Clinical
Presentation: Patient is a
37-year-old male status post-blunt trauma injury to chest. A 1600 pound load of paper fell onto patient's chest from height of six feet.
Imaging Findings: There is narrowing of the right internal carotid artery just past the carotid bifurcation with a beaded appearance. The left internal carotid artery also demonstrates some narrowing after the carotid bifurcation with a beaded appearance.
Figure 1.
Figure 2.
Figure 3.
Figures 1-3: Multiple 3D TOF MIP images demonstrate narrowing of the right ICA distal to the carotid bifurcation with classic string of beads appearance. There is also narrowing of the left ICA with some beading, although not as extensive as the right side.
Diagnosis: Fibromuscular dysplasia
Discussion:Fibromuscular dysplasia (FMD) is an arterial disease of unknown etiology typically affecting the medium and large arteries of young to middle-aged women. FMD is an arterial disease which usually affects the renal arteries (85% of patients). The second most common location that FMD occurs is the internal carotid artery. More than half of the time there is bilateral involvement. FMD affecting the ICA can present as cerebral ischemia, TIA, and thromboembolic stroke. FMD has also been associated with intracranial aneurysms in as many as 30% of patients and spontaneous carotid artery dissection in 10-20%.
There are 3 distinct types of FMD: 1) intimal, 2) medial, and 3) subadventitial. The medial type of FMD is the most common and gives the classic "string of beads" appearance. This appearance can be explained by the presence of luminal stenosis with alternating areas of aneurysmal dilatation.
FMD is more common in females with typically age of onset at 25-50 years.
Angiography is the gold standard for diagnosing FMD. The string of beads appearance is considered pathognomonic for medial fibroplasia on diagnostic angiography. CT angiography (CTA) and MR angiography (MRA) also may identify the pathognomonic string of beads appearance of the internal carotid artery. However, current resolution (voxel sizes) of MRA and CT may limit diagnostic ability for subtle cases. In addition, signal and noise artifacts or reconstruction artifacts in CTA and MRA occasionally can mimic the contour irregularity of FMD.
The principal risk of FMD, as with any occlusive disorder affecting the cervicocerebral arterial circulation, is thromboembolism. Many patients with FMD may be asymptomatic. Surgical treatment or percutaneous transluminal balloon angioplasty is indicated only in those patients with symptomatic carotid arterial disease. FMD, when it produces minimally stenotic lesions, even those affecting a long segment of vessel, can be managed conservatively using antiplatelet and/or anticoagulant therapy.
