Anosognosia
Anosognosia is a condition where people who suffer disability due to brain injury may seem unaware or deny their handicap. This may include unawareness of quite dramatic handicaps, so that people who are blind or paralysed may seem unaware that this is the case and believe otherwise, despite a complete lack of function in these areas. The exact causes are still mysterious and relatively little is known about this condition.It is relatively common following brain injury (e.g. 20-30% in the case of hemiplegia after stroke) and can seem to occur for virtually any impairment. However, it is not related to global mental confusion (see delirium), cognitive flexibility, or other major intellectual disturbance. Anosognosia can be selective in that an affected person with multiple impairments may only seem unaware of (for example) one handicap, whilst seemingly to be fully aware of others.
It does not seem to be directly related to sensory loss and is thought to be caused by damage to higher level neurocognitive processes which are involved in integrating sensory information with processes which support spatial or bodily representations.
It is thought to be related to spatial neglect, a condition often found after damage to the right hemisphere of the cortex, where sufferers seem unable to attend to, or sometimes conceive of, anything on (usually) the left hand side of space.
Although largely used to describe unawareness of impairment after brain injury, the term 'anosognosia', is occasionally used to describe the lack of insight shown by some people who shows signs of psychosis, and who may be unaware that their outlandish beliefs and experiences are in any way unusual. However, this usage of the term is uncommon and its usage is usually restricted to neurological injury.
There are currently no long-term treatments for anosognosia, although, like spatial neglect, vestibular caloric stimulation (squirting ice cold water into the left ear) is known to temporarily ameliorate unawareness of impairment. It is not entirely clear how this works, although it is thought that the shift of attentional focus caused by the intense stimulation temporarily influences awareness.
Due to its disabling effects, anosognosia is now being increasingly researched. Researchers interested in this condition include the well known neurologist Vilayanur S. Ramachandran, and neuropsychologist George Prigatano.
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Further reading