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The ABCs of Anosognosia for Hemiplegia
Abstract & Commentary
By John Caronna, MD, Professor of Clinical Neurology, Weill Cornell Medical College. Dr. Caronna reports no financial relationships relevant to this field of study.
Synopsis: Anosognosia is an important, but often neglected, part of the neurological examination in a patient with stroke.
Source: Vocat R, Staub F, Stroppini T, Vuilleumier, P. Anosognosia for hemiplegia: A clinical-anatomical prospective study. Brain 2010;133:3578-3597.
The term anosognosia was introduced by babinski to describe unawareness of hemiplegia, a phenomenon that he thought was caused by sensory deafferentation.1 Anosognosia occurs in other conditions such as hemianopia, cortical blindness, hemineglect, prosopagnosia, amnesia, aphasia, and dementia. Unawareness of hemiplegia is the most common form of anosognosia and occurs most frequently after damage to the right parietal lobe.
Vuilleumier has proposed that denial of hemiplegia is the result of a combination of disturbances, including not only sensory deafferentation, neglect, and phantom sensations, but also deficits in putative belief and check systems that prevent verification of experiential evidence of motor deficit.2
In the present study, Vuilleumier and associates evaluated the incidence, clinical presentation, time course, and neuroanatomical correlates of anosognosia for hemiplegia. Fifty-eight patients with right hemisphere stroke and significant left hemibody motor deficits, were examined using a comprehensive neuropsychological battery at 3 days, 1 week, and 6 months after stroke onset. Fifty patients (22 women, mean age 65 ± 14 years, all right-handed) were examined in the hyperacute phase (mean 2.7 days, range 1-5); 44 patients were examined in the subacute phase (mean 8.3 days, range 7-12); 19 patients were examined in the chronic phase (mean 223 days, range 180-273). Only 14 patients participated in all three evaluations.
Anosognosia for hemiplegia was frequent in the hyperacute phase (32%), declined by almost one-half at 1 week (18%), and was present at 6 months in only 5%. The phenomenon correlated with the severity of other deficits: loss of proprioception, spatial neglect, and disorientation. Proprioceptive loss was the most determinant factor in the hyperacute period; visuospatial neglect and disorientation were more determinant in the subacute phase. Patients with both proprioceptive loss and neglect had a higher incidence of anosognosia for hemiplegia than those with no or only one deficit.
Personality and emotional traits did not reveal any association with anosognosia. However, certain behaviors closely related to the definition of anosognosia for hemiplegia (confabulation, passivity, and unconcern) were noted in the hyperacute but not the subacute stage.
The location and extent of brain damage were delineated in each patient, based on either a CT or MRI scan obtained after the first week post-stroke. Damage to the insula (particularly its anterior part) and adjacent subcortical structures was determinant for unawareness of motor deficit in the hyperacute period. Additional lesions in the premotor cortex, cingulate gyrus, parietotemporal junction, hippocampus, and amygdala were associated with persistence of anosognosia for hemiplegia in the subacute stage.
These results suggest that anosognosia for hemiplegia reflects a multicomponent disorder, due to lesions affecting a distributed set of brain regions that can lead to several co-existing deficits in sensation, attention, bodily representation, error monitoring, memory, and others, with different combinations in different patients. The authors, therefore, propose a "two-factor theory"2 or ABC hypothesis2 of anosognosia for hemiplegia, according to which impairments in components necessary for "Appreciation" of the deficits (e.g., proprioception and spatial attention) might or might not cause unawareness of hemiplegia depending on the severity of addition dysfunction in "Belief" and "Check" components related to self- and reality-monitoring and verification processes.
For most of us, the examination of a patient with hemineglect by a senior neurologist is a well-remembered highlight of neurology student clerkship or residency training. If the examiner had a flair for the theatrical like the late Fred Plum, then the patient-physician encounter became the source of endless anecdotes, told and retold by his trainees.
Recently, physicians have recognized that patients with right hemisphere strokes are much less likely to receive rTPA than those with left hemisphere strokes. The reasons are twofold; patients with hemineglect fail to recognize the signs of left hemiparesis resulting in prehospital delay; likewise, physicians may not detect anosognosia because of a lack of standardized scores for neglect.4 Gurol et al have pointed out that the NIH Stroke Scale is biased toward left, i.e., dominant, hemisphere deficits.5 Ostrow and Llinas, therefore, have proposed the Eastchester Clapping Sign as a screening test for neglect in the acute stroke setting.6
Vocat et al have provided an exhaustive review of the phenomenon of anosognosia for hemiplegia and a prospective assessment of a large group of stroke patients with the disorder. The ABC combinatorial rule is clinically useful and explains the present of anosognosia for hemiplegia in some patients, despite a minor loss of proprioception and an absence of hemineglect. In such cases, the primary deficit is in "Belief" or "Check" components. The authors have provided clinicians with useful insights about the multifactorial determinants and temporal evolution of anosognosia for hemiplegia following stroke.
1. Babinski J. Revue Neurologique 1914; 27:845-848.
2. Vuilleumier P. Anosognosia: The neurology of beliefs and uncertainties. Cortex 2004;40:9-17.
3. Davies M, Davies AA, Coltheart M. Mind and Language 2005; 20:209-236.
4. Di Legge S, Fang J, Saposnik G, Hachinski V. The impact of lesion on acute stroke treatment. Neurology 2005;65:81-86.
5. Gurol ME, Steib CD, Davis PH, et al. Ann Neurol 2008;64:S14-S15.
6. Ostrow CW, Llinas RH. Eastchester clapping sign: A novel test of parietal neglect. Ann Neurol 2009;66:114-117.