DMT03: Types of Dementia

ALZHEIMER’S DISEASE

Alzheimer’s is by far the most common type of dementia, attributed to  approximately 2/3 of cases. It was first identified 100 years ago.

The onset of Alzheimer’s can be slow and subtle, followed by a gradual decline. Changes in short term memory are noticeable, i.e. memory of recent events. This is typically the primary first complaint.

Those at greater risk of contracting Alzheimer’s include:

• The Elderly – there is an increased risk after the age of 65. By age 85 or more, there is an almost 50% risk of acquiring the disease.
• Females – females are at a greater risk of contracting the disease than males.
• Genetics – if there is a genetic history of Alzheimer’s in the family, there is a greater risk of developing the disease. 

VASCULAR DEMENTIA

Vascular, or multi-infarct, dementia is the second most common cause of dementia, estimated to be 20% of cases. It is caused by reduced blood flow to parts of the brain, often as a consequence of tiny strokes that block small arteries.

The onset of symptoms may seem more sudden and clear. Memory may or may not be as seriously affected as is the case with Alzheimer’s. This can depend on whether blockage has occurred in the memory regions of the brain.

FRONTO –TEMPORAL DEMENTIA  (FTD)

FTD causes personality and behavioural changes and loss of language functions at an early stage. This is different from the memory complaints typical of Alzheimer’s.

FTD represents approximately 10-15% of dementia cases and nearly half of these cases occur in people under 65 years of age.

It is distinguished from Alzheimer’s by some or all of following: 

• Inappropriate and anti-social behaviours.
• Apathy; compulsions (relative preservation of visual spatial and cognitive skills).
• Language deficits progressing to mutism.
• Changes in the brain include shrinkage of the frontal and temporal lobes (which can be seen on PET scans).

LEWY BODY

Lewy Body Dementia is caused when abnormal protein deposits called Lewy bodies are left in the brain. Symptoms include hallucinations and memory loss.

This is similar to Alzheimer’s disease, but characterized more often by early changes in movement or the development of extra pyramidal symptoms. This includes: tremors; tics; rigidity; shuffling; gait, which can make individuals look like they have Parkinson’s disease.

Alertness and severity of cognitive symptoms may fluctuate significantly on a day to day basis. There is often a poor tolerance to medications, as well as autonomic nervous system dysfunction. An example would be wild swings in blood pressure.

Lewy body dementia can be challenging to diagnose because of it’s similarities to Alzheimer’s and Parkinson’s disease.

Other Types Of Dementia

There are a range of less common forms of dementia which are outlined here:

Parkinson’s Disease is characterised by tremors, stiffness, speech difficulties and problems initiating movement. When muscle stiffness affects the face, the person may have a mask-like stare. Persons with Parkinson’s may develop dementia late in the course of the disease. A clear sign of Parkinson’s is the presence of Lewy bodies (abnormal proteins) specifically in the area of the brain that controls physical movement.

Huntington’s Disease is an inherited degenerative and fatal brain disease starting in mid life. Characteristics include personality changes, depression and the development of involuntary movements

Jakob’s Disease is a rare and rapidly fatal brain disorder causing Dementia. It affects coordination and causes behavioral changes. It is caused by an abnormal protein (called prion) that turns normal proteins into infectious ones. This disease is related to Mad Cow Disease.

HIV Dementia is direct infection of the brain with toxic viro-proteins. It is believed to cause dementia in 20-30% of people with advanced HIV and 50% of those with fully developed AIDS. Initial signs are poor concentration, forgetfulness, depression, apathy, weakness and myoclonus (sudden, involuntary twitching of muscles).