|Classification and external resources|
Vascular dementia or multi-infarct dementia is dementia caused by problems in the supply of blood to the brain, typically by a series of minor strokes. Vascular dementia is the second most common form of dementia after Alzheimer's disease (AD) in older adults. Multi-infarct dementia (MID) is thought to be irreversible and it is caused by a number of small strokes or sometimes a large stroke preceded or followed by other smaller strokes. The term refers to a group of syndromes caused by different mechanisms all resulting in vascular lesions in the brain. Early detection and accurate diagnosis are important, as vascular dementia is at least partially preventable.
Some main presenting signs of this disease are: a single strategic infarct (affecting the thalamus, the anterior cerebral artery, the parietal lobes or the cingulate gyrus), multiple brain infarcts, haemorrhagic lesions.
Vascular lesions can be the result of diffuse cerebrovascular disease, such as small vessel disease or focal lesions, but usually both. Mixed dementia is diagnosed when patients have evidence of Alzheimer's Dementia and cerebrovascular disease, either clinically or based on neuro-imaging evidence of ischaemic lesions. In practice, vascular dementia and Alzheimer's disease often coexist, especially in older patients.
Multi-infarct or vascular dementia is sometimes triggered by cerebral amyloid angiopathy, which involves accumulation of beta amyloid plaques in the walls of the cerebral arteries, leading to breakdown and rupture of the vessels. Since amyloid plaques are a characteristic feature of Alzheimer's Disease, vascular dementia may occur as a consequence. However, cerebral amyloid angiopathy can also appear in people with no prior dementia condition and some beta amyloid plaques are often present in cognitively normal elderly persons.
Signs and symptoms
Dementias present similarly to one another and are very difficult to differentiate clinically, despite having different organic causes (particularly with Alzheimer's Dementia). Patients suffering from vascular dementia present with cognitive impairment, acutely or subacutely as in mild cognitive impairment, after one or many cerebrovascular events. The symptoms of dementia may progress gradually or step-wise after each small stroke. Some people may appear to improve between events and decline after more silent strokes.
The incidence peaks between the 4th and the 7th decades of life and 80% will have a history of hypertension. Patients develop progressive cognitive, motor and behavioural signs and symptoms. A significant proportion also develop affective symptoms. These changes typically occur over a period of 5–10 years. If the frontal lobes are affected, which is often the case, patients may present as apathetic or abulic. This is often accompanied by problems with attention, orientation and urinary incontinence. Although atheroma of the major cerebral arteries is typical in vascular dementia, smaller vessels and arterioles are mainly affected.
Rare genetic disorders which result in vascular lesions in the brain have other patterns of presentation. As a rule, they tend to present earlier in life and have a more aggressive course. In addition, infectious disorders such as syphilis lead to artery damage and strokes along with bacterial inflammation of the brain.
Several specific diagnostic criteria can be used to diagnose vascular dementia, including the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria, the International Classification of Diseases, Tenth Edition (ICD-10) criteria, the National Institute of Neurological Disorders and Stroke- Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN) criteria, the Alzheimer's Disease Diagnostic and Treatment Center criteria, and the Hachinski ischemic score.
Signs are typically the same as in other dementias, but mainly include cognitive decline and memory impairment, sufficient severity as to interfere with activities of daily living, presence of focal neurologic signs (e.g., hemiparesis, sensory deficit, hemianopsia, Babinski sign, etc.) and evidence of relevant features consistent with cerebrovascular disease on brain imaging (CT or MRI). Patients have patchy deficits in terms of cognitive testing. They tend to have better free recall and fewer recall intrusions compared with patients with Alzheimer's disease. In the more severe patients, or those patients affected by strategic infarcts in Wernicke's or Broca's areas, dysarthrias and aphasias may be present.
