Elsevier

Cortex

Volume 61, December 2014, Pages 30-42
Cortex

Special issue: Review
Possible mechanisms of anosognosia of hemiplegia

https://doi.org/10.1016/j.cortex.2014.06.007Get rights and content

Abstract

Unawareness of hemiplegia was first called anosognosia by Babinski one century ago. This paper reviews some of the major theories that may account for this disorder. Weinstein and Kahn posited that anosognosia was a psychological defense mechanism; however, clinical as well as studies using transient hemispheric anesthesia reveal anosognosia for hemiplegia is more commonly associated with right than left hemisphere dysfunction, which is not entirely compatible with this denial hypothesis. Discovery is dependent on sensory feedback. Some patients with anosognosia will recognize their hemiparesis when their paretic hand is placed into ipsilesional hemispace suggesting that de-afferentation and inattention-neglect may be important mechanisms. Some patients with anosognosia have asomatognosia and hence being unaware that their paretic arm belongs to them they do not recognize that they have a deficit. Some patients have phantom movements and some may confabulate because they have a hemispheric disconnection. The feed-forward hypothesis posits that without an attempt to move, there is no expectation of movement and in the absence of arm movement there will be no discord that leads to discovery. Thus, motor neglect may be another cause of anosognosia. A defect in a theoretical comparator where expectations are compared to feedback may also be a cause of anosognosia, but further evidence is needed to support this postulate. Based on the studies of anosognosia for hemiplegia we have reviewed it appears that normal self-awareness depends on several modular systems. Further research of these possible mechanisms is needed to discern their relative importance and treatment. If these mechanisms do not fully account for anosognosia, investigators will need to develop and test new hypotheses.

Introduction

Whereas the first description of unawareness of illness is often attributed to Von Monakow (1885), as noted by Bisiach and Geminiani (1991), it was Seneca the stoic philosopher who more than 2000 years ago wrote a letter to Lucilius and in this letter he stated, “This foolish woman suddenly lost her sight…Incredible as it may appear…She does not know she is blind.” It was 100 years ago that Babinski, 1914, Babinski, 1918 coined the term ‘anosognosie’ to describe the phenomenon where patients with a left hemiplegia were unaware of their weakness. The term he selected comes from three morphemes, a = without, noso = disease and gnosis = knowledge. Although initially Babinski used this term to describe unawareness of hemiplegia, there are many other disorders where patients appear to be unaware of their deficit and unawareness of these disorders has also been called anosognosia. Some of the other disorders where patients may be unaware of their disability include sensory disorders such as hemianopia (Celesia, Brigell, & Vaphiades, 1997), cortical blindness (Anton, 1896), and some patients with pure word deafness (Heilman, personal observation). Patients cognitive disorders may also be unaware of their disability, for example patients with aphasia such as Wernicke's aphasia may appear to be unaware of their expressive deficits; however, since these patients are impaired at verbal expression, they cannot explicitly express their unawareness. Patients with amnesia and dementia may also be unaware of their cognitive deficits (Barrett, Eslinger, Ballentine, & Heilman, 2005). Since this volume of Cortex is celebrating the anniversary of Babinski's classic paper we will focus on the possible brain mechanisms that may account for the unawareness of hemiplegia.

Although Babinski (1914) wrote, “…I have seen some hemiplegics who without being ignorant of the existence of their paralysis seem to attach no importance to it. This state may be called anosodiaphoria”, this phenomenon and term was disseminated by the writings of Critchley, 1953, Critchley, 1957. The term anosodiaphoria comes from four morphemes (a = without; noso = disease; dia = apart; phoria = emotional state). Most patients that my coworkers and I have seen with anosodiaphoria initially after they developed a hemiparesis were unaware of their disability (anosognosia), but after days to weeks many of these patients when asked about their disability will verbally admit to having weakness of their arm and/or leg, but do not appear to be upset or concerned. Patients with other disorders such as chorea, either related to diseases such as Huntington's disease or dopaminergic medications often appear unconcerned about their abnormal movements. In this paper, however, we will focus primarily on anosognosia rather than anosodiaphoria.

The failure to be aware (anosognosia) or be unconcerned (anosodiaphoria) about a disability frequently has important ramifications. For example, anosognosia for hemiplegia is often induced by a stroke and the most common cause of strokes are infarctions, caused by vascular thrombosis (e.g., carotid or middle cerebral artery). Currently, if a patient with the sudden onset of a hemiparesis comes to the hospital shortly after the onset of these symptoms, they can be successfully treated with a clot busting treatment; however if there is a several hour delay before the patient comes to the hospital this clot busting treatment becomes dangerous and cannot be given. Currently, only a small percentage of patients who have the symptoms of stroke, such as a hemiparesis, come to the hospital in time to get this treatment. Although there are many reasons for this delay, for some patients, this delay may be related to the presence of anosognosia or anosodiaphoria.

Even when the damage caused by a stroke cannot be reversed, there are now successful means of rehabilitating patients with a variety of deficits; however, if a patient is not aware of this disability or is not concerned about it there is less of a chance this person will seek rehabilitation or be strongly motivated to perform the exercises that are often required. Many of disabilities induced by neurological diseases can interfere with the performance of activities which if not performed correctly may endanger the patient as well as others and patients who are unaware of their disabilities may continue to perform activities that can endanger themselves and others.

Although there are many forms of anosognosia this paper will focus on the same disorder that Babinski described, namely anosognosia of hemiplegia and the primary goal of this paper is to discuss the possible neuropsychological mechanisms that can account for this form of anosognosia. There have been several prior reviews of anosognosia for hemiplegia (Berti et al., 2007a, Berti et al., 2007b, Heilman, 1991, Heilman and Harciarek, 2010, Jenkinson and Fotopoulou, 2010, Fotopoulou, 2014; Starkstein et al., 1992) and in addition to discussing much of the material presented in these reviews, this review will also include some recent finding that may help to explain this disabling disorder.

Section snippets

Psychological denial, repression and pre-morbid personalities

Sigmund Freud recognized that denial is a powerful psychological defense mechanism that helps attenuate the distress, anxiety, and depression that can be induced by a catastrophic event. Edwin A. Weinstein who trained as both a psychiatrist and neurologist and who was a member of the Department of Neurology at Mt. Sinai wrote a book with Robert Kahn titled Denial of Illness (1955). In this book Weinstein and Kahn proposed and provided evidence that patients with severe disabilities, such as

Conclusions

The neurobehavioral syndrome where patients are unaware of the hemiparesis, first called anosognosia by Babinski one century ago, is an important problem which may delay treatment, interfere with rehabilitation and even may cause patients with this disorder to engage in activities that are dangerous to themselves and others. There have been few successful treatments for anosognosia and the anosodiaphoria that often follows the anosognosia. In this article we have reviewed some of the possible

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    In part supported by The State of Florida Memory and Cognitive Disorders Clinic and the Department of Veteran Affairs.

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