Arterial Distribution to the Brain: Basal View

VERTEBRAL ARTERIES IN THE NECK

Atherosclerosis

The origin of the vertebral arteries is the most common location for atherosclerotic disease in the vertebral system. Atheromas often begin in the subclavian arteries and spread to the proximal few centimeters of the vertebral arteries. Disease at this site is often accompanied by internal carotid artery origin occlusive lesions. Risk factors for proximal vertebral artery atherosclerosis are hypertension, smoking, coronary artery, and peripheral vascular occlusive disease.

The most frequently reported symptom during transient ischemic attacks is dizziness. In at least some attacks, dizziness is accompanied by other signs of hindbrain ischemia, such as diplopia, oscillopsia, weakness of the legs, hemiparesis, or numbness. Vertebral artery origin lesions seldom cause chronic, hemodynamically significant hypoperfusion of the vertebrobasilar system. When one vertebral artery occludes, the other takes up the slack. There are also potential collateral blood vessels that originate from the subclavian and external carotid arteries that can reconstitute the distal vertebral artery when the proximal portion occludes. The most important morbidity of vertebral artery occlusive lesions is embolism to the intracranial vertebrobasilar arterial system. In patients with cerebellar and posterior cerebral artery territory infarcts, occlusion of the vertebral arteries in the neck has led to artery-to-artery embolism.

Vertebral Artery Dissection

The most important lesion of the more distal extracranial portions of the vertebral arteries is arterial dissection. Dissections usually involve portions of arteries that are mobile and rarely occur at the origins of arteries. The extracranial vertebral arteries are anchored at their origin from the subclavian artery and during their course through bone within the intervertebral foramina (V₂ portion), and by the dura at the point of intracranial penetration. The short movable segments between these anchored regions are most vulnerable to tearing and stretching. Dissections can involve the proximal (V₁) portion of the arteries above their origins before they enter the intervertebral foramina at C5 or C6. The distal extracranial portion (V₃) is the most common location for dissection. This segment is relatively mobile and so vulnerable to tearing by sudden motion and stretching as might occur during chiropractic manipulation. Distal vertebral artery dissections may extend into the intracranial vertebral artery. The symptoms and signs are attributable to lateral medullary and cerebellar ischemia and are the same as those found in patients with intracranial vertebral artery occlusive disease. Distal extracranial vertebral artery dissections are often bilateral.

Only gold members can continue reading. Log In or Register to continue