Summer 2000
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Vascular Dementia

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  Vascular Dementia


by Daniel Pendick
Copyright 2000 Memory Loss and the Brain

One of the most feared consequences of aging is dementia, a set of symptoms marked by profound memory loss and impaired thinking. Thanks to a lot of research and public education, most people are aware that dementia is not an inevitable part of growing older. In fact, it is most often the result of a specific illness, Alzheimer's disease, that strikes many-but by no means all-people in their senior years. The bottom line is that aging does not necessarily lead to "senility," unless Alzheimer's or some other disease is present.

One of those "other" diseases is vascular dementia. It is probably the second leading cause of dementia, but has been somewhat overshadowed by the more well-known Alzheimer's disease. Caused by blockages and breaches in the brain's blood supply that damage the brain, vascular dementia can be prevented and, in some cases, even reversed.



Graphic: © Grant Jerding
 
  Vascular Dementia and Alzheimer's

The cardinal sign of dementia is a decline in a person's normal intellectual functions--most notably, a decline in memory. Problems with short-term memory typically show up first. There may be general forgetfulness, or a tendency to misplace household items. But over time, the memory lapses become more severe, and the dementia begins to take a debilitating toll on thinking, judgment, communication, and emotional stability.

In people 65 or older, the most common cause of these crippling symptoms is Alzheimer's disease. But they are not the only causes. Dementia can also be a symptom, sometimes temporary, of dozens of diseases and disorders. These include poisoning, viral infections, malfunctioning glands, benign brain tumors, and severe nutritional deficiencies. About 10 percent of the time, these causes of dementia can be completely halted and reversed.

Not so in Alzheimer's disease: In lieu of a major medical breakthrough, Alzheimer's dementia cannot be prevented or cured. The drugs current prescribed for Alzheimer's temporarily alleviate, but do not reverse, some of the symptoms. Estimates of the number of people with Alzheimer's are uncertain, but most experts agree that up to 4 million people in the United States, or about 10 percent of people over the age of 65, now suffer from the illness.

It is less clear how often dementia traces to vascular problems. According to various estimates reported in the scientific literature, vascular dementia may account for one-tenth to one-third of all cases of dementia. Further complicating the situation, about one-fifth of people with Alzheimer's disease may also be suffering from vascular dementia. This is known as "mixed" dementia.

One of the few clear distinctions between vascular dementia and Alzheimer's disease concerns the way in which the major symptoms take hold. Alzheimer's is insidiously gradual. Over time, the minor forgetfulness grows more severe and disruptive, and additional symptoms begin to show up, such as disorientation and confusion over ordinary tasks such as shopping and cooking meals.

These gradual changes reflect the slow accumulation of abnormal proteins in the brain. In contrast, the symptoms of vascular dementia can worsen noticeably from one day to the next. This reflects the death of large numbers of brain cells that have been deprived on their blood supply. If Alzheimer's disease is a shallow, downward slope, vascular dementia is a staircase.

Causes of Vascular Dementia

The underlying cause of vascular dementia is an interruption of blood flow to the brain. Starved of oxygen for even a short time, brain cells perish. To understand how vascular dementia progresses, it helps to picture the mind as a vast field of brain cells fed by a complexly branching irrigation system. The main lines enter the brain at the base of the skull and split into smaller arteries, which subdivide into even smaller capillaries.

Over a lifetime, things can go wrong with the brain's irrigation system. For one thing, a weak patch on an artery wall can balloon outward, forming an aneurysm. If the aneurysm bursts, brain cells "downstream" are deprived of oxygen and perish. The cerebral arteries may also develop blockages, or blood clots. A severe blockage may affect a large region of the brain, causing symptoms such as paralysis, loss of speech, and even death.

These symptoms are the hallmarks of a stroke: an interruption of blood flow in the cerebral arteries, causing the death of brain cells. "Stroke" is an umbrella term that applies to a wide range of blockages and bleeding-whether large or small, momentary or prolonged. Stroke specialists suspect that most cases of vascular dementia trace to a series of small, short-lived blockages that affect relatively small patches of brain cells. Over time, however, the cumulative effect of many small strokes can lead to a condition known as multi-infarct dementia. The severity of multi-infarct dementia depends both on the location of the blockages and the number of them.

Preventing and Treating Vascular Dementia

The immediate cause of vascular dementia is stroke-interruptions in blood flow to the brain. So the best way to prevent vascular dementia is to lower the risk of stroke. The risk factors for stroke are well known. The single most important risk factor is high blood pressure, or hypertension. Other important risk factors for stroke are cigarette smoking, untreated diabetes, atherosclerosis ("hardening of the arteries"), and heart disease-particularly abnormal heart rhythms that can lead to the formation of blood clots. The take-home message is simple: by reducing your risk for stroke, you also reduce your risk for vascular dementia.

But even if you have already been diagnosed with vascular dementia, it is not too late to do anything about it. The most important thing is to minimize the likelihood of additional strokes that could cause the dementia to get worse. This involves use of medications and addressing the factors behind cardiovascular disease. These steps, according to some studies, may not just halt the progression of vascular dementia, but may also reduce the symptoms. This does not apply to all people all of the time; however, it does mean that vascular dementia, unlike Alzheimer's disease, does not always mean a permanent and unavoidable decline. And that may be the best news about dementia you ever hear.  


 
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