Dementia is a clinical syndrome that includes loss or decline in memory and other cognitive abilities.
Dementia is caused by various diseases and conditions that result in damaged brain cells. Brain cells can be destroyed by brain diseases, such as Alzheimer’s disease, or strokes (called vascular or multi-infarct dementia), which decrease blood flow to the brain.
Alzheimer's disease is the most common cause of dementia.
Dementia can be caused by any of the following: AIDS, high fever, dehydration, hydrocephalus, systemic lupus erythematosus, Lyme disease, long-term drug or alcohol abuse, vitamin deficiencies, poor nutrition, hypothyroidism or hypercalcemia, multiple sclerosis, brain tumor. Dementia can also result from a head injury that causes hemorrhaging in the brain or a reaction to a medication.
Dementia includes decline in memory, and at least one of the following cognitive inabilities:
Ability to generate coherent speech and understand spoken or written language;
Ability to recognize or identify objects, assuming intact sensory function;
Ability to execute motor activities, assuming intact motor abilities, sensory function and comprehension of the required task;
and Ability to think abstractly, make sound judgments and plan and carry out complex tasks.
The decline in cognitive abilities must be severe enough to interfere with daily life.
Different types of dementia are associated with distinct symptom patterns and distinguishing microscopic brain abnormalities.
Common Types of Dementia and Their Typical Characteristics
Alzheimer’s disease. Most common type of dementia; accounts for 60 to 80 percent of cases.
Difficulty remembering names and recent events is often an early clinical symptom; later symptoms include impaired judgment, disorientation, confusion, behavior changes and trouble speaking, swallowing and walking.
Hallmark abnormalities are deposits of the protein fragment beta-amyloid (plaques) and twisted strands of the protein tau (tangles).
Vascular dementia. Considered the second-most-common type of dementia.
Impairment is caused by decreased blood fl ow to parts of the brain, often due to a series of small strokes that block arteries.
Symptoms often overlap with those of Alzheimer’s, although memory may not be as seriously aff ected.
Characterized by the presence of the hallmark abnormalities of Alzheimer’s and another type of dementia, most commonly vascular dementia, but also other types, such as dementia with Lewy bodies, frontotemporal dementia and normal pressure hydrocephalus.
Dementia with Lewy bodies.
Pattern of decline may be similar to Alzheimer’s, including problems with memory, judgment and behavior changes.
Alertness and severity of cognitive symptoms may fl uctuate daily.
Visual hallucinations, muscle rigidity and tremors are common.
Hallmarks include Lewy bodies (abnormal deposits of the protein alphasynuclein) that form inside nerve cells in the brain.
Many people who have Parkinson’s disease develop dementia in the later stages of the disease.
The hallmark abnormality is Lewy bodies (abnormal deposits of the protein alpha-synuclein) that form inside nerve cells in the brain.
Frontotemporal dementia. Involves damage to brain cells, especially in the front and side regions of the brain.
Typical symptoms include changes in personality and behavior and diffi culty with language.
No distinguishing microscopic abnormality is linked to all cases.
Pick’s disease, characterized by “Pick’s bodies,” is one type of frontotemporal dementia.
Rapidly fatal disorder that impairs memory and coordination and causes behavior changes.
“Variant Creutzfeldt-Jakob disease” is believed to be caused by consumption of products from cattle affected by “mad cow disease.”
Caused by the misfolding of prion protein throughout the brain.
Normal pressure hydrocephalus.
Caused by the buildup of fluid in the brain. Symptoms include difficulty walking, memory loss and inability to control urine.
Can sometimes be corrected with surgical installation of a shunt in the brain to drain excess fluid.
Mild cognitive impairment is a condition in which a person has problems with memory, language or another essential cognitive function that are severe enough to be noticeable to others and show up on tests, but not severe enough to interfere with daily life.
Some people with mild cognitive impairment go on to develop dementia. For others, the symptoms of mild cognitive impairment do not progress to dementia, and some people who have mild cognitive impairment at one point in time later revert to normal cognitive status.
Bob DeMarco is an Alzheimer's caregiver and editor of the Alzheimer's Reading Room. The Alzheimer's Reading Room is the number one website on the Internet for advice and insight into Alzheimer's disease. Bob taught at the University of Georgia, was an executive at Bear Stearns, the CEO of IP Group, and is a mentor. He has written more than 775 articles with more than 18,000 links on the Internet. Bob resides in Delray Beach, FL.