What Is Multi-Infarct Dementia?
Multi-infarct dementia (MID) is loss of brain function caused by a series of small strokes. A stroke (also called a brain infarct) occurs when the blood flow to any part of the brain is interrupted or blocked. Blood carries oxygen to the brain, and without oxygen, brain tissue quickly dies.
The location of the stroke damage determines the type of symptoms that occur. Stroke increases the risk of dementia as much as four to twelve times. The mechanism of this is not fully understood.
MID can cause the loss of memory and cognitive function and can initiate psychological problems. Treatment focuses on controlling the symptoms and reducing the risk for future strokes.
What Causes Multi-Infarct Dementia?
According to the National Institutes of Health, MID is the second most common cause of dementia in people over age 65 (NIH, 2012). Alzheimer’s disease is the most common cause.
MID is caused by a series of small strokes. A stroke (infarct) is the interruption or blockage of blood flow to any part of the brain. “Multi-infract” means many strokes and many areas of damage. If blood flow is stopped for more than a few seconds, brain cells can die from lack of oxygen. This damage is usually permanent.
A stroke can be “silent.” That means it affects such a small area of the brain that it goes unnoticed. Over time, many silent strokes can lead to MID. Large strokes that cause noticeable physical and neurological symptoms can also lead to MID.
Risk Factors for MID
MID generally occurs in people aged 55 to 75 years and is more common in men than in women.
Medical conditions that increase the risk of MID include:
- atrial fibrillation (irregular rapid heartbeat that creates stagnation, which can lead to blood clots)
- previous stroke(s)
- heart failure
- cognitive decline prior to stroke
- high blood pressure
- atherosclerosis (hardening of the arteries)
Lifestyle risk factors include:
- alcohol abuse
- low level of education
- poor diet with little to no physical activity
Recognizing the Signs of Multi-Infarct Dementia
The symptoms of MID may appear gradually over time, or may occur suddenly after a stroke. Some patients will appear to improve then decline again after more small strokes.
The early symptoms of dementia include:
- getting lost in familiar places
- difficulty performing routine tasks, such as paying the bills
- difficulty remembering words
- misplacing things
- loss of interest in things you used to enjoy
- personality changes
As dementia progresses, more obvious symptoms appear:
- changes in sleep patterns
- difficulty with basic tasks such as dressing and preparing meals
- poor judgment
- social withdrawal
- memory loss
How Is MID Diagnosed?
Doctors diagnose MID with radiological imaging and biochemical and cognitive tests. Each case of MID is different. Memory may suffer serious impairment in one case and only mild impairment in another. To gain an understanding of the damage done, doctors will use multiple tests.
Radiological imaging tests can include:
- brain computed tomography (CT): a detailed, cross-sectional X-ray of the brain
- magnetic resonance imaging (MRI) of the brain: a detailed image of the brain obtained using a magnetic field and pulses of radio wave energy
- electroencephalogram (EEG): measures the electrical activity of the brain
- transcranial Doppler (TCD): measures the velocity of blood flow through the brain’s blood vessels
Biochemical tests look for changes in:
- superoxidase dismutatse (SOD): an enzyme that repairs cells and reduces damage from free radicals
- malondialdehyde (MDA): a marker for oxidative stress
- homocysteine (HCY): an amino acid produced as a by-product of eating meat. High levels may be associated with increased risk for atherosclerosis, heart attack, blood clots, Alzheimer’s disease, and stroke.
- testosterone (T): a steroid hormone
- 17 beta-estradiol (E2): an estrogenic hormone
Mental Function Tests
Tests of mental ability include:
- Barthel Index: assesses functional status
- Fluid Object Memory Evaluation: looks at short-term memory
- clock test: assesses your ability to recognize and set time
- cognitive (SS-IQCODE) test: the “Informant Questionnaire on Cognitive Decline in the Elderly,” which uses a close relative to obtain information on a patient’s cognitive status
Ruling Out Other Causes of Dementia
Your doctor may also order tests to rule out other conditions that may cause or contribute to dementia, such as
- brain tumor
- chronic infection
- thyroid disease
- vitamin deficiency
- drug intoxication
How Is MID Treated?
Treatment is tailored to the individual. Both medicinal and nonpharmacological treatments are used.
There are two main types of medication used for MID:
Cholinesterase inhibitors treat memory loss, confusion, and problems thinking and reasoning. These include
Noncholinesterase inhibiting medications include:
- folic acid
Other medication options include:
- selective serotonin reuptake inhibitors (SSRIs): antidepressants that may also help neurons grow and reestablish connections in the brain
- calcium channel blockers for short-term cognitive function
- ACE inhibitor anti-hypertensive therapy to lower blood pressure
Herbal supplements have grown in popularity as treatments for MID. However, not enough studies have been done to prove a significant amount of success through their use. Examples of herbal supplements that are currently being studies for use in treating MID include
- Artemisia absinthium (wormwood): used to improve cognitive function
- Melissa officinalis (lemon balm): used to restore memory
- Bacopa monnieri (water hyssop): used to improve memory and intellectual function
Be sure to discuss these supplements with your doctor before taking them, as they can interfere with other medications.
Nonpharmacological options for treatment include:
- regular exercise to build muscle strength
- cognitive training to regain mental function
- rehabilitation for mobility issues
What Is the Long-Term Outlook for MID?
MID has no cure. While medications and cognitive training may help preserve mental function, the patient will continue to decline. The speed and advance of dementia varies. Some patients die soon after an MID diagnosis, and others survive for years.
How Can MID Be Prevented?
There is no evidence of any completely effective measure to avoid MID. As with many conditions, the best prevention is to take care of your body:
- visit the doctor regularly
- eat a balanced diet
- begin or maintain a regular exercise program