Anosognosia
Anosognosia
Definition
Anosognosia is a disorder in which a person who has suffered brain injury or damage is unaware of sensory, perceptual, motor, affective, or cognitive deficits.
Description
The term anosognosia was first adopted by J. Babinski in 1914, to refer to a lack of knowledge, awareness, or recognition, of deficits, observed in patients with neurological impairments. The term is derived from the roots a (without), noso (illness), and gnosia (knowledge). The terms anosognosia, impaired awareness, unawareness of deficits, and lack of insight are sometimes used interchangeably in the scientific literature. Some researchers also use the term anosognosia interchangeably with the term denial of illness, which is a condition in which patients do not acknowledge that they have a deficit or disease. Others, however, distinguish anosognosia from denial of illness based on its primary etiology. Anosognosia is thought to be due primarily to a neurological lesion. Denial of illness, on the other hand, is thought to be due primarily to a psychological process in which a patient tries to manage the distressing emotions related to having the illness or disability.
Some researchers have suggested that denial of illness and anosognosia can co-occur in patients with brain injury. Efforts to distinguish between the two syndromes have revealed that brain injury patients with denial of illness and brain injury patients with anosognosia react differently when confronted with information about their deficits. Patients who deny their deficits show an implicit or partial awareness of these deficits, become angry or resistant when confronted with information about the deficits, and struggle actively when asked to perform tasks after being confronted with such information. Patients with anosognosia, on the other hand, do not have information about their deficits, are perplexed when given feedback about their functional or behavioral deficits, and are cautiously willing or indifferent when asked to perform tasks with this new information about themselves.
Anosognosia can include unawareness of many different kinds of deficits, such as blindness, aphasia, amnesia, paralysis, and weakness of limbs. The first detailed description of anosognosia, provided by C. von Monakow in 1885, was of a man who was unaware of being blind after damage to the cortex of the brain. In 1889, G. Anton described a case of a man who, after damage to the right side of his brain, was unaware of that he was unable to move his left limbs, that he was blind in his left eye, and that he could not feel anything on his left side.
Patients with anosognosia often appear unaware of deficits even when these deficits are clearly evident. Anosognosic patients with hemiplegia (paralysis on one side of the body) might, for example, reply in the affirmative when asked if they can walk. When asked to raise their arms, they might raise only the unimpaired arm, but insist that both arms are raised. When confronted with the truth, they often admit to it, but then shortly afterwards, appear once again unaware of their deficits. Patients with anosognosia sometimes fabricate information to explain their deficits. For example, when a patient with paralysis of the left side is asked to move his left arm, he might explain his inability to do so by stating that because he is right-handed, his left side is weaker than his right. Confabulations can sometimes be illogical or bizarre. For example, a patient, when shown his paralyzed left arm, might insist that the arm belongs to someone else. Patients with anosognosia may not be motivated to engage in rehabilitation therapy because they do not recognize that they have deficits.
Anosognosia can be selective. A patient may admit to one kind of deficit, such as blindness in one visual field, but appear unaware of another deficit, such as paralysis of a limb. Anosognosia can also vary in degree. In its most extreme form, patients may completely deny a deficit, or fail to recognize it. In less extreme forms, patients may minimize the deficit or appear unconcerned about it, a condition referred to as anosodiaphoria.
Causes and symptoms
Causes
Scientists still have a poor understanding of anosognosia and its causes. Many different kinds of theories have been proposed to account for anosognosia. For many years after ansosognosia was first described, researchers thought of it as a psychological phenomenon arising from, for example, an attempt to cope with the stress of having a disability. However, other researchers pointed out that a psychological account does not explain why most cases of anosognosia are seen in patients with damage to the right hemisphere, and why ansosognosic patients sometimes deny one kind of disability but admit to being aware of others. Another kind of theory suggests that anosognosia may be the result of damage to areas and processes in the brain that represent the position, movement and sensation of different parts of the body. According to this type of theory, if, for example, a part of the brain that represents the left arm is damaged, the person may no longer be aware of an inability to move the left arm. Attentional theories, posed by some researchers, propose that anosognosia is due, not to a problem with representing a particular body area, but an inability to direct attention to a particular part of the body. Other theories focus on the fact that damage to the right hemisphere of the brain affects the ability to perceive and express emotions, and suggest that such damage may in part explain why anosognosic patients appear unconcerned about their deficits. Yet others have suggested that anosognosia arises when normal connections between the two hemispheres of the brain are lost.
KEY TERMS
Aphasia —The loss of the ability to speak or understand language, due to brain injury or disease.
Amnesia —Memory loss.
Confabulation —The filling in of gaps in memory with false or imagined details.
Hemiplegia —Paralysis of one side of the body. Lesion—An injured, diseased, or damaged area.
Vestibular system —The body system that helps to maintain balance and orient the body.
Demographics
Although there are no reports of exact percentages, the majority of patients with acquired brain injuries are thought to show some unawareness of their deficits. Most research, however, has not attempted to distinguish between anosognosia and denial of illness in these patients. Lesions in the right hemisphere of the brain appear to be more likely to result in anosognosia than lesions in the left hemisphere.
Treatments
Cases of anosognosia often resolve themselves over time. In long-term cases, cognitive therapy may help patients cope with their impaired function, but may not relieve the anosognosia. Researchers have found that caloric reflex testing—stimulating the vestibular system by squirting cold water into one ear—temporarily removes the anosognosia in some patients. The reasons for this temporary effect are unknown.
See also Anton’s syndrome; Confabulation; Unilateral neglect.
Resources
BOOKS
Butcher, James N., Susan Mineka, and Jill. M. Hooley. Abnormal Psychology. Boston, MA: Pearson Education, 2007.
Hirstein, William. Brain Fiction: Self-Deception and the Riddle of Confabulation. Cambridge, MA: MIT Press. 2005.
PERIODICALS
Kortee, Kathleen B., and Stephen T. Wegener. “Denial of Illness in Medical Rehabilitation Populations: Theory, Research and Definition.” Rehabilitation Psychology 49. 3 (2004): 187–99.
Kortte, Kathleen Bechtold, Stephen T. Wegener, and Kathleen Chwalisz. “Anosognosia and Denial: Their Relationship to Coping and Depression in Acquired Brain Injury.” Rehabilitation Psychology 48. 3 (2003): 131–36.
Vuilleumier, Patrik. “Anosognosia: The Neurology of Beliefs and Uncertainties.” Cortex 40 (2004): 9–17.
Ruvanee Pietersz Vilhauer, PhD