The word cerebrovascular is made up of two parts – "cerebro" which refers to the large part of the brain, and "vascular" which means arteries and veins. Together, the word cerebrovascular refers to blood flow in the brain. The term cerebrovascular disease includes all disorders in which an area of the brain is temporarily or permanently affected by ischemia or bleeding and one or more of the cerebral blood vessels are involved in the pathological process. Cerebrovascular disease includes stroke, carotid stenosis, vertebral stenosis and intracranial stenosis, aneurysms, and vascular malformations.
Restrictions in blood flow may occur from vessel narrowing (stenosis), clot formation (thrombosis), blockage (embolism) or blood vessel rupture (hemorrhage). Lack of sufficient blood flow (ischemia) affects brain tissue and may cause a stroke.
The heart pumps blood up to the brain through two sets of arteries, the carotid arteries and the vertebral arteries. The carotid arteries are located in the front of the neck and are what you feel when you take your pulse just under your jaw. The carotid arteries split into the external and internal arteries near the top of the neck with the external carotid arteries supplying blood to the face and the internal carotid arteries going into the skull. Inside the skull, the internal carotid arteries branch into two large arteries – the anterior cerebral and middle cerebral arteries and several smaller arteries – the ophthalmic, posterior communicating and anterior choroidal arteries. These arteries supply blood to the front two-thirds of the brain.
The vertebral arteries extend along side the spinal column and cannot be felt from the outside. The vertebral arteries join to form a single basilar artery near the brain stem, which is located near the base of the skull. The vertebrobasilar system sends many small branches into the brain stem and branches off to form the posterior cerebellar and posterior meningeal arteries, which supply the back third of the brain. The jugular and other veins carry blood out of the brain.
Because the brain relies on only two sets of major arteries for its blood supply, it is very important that these arteries are healthy. Often, the underlying cause of an ischemic stroke is carotid arteries blocked with a fatty buildup, called plaque. During a hemorrhagic stroke, an artery in or on the surface of the brain has ruptured or leaks, causing bleeding and damage in or around the brain.
Whatever the underlying condition and cause are, it is crucial that proper blood flow and oxygen be restored to the brain as soon as possible. Without oxygen and important nutrients, the affected brain cells are either damaged or die within a few minutes. Once brain cells die, they cannot regenerate, and devastating damage may occur, sometimes resulting in physical, cognitive and mental disabilities.
The majority of cerebrovascular problems can be identified through diagnostic imaging tests. These tests allow neurosurgeons to view the arteries and vessels in and around the brain and the brain tissue itself.
Cerebral angiography (also called vertebral angiogram, carotid angiogram): Arteries are not normally seen in an X-ray, so contrast dye is utilized. The patient is given a local anesthetic, the artery is punctured, usually in the leg, and a needle is inserted into the artery. A catheter (a long, narrow, flexible tube) is inserted through the needle and into the artery. It is then threaded through the main vessels of the abdomen and chest until it is properly placed in the arteries of the neck. This procedure is monitored by a fluoroscope (a special X-ray that projects the images on a TV monitor). The contrast dye is then injected into the neck area through the catheter and X-ray pictures are taken.
Carotid duplex (also called carotid ultrasound): In this procedure, ultrasound is used to help detect plaque, blood clots or other problems with blood flow in the carotid arteries. A water-soluble gel is placed on the skin where the transducer (a handheld device that directs the high-frequency sound waves to the arteries being tested) is to be placed. The gel helps transmit the sound to the skin surface. The ultrasound is turned on and images of the carotid arteries and pulse wave forms are obtained. There are no known risks and this test is noninvasive and painless.
Computed tomography (CT or CAT scan): A diagnostic image created after a computer reads x-rays. In some cases, a medication will be injected through a vein to help highlight brain structures. Bone, blood and brain tissue have very different densities and can easily be distinguished on a CT scan. A CT scan is a useful diagnostic test for hemorrhagic strokes because blood can easily be seen. However, damage from an ischemic stroke may not be revealed on a CT scan for several hours or days and the individual arteries in the brain cannot be seen. CTA (CT angiography) allows clinicians to see blood vessels of the head and neck and is increasingly being used instead of an invasive angiogram.
Doppler ultrasound: A water-soluble gel is placed on the transducer (a handheld device that directs the high-frequency sound waves to the artery or vein being tested) and the skin over the veins of the extremity being tested. There is a "swishing" sound on the Doppler if the venous system is normal. Both the superficial and deep venous systems are evaluated. There are no known risks and this test is noninvasive and painless.
Electroencephalogram (EEG): A diagnostic test using small metal discs (electrodes) placed on a person's scalp to pick up electrical impulses. These electrical signals are printed out as brain waves.
Lumbar puncture (spinal tap): An invasive diagnostic test that uses a needle to remove a sample of cerebrospinal fluid from the space surrounding the spinal cord. This test can be helpful in detecting bleeding caused by a cerebral hemorrhage.
Magnetic Resonance Imaging (MRI): A diagnostic test that produces three-dimensional images of body structures using magnetic fields and computer technology. It can clearly show various types of nerve tissue and clear pictures of the brain stem and posterior brain. An MRI of the brain can help determine whether there are signs of prior mini-strokes. This test is noninvasive, although some patients may experience claustrophobia in the imager.
Magnetic Resonance Angiogram (MRA): This is a noninvasive study which is conducted in a Magnetic Resonance Imager (MRI). The magnetic images are assembled by a computer to provide an image of the arteries in the head and neck. The MRA shows the actual blood vessels in the neck and brain and can help detect blockage and aneurysms.