Cerebrovascular Disease 177 Figure 5-88. Vertebral artery dissection. Dissection of the cervical vertebral artery can occur spontaneously or in the setting of trauma with rotational forces [ 140 , 144–146 ]. Many cases have been associated with chiropractic or other neck manipulations, minor falls, automobile accidents, sudden head turning, or excessive coughing [ 146 ]. Spontaneous dis- sections associated with cystic medial degeneration, arteritis, fibromuscular dysplasia, Marfan syndrome, and migraine have been reported [ 146 ]. Symptoms are usually characterized by the sudden onset of severe pain in the posterior craniocervi- cal region, often radiating behind the ipsilateral ear. The onset of ischemic symptoms may be hours or weeks after the pain begins. The most common ischemic presentation is a partial or complete lateral medullary syndrome [ 147 ]. Isolated intra- cranial dissections arising in the vertebral artery between the posterior inferior cerebellar artery and the basilar artery more frequently present with subarachnoid hemorrhage from pseudoaneurysm formation, but even this is uncommon. The most common origin of vertebral dissections is at C1 and C2. The vertebral artery is most mobile and thus most susceptible to mechanical injury at this level as it leaves the transverse foramen and abruptly turns to enter the intracranial cavity. Dissections at this site are more common in women, whereas intracranial dissections are more common in men. Dissecting hemorrhage Adventitia Intima Media Figure 5-89. Cross section and longitudinal section of a ves- sel showing different types of vertebral dissections. Gener- ally, vertebral artery dissections occur between the internal elastic lamina and the media. The hematoma may occlude the lumen, creating the possibility for strokes because of low ﬂ ow or artery-to-artery mechanisms. In rare instances, the plane of the dissection lies within the media or between the media and adventitia, making pseudoaneurysm formation and subarach- noid hemorrhage more likely. Small gap defects in the internal elastic lamina have been reported. It is clear from their histo- logic appearance that gaps have been present long before the occurrence of the dissection, probably since birth. Intimal tears are of importance in spontaneous dissection, because they can form a focus at which thrombus formation can occur. The treatment of carotid or vertebral dissections remains con- troversial, accompanied by debate as to whether anticoagulation or antiplatelet therapy is best. Unfortunately, until a clinical trial is performed, the decision is left to the treating clinician’s best judg- ment. Given the high risk of thrombus formation, the practice at our institution is to anticoagulate for 3 to 6 months and then place the patient on antiplatelet therapy. Vertebral dissections that form pseudoaneurysms represent a more diffi cult problem, however, because of the high risk for subarachnoid hemorrhage.
- Fall '19
- The American, Atherosclerosis, Internal carotid artery, Arteries of the head and neck, Anterior cerebral artery, Circle of Willis