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Overview of degenerative conditions

Alzheimer’s is just one of a large group of similar conditions that are the underlying cause of dementia. It is the most common and accounts for up to 70 per cent of cases. Other common degenerative conditions include:

  • vascular dementia
  • fronto temporal dementia
  • dementia with Lewy bodies.

A person may have more than one degenerative condition as an underlying cause of dementia.  Although less common, they can include:

  • Parkinson’s disease dementia
  • Huntington’s disease
  • prion diseases
  • Wernicke-Korsakoff syndrome.

Cause

In most cases, degenerative conditions develop when abnormal proteins accumulate to form aggregates that damage and kill brain cells. This differs in the case of vascular dementia, which occurs when blood and oxygen flow is restricted to parts of the brain.

Degenerative conditions that lead to dementia develop primarily as people age, although they are not an inevitable part of aging. Research into specific underlying causes is still ongoing.  Genetics is a factor in dementias such as younger-onset Alzheimer’s, with environment and lifestyle factors considered likely to play a part across the spectrum.

Common types of degenerative conditions

Alzheimer’s disease: develops in people over the age of 65 and leads to a decline in brain function, memory loss and dependence on others. Younger-onset Alzheimer’s affects people under the age of 65, with symptoms usually appearing when a person is in their 40s, 50s and occasionally 30s. While the underlying cause of Alzheimer’s in older people is still unknown, younger-onset Alzheimer’s has been found to be genetic and affects around five per cent of all cases.

Vascular dementia: develops when blood and oxygen is restricted to certain parts of the brain. This can occur during a single stroke, or can be the cumulative effect of many smaller strokes, also known as multi-infarct dementia. High blood pressure and thickened arteries can affect blood circulation and lead to another type of vascular dementia called Binswanger’s disease.  The decline of brain function and impact on mood and behaviour depends on which areas of the brain are affected.

Fronto temporal dementia: can be genetic and affects the frontal and temporal lobes, which progressively shrink due to different types of small dementias in those areas. It can lead to changes in personality, emotions and behaviour, and affects cognitive and language abilities. Memory can be affected although it is not always the case. Symptoms of this condition can appear when a person is in their 40s and 50s, which is earlier than most dementias.

Dementia with Lewy bodies: occurs when abnormal deposits called Lewy bodies develop within nerve cells in the brain.  It is similar to Alzheimer’s disease in the way it affects a person’s memory, ability to think and eventual loss of independence. People with this condition also develop Parkinsonism and experience the shared symptoms of Parkinson’s disease such as stiffness and tremors.

Although similar, Parkinson’s disease is a separate condition in which a person experiences Parkinsonism and may or may not go on to develop Parkinson’s disease dementia.