Rather than a specific disease, the term dementia describes a group of particular symptoms. It is defined as the significant impairment of two or more brain functions that controls language, memory, reasoning and judgment. The loss of capacity severely reduces mental abilities used in everyday activities, problem solving, emotional control and relationships.
Dementia arises from various neurological disorders. With some types of dementia, proper treatment can reverse the symptoms. Others, such as Alzheimer’s disease.(AD) – the most common type of dementia – are degenerative, causing nerve cells to stop functioning and die, leading to an incurable, progressive loss of brain function. While dementia primarily affects older individuals, it is not a normal process of aging.
Types of Dementia
Doctors classify the different forms of dementia based on what areas of the brain they affect and if they are progressive. Among the categories of dementia are:
- Cortical – damage in the brain’s cortex, affecting memory, thinking, language, behavior and social skills
- Subcortical – occurring below the cortex affecting memory, emotion and movement
- Primary – resulting from a single disorder
- Secondary – caused by a physical disease or head trauma
- Progressive – over time continues to become worse
Some types into more than one category, like AD that is described as both progressive and cortical.
The different types of dementia include:
- Lewy body dementia – the most common type of progressive dementia, named for the abnormal structures in the brain that are unique to the disorder, is incurable. It impairs memory and judgment and often causes problems with posture, walking and hallucinations.
- Vascular dementia – the second most common cause of dementia, found in 20 percent of all cases, usually is the result of a stroke or heart problems. Patients often wander at night and experience incontinence and depression.
- Frontotemporal dementia – also called frontal lobe dementia, found in 2 to 10 percent of cases, is related to abnormalities in the ‘tau’ protein, which collects into neurofibratory tangles. Some patients experience only a slow decline, while others have rapid loss of function.
- Huntington’s disease – an inherited disease related to an abnormal gene that controls the huntingtin protein. It causes degeneration of the brain and spinal cord leading to jerky movements (chorea), personality changes that become progressively more severe and eventually death.
- HIV-associated dementia – caused by the human immunodeficiency virus, it causes extensive damage to the brain’s white matter. Drugs to treat AIDs may help reduce symptoms or delay onset of the condition.
- Dementia pugilistica - also called Boxer’s syndrome because repeated blows to the head like those experienced by people who box cause it. In addition to dementia, it leads to Parkinson’s-like symptoms such as a clumsy walk, poor coordination and slurred speech.
- Creutzfeldt-Jakob disease – a rare, degenerative and fatal disorder often with no known cause, it leads to changes in personality, muscle control and vision problems. Death usually occurs from pneumonia or other infections.
- Corticobasal degeneration – a progressive form that kills nerve cells and causes the brain to atrophy, impairing coordination, speech, vision and swallowing, Death usually occurs from other problems such as pneumonia.
Health problems that affect movement and other brain functions can lead to secondary dementias, but the causes are not fully understood. Examples include Parkinson’s disease, multiple sclerosis, ALS, normal pressure hydrocephalus, Wilson’s disease and oliopontocerebellar atrophy.