Dementia (meaning "deprived of mind") is a serious
cognitive disorder. It may be static, the result of a unique global
brain injury or progressive, resulting in long-term decline in
cognitive function due to damage or
disease in the body beyond what might be
expected from normal
aging. Although dementia
is far more common in the
geriatric
population, it may occur in any stage of adulthood. This age cutoff
is defining, as similar sets of symptoms due to
organic brain syndrome or
dysfunction, are given different names in populations younger than
adult. Up to the end of the nineteenth century, dementia was a much
broader clinical concept.
Dementia is a non-specific illness
syndrome
(set of signs and
symptoms) in which
affected areas of cognition may be
memory,
attention,
language, and
problem
solving. It is normally required to be present for at least 6
months to be diagnosed; cognitive dysfunction that has been seen
only over shorter times, in particular less than weeks, must be
termed
delirium. In all types of general
cognitive dysfunction, higher mental functions are affected first
in the process. Especially in the later stages of the condition,
affected persons may be
disoriented
in time (not knowing what day of the week, day of the month, or
even what year it is), in place (not knowing where they are), and
in person (not knowing who they are or others around them).
Dementia, though often treatable to some degree, is usually due to
causes that are progressive and incurable.
Symptoms of dementia can be classified as either reversible or
irreversible, depending upon the
etiology
of the disease. Less than 10 percent of cases of dementia are due
to causes that may presently be reversed with treatment. Causes
include many different specific disease processes, in the same way
that symptoms of organ dysfunction such as shortness of breath,
jaundice, or
pain are
attributable to many etiologies. Without careful assessment of
history, the short-term syndrome of
delirium (often lasting days to weeks) can easily
be confused with dementia, because they have all symptoms in
common, save duration, and the fact that delirium is often
associated with over-activity of the sympathetic nervous system.
Some
mental illnesses, including
depression and
psychosis, may also produce symptoms that must be
differentiated from both delirium and dementia.Chronic use of
substances such as
alcohol as
well as chronic
sleep deprivation
can also predispose the patient to cognitive changes suggestive of
dementia.
Signs and symptoms
Comorbidities
Dementia is not merely a problem of memory. Additional mental and
behavioral problems often affect people who have dementia, and may
influence quality of life, caregivers, and the need for
institutionalization.
Depression affects 20-30% of people who have dementia, and about
20% have anxiety. Psychosis (often delusions of persecution) and
agitation/aggression also often accompany dementia. Each of these
needs to be assessed and treated independent of the underlying
dementia.
Risk to self and others
The Canadian Medical Association Journal has reported that
driving with dementia could lead to severe injury or
even death to self and others. Doctors should advise appropriate
testing on when to quit driving.
In the
United
States
, Florida's Baker Act
allows law enforcement and the judiciary to force mental evaluation for those suspected of
suffering from dementia or other mental incapacities.
In the
United
Kingdom
, as with all mental disorders, where a sufferer
could potentially be a danger to themselves or others, they can be
detained under the Mental Health Act 1983 for the purposes of
assessment, care and treatment. This is a last resort, and
usually avoided if the patient has family or friends who can ensure
care.
The
United
Kingdom DVLA (Driving & Vehicle
Licensing Agency) states that Dementia sufferers who specifically
suffer with poor short term memory, disorientation, lack of insight
or judgement are almost certainly not fit to drive - and in these
instances, the DVLA must be informed so said license can be
revoked. They do however acknowledge low-severity cases and
early sufferers, and those drivers may be permitted to drive
pending medical report.
Diagnosis
Proper differential diagnosis between the types of dementia
(
cortical and
subcortical - see below)
will require, at the least, referral to a specialist, e.g., a
geriatric internist, geriatric psychiatrist,
neurologist,
neuropsychologist or geropsychologist.
However, there exist some brief tests (5–15 minutes) that have
reasonable reliability and can be used in the office or other
setting to screen cognitive status for deficits that are considered
pathological. Examples of such tests
include the
abbreviated
mental test score (AMTS), the
mini mental state examination
(MMSE), Modified Mini-Mental State Examination (3MS), the Cognitive
Abilities Screening Instrument (CASI), and the clock drawing
test.An AMTS score of less than six (out of a possible score of
ten) and an MMSE score under 24 (out of a possible score of 30)
suggests a need for further evaluation. Scores must be interpreted
in the context of the person's educational and other background,
and the particular circumstances; for example, a person highly
depressed or in great pain will not be expected to do well on many
tests of mental ability.
