There is mild tapered stenosis at the level of the flap. Arterial dissection is a relatively common injury seen in high speed deceleration injuries, with common association of cervical spine injuries. Dissection is usually treated with anticoagulation if there is no contraindication, and the majority of dissections either remain stable or resolve. Few dissections progress to complete occlusion, and this is usually seen on the initial arteriogram.
Dissections are common just below the skull base where there is increased shear force.
Dissection may occur with relatively minor trauma, and vessel kinks may predispose to dissection.