Abstract 1122‐000020: Assessing Correlation Between Styloid Length and Internal Carotid Artery Dissection in EAGLE Syndrome Patients
Authors: Shah Smit , Sen Souvik , Mascari Rachel , King Jonathan , Gambrell Aaron 
Published: December 2021

Introduction
: Eagle Syndrome (ES) also known as styloid–carotid artery syndrome is a caused by elongation of the styloid process or calcification of the stylohyoid ligament. Usually, normal stylohyoid process is 2.5 cm in length. However, it is classified as an elongated styloid process if its length is more than 2.5 cm. Carotid Artery dissection which is a significant cause of ischemic stroke in all age groups is a known rare complication of ES. Goal of our study is to assess for correlation between degree of styloid process lengthening and grades of Carotid and Vertebral Dissections in adult population.

Methods
: Retrospective database review of adult patients with known cervical dissections (traumatic and non‐traumatic) were analyzed from Level I Comprehensive Stroke Center. Patients in pediatric age group (less than age 18 years) were excluded. Deidentified patient information including patient’s age, demographics, past medical history, mechanism of injury (if applicable) prior to initial clinical presentation, initial clinical presentation, methodology for diagnosis of cervical dissection (Internal Carotid vs External Carotid vs Vertebral Arteries) along with measurements of stylohyoid ligaments and degrees of dissections bilaterally were retrieved and analyzed. Data analysis was performed by using IBM SPSS Statistics Software 28.0.

Results
: Total number of patients were 111 (N). Mean age of patients was 52.97 (±16 years). Demographic distribution: African Americans (47/111), Caucasians (62/111) and Others (2/111). Gender distribution: Males (55/111) and Females (56/111). Mechanisms of injury based on available data were as follows: Mechanical Fall (21); MVC (21) and other mechanisms (12). 43/111 patients did have a headache as compared to 68/111 who did not during initial clinical presentation. Imaging confirmation for arterial dissection was performed via MRA (6/111); CTA (98/111) and DSA (7/111). Average styloid length for patients with Eagle syndrome was 3.1 cm vs non‐Eagle group which was 2.38 cm. In Non‐Eagle Syndrome group (Styloid length <2.5 cm), average grades of arterial dissections were as follows: Left Vertebral Artery dissection‐2.1; Left Internal Carotid Artery‐2.1; Right Internal Carotid Artery‐0.40 and Right Vertebral Artery‐2.5. For Eagle Syndrome patients (Styloid length >2.5 cm), average grade of arterial dissections were as follows: Left Vertebral Artery‐2.6; Left Internal Carotid Artery‐3.38; Right Internal Carotid Artery dissection‐2.3 and Right vertebral artery dissection‐1. Based on statistical analysis (paired samples T‐test), styloid length of more than 2.5 cm was significantly correlated with left internal carotid artery dissection (p value 0.012; p<0.05***). For dissections in other arteries including Right Internal Carotid (p value 0.91), Right Vertebral (p value 0.12) and Left vertebral (p value 0.488) no statistical significance was found when both groups were compared.

Conclusions
: From our study we can conclude that in patients with EAGLE syndrome styloid length more than 2.5 cm is significantly correlated with higher risk of Left Internal Carotid Artery dissection.