Dementia is a term used to describe a global malfunction of the brain, which causes memory loss and changes in behavior and personality for the affected person.
There are over 400 different types of dementia, which affect three areas of the brain — language, memory and decision-making.
The most common cause of dementia is Alzheimer’s disease, about 60% to 80% . Some warning signs of Alzheimer’s include short-term memory loss, confusion and disorientation, difficulty performing daily tasks, mood changes and challenges in solving or working through problems.
Vascular dementia has been traditionally recognized as another common cause of dementia. It is caused by the lack of blood flow to the brain and is related to atherosclerotic disease (plaque build-up in arteries) or stroke.
Dementia with Lewy bodies is caused by protein deposits in nerve cells that interrupt chemical messages in the brain, resulting in memory loss and disorientation. Affected people typically experience visual hallucinations and sleep disturbances.
Many people with advanced Parkinson’s disease will develop dementia, and Parkinson’s shares some similar symptoms with Lewy body dementia in that people with both diseases may develop trembling in their hands, have difficulty walking and often feel weak and unsteady. Early signs of Parkinsonian dementia include problems with reasoning and judgment, and, like Lewy body dementia, people also experience visual hallucinations.
A rare degenerative dementia, Creutzfeldt-Jakob disease, is a fatal brain disorder and usually appears in later life and progresses rapidly. Onset of symptoms occur around age 60, and about 90% of affected people die within a year. Symptoms of Creutzfeldt-Jakob disease include failing memory, behavioral changes, lack of coordination and visual disturbances.
Frontotemporal dementia is oftentimes misdiagnosed as Alzheimer’s disease or even a psychiatric problem, and it tends to affect people at a younger age, typically between ages 40 and 65. It affects the frontal and temporal lobes of the brain, the areas of the brain associated with personality, behavior and language. Affected people experience compulsive behaviors, speech difficulties, lack of inhibition and abrupt mood changes, among others.
Other common causes of dementia include:
- Wernicke-Korsakoff syndrome, a neurological disorder caused by a deficiency in the B vitamin thiamine, appears to be alcohol related and is characterized by mental confusion, gaps in memory, double vision and agitation
- Huntington's disease, which produces Alzheimer's-like dementia, is a neurodegenerative genetic disorder that leads to cognitive decline, psychiatric problems and affects muscle coordination
- Mixed dementia is a term used when a person has more than one type of dementia, such as Alzheimer’s disease and any other type of dementia. Physicians sometimes call this condition “dementia-multifactorial."