Posterior circulation ischemia

Definition

Vertebrobasilar circulatory disorders are disorders in which blood supply to the back of the brain is disrupted.

Alternative Names

Causes

The vertebrobasilar system is also called the posterior (back) circulation of the brain. There are 3 main blood vessels that provide circulation to the back of the brain -- 2 vertebral arteries and 1 basilar artery.

The back of the brain contains structures that are crucial for sustaining life. For instance, the brainstem controls breathing, 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 (movement coordination).

Blood flow in the posterior circulation of the brain may be disrupted by many different conditions. The most common cause is a stroke caused by hardening of the arteries (atherosclerosis).

Atherosclerosis occurs when fat accumulates 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 sudden 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.

Vertebrobasilar vascular disorders may also be caused by dissection

Dissection can be caused by plaques, other diseases of the arteries (such as fibromuscular 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 and vasculitis.

Symptoms

• Loss of vision, particularly affecting same part of the visual field on both eyes
• Double vision
• Vertigo (sensation of things spinning around)
• Numbness or tingling
• Nausea and vomiting
• Difficulty swallowing
• Problems with balance
• Poor coordination
• Headache
• Neck ache
• Loss of hearing
• Slurred speech

Exams and Tests

Tests will be ordered based on what the underlying cause is likely to be. These may include:

• Imaging of the brain, especially CT scans and MRI
• Imaging of the blood vessels including MRI angiography (MRA) or ultrasound
• Computed tomography angiography (CTA), another type of blood vessel imaging
• Imaging of the heart (echocardiogram)
• Conventional angiogram (x-rays of the arteries using injected dye)
• Lumbar puncture (spinal tap) -- rarely needed
• Blood tests
• Electrocardiogram (ECG) and Holter monitor (a prolonged ECG to look for abnormal heart rhythms)
• X-rays
• Transcranial Doppler (ultrasound of the blood vessels of the skull)

Occasionally, special coagulation (blood clotting) tests are requested when the diagnosis is unclear, to see if the patient has an abnormal tendency to form clots.

Treatment

Treatment can be divided into emergency treatment, and the prevention of recurrences. It is critical to seek medical attention as fast as possible. A stroke is a brain attack and this type of stroke is one in which rapid medical attention can be the difference between life and death, or between mild and severe disability.

When the patient arrives at the hospital within 3 hours after the onset of symptoms, the use of a medication called t-PA may be considered. This medication, known as a clot-buster, is given intravenously (injected into the veins), and has been shown to improve the chances of a meaningful recovery.

Unfortunately, t-PA is a potentially dangerous drug because it can cause bleeding in the brain. Since it can be hard to tell whether a stroke has been caused by a clot or by bleeding, and since giving this medication in the case of a stroke caused by bleeding could be fatal, careful evaluation must be done. Physicians must order several tests and do careful physical examinations to make sure that t-PA is the right treatment.

In some cases, physicians may deliver the clot-buster using a small catheter inserted through the skin, which is then advanced to the blocked area of the brain circulation with the aid of x-ray angiography.

This may be tried when the patient arrives too late for the 3-hour window required for the intravenous t-PA. It is unclear at this time, however, if this is better than using other treatments.

The prevention of new strokes depends on the underlying cause. It is always critically important that blood pressure, heart conditions, blood sugar, and cholesterol problems are all addressed.

When plaques have caused a stroke, blood thinners that block the function of some sticky cells of the blood (the platelets) may be used. The most important of these drugs is aspirin. Anti-coagulation drugs, such as heparin and warfarin, can also be used.

However, some other drugs of similar effectiveness are available, like clopidogrel, ticlopidine, and dipyridamole. One recent European study showed that the combination of 2 of these anti-platelet drugs (aspirin and dipyridamole) is better than either drug alone to prevent first or recurring strokes.

If a dissection is found, it may be left to disappear on its own, or it may be treated with aspirin or warfarin for 3-6 months.

If there is a significant blockage of a blood vessel, an angioplasty may open up the artery with a balloon, and a stent can be used to keep it open. However, stents are not universally available and contrarily, their placement may cause a stroke.

If blood vessel problems exist as a result of another illness (such as vasculitis), steroids or other immune-suppressing drugs may be used.

Outlook (Prognosis)

The outlook depends in part on the underlying cause. Strokes of the brainstem region are potentially life-threatening, and require urgent medical care. The most important factors in determining the outlook for recovery are age, and associated medical problems.

When patients are young and have no significant medical problems, a substantial recovery can be expected.

Recovery also depends on the area of the brain that has been affected. The prognosis is very poor when the patient is in a coma or cannot move both arms and legs.

Possible Complications

Complications of vertebrobasilar circulatory disorders are stroke and its complications. The complications of stroke include:

• Respiratory (breathing) failure (which may require use of a machine to help the patient breathe)
• Lung problems (especially lung infections)
• Heart attack
• Dehydration and swallowing problems (sometimes leading to the placement of tubes in the stomach for artificial feeding)
• Problems with movement or sensation, including paralysis and numbness
• Formation of clots in the legs

Patients may have visual loss in one eye.

Complications caused by medications or surgery may also occur.

When to Contact a Medical Professional

Call 911 or your local emergency number, or get to the emergency room if you have any symptoms that may suggest a vertebrobasilar circulatory disorder. Remember the motto of the stroke doctor -- "Time is brain."

Prevention

General prevention of strokes caused commonly by atherosclerosis includes cessation of smoking, regular exercise, blood pressure control, healthy diet, and management of diabetes. Prevention of dissection includes avoidance of neck manipulation, and prevention of trauma to the neck.