Dementia, in and of itself, is not a disease but rather a "syndrome.
" A syndrome is a group of symptoms that occur simultaneously (together) and chronically (over a long period of time).
In dementia, symptoms may be more obvious on some days rather than others but, as a rule, once a symptom occurs it can be expected reoccur in the future.
The majority of dementias are age-related, meaning that they occur in older individuals.
The symptoms of dementia are related to a decline in the victim's so-called cognitive functions.
These functions include processes such as short and long term memory, reasoning ability, or the ability to understand new information.
Although there are many different etiologies (causes) of dementia, the syndrome can be categorized based on the general area of the central nervous system that is being affected: the cerebral cortex or the subcortical structures.
The cerebral cortex refers to the exterior of the brain.
It is in this area, within the "gray matter" of the brain, that information received from the senses is first processed, then interpreted and stored for possible future recall.
O the cortical (cortex-related) dementias, the most widely known is Alzheimer's syndrome.
Other cortical dementias include vascular dementia (dementia arising from insufficient blood flow to the brain which typically causes multiple small strokes), alcohol-induced dementia, and a type of genetically-caused dementia known as "Fragile X-related syndrome.
" The subcortical areas of the brain are associated with physical activities such as walking, eating, swallowing, or using the hands to manipulate other objects.
A well known example of a subcortical dementia is the slow decline in cognitive function that is associated with Parkinson syndrome.
Another subcortical dementia is Huntington's disease, which is known to be genetically transmitted from father to son.
In addition to identifying the area of the brain that is affected, dementias are also classified by their etiology, or underlying cause.
One prominent etiology of dementia is known as metabolic dementia.
Metabolic dementia is caused by a defect in the way the body metabolizes, or uses, certain substances such as the hormones produced by the body's thyroid or adrenal glands.
Metabolic dementias, if they are detected early, respond very well to medical treatment.
Yet another potential cause of dementia is heavy metal toxicity.
Heavy metals include common elements such as lead and mercury or more exotic elements such as thallium or titanium.
These substances are generally deposited in the brain over long periods of time via foodstuffs or in the drinking water supply.
A final class of dementia is dementia that arises following an infection or an otherwise relatively minor illness such as measles.
In the past, poorly treated syphilis accounted for a significant number of dementia cases throughout both the nation and the world.
Today, thanks to antibiotics and other related drugs, dementia due to syphilis is a medical rarity.
Unfortunately, the number of dementia cases associated with AIDS is rising as those with the disease are surviving for longer periods.
The number of cases of dementia that are associated with previous infection with viral illnesses such as measles are now rare thanks to the aggressive use of childhood immunizations.
The many causes of dementia are thus reflected in the many specific dementias now recognized as distinct clinical syndromes.