New insights from the international registry for extracranial carotid artery aneurysms. Perspectives on etiology and follow-up.

The thesis describes various aspects on how to improve healthcare for patients with aneurysmal disease of the extracranial carotid artery (ECAA). Due to the rarity of these aneurysms, the natural clinical course and risk factors for adverse outcome are unknown. Consequently evidence-based guidelines for the treatment of ECAA are non-existent. The ultimate goal of the research discussed in this thesis is to identify clinical and radiological risk factors, and with that improve individualized treatment strategies for ECAA patients in the future. Part I describes various international multi-center projects designed to provide insight in contributing factors of ECAA. The following associated features of patients at risk of aneurysm development are identified; classical vascular risk (increased age, hypertension, atherosclerosis), genetic susceptibility, many turns and loops of the affected arteries (tortuosity), presence of a tear within the vascular wall, or whether the patient harbors more than two aneurysms. Part II describes novel imaging techniques to monitor patients in the course of ECAA disease. A volumetric protocol for measuring aneurysm growth instead of conventional diameter assessment is introduced. The feasibility of ECAA wall imaging is described by use of magnetic resonance imaging with gadolinium contrast as surrogate marker for aneurysm wall instability. Finally, arterial tortuosity is quantitatively assessed by computed tomography-angiography and shown to be associated with presence of ECAA. Ideally, these clinical, genetic and radiological features can be deployed in selection of high-risk ECAA patients that possibly benefit from invasive treatment whereas follow-up imaging can be scaled back in conservatively treated low-risk patients.