Implicating the long styloid process in cervical carotid artery dissection

To look for the presence and strength of association of cervical carotid artery dissection (CCAD) with a long styloid process.

This case-control analysis included 35 patients with 37 affected carotid arteries. CT angiograms of these patients were analyzed by two raters blinded to clinical and radiological diagnosis. Parameters assessed were styloid process length, its proximity to the cervical internal carotid artery, and its medial and anterior angulations. The same parameters were assessed in 70 CT angiograms in age and sex matched controls.

Interrater correlations were 0.87, 0.40, 0.71, and 0.79 for styloid process length, contact distance, medial angulation, and anterior angulation, respectively. The mean styloid process length on the affected side was significantly more than on the contralateral side (37.8 vs. 34.6 mm, p = 0.006). There were also significant length and contact distance differences between the styloid processes ipsilateral to dissection and ipsilateral styloid processes of controls (38.9 vs. 36.2 mm, p = 0.05 and 3.1 vs. 5.0 mm, p = 0.05, respectively). There were increasing odds ratios (OR) for dissection with increasing styloid process length, with OR of 4.36 (95% CI = 1.04 to 18.4, p = 0.04) for length more than 50 mm. ORs for dissection increased with decreasing contact distance, with OR for distances less than 5 mm being 7.58 (95% CI = 0.93 to 62.1, p = 0.06). There was no significant association of CCAD with angulation of the styloid process.

Length and contact distance of the styloid process are risk factors for CCAD, suggesting mechanical impingement.