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Types of dementia

What is dementia?

Dementia describes symptoms affecting a person's memory, thinking and reasoning caused by brain diseases, such as Alzheimer's disease.

Dementia affects around 850,000 people in the UK

There is no cure for dementia, but depending on the causes of dementia, treatment may help manage or delay symptoms and their progression.

What causes dementia?

The most common causes of dementia include:

  • Degenerative neurological diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease (a rare inherited disorder) and some types of multiple sclerosis
  • Vascular disorders, such as vascular dementia (multi-infarct dementia), which is caused by multiple strokes in the brain
  • Traumatic brain injury caused by motor vehicle accidents, falls, etc.
  • Infections of the central nervous system such as meningitis, HIV and Creutzfeldt-Jakob disease, a quickly progressing and fatal disease that is characterised by dementia and muscle twitching and spasm
  • Chronic alcohol or drug use
  • Depression
  • Certain types of hydrocephalus, an excess accumulation of fluid in the brain that can result from developmental abnormalities, infections, injury, or brain tumours.

Types of dementia

Dementia can be split into two broad categories, the cortical dementias and the subcortical dementias, based on which part of the brain is affected.

  • Cortical dementias arise from a disorder affecting the cerebral cortex, the outer layers of the brain that play a critical role in thinking abilities like memory and language. Alzheimer's and Creutzfeldt-Jakob disease are two forms of cortical dementia. People with cortical dementia typically show severe memory loss and aphasia, the inability to recall words and understand language.
  • Subcortical dementias result from dysfunction in the parts of the brain that are beneath the cortex. Usually, the forgetfulness and language difficulties that are characteristic of cortical dementias are not present. Rather, people with subcortical dementias, such as Parkinson's disease, Huntington's disease, and AIDS dementia complex, tend to show changes in their speed of thinking and ability to initiate activities.

There are cases of dementia where both parts of the brain tend to be affected, such as vascular dementia.

Are there treatments for dementia?

Some forms of dementia can be treated. These include dementia caused by:

  • Chronic alcohol or drug abuse
  • Tumours that can be removed
  • Subdural haematoma, a blood clot beneath the outer covering of the brain that results from a broken blood vessel, usually as a result of a head injury
  • Normal pressure hydrocephalus (a brain disorder that occurs when the flow of cerebrospinal fluid is blocked)
  • Metabolic disorders, such as a vitamin B12 deficiency
  • Hypothyroidism, a condition that results from low levels of thyroid hormone
  • Hypoglycaemia, a condition that results from low blood sugar

Non-treatable causes of dementia include:

  • Alzheimer's disease
  • Vascular dementia
  • Dementias associated with Parkinson's disease and similar disorders
  • AIDS dementia complex
  • Creutzfeldt-Jakob disease

 

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WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on April 20, 2016

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