di
Anna Giulia Cattaneo, M.D.
A previous Editorial was aimed to describe most relevant
features of Alzheimer disease (AD), recognized as the most
frequent cause of cognitive impairment in aged people: however,
cognitive impairment accompanying aging processes in humans
is frequently associated to risk factors and eventually morphological
alterations different from AD. The aim of this Editorial
is to focus attention on this condition, and especially on
reversible dementias and cerebral vascular disease (VaD).
Differential diagnosis, risk factors and possible prevention
of other types of mental decline are discussed. It
should be reminded that VaD is frequently associated with
AD: the two conditions can have closer relation than a simple
co-existence, the last one being a possible long-term sequel
of poor cerebral irroration.
Classification of causes for mental impairment in aging: a diagnostic
algorithm.
Difficulties in exhaustive
diagnosis of mental decline rise from the frequency of criteria
redefinition, and the complexity of pathological changes,
frequently coexisting with those of other pathologies. Memory,
orientation (time and space relationships), social judgment
and ability to manage complex problems, home affairs and hobbies,
relationships with other people, and taking care of himself
are affected in different measure in dependence from the degree
and the type of cognitive defect.
The American Academy of Neurology proposed in recent years a diagnostic algorithm in the case of
cognitive impairment. The multi-step evaluation of the patient starts with history,
physical, mental and cognitive testing, aimed to detect the
presence of cognitive defect involving multiple domains.
If this condition is stated or suspected, it is mandatory
to exclude reversible cases of cognitive impairment (depression,
delirium, metabolic conditions like hypothyroidism or hypovitaminosis,
intracranial space-occupying lesions, medication encephalopathy),
and eventually treat it. Once reversible causes are carefully,
it is appropriate to proceed with neuropsychological testing
with the addition of imaging, laboratory and molecular testing
(Corey-Bloom J, Thal LJ, Galasko D, et al. Diagnosis
and evaluation of dementia. Neurology 1995 (45) p 211
~ 218).
1. Secondary dementias
In aged individuals, mental impairment can be secondary to metabolic
disorders (hypothyroidism, hypovitaminosis as an example),
hypertensive encephalopathy, drugs and heavy metals intoxications,
intracranial space-occupying lesions (tumours, haematomas,
hydrocephalus) or chronic infections (intracranial TBC and
chronic meningitis due to different agents, syphilis between
others).
A
wide number of medications, often used to treat symptoms associated
to aging, can cause encephalopathy, and it will be always
remembered that old people is much more prone to develop side
effects than younger individuals. The need to treat depression,
insomnia, tremors, agitation and other neurological symptoms
is often impeded by the toxicity of drugs. These precipitate
dementia or delirium, both by direct interfering with neurotransmission,
and as an idiosyncratic complication. The most common cause
of delirium is the inappropriate use of long-acting benzodiazepines,
but even sedative-hypnotics, histamine antagonists, and
neuroleptics between others. . The central cholinergic
deficiency documented in a number of degenerative dementias
frequent in elderly patients (Alzheimer's and Parkinson's
disease, or dementia with Lewy’s bodies) has been proposed
as the reason for serious symptoms of mental decline induced
in aged people by some anticholinergic drugs prescribed
as antidepressive, sleep inducers, or to treat motion symptoms
of Parkinson disease. Digoxin is another drug frequently
used in the elderly to treat cardiac pathologies. While
formulation is generally well tolerated, a particular care
should be used because of renal excretion can be compromised
in aged patients: the toxic effects can even be lethal for
at the cardiac level, but a delirium, proposed on a n idiosyncratic
base, can develop. A special case is that of antipsychotic
drugs, frequently used to cure agitation in aged subjects.
Clinical suspicion that the use of these agents (at least
several of them) could precipitate acute ischemia and strokes
has been discussed: while results are controversial, a cautious
use of these agents seems to be appropriate.
Cognitive impairment associated with a treatable condition represent
10% to 20% of all cases of dementia: it has been evaluated
that only 10% to 15%% of these are completely reversible,
and an additional 10% has a partial response to treatment
of underlying condition. Depression, medication encephalopathy, and
metabolic disorders dominated the reversible cases. Secondary
dementia is often superimposed to another condition, such
as Alzheimer or Parkinson disease: these cases are partially
or non-responders. Infectious diseases are frequently poorly
responsive to treatment in aged people, for immunity depression
and for pharmacological hypersensitivity.
