Stroke is the term commonly used to describe the sudden onset of a neurological deficit due to disturbances of the blood flow to the brain.
It is considered to be the third highest cause of death in most western countries, after heart disease and cancer. The incidence of stroke varies from 50-200 cases per 1,000,000 population per year. Wolf (1984) reported a doubling of the incidence of stroke in each decade of life after the age of 50. The initial 30-day mortality rate is high, and varies from 15-58% depending on the location and type of lesion. The 7-year survival rate of those that pull through the acute stage is 40%.
In the USA, there are 1.7 million stroke survivors at any given time and 75% of these are between the ages of 55 and 84 years (Grotta 1988). It has been estimated that only 10% of the stroke survivors return to work without disability, 40% have mild disability, 40% are severely disabled and 10% require institutionalization (Grotta 1988).
‘Cerebrovascular disease’ is used to mean any abnormality of the brain resulting from pathological processes of the blood vessels. Pathological processes are defined as any lesions of the vessel wall, occlusion of vessel lumen by an embolus or thrombosis, rupture of the vessel, altered permeability of the vessel wall or increased viscosity or other changes of the blood quality. Equally important are the metabolic and chemical changes that occur within the brain.
Two major types of stroke are ischemic and hemorrhagic. Most ischemic lesions (infarcts) are due to occlusion of the cerebral vessels. The brain requires 500-600 ml of oxygen per minute (25% of the total body consumption of oxygen). One litre of blood circulates through the brain every minute. If this flow is interrupted, neuron metabolism is disturbed after six seconds, brain activity ceases after two minutes, and brain damage begins after five minutes.
Brain tissue deprived of its oxygen supply undergoes necrosis or infarction (also called zone softening or encephalomalacia). The infarct may be pale if devoid of blood, or hemorrhagic if blood extravasates from small vessels in the area of infraction. The most common vascular disorder that results in stroke is atherosclerosis, a non-inflammatory degenerative disease that affects segments of almost every blood vessel in the body.
SPECT scanning has ushered in a new age of neurological investigation with patients who have developed disorders of the brain and related functions. SPECT has the ability to image the pathophysiological blood flow throughout the brain (Raynaud 1987). MRI is used to evaluate structural integrity, SPECT evaluates functional integrity.
For more about strokes, contact Johnson Medical Associates today by calling 972-479-0400.