Imaging description

Vertebral artery dissections (VADs) result from intimal injury, laceration of the arterial wall, or spontaneous hemorrhage of the vasa vasorum causing a subintimal or intramural hematoma. Spontaneous dissections are presumably related to an inherent arteriopathy due to genetic factors and connective tissue disorders such as Ehlers–Danlos syndrome type IV, Marfan syndrome, and fibromuscular dysplasia. Traumatic and iatrogenic dissections are predominantly due to blunt/penetrating injuries, chiropractic manipulation, or catheter angiography.

The imaging findings of VAD are similar to carotid artery dissection (CAD, see Case 84) with characteristic MR imaging findings of wall thickening or hematoma, crescentric high signal in subacute phase, and narrowing of the flow void (Fig. 4.1). In some cases, however, the lumen many be enlarged due to development of dissecting aneurysm. MRA and CTA are both utilized in the diagnosis of VAD, although CTA may be superior in identifying subtle signs of VAD (Fig. 4.2) such as small dissection flaps and dissecting aneurysms [1]. Lum et al. have described a “suboccipital rind sign” in VADs that involve the V3 segment [2]. They argue that in some cases of V3 dissections, the only imaging abnormality is the vertebral artery wall thickening, and the lumen appears normal in caliber.