Multi-infarct dementia

Definition:

A disorder involving deterioration in mental function caused by changes or damage to the brain tissues from lack of oxygen as a result of multiple blood clots throughout the brain.

Causes, incidence, and risk factors:

Multi-infarct dementia (MID) affects approximately 4 out of 10,000 people. It is estimated that 10 to 20% of all dementias are multi-infarct dementia (MID and Alzheimer's disease together account for about 30 to 60% of all dementia). MID affects both sexes but affects men more often than women. The disorder usually affects older people, over 55 years, with the onset averaging around age 65.

The disorder is associated with atherosclerosis, a condition where fatty deposits occur in the inner lining of the arteries. Atherosclerotic plaque damages the lining of an artery. Platelets clump around the area of injury (a normal part of the clotting and healing process). Cholesterol and other fats also collect at this site, forming a mass within the lining of the artery. MID is not caused directly from deposits of atherosclerotic plaque in the blood vessels of the brain, but by a series of strokes that leave areas of dead brain cells (infarction). This occurs when atherosclerotic plaques cause multiple, scattered blood clots (thrombi) that block off the small blood vessels and prevent localized areas of the brain from receiving blood flow and oxygen.

The consequences vary depending on the location and severity of the infarctions. Memory impairment is often an early symptom of the disorder, followed by judgment impairment. This often progresses in a step-by-step manner to delirium, hallucinations, and impaired thinking. Personality and mood changes accompany the deteriorating mental condition. Apathy and lack of motivation are common. Catastrophic reaction, where a person reacts to tasks by withdrawal or extreme agitation, is common. Confusion that occurs or is worsened at night is also common.

Risks include a history of MID, stroke, hypertension, smoking, and atherosclerosis. Atherosclerosis is associated with coronary heart disease, cerebrovascular disease, peripheral vascular disease, diabetes mellitus, and kidney disorders that require dialysis. Risks of atherosclerosis include obesity, hypertension, and high levels of blood lipids, including cholesterol and triglycerides.