There are various types of dementia. These include Alzheimer’s disease, vascular dementias, medical conditions, substance abuse-related, and infection-related dementias.
Alzheimer’s Disease
Alzheimer’s disease (AD) is the most common type of dementia and accounts for approximately 50% of dementias. AD is associated with loss of brain cells in parts of the brain that control memory and cognitive functions. This loss of brain cells causes an imbalance of chemicals called neurotransmitters such as achetylcholine, which is decreased in Alzheimer’s disease. As brain cells die, the brain becomes smaller or “atrophies.” The areas of the brain that control memory, logical thinking, and personality are generally the most affected. Abnormal proteins called neurofibrillary tangles and amyloid plaques are found in the brains of those with AD. Research has found genes that are associated with some forms of AD and other genes that predispose one to the disease.
Criteria for diagnosing AD include:
- Memory impairment, poor executive functioning, and one or more of the following:
Aphasia or difficulty speaking - Apraxia or difficulty with movement
Agnosia or difficulty making meaning from one of more of their senses (smell, sight, hearing, touch, taste) - Cognitive impairments represent a decline from baseline functioning and have significant impact on social or occupational functioning.
- Gradual onset with continual decline.
- The memory and cognitive changes are not due to other brain, systemic, or substance-induced conditions or another psychiatric disorder.
Currently AD is progressive, irreversible and incurable. However, medications can slow its progress. For more information, click on this link: FAQ about AD.
Vascular Dementias
Vascular dementia is the next most common type of dementia after Alzheimer’s disease and accounts for approximately 9-15% of dementias. It encompasses a group of syndromes related to poor circulation of blood to the brain that result in strokes. The 3 most common types of vascular dementia are multiple cortical infarcts (multi-infarct dementia), a strategic single infarct, and small vessel disease. Multi-infarct dementia is the most common form of vascular dementia and is associated with atherosclerosis (hardening of the arteries).
Onset is usually later in life and may be sudden following a single major stroke, or may be gradual following multiple strokes. This form of dementia often shows stepwise progression with periods of abrupt decline alternating with “plateau” periods of minimal decline. Symptoms include changes in behavior such as disinhibition, lack of judgment, and loss of social awareness and insight are more common than memory problems. Disturbance of emotions, mood, and speech are frequent. The location in the brain where a stroke occurs may account for the types and degree of symptoms.
Vascular dementia is irreversible and incurable. It is diagnosed based on medical history, symptoms, signs, diagnostic tests, and by ruling out other causes of dementia. The risk factors for this type of dementia include high blood pressure, high cholesterol, smoking, diabetes mellitus, heart disease and cerebrovascular disease.
Dementias Related to Medical Conditions
Parkinson’s disease
This is a progressive disease involving part of the brain that affects motor control. There is a decrease in the neurotransmitter, dopamine, which is important for the brain’s control of muscle activity. Symptoms of Parkinson’s disease include a tremor at rest, stiffness in limbs and joints (which causes them to shuffle when they walk), difficulty in initiating physical movement, and speech problems. Dementia may develop late in the disease, but not everyone with Parkinson’s disease has dementia. Reasoning, memory, speech, and judgment are most likely to be affected.
Lewy body disease
This form of dementia is caused by abnormal deposits of protein, called Lewy bodies, in brain cells, which causes cell death. Lewy body dementia is more likely to affect thinking, attention, and concentration rather than memory and language. Hallucinations are common in this form of dementia. Additional symptoms include a tremor and muscle rigidity. It is irreversible and incurable. Some of the drugs used to treat Alzheimer’s disease may also benefit those with Lewy body disease.
Huntington’s disease
This is an inherited, degenerative brain disease that causes involuntary movement of the limbs and facial muscles. Cognitive symptoms include memory and speech problems, disorientation, intellectual decline, impaired judgment, and personality changes. The disease usually begins during mid-life and is irreversible and incurable.
Pick’s disease (frontotemporal dementia)
Pick’s disease is rare disorder that damages cells in the frontal and temporal lobes of the brain. It typically occurs at an early age and is more common among women. Behavior and personality changes usually precede memory loss and language problems.
Substance Abuse-Related Dementia, Including Alcohol-Related Dementia
Drinking too much alcohol or abusing certain mind-altering substances can result in brain damage with persistent memory loss and cognitive deficits. The progression of this type of dementia may be stopped by giving up drinking alcohol or the substance abuse.
Dementias Related to Infections
Creutzfeldt-jakob disease – Creutzfeldt-Jakob disease is an uncommon, infectious disease caused by the accumulation of an abnormal protein in the brain that leads to rapid destruction of brain cells. Symptoms include memory and behavioral problems with tremor, involuntary movements, and loss of coordination and balance. Death within one to two years of the onset of clinical symptoms is common.
HIV or AIDS dementia complex – This is one of the most common brain complications of late HIV-1 infection. Depending on the severity, it causes three categories of dysfunction: cognitive, motor, and behavioral. Psychosis may also be a symptom.
Mixed Dementias
A person may have two or more types of dementia, with one type usually dominating. Studies suggest that there may not be distinct boundaries between the different types of dementias. For instance, research has shown a strong interaction between AD and vascular dementia. Mixed dementias may require a different approach to medical management than the separate dementias alone.
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