![]() ![]() The dissection may extend superiorly, but generally stops prior to entering the the skull. Carotid dissection most commonly occurs at least 2 cm distal to the bifurcation of the common and internal carotid.Vertebral pseudoaneurysm may compress nearby spinal nerve roots, causing radicular pain.Carotid pseudoaneurysm may compress nearby nerves, causing Horner's syndrome.This may increase the outer diameter of the vessel and compress nearby structures: (iii) Pseudoaneurysm formation may occur if blood dissects into the space between the media and the intima (figure below, lower panel).Thromboembolism is the cause of most strokes (rather than occlusion of the carotid or vertebral artery itself).This may lead to a pattern of multifocal infarction involving a single vascular territory. These clots may subsequently exit into the true lumen and travel downstream, causing artery-to-artery embolic strokes. (ii) Clots may form within turbulent blood within the false lumen (e.g., above figure, panel D).Depending on collateral blood supply within the Circle of Willis, this may cause a catastrophically large ischemic stroke. Rarely, the artery may become completely occluded (e.g., above figure, panel C).This may cause a stenosis with reduced flow (e.g., above figure, panel B). A hematoma or false lumen may compress the true lumen of the artery.(i) Impaired flow through the carotid/vertebral artery:.Potential clinical consequences of dissection However, if the dissection propagates intracranially, the external elastic lamina is thinner so rupture is more likely – which may cause a subarachnoid hemorrhage. Extracranial arteries have a thick external elastic lamina, so this tends not to happen. In practice, imaging modalities aren't yet able to reliably differentiate these types of dissection – so all patients should be anticoagulated if possible. Thus, anticoagulation theoretically would be more important for patients with intimal dissection. Theoretically, dissection into the arterial wall (panel D) would pose a risk of artery-to-artery emboli, whereas an isolated mural thrombus (panel B) would pose no risk of downstream embolic stroke.Diagnosis of an intramural hematoma may be difficult, because small hematomas may have no major impact on the lumen anatomy (as visualized by angiography).(#2) An arteriole may hemorrhage within the arterial wall, creating a self-contained intramural hematoma within the arterial wall (a hematoma that doesn't communicate at all with the artery)(e.g., figure below, panel B).This creates a true lumen and a false lumen (e.g., figure below, panel D). (#1) The true lumen may dissect into the arterial wall.Arterial dissection may begin in two ways: ![]()
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