Alzheimer's Disease and Related Dementia

Alzheimer's disease is a progressive, degenerative disease of the brain, which causes thinking and memory to become seriously impaired. It is the most common form of dementia.

Alzheimer's is characterized by "plaques"- numerous tiny deposits scattered throughout the brain which become toxic to brain cells at excessive levels; and "tangles" which interfere with vital processes eventually choking off the living cells. As well, when brain cells degenerate and die, the brain markedly shrinks in some regions. As Alzheimer's progresses and affects different areas of the brain, various abilities become impaired. The result is changes in abilities and/or behaviour. At present, once an ability is lost, it is not known to return. Research, however, is now suggesting that some relearning may be possible.

What is Dementia?

Any good description of Alzheimer's disease starts with a definition of 'what is dementia?' We hear these two terms used interchangeably and often it can be a source of confusion for persons hearing this diagnosis.

Dementia is a syndrome consisting of a number of symptoms that include loss of memory, impairments in judgment and reasoning abilities, and changes in mood and behaviour. It is not a disease itself, but an umbrella term for the grouping of symptoms. Sometimes symptoms of dementia can be caused by conditions that may be treatable, such as depression, thyroid disease, infections or drug interactions. If the symptoms are not treatable and progress over time, they may be due to damage to the nerve cells in the brain.

Alzheimer's disease is the main cause of non-treatable dementia, accounting for approximately 64% of all cases of dementia in Canada. There are, however, other diseases that cause dementia. The most common forms include:

Vascular Dementia

Vascular Dementia (VaD), also called multi-infarct dementia, occurs when the cells in the brain are deprived of oxygen. A network of blood vessels called the vascular system supplies the brain with oxygen. If there is a blockage in the vascular system, or if it is diseased, blood is prevented from reaching the brain. As a result, cells in the brain die, leading to the symptoms of dementia. After Alzheimer's disease, VaD is the second leading form of dementia, accounting for up to 20% of all cases.

When Alzheimer's disease and VaD occur at the same time, the condition is called mixed dementia. For more information about Vascular dementia, please visit the Alzheimer Society of Canada's website.

Frontotemporal Dementia

Frontotemporal Dementia is an umbrella term for a group of rare disorders that primarily affect the frontal and temporal lobes of the brain - the areas generally associated with personality and behaviour. In some cases, brain cells in these areas shrink or die. In other cases, the brain cells in these areas get larger, containing round, silver "Pick's bodies". Pick's Disease refers to a subtype of Frontotemporal Dementia that has these specific abnormalities. In Frontotemporal Dementia, the changes in the brain affect the person's ability to function. Researchers estimate that approximately 2-5% of all dementia cases are Frontotemporal Dementia. More information about Frontotemporal Dementia.

Lewy Body Dementia

Lewy body Dementia is a form of dementia characterized by abnormal deposits of a protein called alpha-synuclein that form inside the brain's nerve cells. These deposits are called "Lewy bodies" after the scientist who first described them. The process that leads to the formation of Lewy bodies is unknown. Areas of the brain involved in thinking and movement are most affected in Lewy body Dementia. Lewy body Dementia can occur by itself, or together with Alzheimer's disease or Parkinson's. It accounts for 5-15% of all dementias. More information about Lewy body Dementia.

Regardless of the type of dementia, individuals can obtain help and support from the Alzheimer Society.