November 03, 2012

What is Dementia?

Dementia, Cognition and Sundials: 

Dementia is a medical condition in which an individuals’ cognition is so disturbed that their work, usual social activities or relationships with others are affected.  But what exactly do we mean by "cognition?" Well, a simple definition is that it is the use of prior knowledge to help interpret nerve signals received from the eye and other sensory organs.

The word cognition is related to the term “gnomon” - the shadow-casting rod of a sundial.  Both words stem from the Greek terms for “knowledge” and “interpreter.”  The gnomon measures the heavens by the shadows it casts, and this is a useful analogy of the process of cognition; we measure or evaluate our surroundings by interpreting their neurally coded shadows.

Features of dementia:

There are certain core features of dementia, namely:

·       Impairment of more than one area of cognitive function

·       Behavioural changes

·       Impaired social functioning

Areas of cognitive function that can be impaired in dementia include memory, orientation, comprehension, learning ability, language and perception.  Dementia disorders are advanced stages of degenerative brain disorders; however there is good evidence that these diseases may have their onset many years before dementia itself becomes apparent. 

Causes of dementia:

Dementia can have many different causes.  It can arise from many different types of brain pathology such as Alzheimer's Disease, Vascular dementia, Pick's Disease, Huntington's Disease, Parkinson's Disease, etc. It can also arise as a result of hormonal disorders such as an under- or over-active thyroid gland.  As we shall see in later Blogs, it can also be a feature of vitamin deficiencies as well as liver and kidney failure.

The nature of the underlying cause determines whether the dementia is progressive, static, or reversible and to what extent it can be treated.  Dementia must also be distinguished from other conditions that can present with similar symptoms such as depression, schizophrenia and hysteria, as well as drug induced and acute confusional states (delirium). However, Alzheimer's Disease and Vascular Dementia account for the majority of cases.


In our next Blog updates we will take a closer look at Alzheimer's Disease in particular.

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