Neuroscience
Alzheimer’s Disease and Memory Disorders
Overview
Causes and risk factors
Types
Prevention
Symptoms
Diagnosis
Treatment
Alzheimer’s Disease Overview
Alzheimer’s disease, a form of dementia, is a
progressive brain disorder producing impairment of intellectual
function. The rate of progression is different for each person.
Alzheimer’s disease that develops rapidly is likely
to continue to progress rapidly. Conversely, if it has been
slow to progress, it will likely continue at a slow rate of
progression.
Causes, incidence, and risk factors
The cause of Alzheimer’s disease is not yet known.
However, researchers insist that the disease is not a part
of normal aging. Theories regarding the presence of aluminum,
lead, mercury and other substances in the body have been disproved.
A diagnosis of Alzheimer’s disease is made by the
detection of characteristic symptoms, and by the exclusion
of other causes of dementia. It can be confirmed by a post-mortem
microscopic examination of a sample of brain tissue.
The brain tissue of people with Alzheimer’s disease
will show a greater-than-normal incidence of such phenomena
as “neurofibrillary tangles” (twisted fragments
of protein within nerve cells that clog up the cell), “neuritic
plaques” (abnormal clusters of dead and dying nerve
cells, other brain cells, and protein), and “senile
plaques” (areas where products of dying nerve cells
have accumulated around protein).
The destruction of nerve cells, or neurons, leads to a decrease
in neurotransmitters – chemicals that are secreted by
a neuron to send a message to another neuron. The correct
balance of neurotransmitters is essential to the proper functioning
of the brain. Three types of neurotransmitters that are commonly
affected by Alzheimer’s disease are acetylcholine, serotonin,
and norepinephrine.
Researchers theorize that Alzheimer’s disease causes
both structural and chemical problems in the brain. The disease
seems to disconnect areas of the brain that normally work
together.
Types of Alzheimer’s disease
The two types of Alzheimer’s disease are early onset
and late onset. In early onset Alzheimer’s disease,
symptoms first appear before age 60. Some early onset Alzheimer’s
disease runs in families and involves “autosomal dominant”
– inherited mutations that may be the cause of the disease.
So far, three early onset genes have been identified. Early
onset Alzheimer’s disease is the less common form, accounting
for about 5 percent of cases.
Late onset Alzheimer’s disease is the more common
form. It develops in people 60 and older, and is believed
to be less likely to occur in families. In late onset Alzheimer’s
disease, the role of genes is not entirely clear. It is believed
the genes may not cause the problem itself, but simply increase
the likelihood of formation of plaques and tangles or other
related pathologies in the brain.
Prevention of Alzheimer’s
disease
Today, there is no proven way to prevent the onset of Alzheimer’s
disease. A number of investigations are being carried out
to understand the role of common medications in the prevention
of Alzheimer’s disease. These include non-steroidal
anti-inflammatory drugs (NSAIDs), antioxidants (such as Vitamin
E), estrogen replacement therapy, and gingko biloba. It should
be pointed out that none of these are currently recommended,
and all have side effects. And they can all interact with
other medications. Consult a physician before considering
or taking them.
Symptoms of Alzheimer’s disease
In the early stages, the symptoms of Alzheimer’s disease
may be very subtle. Symptoms may include:
- Repeating statements frequently
- Frequently misplacing items
- Trouble finding names for familiar objects
- Getting lost on familiar routes
- Personality changes
- Becoming passive and losing interest in things previously
enjoyed
Some tasks that were once routine become difficult at this
early stage, such as balancing a checkbook, playing complex
games (such as bridge), and learning new and complex information
or routines.
In its more advanced stage, the deficits are becoming more
obvious. Some of the symptoms are:
- A decrease in knowledge of recent events
- Forgetting events in one’s own life
- Problems choosing clothing items
- Hallucinations, arguments, striking out, and violent
behavior
- Delusions, depression, agitation
Normal tasks, such as driving, preparing meals and managing
finances, are likely to present difficulty to a person at
this stage.
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Diagnostic steps
The first step in diagnosing Alzheimer’s disease is
to establish that dementia is present. The second step is
to clarify the type of dementia. This is accomplished via
a thorough history, a physical exam, neurological exam, and
a mental status examination.
Some physicians may order tests to determine if a treatable
condition exists which is causing dementia or is exacerbating
the onset of Alzheimer’s disease. These conditions include
thyroid disease, vitamin deficiency, brain tumor, drug and
medication intoxication, chronic infection, and severe depression.
Alzheimer’s disease usually has an identifiable presentation
of symptoms, and it can be diagnosed accurately by history
and physical exam in 90 to 95 percent of cases. Tests that
are typically used include blood tests, computed tomography,
magnetic resonance imaging and positron emission tomography
(PET scanning).
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Treatment
The progression of Alzheimer’s disease can be slowed
but not stopped. Treatment focuses on:
- attempting to slow the progression
- managing the behavior problems, confusion and agitation
- modifying the home environment
- supporting the family
In recent years, drug treatment has shown promise in slowing
the progression of the disease and potentially improving cognitive
function.
Learn
more about Saint Mary’s Alzheimer’s Disease and
Memory Disorders Program
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