Craniocervical artery dissection: MR imaging and MR angiographic findings

Dissection of the carotid and vertebral arteries is a not so uncommon cause of stroke and has to be considered as a differential diagnosis especially in younger patients. Therapeutic and prognostic im plications are different from those in extracranial atherosclerotic disease. Dissection results fro m hemorrhage into the vessel wall usually between the layers of the media. Digital subtraction angiography (DSA) depicts the resulting luminal comprom ise that may reveal some typical, but not specific, findings. The same is t rue for non-invasive angiographic techniques such as time-of-flight: magnet ic resonance angiography (MRA) and computed tomography angiography(CTA), wh ich have shown accurate results compared with DSA. The main advantage of th ese techniques is the direct visualization of the vessel :wall confirming t he intramural hematoma. This is achieved best with MR imaging due to the hi gh signal of blood degradation products on T1- and T2-weighted images. Ther efore, MRI in combination with MRA is presently the method of choice for in itial diagnosis and follow-up of craniocervical artery dissection (CCAD). I n some questionable cases, CTA is a non-invasive alternative that is indepe ndent of flow phenomena.