Vertebral Artery Dissection with a Normal-Appearing Lumen at Multisection CT Angiography: The Importance of Identifying Wall Hematoma

BACKGROUND AND PURPOSE: CT angiography (CTA) is widely used and may be the only vascular imaging technique ordered for emergent evaluation of neurovascular disease. With thin-section multisection CTA, the resolution of vessel wall imaging has improved. We describe cases of acute vertebral artery dissection (VAD) in which the only abnormality on CTA was a characteristic thickening of the wall of the V3 portion of the vertebral artery (VA). The arterial lumen at the dissection site was normal in caliber. This type of dissection is easily overlooked if only lumen-opacifying studies such as contrast MR angiography (MRA) or conventional angiography are performed. We highlight the importance of recognizing this finding, the "suboccipital rind" sign, in the V3 portion, a segment commonly affected in VAD. The purpose of our study was to review the CTA imaging characteristics of patients with VAD in the V3 portion compared with normal controls. MATERIALS AND METHODS: Our imaging data base was reviewed for cases of acute VAD and the presence of a "suboccipital rind" sign. A control group of 50 patients was randomly recruited from a group of patients undergoing CTA. The VA luminal diameter, the wall thickness (total diameter-luminal diameter), and the ratio of luminal diameter/total diameter were measured along 5 adjacent V3 segments and were compared between the 2 groups. RESULTS: There was no evidence of luminal tapering or narrowing in the dissected VAs compared with controls (P = .1). The average wall thickness of the dissection group was 2.96 mm greater than that for the control group (P < .001; 95% confidence interval, 2.6-3.3). There was a significant difference in the ratio of lumen diameter/lumen+wall diameter in dissected segments compared with controls (P < .001). CONCLUSIONS: Cross-sectional vascular imaging is often performed with multisection helical CTA for a variety of concerns, some without neurologic symptoms. Our study confirms that in cases of the "suboccipital rind" sign, the lumen appears normal in caliber, with wall thickening as the only imaging sign of VAD. In our center, this clinically occult VAD would influence management, with patients usually treated with antiplatelet agents. We caution against using only luminal-opacifying techniques such as contrast-enhanced MRA or conventional angiography to exclude VAD because they are limited in the evaluation of mural hematoma.