Facts about dementia

The ‘what is dementia’ page looks at the meaning of the word dementia, the symptoms and the diseases that cause it. This page covers some of the more detailed facts about dementia including the difference between cortical or subcortical dementia, whether a type of dementia is classified as either primary or secondary dementia and the difference between reversible and irreversible dementia.

Difference between cortical and subcortical dementia

Dementia may be categorised as follows:

The difference between cortical and subcortical dementia

The type of dementia may be classified as either cortical or subcortical depending on which part of the brain is the primary location of dementia.

Overview of the brain – The cerebrum, is the largest and most highly developed part of the human brain, it accounts for about two-thirds of the brain mass and lies over and around most of the structures of the brain.

A deep groove that runs from front to back divides the brain into the left and right halves known as the two cerebral hemispheres. Each hemisphere is in turn divided into four lobes.

The surface of the cerebral hemispheres is covered by a thin layer known as the cerebral cortex or simply the cortex. It contains billions of brain cells called grey matter.

Underneath the cortex are bundles of nerve fibres known as white matter, which transport nerve signals between parts of the cortex and from the cortex to other parts of the brain.

Cortical dementia

Cortical dementia is typically associated with the brains grey matter.

Types of cortical dementia

Primary Symptoms

  • Memory.
  • Language – the inability to find the right words.
  • Processing information – Understanding what others are saying.

Subcortical dementia

Subcortical dementias are believed to initially affect the structures below the cortex and are more associated with the brain’s white matter.

Types of subcortical dementia

Primary symptoms

  • Personality changes.
  • Slow thought processes.

Some types of dementia appear to affect both the cortical and subcortical areas of the brain such as Lewy body dementia and vascular dementia.

Primary or secondary dementia

The type of dementia can also be classified as primary or secondary dementia depending on whether the dementia relates to any other disease.

Primary dementia is where the dementia itself is the major sign of brain disease not directly related to any other illness and include:

Secondary dementias are those caused by or closely related to some other recognisable disease such as aids or a stroke.

Irreversible or reversible dementia

The majority of dementias are progressive i.e. will get worse over time, are irreversible and will result in death.

Irreversible dementias include:

However, there are some that are reversible i.e. it doesn’t inevitably get worse over time and recovery is possible.

Reversible dementias include:

  • B12 deficiency.
  • Thyroid deficiency.
  • Brain tumors.
  • Normal-pressure hydrocephalus.

This section of the website also includes some more in-depth facts about dementia including:

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