The brain is indubitably one of the most important and energy-intensive organs in the human body. A healthy blood vessel (cerebrovascular) network in the brain is vital to manage its high energy and nutrient requirements. Neurons, neuroglia, and other types of brain cells depend on the constant and regulated delivery of oxygen, sugars, and metabolites to carry out their functions. This complex blood vessel network in our brain is known as the neurovascular unit.
Impaired blood flow in the neurovascular unit can adversely affect our ability to think, move, experience emotions, remember, and much more. Vascular cognitive impairment (VCI) is widely used to describe such cognitive defects, encompassing a range of mild to severe effects that are related to conscious and intelligent thought-processing. Subsequently, the term “vascular dementia” is used when the patient’s memory becomes significantly affected as a result of cerebrovascular disease progression.
What is Vascular Dementia?
Dementia is an irreversible condition causing cognitive decline and is mainly characterized by the loss of memory. Vascular dementia contributes to approximately 20% of all dementia cases and is the second greatest cause of dementia after Alzheimer’s disease. However, recent studies have revealed that vascular dementia and neurodegenerative aspects, such as in Alzheimer’s disease, often occur together in most patients to cause “mixed” dementia.
Vascular dementia refers solely to the impairment of memory caused by blood vessel (vascular) defects in the brain. When blood is unable to reach parts of the brain due to vascular defects, the cells in those parts of the brain are starved and eventually die off, causing areas of dead brain cells known as “infarcts”. Infarcts that occur in areas of the brain that control memory, namely the frontal and temporal lobes, cause the loss of ability to register and retain memory. The condition of dementia arises when progressively large infarcts cause this ability to become significantly lost.
Vascular Dementia Symptoms
The symptoms of vascular dementia are broad and much more variable compared to other neurological conditions such as Alzheimer’s disease. This is because the loss of various cognitive abilities depend on the location of the infarcts and the extent of damage caused to specific parts of the brain that control particular cognitive functions. Some commonly observed symptoms include:
- Inability to concentrate and pay attention
- Poor planning and time management
- Difficulty in organizing things
- Difficulty in processing information
- Difficulty in communicating ideas
- Deteriorating speech and language abilities
- Slowing or unsteady movement
- Worsening memory
Non-cognitive impairment related to neuropsychiatric behaviors can also be a symptom of vascular dementia. The most commonly observed features include depression and apathy, while other less common features include delusions and hallucinations.
Some early symptoms of dementia are also helpful in the detection of vascular dementia.
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Vascular Dementia Causes
Vascular dementia is generally caused by vascular diseases and injury. These include heart disease, narrowing or blockage of blood vessels (atherosclerosis), stroke, and neurodegeneration due to Alzheimer’s disease. Genetic defects can also result in vascular dementia.
The mechanism of vascular dementia caused by atherosclerosis or other vascular diseases, such as cerebral amyloid angiopathy (CAA), involve the narrowing and bleeding of blood vessels which result in infarcts and haemorrhages throughout the brain. Milder cases of vascular dementia are often attributed to small vessel disease that causes injuries, known as lesions, in the white matter of the brain. In severe cases of vascular dementia, a greater burden of vascular disease pathology, such as large infarcts, is required to significantly affect the brain’s ability to manage memories.
Stroke is also a major cause of vascular dementia as a blockage in the blood vessels causes an infarct in the brain that may disrupt normal memory function. Vascular dementia caused by multiple strokes is known as multi-infarct dementia. Post-stroke dementia has been found to develop in 15–30% of all stroke patients within the first three months after a stroke. However, dementia in these instances is often caused by a combination of vascular defects as well as neurodegeneration.
Neurodegenerative diseases disrupt the structure and function of neurons in the brain. Advanced neurodegeneration leads to cerebral atrophy, which is the significant loss of neurons and decreased brain mass due to the breakdown of tissues, directly diminishing the function of affected brain areas. Alzheimer’s disease is a neurodegenerative disease that is widely accepted as the leading cause of dementia. However, recent research has shown that vascular dementia has been observed to develop alongside Alzheimer’s disease in up to 50% of dementia patients. Other age-related neurodegenerative diseases, such as synucleinopathies, hippocampal sclerosis, and frontotemporal lobar degeneration, have also been found to coexist with vascular defects in dementia patients. Doctors and researchers are continuing to uncover more overlap between pathology, which is the causes and effects of disease, of both vascular and neurodegenerative diseases in the brain, revealing that both eventually contribute to the onset of dementia in most patients.
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A rare hereditary disease that causes vascular dementia, known as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), is caused by a mutation in the notch gene on chromosome 19. This mutation results in the abnormal thickening of the blood vessel walls and restricts blood flow to many parts of the brain and eventually leads to dementia. Also, this severe disease afflicts migraines, seizures, multiple strokes, poor vision, and cognitive and psychiatric problems.
Ongoing research has shown that associations of vascular dementia with genetics overlap those of neurodegenerative diseases. This means that there may be shared pathological mechanisms between vascular dementia and the more well-established mechanisms of neurodegenerative disorders. More research is still required to identify the underlying genetic mechanisms that cause vascular dementia.
