Anosognosia is known as a lack of insight

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Anosognosia is a form of unawareness and not-cognitive deficit. It often refers to people who are chronically ill or to people with disabilities due to neurological damage, such as strokes or traumatic brain injury (TBI). Those rare individuals who recognize their deficits and need for help, after recovery from the acute episode, when their attention is no longer focused on their disability, are also included.

Anosognosia is usually caused by brain damage that fails to recognize hemiplegia or other neurological deficits. Neurological research suggests that anosognosia may result from unilateral neglect of sensory input on the side opposite the damaged hemisphere where the lesion is found, though not everyone presenting with neglect displays anosognosia.

Anosognosia comes from the Greek words

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The term comes from the Greek words “ὄνος” (ónos), meaning ‘mind’, and “γνῶσις” (gnōsis), meaning ‘knowledge’. It was coined by Joseph Babinski in 1914 to describe the behavior of some of the patients he had seen at the Salpêtrière Hospital in Paris.

If a person is fully aware that they are ill or injured, they will experience distress and suffering as a result – this is described as pathognomonic for the condition. However, some people with mild to moderate forms of anosognosia may not recognize their deficits and, therefore, deny their illness. In these cases, the person is aware of the deficit but does not feel it directly. 

Other individuals presenting with anosognosia may state that there is nothing wrong with them, despite clear evidence to the contrary. This type of presentation is typical of frontotemporal dementia and other neurodegenerative disorders associated with early dementia or Alzheimer’s disease. Some researchers believe that denial and unawareness are typical of dementia in general, though this view is not supported by rigorous research.

Multiple explanations for how anosognosia arises

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There are multiple explanations for how anosognosia arises. It can be seen as a psychological reaction to loss or trauma associated with the disorder or it may result from direct damage to the brain regions responsible for integrating information about ourselves.

Psychological theories

Psychological theories state that anosognosia is a coping mechanism. In other words, the person denies their problems not as a result of brain damage directly but as a form of psychological protection from emotions such as anxiety and depression, which often occur in conjunction with neurological disorders.

Anatomical theories

Anatomical theories suggest that different types of anosognosia exist and depend on the area of the brain that is damaged and the exact type of neglect or disorientation a person experiences. For example, one form of anosognosia has been attributed to frontal-parietal lobe damage with construction difficulties, while another has been linked to right hemisphere lesions and left unilateral neglect.

Neuropsychological theories

Neuropsychological theories propose that anosognosia results from a person’s impaired cognitive ability. They also disagree on whether or not the deficit is specific to particular categories of knowledge – that is, whether anosognosia is hypothetically unable to recognize their lack of language skills, visual abilities, etc. Some researchers believe that anosognosia results from an impaired ability to recognize familiar stimuli; others suggest that it is more due to the loss of the ability to recognize the significance of unfamiliar or novel stimuli. While most researchers agree on anosognosia’s correlation with damage to certain areas of the brain, they disagree about which areas are responsible for each type of recognition impairment.


Most cases of anosognosia for hemiplegia are associated with lesions to the right hemisphere, but it has been reported in association with left frontal and right parietal lesions as well. In 1925, Foerster described a patient who experienced this condition following damage to his right posterior cerebral artery, which resulted from an experiment in which he shot himself in the head. The patient was unable to recognize that he had lost movement and sensation on one side of his body but recognized it when tested with an object held in his hand.

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