Association of styloid process length with cervical carotid artery dissection: Meta-analysis

This meta-analysis was conducted to investigate the association of elongated styloid process (Eagle syndrome) and cervical artery dissection (CeAD), particularly carotid. Medline, PubMed Central, CINAHL and ProQuest were searched for case-control studies investigating the association of styloid process length (SPL) and CeAD, particularly carotid. SPL was treated as a continuous variable and mean difference was calculated from means and standard deviations with 95 % confidence interval (CI). SPL >30 mm was compared between cases and controls as a dichotomous variable and odds ratio (OR) was calculated with 95 % CI. Heterogeneity was quantified with χ2-based Cochran's Q-test and I²-statistic. Four studies were included comparing 185 dissection cases with 278 controls. Heterogeneity was 50 %, but was reduced to 0 % with sensitivity analysis. Styloid process was significantly longer in dissection group with a mean difference of 2.50 [-0.35, 5.35], P = 0.09. Elimination of one study with high risk of bias resulted in a mean difference of 3.61 [1.47, 5.75], P = 0.0009, and a heterogeneity of 0 %. Two studies showed SPL >30 mm to be more significant in dissection group (OR = 1.53 [0.84,2.80], P = 0.17). With sensitivity analysis the pooled OR was 2.09 [1.04, 4.19], P = 0.04. Three studies showed that mean SPL was significantly longer ipsilateral compared to contralateral side of dissection (mean difference 2.63 [0.46, 4.79], P = 0.02. This meta-analysis suggests that CeAD is significantly associated with styloid process mean length and SPL >30 mm. Case-control studies with bigger numbers are required to substantiate this association.