Risk Factors of Vascular Dementia
Vascular dementia is strongly tied to general vascular health, meaning that risk factors that adversely affect vascular health are also major risk factors for vascular dementia. These include:
- Hypertension (high blood pressure)
- High cholesterol
- High homocysteine levels
- Atrial fibrillation (arrhythmia)
- Ischemic heart disease and other vascular diseases
- Possession of the APOE-e4 allele
It is important to note that the presence of these factors in mid-life are more indicative as prior to the onset of dementia in old age, cholesterol levels, blood pressure and weight tend to drop and the risk association becomes less obvious.
Other major risk factors for vascular dementia include:
- Increasing age
- Incidence and location of strokes
- Neurodegenerative diseases
- Late-life depression
Diagnosing Vascular Dementia
A doctor will first assess the medical history of the patient, with emphasis on the presence of any vascular disorders, heart disease, and occurrence of strokes. Laboratory tests will also be carried out to assess blood pressure, blood glucose, and cholesterol and homocysteine levels.
Clinical cognitive assessments, namely the Montreal Cognitive Assessment and the vascular dementia assessment scale (VADAS-cog), are carried out by a specialist. These tests include aspects which are more specific and sensitive in the diagnosis of vascular dementia, such as problem-solving activities.
If a cognitive impairment is ascertained, brain imaging, such as computer tomography (CT) and magnetic resonance imaging (MRI), is then used to detect cerebrovascular disease and determine if dementia is indeed caused by any observed infarcts, lacunes, lesions, or atrophy. White matter lesions are especially diagnostic for vascular dementia as they often reflect vascular disease in the subcortical region of the brain which controls memory.
New technologies and ongoing biomarker discoveries are improving the accuracy of the diagnosis of different types of dementia. These include amyloid positron emission tomography (PET) scan, cerebrospinal fluid markers for tau, and in vivo tau imaging. Prospective biomarkers that are more specific to vascular dementia include albumen, metalloproteinases, and inflammatory biomarkers.
Subtypes of Vascular Dementia
Vascular dementia is further categorized based on the type, location, and extent of cerebrovascular disease as determined by brain imaging. The subtypes and their characteristic features are listed as follows:
- Multi-infarct dementia (cortical vascular dementia): multiple cortical infarcts, possibly as a result of multiple strokes
- Small vessel dementia (subcortical vascular dementia): Lacunes, extensive white matter lesions, demyelination, and gliosis
- Strategic infarct dementia: an infarct in a key location such as the thalamus
- Hypoperfusion dementia: Watershed (border-zone) infarcts and white matter lesions
- Haemorrhagic dementia: Bleeding in the brain that may be associated with cerebral amyloid angiopathy (CAA)
- Hereditary vascular dementia (CADASIL): frameshift mutation in the notch gene on chromosome 19 with multiple lacunes and white matter lesions in the white matter of the temporal lobe
- Alzheimer’s disease with cardiovascular disease: a combination of vascular defects and neurodegenerative atrophy especially in the medial temporal lobe
Vascular Dementia Prognosis and Treatment
Unfortunately, vascular dementia is a progressive disease that is irreversible with no effective drug treatments at present. The average rate of cognitive decline is similar to that of Alzheimer’s disease but, unlike Alzheimer’s disease, there are no predictable patterns nor stages for the progression of vascular dementia. Owing to the severity of cardiovascular and cerebrovascular disease, the mean survival period for patients diagnosed with vascular dementia ranges from 3–5 years.
Nonetheless, its progression can be slowed down with physical and psychiatric treatments, which are achievable through professional in-home therapy. Providing proper palliative care and information for the patient and caretakers can also aid in the early recognition and better management of non-cognitive symptoms, such as depression, to improve the patient’s quality of life.
Vascular dementia can also be decelerated by reducing vascular risk factors as well as assessing and treating comorbidities, which refer to co-existing health conditions such as hypertension.
Well-established drug treatments for Alzheimer’s disease, for instance, cholinesterase inhibitors and memantine, can be used to provide modest improvements for “mixed” dementia patients but offer little benefit in treating “pure” vascular dementia. Ongoing drug treatment trials for vascular dementia have shown promising results for the use of calcium channel blockers or daily infusion of cerebrolysin to improve cognitive function.
Vascular Dementia Prevention
There are no proven direct preventive measures for vascular dementia but anti-hypertensive treatment can indirectly prevent vascular dementia by preventing stroke. Similarly, maintaining good vascular health through vascular risk reduction, cognitive training, nutritional advice, and exercise can generally protect the neurovascular unit from damage that may lead to vascular dementia. Some lifestyle changes can also help to prevent dementia altogether.
Vascular Dementia Support & Resources in Singapore
Suffering from or caring for someone with vascular dementia can be a tough journey. Engaging professional services to manage other associated impairments through post-stroke speech therapy and physiotherapy can greatly improve the quality of life and prognosis for a patient with vascular dementia. Caregivers can also cope better by understanding palliative care, managing stress, or joining a local support group.
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