Thursday, November 7, 2013

Vascular Dementia or Alzheimer's Disease?

Vascular Dementia vs. Alzheimer’s

Vascular dementia is the second leading form of dementia after Alzheimer's disease. Although it is estimated that 60% of all dementia cases are due to Alzheimer’s disease and 20% to vascular dementia, the more recent studies have suggested that a common type of vascular dementia, multi-infarct dementia, may actually cause Alzheimer’s disease.  At the very least, multi-infarct dementia exacerbates Alzheimer’s disease, establishing an important connection between the two diseases. 

However, many important questions still remain:

  • Do infarcts cause Alzheimer’s?
  • Does Alzheimer’s disease induce more infarcts?
  • Why does the disruption in cerebralcirculation affect cognition?  (ischemia, pressure of hemorrhage, accumulation of iron, etc.?)

The differences between Alzheimer’s disease and vascular dementia symptoms are minor and difficult to distinguish.  Typically, vascular dementia has less memory impairment and progresses in a sudden, stepwise fashion, as more strokes accumulate.  Alzheimer’s disease has a more gradual cognitive declined.  Additionally, focal symptoms and behavioral abnormalities such as mood disorders, inappropriate laughing/crying, and decision making may occur earlier in vascular dementia.

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About Vascular Dementia

Inadequate blood flow can damage and eventually kill cells anywhere in the body. The brain has one of the body's richest networks of blood vessels and is especially vulnerable.

In vascular dementia, changes in thinking skills sometimes occur suddenly following strokes that block major brain blood vessels. Thinking problems also may begin as mild changes that worsen gradually as a result of multiple minor strokes or other conditions that affect smaller blood vessels, leading to cumulative damage. A growing number of experts prefer the term "vascular cognitive impairment (VCI)" to "vascular dementia" because they feel it better expresses the concept that vascular thinking changes can range from mild to severe.

Symptoms of Vascular Dementia

Vascular dementia affects different people in different ways and the speed of the progression varies from person to person. Typically, the symptoms of vascular dementia begin suddenly, for example after a stroke. Vascular dementia often follows a 'stepped' progression, with symptoms remaining at a constant level for a time and then suddenly deteriorating. Some symptoms may be similar to those of other types of dementia, such as Alzheimer's disease. However, people with vascular dementia may particularly experience:

  • problems with speed of thinking, concentration and communication
  • depression and anxiety accompanying the dementia
  • symptoms of stroke, such as physical weakness or paralysis
  • memory problems (although this may not be the first symptom)
  • seizures
  • periods of severe (acute) confusion.

Other symptoms associated with vascular dementia may include:

  • visual mistakes and mis-perceptions (for example, seeing a rug as a pond)
  • changes in behavior (such as restlessness)
  • difficulties with walking and unsteadiness
  • hallucinations (seeing or hearing things that aren't there) and delusions (believing things that are not true)
  • problems with continence
  • psychological symptoms such as becoming more obsessive.

It is important to note that some of these symptoms may not always be direct consequences of the disease. Other factors can also play a part. For example, visual misperceptions may be the result of poor lighting or the particular way a home has been decorated, and some behavioral changes may be a consequence of care needs not being fully met.

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How does vascular dementia develop?

To be healthy and function properly, brain cells need a good supply of blood. Blood is delivered through a network of blood vessels called the vascular system. If the vascular system within the brain becomes damaged and blood cannot reach the brain cells, the cells will eventually die. This can lead to the onset of vascular dementia.

A number of conditions can cause or increase damage to the vascular system. These include high blood pressure, heart problems, high cholesterol and diabetes. This means it is important that these conditions are identified and treated at the earliest opportunity. Effective treatment of these conditions may significantly delay or stop the development of vascular dementia.

Types of vascular dementia

There are different types of vascular dementia. The difference between these types depends on what has caused the damage in the brain, and which part of the brain has been damaged.

Stroke-related dementia

A stroke occurs when the blood supply to part of the brain is cut off. This interruption in blood supply causes permanent damage to the brain. A stroke is usually the result of a burst blood vessel (known as haemorrhagic stroke) or a blood clot (known as an ischemic stroke).

The symptoms that a person experiences as a result of a stroke depend on which area of the brain has been damaged. For example, if the area affected is responsible for movement of an arm or leg, paralysis might occur. If it is responsible for speech, the person might have problems communicating. Equally, damage to particular areas in the brain can cause the symptoms of dementia.

The most common type of vascular dementia is called multi-infarct dementia, which is caused by a series of small strokes. These can be so tiny that the person might not notice any symptoms, or the symptoms may only be temporary.

