Dementia - Wikipedia
Dementia (taken from Latin) originally meaning madness, from de- (without) + ment, the root of mens (mind) is a serious loss of global cognitive ability in a previously unimpaired person, beyond what might be expected from normal ageing. It may be static, the result of a unique global brain injury, or progressive, resulting in long-term decline due to damage or disease in the body. Although dementia is far more common in the geriatric population, it can occur before the age of 65, in which case it is termed "early onset dementia".[1]Dementia is not a single disease, but a non-specific illness syndrome (i.e., set of signs and symptoms). Affected cognitive areas can be memory, attention, language, and problem solving. Normally, symptoms must be present for at least six months to support a diagnosis.[2] Cognitive dysfunction of shorter duration is called delirium. In all types of general cognitive dysfunction, higher mental functions are affected first in the process.
Especially in later stages of the condition, subjects may be disoriented in time (not knowing the day, week, or even year), in place (not knowing where they are), and in person (not knowing who they, or others around them, are). Dementia, though often treatable to some degree, is usually due to causes that are progressive and incurable, as observed in primary progressive aphasia (PPA).[3][4][5]
Symptoms of dementia can be classified as either reversible or irreversible, depending upon the etiology of the disease. Fewer than 10% 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.
Delirium can be easily confused with dementia due to similar symptoms. Delirium is characterized by a sudden onset, fluctuating course, a short duration (often lasting from hours to weeks), and is primarily related to a somatic (or medical) disturbance. In comparison, dementia has typically an insidious onset (except in the cases of a stroke or trauma), slow decline of mental functioning, as well as a longer duration (from months to years).[6] Some mental illnesses, including depression and psychosis, may produce symptoms that must be differentiated from both delirium and dementia.[7]
There are many specific types (causes) of dementia, often showing slightly different symptoms. However, the symptom overlap is such that it is impossible to diagnose the type of dementia by symptomatology alone, and in only a few cases are symptoms enough to give a high probability of some specific cause. Diagnosis is therefore aided by nuclear medicine brain scanning techniques. Certainty cannot be attained except with brain biopsy during life, or at autopsy in death.
Some of the most common forms of dementia are: Alzheimer's disease, vascular dementia, frontotemporal dementia, semantic dementia and dementia with Lewy bodies. It is possible for a patient to exhibit two or more dementing processes at the same time, as none of the known types of dementia protects against the others. Indeed, about ten per cent of people with dementia have what is known as mixed dementia, which may be a combination of Alzheimer's disease and multi-infarct dementia.[8][9]
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Signs and symptoms
Comorbidities
Dementia is not merely a problem of memory. It reduces the ability to learn, reason, retain or recall past experience and there is also loss of patterns of thoughts, feelings and activities (Gelder et al. 2005). Additional mental and behavioral problems often affect people who have dementia, and may influence quality of life, caregivers, and the need for institutionalization. As dementia worsens individuals may neglect themselves and may become disinhibited and may become incontinent. (Gelder et al. 2005).Depression affects 20–30% of people who have dementia, and about 20% have anxiety.[10] Psychosis (often delusions of persecution) and agitation/aggression also often accompany dementia. Each of these must be assessed and treated independently of the underlying dementia.[11]
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 generalized damage to the white matter of the brain (diffuse axonal injury), or more localized 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 alcohol dementia, Wernicke's encephalopathy and/or Korsakoff's psychosis.Slowly progressive dementia
Dementia that begins gradually and worsens progressively over several years is usually caused by neurodegenerative disease—that is, by conditions that affect only or primarily the neurons of the brain and cause 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.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 dementia cases are caused by Alzheimer's disease, vascular dementia, or both. Dementia with Lewy bodies is another commonly exhibited form, which again may occur alongside either or both of the other causes.[12][13][14] 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 recognize 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.[15] 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 football players, are at risk of chronic traumatic encephalopathy[16] (also called dementia pugilistica in boxers).
