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.
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.
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.
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.
Diagnosis
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:
- 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.
- 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:
http://stroke.ahajournals.org/content/35/11_suppl_1/2620.full
