According to World Health Organization diagnostic criteria, a stroke consists of "rapidly developing clinical signs of focal (at times global) disturbance of cerebral function, lasting more than 24 hours or leading to death with no apparent causes other than that of vascular origin." "Global" refers to patients in deep coma and those with subarachnoid hemorrhage (SAH). This definition excludes transient ischemic attacks (TLA), a condition in which signs last less than 24 hours.

Distribution and Incidence

Strokes are the most common life-threatening neurological disease and the third leading cause of death, after heart disease and cancer, in Europe and the United States. Death rates from strokes vary with age and sex; for example, in the United States, the rates for males are 11.9 per 100,000 for those aged 40 to 44, and 1,217 per 100,000 for those aged 80 to 84. For females the rates are 10.9 (aged 40 to 44) and 1,067 (aged 80 to 84). In France, in the 30- to 34-year-old group, fully times more men than women die of the disease. The differential, however, declines progressively with increasing age so that at over age 84 the sex ratio is equal. Large differences in cerebrovascular disease (CVD) mortality have been noted among races. For example, in the United States, mortality is 344 per 100,000 for nonwhites but just 124 per 100,000 for whites. Among countries differences in mortality due to stroke ranged from 70 in Switzerland to 519 per 100,000 in Japan. Within the same region, mortality from stroke is higher in Scotland than it is in England and Wales.

Decline in CVD deaths has occurred in all developed countries since 1915, and the decline has accelerated during the last two decades. The acceleration seems related to decline in incidence, because 30-day case fatality rates were unchanged over this 20-year period. Interestingly, this decrease in incidence was demonstrated in a Rochester study (Schoenberg 1978).

The incidence in Rochester, New York, in 1983 was 103 per 100,000. The 3-week mortality rate was within the range of 25 to 35 percent. But strokes are more disabling than lethal: 20 to 30 percent of survivors became permanently and severely handicapped. Moreover, recurrent strokes have been observed in 15 to 40 percent of stroke survivors.

Risk Factors

Apart from age, the most important risk factor for CVD is arterial hypertension. Control of severe and moderate, and even mild, hypertension has been shown to reduce stroke occurrence and stroke fatality. Cardiac impairment ranks third, following age and hypertensive disease. At any level of blood pressure, people with cardiac disease, occult or overt, have more than twice the risk of stroke. Other risk factors are cigarette smoking, increased total serum cholesterol, blood hemoglobin concentration, obesity, and use of oral contraceptives.

Etiology and Pathology

Strokes are a heterogeneous entity caused by cerebral infarction or, less commonly, cerebral hemorrhage. Cerebral infarction accounts for the majority of strokes (63 percent, as documented by the New York Neurological Institute, in 1983-4). When perfusion pressure falls in a cerebral artery below critical levels, brain ischemia (deficiency of blood) develops, progressing to infarction if the effect per sists long enough. In most cases, ischemia is caused by occlusion of an intracerebral artery by a thrombus or an embolus arising from extracranial artery disease or cardiac source. The main cause of ischemic strokes (40 to 56 percent of the cases) is atherosclerotic brain infarction, the result of either intracerebral artery thrombosis or embolism arising from stenosed (narrowed or restricted) or occluded extracranial arteries. Lacunar infarction (14 percent of the ischemic strokes) is a small, deep infarct in the territory of a single penetrating artery, occluded by the parietal changes caused by hypertensive disease. Cerebral embolism from a cardiac source accounts for 15 to 30 percent of ischemic strokes. The main cause is atrial fibrillation related to valvular disease or ischemic heart disease. Other causes of cerebral infarction are multiple, resulting from various arterial diseases (fibromuscular dysplasia, arterial dissections, arteritis), hemopathies, systemic diseases, or coagulation abnormalities. However in 20 percent of the cases, the cause of cerebral infarction, despite efforts to arrive at a diagnosis, remains undetermined.

Intracranial hemorrhages (ICH) account for 37 percent of strokes. The main cause of ICH is the rupture of miliary aneurysms that have developed in the walls of interior arteries because of hypertensive disease (72 to 81 percent of the ICH). Nonhypertensive causes of ICH are numerous and include substance abuse, cerebral amyloid angiopathy, intracerebral tumors, and coagulation abnormalities.

Clinical Manifestations and Classification

Clinical manifestations of strokes depend on both the nature of the lesion (ischemic or hemorrhagic) and the part of the brain involved. In the early 1960s, a classification of strokes according to their temporal profile was proposed to promote the use of common terminology in discussion of natural history and treatment programs.

The term incipient stroke (TIA) was defined as brief (less than 24 hours), intermittent and focal neurological deficits due to cerebral ischemia, with the patient normal between attacks. The term "reversible ischemic neurological deficit" (RIND) was coined for entirely reversible deficits occurring over more than 24 hours.

The term progressing stroke (stroke-in-evolution) is applied to focal cerebral deficits observed by the physician to progress in the severity of the neurological deficit over a period of hours or, occasionally, over a few days.

The term completed stroke is used when the neuro logical signs are stable and no progression has been noted for 18 to 72 hours. Major stroke is a term applied when immediate coma or massive neurological deficit occurs. In these cases, hope of recovery and of effective treatment are minimal. Minor stroke, by contrast, is a term applied to cases where the deficits relate to only a restricted area of a cerebral hemisphere, or where the symptoms experienced are of only moderate intensity. With minor strokes, diagnosis and institution of treatment should be rapidly combined to avoid further deterioration and, if possible, facilitate the regression of deficit.

These definitions contain some obvious uncertainties, particularly in categorizing a stroke during the early hours. However, they underscore the fact that the management of a stroke often depends more on its temporal profile and on the severity of the neurological deficit than on the nature of the lesion.

Jacques Poirier and Christian Derouesné

Your Heart and Nutrition

Your Heart and Nutrition

Prevention is better than a cure. Learn how to cherish your heart by taking the necessary means to keep it pumping healthily and steadily through your life.

Get My Free Ebook

Post a comment