Definition of Multi-infarct dementia:

Multi-infarct dementia (MID) is a form of dementia caused by a series of small strokes.

Dementia is a loss of brain function that occurs with certain diseases. It affects memory, thinking, language, judgment, and behavior.

Causes, incidence, and risk factors:

Multi-infarct dementia (MID) is the second most common cause of dementia (after Alzheimer's disease) in people over age 65. MID affects men more often than women. The disorder usually affects people between ages 55 and 75.

MID is caused by a series of small strokes.

• A stroke is an interruption in or blockage of the blood supply to any part of the brain. A stroke is sometimes called an infarct. "Multi-infarct" means that many areas in the brain have been injured due to a lack of blood.
• If blood flow is stopped for longer than a few seconds, the brain cannot get oxygen. Brain cells can die, causing permanent damage.
• When these strokes affect a small area, there may be no symptoms of a stroke. These are often called silent strokes. Over time, as more areas of the brain are damaged, the symptoms of MID begin to appear.
• Not all strokes need to be "silent." Larger strokes that have clear affects on strength, sensation, or other brain and nervous system (neurologic) function also can lead to MID.

Risk factors for MID include a history of:

• Diabetes
• Hardening of the arteries (atherosclerosis)
• High blood pressure (hypertension)
• Smoking
• Stroke

See also: Stroke risk factors and prevention

Symptoms of dementia in any one person may be caused by either Alzheimer's disease or MID. The symptoms for each problem are very similar, and MID may be a risk factor for Alzheimer's disease.