Dementia is a catch-all term for a variety of brain conditions that cause mental impairment, usually later in life. Senile dementia was a term once used to describe all the forms of dementia that occur in older people. It is no longer used as a diagnosis. These 10 categories define the most common types of dementia more precisely.
1. Alzheimer's Disease
Alzheimer's (or Alzheimer) disease, which is also known as Alzheimer's dementia, is the most common cause of dementia. The cause of Alzheimer's is unknown. Most but not all Alzheimer's patients have tangled plaques of proteins around the neurons of their brains, but it is not known whether these plaques cause or result from the condition. About 6.1 million people over the age of 65 and 200,000 people who are not yet 65 have the disease in the United States. The risk of Alzheimer's is closely tied to the APOE gene. For people who carry a variation of the gene called for APOE 4/4, lifetime risk of developing the disease is 51 percent for men and 60 percent for women. For people who carry the APOE 3/4 genes, risk is 23 percent for men and 30 percent for women. Otherwise, about 11 percent of men and about 14 percent of women will be diagnosed with Alzheimer's if they live to be 85.
2. Vascular dementia
The second most common form of dementia is vascular dementia. It is caused by the accumulation of "mini-strokes" in the brain. People who have untreated high blood pressure are at relatively high risk for the disease. It may cause loss of vision or muscle weakness years before dementia is obvious.
3. Frontotemporal dementia
Frontotemporal dementia is associated with decreases in the volume and function of the frontal and temporal lobes of the brain. It can cause marked changes in personality, impulsivity, and poor judgment. Sometimes people who have frontotemporal dementia develop stiffness in their muscles.
4. Huntington's disease
Once known as Huntington's chorea, Huntington's disease (or Huntington disease) is recognized by a "chorea" of involuntary movements in its later stages. Memory loss can precede motion problems by several years. Huntington's disease is relatively rare except in a few locations: Lake Maracaibo in Venezuela, Tasmania, and Mauritius.
5. Normal pressure hydrocephalus
Normal pressure hydrocephalus results from an abnormal enlargement of the fluid-filled ventricles that puts pressure on the rest of the brain. It most commonly causes problems with walking, memory, and urinary incontinence. It is diagnosed with MRI or CT scan but confirmed with further diagnosis. Sometimes hydrocephalus is treated by installing a shunt into the brain.
6. Alcoholic dementia and Wernicke-Korsakoff syndrome
Heavy drinkers sometimes become deficient in B vitamins and develop alcoholic dementia, also known as Korsakoff or Wernicke-Korsakoff syndrome. (A severe deficiency of vitamin B1, also known as thiamine, causes changes to the brain known as Wernicke encephalopathy. The resulting psychiatric condition is Korsakoff syndrome.) The most prominent symptom of this form of dementia is memory loss. Sometimes thiamine deficiency does not involve heavy drinking in rare cases of severe malnutrition.
7. Traumatic brain injury (TBI)
Traumatic brain injury, often abbreviated TBI, results from impacts to the skull that damage the brain. TBI may result from accidents or from cumulative head trauma from playing sports. An older term for this condition referred to the condition in boxers, dementia pugilistica.
8. Lewy body dementia/Lewy body disease
While Alzheimer's disease is associated with abnormal proteins that accumulate outside neurons, Lewy body dementia or Lewy body disease is caused by abnormal proteins that accumulate inside neurons. Public interest in this condition grew after the suicide of comedian Robin Williams, who had been diagnosed with the disease. Memory loss is a prominent symptom of Lewy body disease. Many patients also suffer hallucinations.
9. Creutzfeldt-Jakob disease
Creutzfeldt-Jakob disease results from the accumulation of yet another abnormal protein in the brain. It may be an inherited condition, or it may be transmitted through a protein called a prion, as in "mad cow disease." The condition progresses rapidly, over just a few years.
10 Mixed dementias
Mixed dementias are a combination of one or more other forms of the disease. It is more common to have more than one disease process causing dementia than it is to have only one.
Other, rarer forms of dementia
These 10 kinds of dementia are the most common forms of the disease, but there are other conditions that result in similar impairment. Parkinson's disease and vascular Parkinson's frequently result in mood swings, personality changes, and hallucinations. Corticobasilar dementia results from shrinkage of tissues at the base of the brain. Niemann-Pick disease type C is a rare inherited condition. It is not related to frontotemporal dementia, which is also known as Pick disease. Posterior cortical atrophy (PCA), also known as Benson's syndrome, is a loss of brain matter at the back of the brain, it is often associated with Alzheimer's. Progressive supranuclear palsy is a rare form of dementia that is becoming more frequently diagnosed. Dementia can be a complication of HIV, multiple sclerosis, and certain kinds of infections.