Dementia itself is not a disease. According to Thomas D. Bird, writing in "Harrison's Principles of Internal Medicine," it is a deterioration in mental abilities that impairs the successful performance of activities of daily living. Memory is the most common cognitive ability lost with dementia, but language, visual and spatial abilities, thinking and reasoning skills, judgment and problem solving are also affected. Persons suffering from dementia are unable to maintain emotional control; they may experience personality changes such as depression, withdrawal, delusions, hallucinations, agitation or insomnia.
Alzheimer's Disease
Alzheimer's disease (AD) is the most common cause of dementia in western countries. According to Eric D. Caine, M.D., writing in "Kaplan & Sadock's Comprehensive Textbook of Psychiatry," AD is a progressive, degenerative brain disease that creates irreversible changes in brain cells. These changes result in progressively impaired memory and thinking, language problems, lapses of judgment and personality changes, which, according to Thomas D. Bird, M.D., writing in "Harrison's Principles of Internal Medicine," increasingly interfere with daily activities. Patients often suffer from delusions, become disoriented with respect to places and times, and slowly lose the ability to control their motor functions. MayoClinic.com points out that amyloid plaques, which are abnormal clumps of protein that form between brain cells, and neurofibrillary tangles among brain cells are suspected culprits in the cause of AD.
Parkinson's Disease
Parkinson's disease (PD) is a degenerative disease of the brain. According to MedicineNet.com, it is caused by the death or impairment of nerve cells in a part of the brain known as the substantia nigra. In a healthy brain, nerve cells in the substantia nigra produce a chemical called dopamine, which acts as a chemical messenger between areas of the brain responsible for the smooth, coordinated movement of muscles. The absence of dopamine in the brain results in erratic and irregular firing patterns in the brain, producing uncontrolled movement. In addition to muscular rigidity and tremor, PD often causes a cognitive problems and a condition known as Parkinson's dementia, which results in impaired memory, slowness in thinking, a lack of social judgment, and language problems.
Vascular Dementia
Vascular dementia (VD) is the second most common cause of dementia, after AD. According to Thomas D. Bird, M.D., writing in "Harrison's Principles of Internal Medicine," this dementia usually follows a stroke, which results in damage or the death of a localized area of brain tissue. Symptoms often begin suddenly after the stroke, and the individual may develop chronic cognitive deficits. Eric D. Caine, M.D. writing in "Kaplan & Sadock's Comprehensive Textbook of Psychiatry" points out that the characteristics of vascular dementia depend on the area of the brain which has sustained the stroke. These resulting characteristics are similar to those of AD. However, unlike AD, the personality and emotional responsiveness of persons with vascular dementia usually remain intact until the disease progresses to the later stages.
Dementia with Lewy Bodies
Dementia with Lewy bodies (DLB) is characterized by the death of cells in the brain's cortex, or outer layer, and in an area in the center of the brain known as the substantia nigra. The nerve cells in the substantia nigra, which do survive contain abnormal clumps of protein known as Lewy bodies. According to the Mayo Clinic, Lewy bodies are also found in the brains of persons with AD and PD. Many of the symptoms of DLB are similar to those of AD, but features that are unique to this dementia include daily fluctuations between confusion and clear thinking, visual hallucinations, and the bodily rigidity and tremor that are characteristic features of PD.
Frontotemporal Dementia
The hallmark of frontotemporal dementia (FTD) is a marked deterioration of the temporal and/or frontal lobes of the brain, areas associated with language, behavior, and personality, according to Kyle Brauer Boone, Ph.D., writing in "Kaplan & Sadock's Comprehensive Textbook of Psychiatry." The cause of this disease has been linked to genetic mutations on several chromosomes. Memory is typically spared, but problems arise with planning, judgment, speech or language. Personality changes include disinhibition, social misconduct and lack of insight. Common behavioral problems include apathy, weight gain, food fetishes, compulsions and euphoria. Patients often experience problems with physical coordination.
Huntington's Disease
Huntington's disease (HD) is a hereditary degenerative brain disorder caused by a faulty gene that encodes for a protein called huntingtin. It is a movement disorder characterized by chorea (jerky, involuntary movements, chiefly of the face and extremities) and dementia. According to David Gordon Daniel, M.D., writing in "Kaplan & Sadock's Comprehensive Textbook of Psychiatry," this disorder typically appears around 35 years of age and is relentlessly progressive, ending in death within 15 years after diagnosis. HD is also characterized by language impairment, and abnormalities in memory, problem solving, insight, judgment, abstraction, attention and motivation as it progresses to severe dementia.
Creutzfeldt-Jakob Disease
Prions are infectious proteins that cause degeneration of the central nervous system, according to Stanley B. Prusiner, M.D., writing in "Harrison's Principles of Internal Medicine." The most common prion disease in humans is called Creutzfeldt-Jakob disease (CJD), a rare, fatal brain disorder. Typical characteristics of CJF are dementia and irregular involuntary contraction of muscles. It is relentlessly progressive, and generally causes death within a year of onset. Symptoms include fatigue, sleep disturbance, weight loss and headache. Most people with CJD display mental deficits which rapidly progress to a state of profound dementia characterized by memory loss, impaired judgment, and a decline in all aspects of intellectual function.
References
- "Harrison's Principles of Internal Medicine"; Thomas D. Bird, M.D.; 2005
- "Kaplan & Sadock's Comprehensive Textbook of Psychiatry, Volume 1"; Eric D. Caine, M.D.; 2000
- Mayo Clinic:Dementia
- Medicine Net.com: Parkinson's Disease
- "Kaplan & Sadock's Comprehensive Textbook of Psychiatry, Volume 2;" Kyle Brauer Boone, Ph.D.; 2000
