The proximity between styloid process and internal carotid artery as a possible risk factor for dissection: a case-control study.

PURPOSE: The anatomical proximity of the styloid process (SP) to the ipsilateral internal carotid artery (ICA) has been recently recognized as a possible risk factor for carotid artery dissection (CAD). We aimed to verify this hypothesis by comparing the minimum distance between SP and ICA in young adult patients (< 55 years) with and without CAD.

METHODS: Thirty-one CAD patients (cases) were compared with 41 sex-matched patients without dissection, group one of control (G1), and with 16 sex-matched patients with vertebral artery dissection (VAD), group two of control (G2). Two independent observers measured, on CT angiography images, the minimum distance on the axial plane between the SP and ICA in cases and controls. They evaluated both the intercentric and the marginal distance. Differences between groups were estimated by Student t-test.

RESULTS: SP-ICA intercentric distance ipsilateral to dissection was significantly shorter compared to that of the contralateral side of cases (p < 0.001), to those of left and right side of G1 patients (p < 0.001 for both), and to those of left and right side of G2 patients (p < 0.001 for both). SP-ICA marginal distance of cases was significantly shorter compared to those of left and right side of G1 patients (p < 0.001 for both) and to those of left and right side of G2 patients (p < 0.001 for both).

CONCLUSION: A short SP-ICA distance appears to be a risk factor for CAD as it likely induces a continuous microtraumatism of the vessel wall during normal head and neck movements.