Published 2023-11-15

FMD classification

1. Monofocal (focal) FMD – can occur in any part of the artery;
2. Multifocal FMD, alternating areas of narrowing and widening (so-called “string of beads”) – most often occurs in the middle and distal part of the artery.

FMD is primarily a stenotic disease (with changes classified based on the angiographic image as above). 

Aneurysm, tortuosity, dissection.

It is recognized that the presence of aneurysms, dissections and excessive tortuosity of arteries may occur with a much greater frequency in affected patients. However, it should be emphasized that the mere presence of aneurysms, dissections or tortuosity in the absence of a focal or multifocal FMD lesion is not sufficient to establish the diagnosis of FMD. Aneurysm, dissection, and arterial tortuosity are not unique to FMD and have been reported in many other vascular diseases. 

The occurrence of aneurysms is a characteristic feature of fibromuscular dysplasia.

Aneurysms may occur in both focal and multifocal FMD.

The location of aneurysms may involve all arteries of the body, including intracranial, renal and visceral arteries. Aneurysms may be asymptomatic or present with distal embolism of thrombotic contents or rupture. Maintaining adequate control of hypertension and completely stopping smoking is especially important in patients with aneurysms. 

If intervention is not required, patients with an unruptured intracranial aneurysm are often recommended to undergo imaging to monitor aneurysm growth. However, the optimal frequency of follow-up visits is unknown. The risk of intracranial aneurysm rupture depends on many factors, including aneurysm-related factors (number, size, shape, and location of the aneurysm) and patient characteristics (geographic region, hypertension, history of smoking, alcohol consumption, history of previous rupture).