Mini-mental state examination
The
U.S. Preventive Services Task Force (USPSTF)
reviewed tests for cognitive impairment and concluded:
- sensitivity 71% to 92%
- specificity 56% to 96%
Modified Mini-Mental State examination (3MS)
A copy of the 3MS is online. A
meta-analysis concluded that the Modified
Mini-Mental State (3MS) examination has:
- sensitivity 83% to 93.5%
- specificity 85% to 90%
Abbreviated mental test score
A meta-analysis concluded:
- sensitivity 73% to 100%
- specificity 71% to 100%
Duration of symptoms
Duration of symptoms must normally exceed 6 months for a diagnosis
of dementia or organic brain syndrome to be made.
Other examinations
Many other tests have been studied including the clock-drawing test
(
example form). Although some may emerge as
better alternatives to the MMSE, presently the MMSE is the best
studied. However, access to the MMSE is now limited by enforcement
of its copyright.
Another approach to screening for dementia is to ask an informant
(relative or other supporter) to fill out a questionnaire about the
person's everyday cognitive functioning. Informant questionnaires
provide complementary information to brief cognitive tests.
Probably the best known questionnaire of this sort is the
Informant Questionnaire on Cognitive Decline in the Elderly
.
The
General
Practitioner Assessment Of Cognition combines both, a patient
assessment and an informant interview. It was specifically designed
for the use in the primary care setting and is also available as
web-based test. It can be accessed on
www.gpcog.com.au.
Further evaluation includes retesting at another date, and
administration of other (and sometimes more complex) tests of
mental function, such as formal
neuropsychological testing.
Laboratory tests
Routine
blood tests are also usually
performed to rule out treatable causes. These tests include
vitamin B12,
folic
acid,
thyroid-stimulating hormone
(TSH),
C-reactive protein,
full blood count,
electrolytes,
calcium,
renal
function, and
liver enzymes.
Abnormalities may suggest
vitamin
deficiency,
infection or other
problems that commonly cause confusion or disorientation in the
elderly. The problem is complicated by the fact that these cause
confusion more often in persons who have early dementia, so that
"reversal" of such problems may ultimately only be temporary.
Testing for alcohol and other known dementia-inducing drugs may be
indicated.
Imaging
A
CT scan or
magnetic resonance imaging (MRI
scan) is commonly performed, although these modalities do not have
optimal sensitivity for the diffuse metabolic changes associated
with dementia in a patient that shows no gross neurological
problems (such as paralysis or weakness) on neurological exam. CT
or MRI may suggest
normal
pressure hydrocephalus, a potentially reversible cause of
dementia, and can yield information relevant to other types of
dementia, such as infarction (
stroke) that
would point at a vascular type of dementia.
The
functional neuroimaging
modalities of
SPECT and
PET are more useful in
assessing long-standing cognitive dysfunction, since they have
shown similar ability to diagnose dementia as a clinical exam. The
ability of SPECT to differentiate the vascular cause from the
Alzheimer disease cause of dementias, appears to be superior to
differentiation by clinical exam.
Recent research has established the value of PET imaging using
carbon-11 Pittsburgh Compound B as a contrast medium (PIB-PET) in
predictive diagnosis of various kinds of dementia, in particular
Alzheimer's disease. Studies
from Australia have found PIB-PET to be 86% accurate in predicting
which patients with mild cognitive impairment would develop
Alzheimer's disease within two years. In another study, carried out
using 66 patients seen at the University of Michigan, PET studies
using either PIB or another contrast agent, carbon-11
dihydrotetrabenazine (DTBZ), led to more accurate diagnosis for
more than one-fourth of patients with mild cognitive impairment or
mild dementia.
Causes
Fixed cognitive impairment
Various types of brain injury, occurring as a single event, may
cause irreversible but fixed cognitive impairment.
Traumatic brain injury may cause
generalised damage to the white matter of the brain (
diffuse axonal injury), or more
localised damage (as also may
neurosurgery). A temporary reduction in the
brain's supply of blood or oxygen may lead to
hypoxic-ischemic injury.
Strokes (ischemic stroke, or intracerebral,
subarachnoid, subdural or extradural hemorrhage) or infections
(
meningitis and/or
encephalitis) affecting the brain, prolonged
epileptic
seizures and acute
hydrocephalus may also have long-term effects
on cognition. Excessive alcohol use may cause either
alcohol dementia or
Korsakoff's psychosis (and certain
other recreational drugs may cause substance-induced persisting
dementia); once overuse ceases, the cognitive impairment is
persistent but non-progressive.
Slowly progressive dementia
Dementia which begins gradually and worsens progressively over
several years is usually caused by
neurodegenerative disease, that
is, by conditions affecting only or primarily the neurons of the
brain and causing gradual but irreversible loss of function of
these cells. Less commonly, a non-degenerative condition may have
secondary effects on brain cells, which may or may not be
reversible if the condition is treated.
The causes of dementia depend on the age at which symptoms begin.