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, SCA17 (dominant inheritance); adrenoleukodystrophy (X-linked); Gaucher's disease type 3, metachromatic leukodystrophy, 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. Recent research published in the Journal of Alzheimers Disease suggests an association of vitamin C and β-carotene with dementia. However, the authors stressed that this is limited to the cross-sectional character of the study and that longitudinal data will give further insight into this association.[17]
Rapidly progressive dementia
Creutzfeldt-Jakob disease typically causes a dementia that worsens over weeks to months, being caused by prions. 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); tumors such as lymphoma or glioma; drug toxicity (e.g. anticonvulsant drugs); metabolic causes such as liver failure or kidney failure; and chronic subdural hematoma.
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.[citation needed] When dementia occurs in Parkinson's disease, the underlying cause may be dementia with Lewy bodies or Alzheimer's disease, or both.[18] 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 that can cause dementia (alongside other symtoms) include:[19]
Diagnosis
Proper differential diagnosis between the types of dementia (cortical and subcortical) requires, at the least, referral to a specialist, e.g., a geriatric internist, geriatric psychiatrist, neurologist, neuropsychologist, or geropsychologist.[citation needed] Duration of symptoms must evident for at least six months to support a diagnosis of dementia or organic brain syndrome (ICD-10).Cognitive testing
| Test | Sensitivity | Specificity | Reference |
| MMSE | 71%-92% | 56%-96% | [20] |
| 3MS | 83%-93.5% | 85%-90% | [21] |
| AMTS | 73%-100% | 71%-100% | [21] |
While many tests have been studied,[26][27][28] and some may emerge as better alternatives to the MMSE, presently the MMSE is the best studied and most commonly used.
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 (IQCODE).[29] On the other hand 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 a web-based test.
Further evaluation includes retesting at another date, and administration of other tests of mental function.
Increasingly, clinical neuropsychologists provide diagnostic consultation following administration of a complex full battery of cognitive testing, often lasting several hours, to determine functional patterns of decline associated with varying types of dementia. Tests of memory, executive function, processing speed, attention, and language skills are relevant, as well as tests of emotional and psychological adjustment. These tests assist with ruling out other etiologies and determining relative cognitive decline over time or from estimates of prior cognitive abilities.
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.[citation needed]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 and cognitive testing.[30] The ability of SPECT to differentiate the vascular cause (i.e., multi-infarct dementia) from Alzheimer's disease dementias, appears superior to differentiation by clinical exam.[31]
Recent research has established the value of PET imaging using carbon-11 Pittsburgh Compound B as a radiotracer (PIB-PET) in predictive diagnosis of various kinds of dementia, in particular Alzheimer's disease. Studies from Australia have found PIB-PET 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 radiotracer, carbon-11 dihydrotetrabenazine (DTBZ), led to more accurate diagnosis for more than one-fourth of patients with mild cognitive impairment or mild dementia.[32]
Prevention
Main article: Prevention of dementia
A study done at the University of Bari in Italy, found that a group drinking alcoholic beverages moderately had a slower progression to dementia. In a group of 1,566 elderly Italians, 1,445 had no cognitive impairment and 121 had suffered mild cognitive impairment, the study found that that over the duration of 3.5 years the people with MCI who drank less than one alcoholic beverage a day progressed to dementia at a rate that was 85% slower than those who drank no alcoholic beverages. However, the authors of the study commented that since it was epidemiologic, the findings might only be a marker of lifestyle, showing that "moderate lifestyle" in general is associated with slower dementia-progression.[33] A study failed to show a conclusive link between high blood pressure and developing dementia. The study, published in the Lancet Neurology journal July 2008, found that blood pressure lowering medication did not reduce dementia but that meta analysis of the study data combined with other data suggested that further study could be warranted.[34]Brain-derived neurotrophic factor (BDNF) expression is associated with prevention of some dementia types.[35][36][37]
A Canadian study found that a lifetime of bilingualism delays the onset of dementia by an average of four years when compared to monolingual patients.[38][39][40]