In small vessel disease, the frontal lobes are often affected. Apathy early in the disease is more suggestive of vascular dementia because it usually occurs in the later stages of Alzheimer's dementia. Consequently, patients with vascular dementia tend to perform worse than their Alzheimer's disease counterparts in frontal lobe tasks, such as verbal fluency. They also tend to exhibit more perseverative behavior. They may also present with general slowing of processing ability, difficulty shifting sets and impairment in abstract thinking.
The recommended investigations for cognitive impairment should be carried out, including blood tests (for anaemia, vitamin deficiency, thyrotoxicosis, infection, etc.), chest X-Ray, ECG, and some type of neuroimaging, preferably a scan with a functional or metabolic sensitivity beyond simple CT or MRI. When available as a diagnostic tool, single photon emission computed tomography (SPECT) and positron emission tomography (PET) neuroimaging may be used to confirm a diagnosis of multi-infarct dementia in conjunction with evaluations involving mental status examination. In a person already having dementia, SPECT appears to be superior in differentiating multi-infarct dementia from Alzheimer's disease, as compared with the usual attempts to differentiate the dementing processes by employing mental testing and medical history analysis. Advances have led to the proposal of new diagnostic criteria.
The screening blood test would typically include full blood count, liver function tests, thyroid function tests, lipid profile, erythrocyte sedimentation rate, C reactive protein, syphilis serology, calcium serum level, fasting glucose, urea and electrolytes, vitamin B-12, folate. In selected patients HIV serology and autoantibody testing may be done.
Pathology and necropsy
Gross examination of the brain may reveal noticeable lesions and artery damage. Accumulation of various substances such as lipid deposits and clotted blood appear on microscopic views. The white matter is most affected, with noticeable atrophy and tissue loss, in addition to calcification of the arteries. Microinfarcts may also be present in the gray matter (cerebral cortex), sometimes in large numbers. On rare occasion, infarcts in the hippocampus or thalamus are the cause of dementia.
Other risk factors include geographic origin, genetic predisposition, and prior strokes. Further strokes must be prevented through surgical or medical therapy to lessen the chance of developing Multi-Infarct Dementia.
The goal of the management is the prevention of further cerebrovascular lesions. This includes administering antiplatelet drugs and controlling major vascular risk factors such as hypertension, hypercholesterolemia, smoking and diabetes mellitus.
The general management of dementia includes referral to community services, judgment and decision-making regarding legal and ethical issues (e.g., driving, capacity, advance directives), and consideration of caregiver stress.
Behavioral and affective symptoms are particularly important in this patient group and deserve special consideration. These problems, if they develop, tend to be resistant to conventional psychopharmacological treatment and in many cases lead to hospital admission and placement in permanent care.
The 5-year survival rate is 39% for patients with vascular dementia compared with 75% for age-matched controls. Unlike Alzheimer's Disease, which merely weakens the victim to the point where he succumbs to bacterial infections like pneumonia, vascular dementia is a direct cause of death due to the possibility of a fatal interruption in the brain's blood supply.
The prognosis for MID is usually not very promising. Symptoms may begin suddenly with the onset of the disease and steadily become more prevalent with each progressive small stroke. Even though it may seem that people with MID improve over time, their condition often steadily declines after ensuing silent strokes. A rapidly deteriorating condition may lead to death from a stroke, heart disease, or infection.
Vascular dementia is the second most common type of dementia in the United States and Europe in the elderly, but it is the most common form in some parts of Asia. The prevalence of the illness is 1.5% in Western countries and approximately 2.2% in Japan. It accounts for 50% of all dementias in Japan, 20% to 40% in Europe and 15% in Latin America. The incidence of dementia is 9 times higher in patients who have had a stroke than in controls. 25% of stroke patients develop new-onset dementia within 1 year of their stroke. The relative risk of incident dementia is 5.5% within 4 years of suffering a stroke.
One study found that in the United States specifically, the prevalence of vascular dementia in all individuals over the age of 71 is 2.43%, and another found that the prevalence of the dementias doubles with every 5.1 years of age.
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