Rapid Formation of a Large Aneurysm in a Patient with Fibromuscular Dysplasia.

Objective: The authors report the first case of intracranial fibromuscular dysplasia (FMD) presenting with rapid formation of an unruptured large vertebral artery (VA) fusiform aneurysm.

Case Presentation: A 41-year-old man presented with left hemiparesis. He had a giant thrombosed aneurysm at the basilar artery-superior cerebellar artery (BA-SCA) junction and a left extracranial VA aneurysm.