In the elderly population (usually defined in this context as over
65 years of age), a large majority of cases of dementia are caused
by
Alzheimer's disease,
vascular dementia or both.
Dementia with Lewy bodies is
another fairly common cause, which again may occur alongside either
or both of the other causes.
Hypothyroidism sometimes causes slowly
progressive cognitive impairment as the main symptom, and this may
be fully reversible with treatment.
Normal pressure hydrocephalus,
though relatively rare, is important to recognise since treatment
may prevent progression and improve other symptoms of the
condition. However, significant cognitive improvement is
unusual.
Dementia is much less common under 65 years of age. Alzheimer's
disease is still the most frequent cause, but inherited forms of
the disease account for a higher proportion of cases in this age
group.
Frontotemporal
lobar degeneration and
Huntington's disease account for most
of the remaining cases.
Vascular
dementia also occurs, but this in turn may be due to underlying
conditions (including
antiphospholipid syndrome,
CADASIL,
MELAS,
homocystinuria,
moyamoya and
Binswanger's disease). People who
receive frequent head trauma, such as boxers or some martial
artists, are at risk of
dementia
pugilistica. An
association between
coeliac
disease and dementia has been proposed, but this is
controversial.
In young adults (up to 40 years of age) who were previously of
normal intelligence, it is very rare to develop dementia without
other features of neurological disease, or without features of
disease elsewhere in the body. Most cases of progressive cognitive
disturbance in this age group are caused by psychiatric illness,
alcohol or other drugs, or metabolic disturbance. However, certain
genetic disorders can cause true neurodegenerative dementia at this
age. These include
familial Alzheimer's
disease,
metachromatic
leukodystrophy,
SCA17
(
dominant inheritance);
adrenoleukodystrophy (
X-linked);
Gaucher's disease type 3,
Niemann-Pick disease type C,
pantothenate
kinase-associated neurodegeneration,
Tay-Sachs disease and
Wilson's disease (all
recessive). Wilson's disease is
particularly important since cognition can improve with
treatment.
At all ages, a substantial proportion of patients who complain of
memory difficulty or other cognitive symptoms are suffering from
depression rather than a
neurodegenerative disease. Vitamin deficiencies and chronic
infections may also occur at any age; they usually cause other
symptoms before dementia occurs, but occasionally mimic
degenerative dementia. These include deficiencies of
vitamin B12,
folate or
niacin,
and infective causes including
cryptococcal meningitis,
HIV,
Lyme
disease,
progressive
multifocal leukoencephalopathy,
subacute sclerosing
panencephalitis,
syphilis and
Whipple's disease.
Rapidly progressive dementia
Creutzfeldt-Jakob disease
typically causes a dementia which worsens over weeks to months. The
common causes of slowly progressive dementia also sometimes present
with rapid progression:
Alzheimer's
disease,
dementia with
Lewy bodies,
frontotemporal lobar
degeneration (including
corticobasal degeneration and
progressive supranuclear
palsy).
On the other hand,
encephalopathy or
delirium may develop relatively slowly and
resemble dementia. Possible causes include brain infection
(
viral encephalitis,
subacute sclerosing
panencephalitis,
Whipple's
disease) or inflammation (
limbic
encephalitis,
Hashimoto's
encephalopathy,
cerebral
vasculitis); tumours such as
lymphoma or
glioma; drug toxicity (e.g.
anticonvulsant drugs); metabolic causes such
as
liver failure or
kidney failure; and chronic
subdural hematoma.
Dementia as a feature of other conditions
There are many other medical and neurological conditions in which
dementia only occurs late in the illness, or as a minor feature.
For example, a proportion of patients with
Parkinson's disease develop dementia,
though widely varying figures are quoted for this proportion . When
dementia occurs in Parkinson's disease, the underlying cause may be
dementia with Lewy bodies
or
Alzheimer's disease, or both.
Cognitive impairment also occurs in the Parkinson-plus syndromes of
progressive supranuclear
palsy and
corticobasal
degeneration (and the same underlying pathology may cause the
clinical syndromes of
frontotemporal lobar
degeneration). Chronic inflammatory conditions of the brain may
affect cognition in the long term, including
Behçet's disease,
multiple sclerosis,
sarcoidosis,
Sjögren's syndrome and
systemic lupus erythematosus.
Although the acute
porphyrias may cause
episodes of confusion and psychiatric disturbance, dementia is a
rare feature of these rare diseases.
Aside from those mentioned above, inherited conditions which may
cause dementia alongside other features include:
Prevention
It appears that the regular moderate consumption of alcohol (beer,
wine, or distilled spirits) and a Mediterranean diet may reduce
risk. A study has shown a link between high blood pressure and
developing dementia. The study, published in the Lancet Neurology
journal July 2008, found that blood pressure lowering medication
reduced dementia by 13%.
