The back of the brain contains structures that are crucial for sustaining life. For instance, the brainstem controls respiration, swallowing, and the level of consciousness. Other structures of the back of the brain are the occipital lobes (the vision areas of the brain) and the cerebellum (motor coordination).
Blood flow in the posterior circulation of the brain may be disrupted by many different conditions. The most common cause is stroke caused by hardening of the arteries (atherosclerosis).
Atherosclerosis occurs when fat accummulates in a blood vessel wall, causing local inflammation (irritation and swelling). The areas of inflammation are called plaques, and they may break off and cause blood clots inside the vessel.
These clots may then travel inside the arteries and get stuck in the brain, blocking the blood supply to the area normally fed by the artery. This abrupt stopping of blood supply causes rapid malfunction and even death of the affected brain cells, which are very sensitive to lack of circulation. This is what happens when a person suffers a certain type of stroke.
VCD also may be caused by dissection, which is a tear of the artery wall. This involves bleeding through the artery wall and sometimes the release of a clot which then blocks blood flow.
Dissection can be caused by plaques, other diseases of the arteries (such as fibro-muscular dysplasia), or by trauma (such as a car accident). It may even be caused by manipulations of the neck by a chiropractor or during massage.
However, most of the time, no apparent cause of dissection can be identified. Other less common causes of vertebrobasilar vascular disorders include connective tissue diseases—for instance, lupus, and other forms of arthritis—or vasculitis.