Anatomical Relationship Between Carotid Artery and Hyoid Bone in Stenotic and Non-stenotic Carotids

Ischaemic stroke is attributable to thromboembolism caused by carotid atherosclerotic disease in 18-25% of patients. Guidelines for prevention of stroke (especially carotid endarterectomy) in patients with carotid atherosclerotic plaque are based on the quantification of the degree of stenosis. The hyoid bone, in proximity to the carotid artery, has been implicated in the pathophysiology of carotid artery dissection, atherosclerotic carotid disease, and compressive syndromes. In atherosclerotic carotid disease, pressure on the carotid artery induced by these bone structures has been proposed to play a possible role in plaque formation and rupture, leading to stenosis, occlusion, or artery-to-artery embolism. In a recent ultrasound study, dynamic displacement of the carotid artery with interference of the hyoid bone during swallowing, named as "flip-flop" phenomenon (FFP) has been associated with carotid artery stenosis and stenosis-related stroke. Another study based on CTA assessment observed no association between hyoid-carotid distance and plaque thickness, stenosis, or progression of thickness/stenosis. In that study, in almost two-third of the patients CTA was performed for stroke/transient ischemic attack work-up, including a vast majority of patients with absence of carotid stenosis (median degree of carotid stenosis was 7%), and plaque-related stroke was not assessed. The objective of this study is to determine the anatomic hyoid-carotid interaction (ie, hyoid-carotid distance, carotid position relative to the hyoid bone, and hyoid morphology) based on CTA and its relation to the degree of carotid stenosis and stenosis-related stroke.