One of the biggest causes of dementia is cortical dementia which results in Alzheimer’s Disease. It is a disease which effects the area of the brain called the cortex. Sub-cortical dementia is when a person has dementia as part of another disease such as Parkinson’s Disease or Huntingdon’s Chorea. Other parts of the brain are affected. Cardio-vascular dementia is caused by a single stroke or a series of strokes. There can also be other causes such as infectious diseases and tumours.
The Alzheimer’s Society describes how the causes of dementia affects the brain in different ways producing different symptoms.
Neuron death is the main cause of dementia and is often related to malfunctions in the communication system that a neuron needs to survive. However, if the immune system of the brain is too active and causes inflammation, this can also damage cells. Unlike most cells, when neurons die, other cells do not divide and replace them. Therefore most dementias are progressive and cannot be reversed.
Alzheimer’s Disease
Alzheimer’s Disease is associated with accumulation of two proteins – amyloid and tau – into plaques and tangles in the brain.
Amyloid
Beta amyloid is a small protein that is produced in all nerve cells. It is a by-product that is formed when a much larger protein, called amyloid precursor protein (APP), is broken down. Beta-amyloid accumulates as plaques in Alzheimer’s Disease and is a hallmark of the disease.
Tau
Tau is also produced by healthy neurons. It is essential for maintaining the shape of the cells, as well as ensuring that cells can communicate effectively with each other. Research suggests that in Alzheimer’s Disease an abnormal version of tau is produced, preventing it from performing its job properly and causing it to accumulate into tangles (known as neurofibrillary tangles or NFT). This disrupts the structure and communication within the nerve cells, leading to cell death. Current research is focused on understanding how abnormal tau is produced and what it does.
Vascular dementia
Blood carries all the oxygen and nutrients to the brain and there are thousands of blood vessels that feed the different regions. If blood flow is reduced, cells in the brain begin to starve and die. This can lead to vascular dementia. One type of vascular dementia, called multi-infarct dementia, is caused when blood vessels become blocked, for example during a stroke. The other type, small-vessel disease occurs when the walls of blood vessels are damaged causing little bleeds. This leads to localised damage, and disrupted blood flow, throughout the brain.
Dementia with Lewy bodies
Dementia with Lewy Bodies and Parkinson’s disease dementia (PDD) are linked to Parkinson’s disease. In this type of dementia, an abnormal version of a protein called alpha synuclein accumulates in clumps in the brain. This is associated with a loss of communication between cells, leading to loss of specific types of neurons. Symptoms include impaired mental ability, movement difficulties, and a rapid progression of symptoms.
Fronto-temporal dementia
Fronto-temporal dementia which includes Pick’s disease, is associated with deterioration of the frontal and temporal lobes of the brain. Symptoms include changes in personality and mood, and language difficulties. Fronto-temporal dementia often affects younger people and has been linked to certain genes.
For more information go to: www.alzheimers.org.uk
Written by Rachel Harrison
Speech and Language Therapist
On behalf of Integrated Treatment Services.
www.integratedtreatmentservices.co.uk
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