Dementia manifests as progressive mental impairment that accompany any of several disease processes of the brain and nervous system, according to the Cleveland Clinic. Symptoms can include forgetfulness, personality changes, movement problems and mood changes. Several different forms of dementia exist, with four of the most common including Alzheimer's disease, Lewy body dementias, vascular dementia and fronto-temporal dementias.
Alzheimer's Disease
Although prevalence of Alzheimer's disease can be difficult to calculate due to suspected under-recognition of many cases, research published in the 2007 issue of the journal Neuroepidemiology estimates that it affects approximately 10 percent of Americans older than age 70. The most common form of dementia, Alzheimer's pathology includes the development of plaques, specifically deposits of amyloid peptide, in the brain as well as neurofibrillatory tangles, which are clusters of proteins found in dead brain cells.
Definitive diagnosis can only be determined after death using biopsy or autopsy. A clinician can infer a diagnosis based on characteristic clinical features and exclusion of other possible explanations. For a diagnosis of Alzheimer's disease, an individual must be experiencing memory impairment, one other cognitive impairment such as language or critical thinking problems, and problems in social and occupational functioning, according to the Surgeon General. Patients experience a gradual decline in functioning and many ultimately die from the disease.
Lewy Body Dementias
Lewy body dementias affect 1.3 million Americans and their families, according to the Lewy Body Dementia Association. This umbrella term includes both Parkinson's disease dementia and dementia with Lewy bodies. Lewy bodies are proteins found in the brain stem that deplete the neurotransmitter dopamine, which in turn affects movement resulting in Parkinsonian symptoms. In Lewy body dementia, these proteins diffuse throughout the brain, including the cortex. This results also in the depletion of the neurotransmitter acetylcholine, which causes behavior, thinking and perception disturbances, according to the Lewy Body Dementia Association.
Vascular Dementia
Vascular dementia occurs as a result of problems with the blood vessels that enter the brain, according to the Mayo Clinic. A blood vessel may be blocked, as in a stroke, or the blood vessels may narrow. Multiple infarct dementia can be caused by several mini-strokes in the brain, according to the Cleveland Clinic. These blood vessel problems lead to disruption of blood flow and damaged tissue. Vascular dementia afflicts 1 to 4 percent of adults older than 65, according to the Mayo Clinic.
Frontotemporal Dementia
Frontotemporal dementia, or FTD, serves as an umbrella term for several brain disorders that affect the frontal and temporal lobes of the brain. It used to be known as Pick's disease, which now indicates a specific subtype of the disorder. The causes of FTD remain largely unknown. In FTD, the frontal and temporal lobes begin to shrink due to loss of neurons, leading to behavioral changes, speech and language problems and movement disorders.
FTD tends to occur earlier than Alzheimer's, between the ages of 40 and 70, according to the Mayo Clinic. No cure or effective treatment exists.
References
- "Neuroendocrinology" journal; Prevalence of Dementia in the United States: The Aging, Demographics, and Memory Study; B.L. Plassman and colleagues; vol 29, no 1-2; 2007
- Surgeon General of the United States: Mental Health --Alzheimer's Disease
- Mayo Clinic: Vascular Dementia
- Mayo Clinic: Frontotemporal Dementia
- Lewy Body Dementia Association: What is Lewy Body Dementia?
