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Differences in Vertebrobasilar Artery Morphology between Spontaneous Intradural Vertebral Artery Dissections with and without Subarachnoid Hemorrhage

Background: Patients with spontaneous intradural vertebral artery dissection (siVAD) developing subarachnoid hemorrhage (SAH) have been observed to have poor outcomes. Factors predisposing siVAD patients to SAH are not well known. We aimed to investigate the clinical and vertebrobasilar artery morphological characteristics associated with SAH in patients with siVAD. Methods: We reviewed 103 consecutive patients with siVAD managed at our facility between July 2003 and June 2012. We divided the patients into groups, with (n = 22) and without (n = 81) SAH, and compared clinical and vertebrobasilar artery morphological characteristics between them. The vertebral-union-basilar angle (VUBA) was defined as the most acute angle between the line of the basilar artery trunk and the line of the vertebral artery at the vertebral union on 3-dimensional magnetic resonance angiography, computed tomographic angiography, or digital subtraction angiography. ‘Steep vertebral artery’ was defined as VUBA >45°. Basilar artery bending was defined as the longest distance from the line which connected the basilar top and vertebral artery union to the greatest bending point of the basilar artery. Results: Stepwise logistic regression analysis was performed using variables that were marginally or significantly associated with SAH on univariate analysis (p < 0.10) and that were thought to be clinically important for SAH. It showed SAH patients to have significantly higher proportions of current smoking (OR: 7.7; 95% CI: 2.7–22; p = 0.0015), dissection of the dominant vertebral artery (OR: 4.9; 95% CI: 1.8–13; p = 0.043), steep vertebral artery of the dissecting side (OR: 7.2; 95% CI: 2.6–20; p = 0.0023), posterior inferior cerebellar artery involvement (OR: 4.0; 95% CI: 1.3–13; p = 0.011), basilar artery bending <3 mm (OR: 3.4; 95% CI: 1.3–9.5; p = 0.0040), and pearl-and-string sign (OR: 5.7; 95% CI: 2.0–16; p = 0.0033). Conclusions: We suggest that the clinical and vertebrobasilar artery morphological characteristics demonstrated in the present study may be related to SAH induced by siVAD. Although all patients with siVAD should be closely monitored, those with siVAD who have these characteristics should perhaps be more closely followed than those who do not have such features.