Fibromuscular dysplasia and the brain. II. Current concept of the disease.

Eleven hundred cases from the literature of fibromuscular dysplasia (FMD) are reviewed including 300 cases with aortocranial lesions. The male-female ratio is 1:2, and the prevalence seems increased among Caucasians. The clinical diagnosis of FMD is made by angiography, ten years earlier in patients with hypertension (mean age 39 years) than in those with cerebrovascular symptoms (mean age 50 years). Segmental dysplastic lesions are found mainly in primary aortic branches. All age groups may be affected and follow-up studies give evidence for stationary as well as slowly progressive lesions. A multifactorial hypothesis of etiology is presented: congenital minor lesions of tunica medial might predispose to aneurysms and to an abnormal fibroproliferative response to mechanical or circulatory stimuli. The association of FMD and intracranial aneurysmal disease in females is discussed. Inheritance as a dominant trait with reduced penetrance in males is suspected. Current aspects on morphology, symptomatology and clinical management are presented.