Styloid Process Length and Arterial Proximity in Internal Carotid Artery Dissection

Background and Purpose: Internal carotid artery dissection is a leading cause of ischemic stroke in younger patients, though many cases lack a definitive etiology for the wall injury. This study evaluated whether the length of the styloid process (SP) and its spatial proximity to the internal carotid artery (ICA) are associated with ICA dissection. Methods: We included patients with extracranial ICA dissection and control subjects without ICA dissection treated between 2005 and 2025 at a German tertiary stroke center in a propensity score matched (1:2) cohort study. SP length and minimal SP-ICA distance were measured bilaterally on CT angiography using standardized multiplanar reconstructions. Characteristics of SP were compared by etiology (spontaneous vs. traumatic). Conditional logistic regression accounting for the matched design was used to evaluate associations between SP anatomy and ICA dissection. Results: The cohort included 65 patients with ICA dissection (median age 48 years [43–55, IQR], 44.6% females, 73.8% spontaneous, 26.2% traumatic) and 130 matched controls. Patients with ICA dissection exhibited significantly longer SP (median 33.0 [29.0–39.8, IQR] mm versus 31.3 [27.2–37.2, IQR] mm; p = 0.033) and a higher SP length/neck length index (p = 0.046). No differences were found in the minimal SP-ICA distance (p = 0.206) or between traumatic and spontaneous etiologies (p = 0.989). In conditional logistic regression, SP length was not independently associated with ICA dissection (adjusted odds ratio [aOR] 1.13 per 5 mm, 95% CI 0.95–1.36), whereas a shorter minimal SP-ICA distance was (aOR 0.89 per mm, 95% CI 0.79–0.99). Conclusions: Our results indicate a modest association between SP length and ICA dissection that was not independent of SP-ICA proximity in the matched multivariable analysis. The styloid complex may contribute to a mechanical predisposition for arterial wall injury in a subset of patients. SP morphometry can be readily assessed on CT angiography; its value as an imaging marker requires prospective validation.