2. Cerebrovascular disease
a) Small vessels disease
Lipohyalinosis
and cerebral amyloid angiopathy are the most common causes
for cerebral small vessels disease, responsible for a syndrome
characterized by lacunar ischaemic small cortical infarct and petechial haemorrhages localized in the white matter. White matter lesions (WML), cerebral infarcts
and generalized brain atrophy were assessed on the baseline
MRI. The clinical aspect is the
subcortical
ischaemic
vascular syndrome, with seizures and cognitive impairment
(SIVD). The syndrome, more frequent in aged people, is associated
with diabetes and arterial hypertension: the prevention of
this risk factors seems to be the only effective therapeutic
means, physiopathology of this disease being poorly understood
at the present. Vasculitis due to bacterial infections
or to autoimmune diseases is distinct clinical entities, not
confined to the late phases of human life. Subcortical lesions can start with unapparent symptoms, like
depression, slowed thought, poor problem solving and memory
recalling abilities. However, recognition, language and
personality are generally unaffected, differently from what
is commonly experienced in cortical degeneration, like in
Alzheimer disease. In addition to small vessels disease,
subcortical syndromes in aged people are frequently due to
degenerative encephalopathies, such as IPD and small vessels
vascular disease.
b)
Large Vessel Atherothrombotic Disease
Neurological focal symptoms dominate this condition that is
the local expression of a generalized arteriosclerosis.
It can be a consequence of local plaques formation, or of
obstruction of cerebral vessels by thrombi formed in distant
district of the body, as observed in poorly treated atrial
fibrillation. Mental decline and true dementia are referred
as vascular dementia (VaD). Clinical suspicion of cerebrovascular
damage is supported by findings like gait disturbances, frequent
falls or unsteadiness, urinary incontinence, pseudobulbar
palsy, but histopathological findings and imaging positive
for arteriosclerosis states the diagnosis. The absence of
neurofibrillary tangles, Lewy’s bodies and neuritic plaques
exceeding those expected for age is typical for “pure” cerebrovascular
disease, while this entity is quite uncommon. Emergencies
like stroke and palsies are events, complicating usually long-standing,
misunderstood or poorly cured conditions. An epidemiological
study carried out in USA demonstrated a lowering of post-ischaemic
dementias prevalence in aged people, during the period 1982-1999.
The phenomenon has been ascribed to a decline of vascular
cognitive impairments, not to the Alzheimer disease: the supposed
reason of that is better use of medication and prevention
of stroke-associated risk factors, in addition to a better
education among the old. This late finding has been supported
by a number of studies, showing lower incidence of cognitive
impairment and better improve from stroke in people with better
cognitive performance and education in the pre-stroke period.
Diagnostics procedures
In recent years physicians can dispose of powerful means for
diagnostics, unpredictable until several decades ago. Neurological
diagnosis is now a multidisciplinary field, starting from
the traditional clinical examination but requiring other technologies,
sometimes sophisticated, to lead to a diagnostic level acceptable
at the present level of knowledge. This fact does not limit
the traditional clinical diagnostic procedures into an obsolete
field of action: a profound knowledge of all mechanisms that
support the cognitive function in man and of the causes of
disturbance are the sole means to lead to an accurate and
precise diagnosis, prompt enough for obtaining the best results
from the preventive or curative measures. However, the possibility
to associate to a well-conducted clinical care a number of
fine and appropriate diagnostic procedures enhances the potential
of the caregivers and the wellness of the patient.
In addition to neuropsychological testing for cognitive
impairments, the Hachinski Ischemic Score is a useful
test aimed to distinguish between VaD and other types of degenerative
dementia. It is based on the recognition of asymmetric neurological
dysfunctions: while unable to distinguish between pure and
mixed VaD, the sensitivity and specificity of this simple
history-based test are estimated at 70% to 80%.
The chemical laboratory combined with molecular biology
methods (both on blood or cerebral fluid samples) can be of
great help in diagnosis of associated causes for mental decline.
Good examples are tests to detect impaired endocrine function,
hypovitaminosis, drug or heavy metal encephalopathies, intracranial
infections (do not forget tertiary syphilis, TBC and the most
recent HIV, all conditions that can cause mental impairment).
The routine EEG can support in several cases a more refined
diagnostic procedure, or be the first sign of the abnormality:
however its role is very limited and additional. The functional
study of coagulation is of great importance: primary or secondary
defects must be diagnosed and treated defect to prevent cerebral
bleeding, and hyperviscosity should be treated to minimize
ischaemic accidents. It should be interesting to recall that
VaD and secondary dementias are not included in so called
“tauopathies”, in which aggregates of the tau protein
are evident around cerebral lesions. When present, this
protein is a signal for associated AD.
