Stroke

As the third major cause of death and disability in America and the leading neurological disorder for morbidity, stroke is a major public health problem. The incidence of strokes is predicted to become worse as the percentage of the aging population, which is predominantly affected, increases. Stroke (or "brain attack") is defined as an acute neurological dysfunction, usually focal in nature, which can be explained by either occlusion of a feeding artery to the brain or the rupture of such a vessel.

Ischemic strokes result from blood clots that originate from more proximal arteries to the brain such as the carotid bifurcation in the neck or even from the heart. The neurological deficits with ischemic strokes depend upon several factors—one being the size of the clot. With large clots, larger arteries with a larger area of brain to feed will be affected, leading to greater neurological impairment. Second, the specific vessel(s) is occluded. If the artery to the speech area is occluded, the patient will be unable to talk, so-called aphasia; or if the artery to the area controlling arm and leg movements is occluded, the patient will become paralyzed on the opposite side. Third is the rapidity of artery occlusion. The cause of clot or thrombus formation is most commonly due to atherosclerotic disease or hardening of the arteries, but other conditions exist that make the blood clot, such as abnormal conditions causing the blood to be very sticky, or what is termed prothrombotic states. With vessel rupture, the two most common conditions are aneurysms, which lie primarily in the subarachnoid space surrounding the brain, and intracerebal hemorrhages, which most commonly result from longstanding uncontrolled hypertension. Other conditions associated with vessel rupture include abnormal formation of arteries and veins.

Strokes, like heart attacks, are most commonly caused by atherosclerosis or hardening of the arteries. The major risk factors for atherosclerosis are high blood pressure (hypertension), smoking, diabetes mellitus, increased lipids (hypercholesterolemia and hypertriglyceridemia), stress, sedentary lifestyle, and obesity. These risk factors are mostly treatable, and therefore greater public health programs to educate the general public are generally viewed by health care practitioners as a partial solution to the problem. Risk factors for less common hereditary conditions predisposing to vascular, cardiac, and thrombotic disorders that result in strokes require preventive intervention as well, with the most common treatment being the thinning of blood (also known as "anticoagulation"). Use of DNA analytical techniques to identify as a yet unknown combination of gene defects leading to strokes as well as a large number of proteins, which also in combination can lead to strokes, an area called proteomics promise to identify stroke-risk predisposition more precisely and at an earlier age.

In addition to knowing one's stroke risk factors, individuals should be aware of stroke symptoms so that urgent workup and appropriate treatment can be instituted, possibly reversing neurological deficits. For example, use of the thrombolytic agent (clot buster) tissue plasminogen activator (tPA) has been proven to be the first statistically significant drug to reverse the effects of a thrombus or embolus causing stroke symptoms. But because this treatment must be instituted within three hours of stroke onset, this short timeframe means that the public, the emergency services, and treating physicians must develop a rapidly responding medical system that can triage and treat patients quickly. Other stroke syndromes that can benefit from therapeutic intervention include intracerebral hemorrhages (bleeding) with surgical evacuation of the clot, particularly cerebellar hemorrhages, and subarachnoid hemorrhages due to berry aneurysms with surgical or interventional ablation of the aneurysm. Embolic strokes, especially from cardiac sources, such as rhythm abnormalities, particularly atrial fibrillation, are prone to cause embolic strokes, and these can be prevented with anticoagulation.

See also: Causes of Death

Bibliography

Barnett, Henry J. M., Jay P. Mohr, Bennett Stein, and Frank M. Yatsu eds. Strokes: Pathophysiology, Diagnosis, and Management, 3rd edition. Philadelphia: W. B. Saunders, 1998.

FRANK M. YATSU