. Intracranial aneurysms are uncommon. CASE DESCRIPTION A case of an intracranial cerebral aneurysm associated with von Recklinghausen's neurofibromatosis is reported. A 55-year-old woman presented with a history of intermittent headache for 2 months and right oculomotor nerve palsy for 1 month. Widespread cutaneous neurofibromas and angiomas were found over her trunk and limbs with prominent cafe-au-lait spots. X-ray showed that her left lung was compressed by a large mass in the left chest with rib defects and lateral spinal curvature. Right internal carotid angiography revealed a saccular aneurysm between C1 and C2. Craniotomy to clip the aneurysm could not be performed because the mass in her chest made intubation for general anaesthesia almost impossible. CONCLUSION The clinical features of this case are discussed together with a review of 15 similar cases in the literature. There are different theories about this disorder. We agree that the malformations are derived not only from ectodermal, but also from mesodermal pathology. In terms of our case, we consider the progression of this disease to be slow. (C) 1998 by Elsevier Science Inc.