Τhe styloid process length and the stylohyoid chain ossification affect its relationship with the carotid arteries

Purpose

The elongated styloid process (SP) is associated with internal carotid artery (ICA) dissection, due to its close relationship with the vessel. However, the relationship with the variable ossified stylohyoid chain (SHC) has been scarcely studied. The current study investigated the relationship between the temporal bone's SP and the external and internal carotid arteries (ECA and ICA). The hypothesis was that the morphological variants of the SP influence this relationship.

Methods

Sixty multidetector computed tomography angiographies (120 heminecks) were randomly selected and retrospectively analyzed. SP elongation and the degree of SHC ossification were assessed. The distances (mm) between the SP and the carotid arteries (CAs) were measured.

Results

Elongated SPs were present in 21 patients (35 %), while 18 patients (30 %) exhibited variable degrees of SHC ossification. The mean distance from the SP tip and ECA was 5.45 ± 3.01 mm from the ECA and 6.16 ± 3.11 mm to the ICA. The minimum distance between SP and ECA was 3.96 ± 2.74 mm, and between SP and ICA was 4.72 ± 2.73 mm. A statistically significant reduction in SP-ICA distance was observed in cases with elongated SP and SHC ossification, while the SP-ECA distance was statistically significantly shorter in cases of SP elongation. Additionally, three novel topographical patterns between the SP and surrounding vascular structures were identified.

Conclusions

SP elongation and variable SHC ossification may impact the spatial relationship between the SP and the ICA/ECA. The proximity of the SP to the carotid arteries, particularly the ICA, holds clinical significance, as a reduced distance may predispose patients to carotid artery dissection, increasing the risk of stroke.