Learn about the six most common types of dementia

Types of Dementia

The six most common forms of dementia

There are more than 100 different types of dementia that have been discovered, however six forms of dementia account for the majority of cases. These are:

  • Alzheimer's disease
    The most common type of dementia. Around 70 per cent of all people living with dementia have Alzheimer’s disease
  • Vascular dementia
    The second most common at 17 per cent, vascular dementia is a group of diseases in which a person’s body is unable to circulate blood to the brain, which causes brain cells to be deprived of oxygen
  • Frontotemporal dementia
    A group of rarer dementias that typically develop earlier than 65 years of age. They are caused by degeneration of the frontal and / or temporal lobes in the brain, which are responsible for language, emotion, and behaviour
  • Lewy body dementia
    A form of dementia that includes the presence of abnormal structures in the brain, known as Lewy bodies, which affect the nerve cells and brain cells
  • Korsakoff syndrome (alcohol-related brain injury)
    A dementia that is usually caused by chronic alcoholism, particularly when combined with a vitamin B1 (thiamine) deficiency, and characterised by severe memory loss
  • Younger onset dementia
    While most people who develop dementia are over the age of 65, it is possible to develop all forms in your 50s, 40s, and even as young as 30. This is known as younger onset dementia

Rare forms of dementia account for only a small percentage of cases. Some of these rare dementias include:

Creutzfeldt-Jakob Disease (CJD)

Creutzfeldt-Jakob disease is a rare degenerative brain disorder in which an abnormally shaped protein called a prion causes rapid loss of memory and muscle control. The most common form of Creutzfeldt-Jakob disease is sporadic CJD, which usually affects people over 40.

Initial symptoms include:

  • Personality changes
  • Depression
  • Memory loss
  • Impaired thinking
  • Blurred vision or blindness
  • Insomnia
  • Difficulty speaking
  • Difficulty swallowing
  • Jerky movements

Before a diagnosis of Creutzfeldt-Jakob disease is given, a range of other causes may be considered including Alzheimer's disease and vascular dementia as there is no known cure for Creutzfeldt-Jakob disease and it is usually fatal within six to twelve months of onset.

Huntington's Disease

Huntington's disease is a neurological condition that is passed down in families, and is characterised by problems with movement and a lack of coordination.

Symptoms of Huntington’s disease include:

  • Growing lack of coordination
  • Twitching and other uncontrolled movements
  • Difficulty walking, speaking or swallowing

While Huntington’s disease is commonly thought of as a motor disorder, cognitive symptoms can occur and dementia can appear at any time through the disease’s progression.

Dementia symptoms include:

  • Mood changes
  • Problems with thinking
  • Trouble concentrating
  • Loss of short term memory

There is no cure for Huntington's disease, however treatment is available to help slow the symptoms and assist with function for as long as possible.

Parkinson's Disease Dementia (PDD)

Very similar to Lewy body dementia, Parkinson's disease dementia is caused by microscopic deposits gathering in the nerve cells in the brain stem, which then transfer to other parts of the brain. Parkinson's disease dementia is diagnosed when someone has already been diagnosed with Parkinson’s disease and then develops dementia symptoms.

People with Parkinson's disease have a higher risk of developing dementia, although around two thirds of people remain unaffected. When dementia symptoms occur, it is typically not until late in the course of the illness.

Everyone with Parkinson’s disease experiences different symptoms, however some of the most common are:

  • Tremor or shaking, usually beginning in a limb such as a hand
  • Trouble walking or moving due to rigid muscles
  • Starting to stoop and problems balancing
  • Loss of automatic movements
  • Speech changes such as speaking softly, quickly, slurring, or hesitating
  • Writing changes

Dementia related symptoms include:

  • Inability to make decisions
  • Disorientation in familiar surroundings
  • Difficulty concentrating
  • Memory loss

The side-effects of certain drugs for Parkinson's disease may make symptoms of dementia worse, so adjusting a person's medication accordingly can sometimes be of benefit.

Posterior Cortical Atrophy (PCA)

Posterior cortical atrophy, also known as Benson's syndrome, is a rare form of dementia which is usually considered to be caused by having Alzheimer’s disease.

The disease causes gradual but progressive degeneration of the outer layer of the brain, known as the cortex, in the part of the brain located in the back of the head (posterior). It causes people to lose the ability to interpret what they are looking at.

The first symptoms of posterior cortical atrophy tend to occur when people are in their mid-50s or early 60s. However, the first signs are often subtle and it may be some time before a formal diagnosis is made.

Symptoms of posterior cortical atrophy include:

  • Blurred vision
  • Challenges reading and writing
  • Inability to see objects in direct line of sight
  • Problems with depth perception

As damage in the brain spreads and the disease progresses, people develop the more typical symptoms of Alzheimer's disease, such as memory loss and confusion.

Corticobasal Degeneration (CBD)

With corticobasal degeneration, multiple areas of the brain including the cerebral cortex and basal ganglia shrink, causing the nerve cells to degenerate and eventually die. Corticobasal degeneration progresses gradually and affects movement on one or both sides of the body. Symptoms typically appear in people from 50 to 70 years of age.

Symptoms usually begin in one limb and include:

  • Shaking (tremors)
  • Uncontrollable limb movements (known as ‘alien limb’)
  • Loss of feeling
  • Muscle stiffness

As corticobasal degeneration progresses, dementia symptoms may start to appear, including:

  • Problems recalling words
  • Short term memory loss
  • Difficulty coping with sudden and unexpected situations

There is no cure or treatment available for corticobasal degeneration, but medication can alleviate some symptoms and allied health therapies such as physiotherapy or occupational therapy can also be beneficial for movement based symptoms.

Niemann-Pick Disease Type C

Unlike most other dementias, Niemann-Pick disease type C is an inherited condition that mainly affects children. It should not be confused with Pick’s disease, which is another name for frontotemporal dementia. People with this rare disease are unable to process cholesterol and other fats. As a result they accumulate in cells, including brain cells, affecting movement.

Symptoms include:

  • Difficulty moving limbs
  • Enlarged spleen
  • Enlarged liver
  • Jaundice at, or shortly after, birth
  • Slurred irregular speech
  • Seizures

The onset of the disease in the teenage years or early adulthood means that people are more likely to experience dementia as part of the disease.

Dementia symptoms include:

  • Confusion
  • Memory problems
  • Difficulties concentrating and learning

There no treatment for the disease, and life expectancy varies. However, researchers have identified the responsible gene and there is continuing research into this area.

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