Abstract:  Internal carotid artery webs (CaW) are a relatively common, but frequently overlooked etiology of cryptogenic strokes, particularly in younger patients. CaW are not related to atherosclerosis, and instead demonstrate atypical fibromuscular dysplasia on histopathology. These lesions appear as shelf-like or pyramidal-shaped projections and occur exclusively in the bulbar segment of the internal carotid artery. Despite generally producing <50% stenosis of the lumen, CaW are thrombogenic and are resistant to standard antiplatelet monotherapy, unlike atherosclerotic plaques associated with a similar degree of luminal narrowing, which are usually asymptomatic. Furthermore, the composition of CaW-associated emboli likely differs from other arterial clots and appears similar to venous clots, suggesting a different mechanism of thrombogenesis. Using a multimodal approach of 4D flow MRI and computational fluid dynamics simulations, we have shown that immediately downstream of CaW, there is increased stagnation with larger areas of the vessel wall exposed to decreased wall shear stress and increased oscillatory index. These persist throughout the cardiac cycle and likely set the stage for thrombosis and subsequent stroke. We have also demonstrated that CaW are amendable to carotid stenting, providing a less invasive treatment option to carotid endarterectomy. As the prevalence of CaW in the general US population is 1-7%, understanding the mechanism of thrombogenesis and the future and recurrent stroke risk in these patients is critical to determining appropriate, patient-centric clinical care.

Biography: Jason W. Allen, MD, PhD, FACR is the Eugene C. Klatte Professor and Chair of the Department of Radiology and Imaging Sciences at the Indiana University School of Medicine. Dr. Allen obtained his MD and PhD in Neuroscience from Georgetown University School of Medicine and completed residencies in Neurology and Diagnostic Radiology as well as a two-year Neuroradiology fellowship at New York University School of Medicine. He previously was a partner at TRA Medical Imaging in Washington as well as a prior Professor at Emory University School of Medicine where he served in several roles, including the Neuroradiology Division Director, Medical Director of the Emory Center for Systems Imaging Core (CSIC), and Director of the Laboratory for Imaging Neuroscience at Emory (LINE). His primary research interests are characterizing the alterations in advanced neuroimaging metrics in the setting of neuronal injury, including stroke, traumatic brain injury, and neurodegenerative disorders, as well as the diagnosis and prognosis of cerebrovascular disease, such as subarachnoid hemorrhage, cerebrovascular reserve, and internal carotid webs. His laboratory is funded through several federal, private foundation, and institutional grants. He is also active in national organizations, particularly the American Society of Functional Neuroradiology (ASFNR) and the American Society of Neuroradiology (ASNR).

~ BME Host: Young Kim ~

Zoom link:  https://purdue-edu.zoom.us/j/5593290378?pwd=eFBOZFlNTU50ZDA2S2gwcnpyOWIwUT09

Note: Students registered for the seminar are expected to attend in-person.