Sub-cortical vascular dementia (small vessel disease or Binswanger's disease) 
Sub-cortical vascular dementia is sometimes referred to as small vessel disease. There is also a specific form of sub-cortical vascular dementia called Binswanger's disease. Sub-cortical vascular dementia is caused by damage to the tiny blood vessels that lie deep within the brain. Symptoms may include difficulties walking, clumsiness, lack of facial expression and speech difficulties. Loss of bladder control early on in the disease is also common. These symptoms, however, are not always present and may come and go. Some people may experience sub-cortical vascular dementia as well as stroke.

Mixed dementia (vascular dementia and Alzheimer's disease)

About 10 per cent of people with dementia have a type known as mixed dementia. A diagnosis of mixed dementia means that Alzheimer's disease, as well as stroke or small vessel disease, may have caused damage to the brain. The symptoms of mixed dementia may be similar to either Alzheimer's disease or vascular dementia, or may be a combination of the two.

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Risk factors

Experts suggest that the Vascular Dementia risk factors are similar to those for stroke. An evidence-based review that I carried out in 1997 confirmed this statement. Risk factors for vascular dementia were divided into 4 major classes: demographic, atherosclerotic, genetic, and stroke-related. The demographic risk factors turned out to be age, male sex, and lower educational level. The major atherosclerotic risk factors were history of hypertension, cigarette smoking, myocardial infarction, diabetes mellitus, and hyperlipidemia. The genetic factors included such familial vascular encephalopathies as cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy (CADASIL) and possibly apolipoprotein (apoE) ε4. The stroke-related factors were volume of cerebral tissue loss, evidence of bilateral cerebral infarction, strategic infarction (e.g., thalamic, angular gyrus, or subcortical frontal infarction), and white matter disease. Silent cerebral infarcts, cerebral atrophy, and ventricular size were also believed to play a role in heightening risk of VCI.

So, in other words, many of the factors that increase the risk of vascular dementia are the same as those that increase the risk of cardiovascular disease (for example, smoking) because the cardiovascular system (made up of the heart and blood vessels) is responsible for delivering blood to the brain.

Some particular factors that can increase a person's risk of developing vascular dementia include:

  • a medical history of stroke, high blood pressure, high cholesterol, diabetes (particularly type II), heart problems or sleep apnea (where breathing stops for a few seconds or minutes during sleep)
  • a lack of physical activity, drinking more than recommended levels of alcohol, smoking, eating a fatty diet, or leaving conditions such as high blood pressure or diabetes untreated
  • a family history of stroke or cardiovascular disease
  • an Indian, Bangladeshi, Pakistani or Sri Lankan ethnic background - differences in vascular risk factors (such as heart disease) in these communities may contribute to the increased risk
  • an African-Caribbean ethnic background - more research is needed to know why African-Caribbean people have an increased risk of vascular dementia.

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Because vascular cognitive impairment may often go unrecognized, many experts recommend professional screening with brief tests to assess memory, thinking and reasoning for everyone considered to be at high risk for this disorder. Individuals at highest risk include those who have had a stroke or a transient ischemic attack (TIA, also known as a "mini-stroke"). Additional high-risk groups include those with high blood pressure, high cholesterol, or other risk factors for heart or blood vessel disease.

Professional screening for depression is also recommended for high-risk groups. Depression commonly coexists with brain vascular disease and can contribute to cognitive symptoms.

If brief screening tests suggest changes in thinking or reasoning, a more detailed assessment is needed. Core elements of a workup for vascular dementia typically include:

  • A thorough medical history, including family history of dementia
  • Evaluation of independent function and daily activities
  • Input from a family member or trusted friend
  • In-office neurological examination assessing function of nerves and reflexes, movement, coordination, balance and senses
  • Laboratory tests including blood tests and brain imaging

According to a 2011 scientific statement issued by the American Heart Association (AHA) and the American Stroke Association (ASA), and endorsed by the Alzheimer's Association and the American Academy of Neurology (AAN), the following three criteria suggest the greatest likelihood that mild cognitive impairment (MCI) or dementia is caused by vascular changes:

  1. The diagnosis of dementia  or mild cognitive impairment is confirmed by neuro-cognitive testing, which involves several hours of written or computerized tests that provide detailed evaluation of specific thinking skills such as judgment, planning, problem-solving, reasoning and memory.
  2. There is brain imaging evidence, usually with magnetic resonance imaging (MRI), showing evidence of either:
* A recent stroke, or
* Other brain blood vessel changes whose severity and pattern of affected tissue are consistent with the types of impairment documented in neuro-cognitive testing
3.  There is no evidence that factors other than vascular changes are contributing to cognitive decline.

The guidelines also discuss cases where the diagnosis may be less clear-cut, such as the common situation where vascular changes coexist with brain changes associated with other types of dementia.

Sources and Additional Information:

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