Signal characteristic alterations of carotid artery dissection on high resolution magnetic resonance imaging: a follow-up study

Relationship of stylohyoid chain and cervical internal carotid artery detected by 3D angiography

OBJECTIVE

The calcification of the stylohyoid chain (SHC), elongated styloid process (SP), larger SP' angle and its shortened distance of cervical internal carotid artery (CICA) are risk factors for bony compression and the stylocarotid syndrome.

METHODS

3D-CTAs of 125 patients were analyzed in terms of the SP length, its angulations, type of the SHC and relationships of its proximity to the CICA.

RESULTS

Elongated SP was observed frequently both in females (47%) and males (55%). The mean distance of the CICA to the SP was calculated as 8.2 ± 3.3 mm. This short distance between the CICA and the SP was observed more frequently in males (28.1%) and females (10.7%). The anterior and medial angulations of the SP were calculated as 71.2 ± 4.3°, and 57.3 ± 9.3°, respectively. In the present study, the SHC was determined as normal SP (54.2%), absence of the SP (1%), duplication of the SP (1%), elongated SP (26%), complete ossification of the SHC (1%), segmentation of the SHC (9%), fracture of ossification of the SHC (1.6%) and pseudo articulations of the SHC (5.6%).

CONCLUSION

3D-CTA was the most appropriate radiological investigation analyzing and measuring SHC (elongated, larger angle, shorter distances with CICA) and identifying types (duplicated, segmented, complete and fractured) resulting from pressures on the CICA. Our study also revealed the pressure on the artery not only arose from the tip of the SP but could also result from types stretching over the artery wall. In those specimens, there is a higher probability of formation of the stylocarotid syndrome due to the long-term pressure on the sympathetic chain around the CICA.

Implicating the long styloid process in cervical carotid artery dissection

INTRODUCTION

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

METHODS

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.

RESULTS

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.

CONCLUSION

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