Brain-derived
neurotrophic factor (BDNF) expression is associated with some
dementia types.
NSAIDs
Non-steroidal
anti-inflammatory drugs (NSAIDs) can decrease the risk of
developing Alzheimer's and Parkinson's diseases. The length of time
needed to prevent dementia varies, but in most studies it is
usually between 2 and 10 years. Research has also shown that it
must be used in clinically relevant dosages and that so called
"baby aspirin" doses are ineffective at preventing and treating
dementia.
Alzheimer's disease causes inflammation in the
neurons by its deposits of
amyloid beta peptides and
neurofibrillary tangles. These
deposits irritate the body by causing a release of e.g.
cytokines and
acute
phase proteins, leading to inflammation. When these substances
accumulate over years they contribute to the effects of
Alzheimer's. NSAIDs inhibit the formation of such inflammatory
substances, and prevent the deteriorating effects.
Management
Except for the treatable types listed above, there is no cure to
this illness, although scientists are progressing in making a type
of medication that will slow down the process.
Cholinesterase inhibitor are
often used early in the disease course. Cognitive and behavioral
interventions may also be appropriate. Educating and providing
emotional support to the
caregiver (or
carer) is of importance as well (
see also elderly care).
A Canadian
study found
that a lifetime of bilingualism has a
marked influence on delaying the onset of dementia by an average of
four years when compared to monolingual patients. The researchers
determined that the onset of dementia symptoms in the monolingual
group occurred at the mean age of 71.4, while the bilingual group
was 75.5 years. The difference remained even after considering the
possible effect of cultural differences,
immigration, formal
education, employment and even
gender as influences in the results.
Some studies worldwide have found that
Music therapy may be useful in helping
patients with dementia.
Medications
Tacrine (Cognex),
donepezil (Aricept),
galantamine (Razadyne), and
rivastigmine (Exelon) are approved by the
United States Food and Drug Administration (FDA) for treatment of
dementia induced by Alzheimer disease. They may be useful for other
similar diseases causing dementia such as Parkinsons or vascular
dementia.
- N-methyl-D-aspartate Blockers. Memantine (Namenda) is a drug
representative of this class. It can be used in combination with
acetylcholinesterase inhibitors.
Off label
- Amyloid deposit inhibitors
Minocycline and
Clioquinoline, antibiotics, may help reduce
amyloid deposits in the brains of persons
with Alzheimer disease.
Depression is frequently
associated with dementia and generally worsens the degree of
cognitive and
behavioral impairment.
Antidepressants effectively treat the
cognitive and behavioral symptoms of depression in patients with
Alzheimer's disease, but evidence for their use in other forms of
dementia is weak.
Many patients with dementia experience
anxiety symptoms. Although
benzodiazepines like
diazepam (Valium) have been used for treating
anxiety in other situations, they are often avoided because they
may increase agitation in persons with dementia and are likely to
worsen cognitive problems or are too sedating.
Buspirone (Buspar) is often initially tried for
mild-to-moderate anxiety. There is little evidence for the
effectiveness of benzodiazepines in dementia, whereas there is
evidence for the effectivess of antipsychotics (at low
doses).
Selegiline, a drug used primarily in the
treatment of Parkinson's disease, appears to slow the development
of dementia. Selegiline is thought to act as an
antioxidant, preventing
free radical damage. However, it also acts as a
stimulant, making it difficult to determine whether the delay in
onset of dementia symptoms is due to protection from free radicals
or to the general elevation of brain activity from the stimulant
effect.
Both
typical antipsychotics
(such as
Haloperidol) and
atypical antipsychotics such as
(
risperidone) increases the risk of
death in dementia-associated psychosis. This means that any use of
antipsychotic medication for dementia-associated psychosis is
off-label and should only be considered after discussing the risks
and benefits of treatment with these drugs, and after other
treatment modalities have failed. In the UK around 144,000 dementia
sufferers are unnecessarily prescribed antipsychotic drugs, around
2000 patients die as a result of taking the drugs each year.
Services
Adult daycare centers as well as
special care units in nursing homes often provide specialized care
for dementia patients. Adult daycare centers offer supervision,
recreation, meals, and limited health care to participants, as well
as providing respite for caregivers.
Prognosis
Severe dementia is frequently complicated by pneumonia, febrile
illnesses, and eating problems. Life expectancy is short at 18
months.
Epidemiology
[[Image:Alzheimer and other dementias world map - DALY -
WHO2002.svg|thumb|
Disability-adjusted life year
for Alzheimer and other dementias per 100,000 inhabitants in
2002.
]]
See also
References
Notes
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