A number of Doppler techniques
for arterial investigation have been developed to localize
the lesion: between other, carotid ultrasonographic studies,
duplex ultrasound, ophthalmic artery transcranial Doppler,
transcranial Doppler (anterior or posterior) are useful, safe
and quite simple.
Ophthalmic examinationand
even retinal vascular imaging, cannot be neglected: this technique
permits to find ocular lesions associated with neurological
conditions and impaired cognitive function, like vascular
or neural hypertension, systemic intoxications, infectious
diseases. It is accurate, non-invasive, quite simple and
inexpensive, and can lead to often-unsuspected diagnosis.
However, the field in which major progress has been done is
that of imaging. MRI, magnetic resonance imaging,
combined with functional imaging (PET, Positron Emission Tomography)
leads to an integrated view of anatomical functional lesions
of the intracranial content, unexpected until several decades
ago, that can be very useful in clinical practice. Thank
to it, more invasive procedures like biopsies can be reserved
to very selected cases. This is very important in frail
patients, often affected by multiple dysfunctions of coagulation
or requiring drugs that can affect it. The main problem
is that imaging is often expensive, and therefore considered
inappropriate to apply to aged people, at least as frequently
as required.
Angiography is invasive and potentially dangerous, and should be limited
in the most frail subjects,
Preventive measures.
While secondary
encephalopathies are intrinsically reversible (with doubt
concerning the entity of recovery), there is no standard symptomatic
treatment for VaD, and still little is known on the measures
for primary prevention: these last can be summarized in a
few points. However, recent works depose for a possible
beneficial effect of preventive measures in reducing gravity
and prevalence of post-Ischemic dementias. Reduced prevalence
(from 5.7 to 2.9% during the period 1982-1999) has been recently
reported in a cohort of more than 40,000 aged individuals
from USA (Adv Gerontol. 2005;16:30-7). The phenomenon can
only be ascribed to a decline of vascular cognitive impairments,
not to Alzheimer disease: the supposed reason of that is better
use of medication and prevention of stroke-associated risk
factors, in addition to a better education among the old.
This late finding has been supported by a number of studies,
showing lower incidence of cognitive impairment and better
improve from stroke in people with better cognitive performance
and education in the pre-stroke period.
Ř
Pre-morbidity factors: a number of studies,
carried out in populations different for social and political
conditions, seems to be concordant in demonstrating that the
degree of education, cognitive and social abilities before
aging and morbidity (especially stroke) are associated with
lower progression into mental decline, at least in non-Alzheimer
diseases.
Ř
Actions against risk factors: Risk factors
for VaD include age, hypertension, diabetes, smoking, cardiovascular
disease, atrial fibrillation and other cardiac arrhythmias,
left ventricular hypertrophy, hyperhomocysteinemia, orthostatic
hypotension, hyperfibrinogenemia, sleep apnoea, infection,
and high C-reactive protein. An adequate identification
of exposure to risk factors followed by measures to discourage
and avoid it can be in selected cases an excellent preventive
measure to avoid mental decline in reversible dementias.
Other potentially beneficial measures concern reduction of
all not necessary drugs, stop smoking habits, control of body
weight and maintenance of an active, and socially normal life
even late in life. Alimentary habits should be maintained
at an acceptable standard, to avoid hypovitaminosis or poor
protein intake: supplementation with vitamins and folate has
been proved non-effective, while safe, when a specific defect
was absent.
Ř
Actions against causative and risk agents:
treatment of dismetabolic or nutritional conditions is
proved to be an efficacious measure in reversible cases of
cognitive impairment. Early treatment of hypertension, diabetes
and hyperlipemias, prevention of bleeding in coagulation defects
or a cautious use of antiplatelets or antithrombotic therapies
when necessary are useful preventive measures, possibly associated
with the reduced prevalence of cognitive vascular impairment
in the elderly found by recent statistics.
Ř
Supportive measures in patients suffering
from serious functional impairment: even in this case,
every possible effort should be necessary to ameliorate the
clinical condition, minimize complications like those caused
by immobilization and lack of regular social relationships.
The supportive presence of the family members, the presence
of motivated, educated and not stressed or depressed caregiver
are additional factors that can ameliorate the wellness and
the function of the patient.
Present address:
DBSM, Università dell'Insubria
via J.H. Dunant,3 - 21100 Varese
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