Self-observation reinstates motor awareness in anosognosia for hemiplegia

We report a patient with severe anosognosia for hemiplegia, who recovered instantly and permanently when viewing herself in a video replay. We believe the observed dramatic reinstatement of the patient's awareness related to her self-observation ‘from the outside’ (3rd person perspective) and ‘off-line’ (at a time later than the actual attempt to execute a movement); her anosognosia had been unaltered when she observed her plegic arm in her ipsilateral visual field (self-observation from a 1st-person perspective and ‘on-line’). To our knowledge, the role of self-observation in videos or mirrors has not being assessed in AHP to date. Our study provides preliminary evidence that, when right hemisphere damage impairs the ability to update one's body representation, judgements relying on 3rd-person and off-line self-observation may be spared in some patients and may facilitate 1st person awareness.     

Imagining the impossible: motor representations in anosognosia for hemiplegia

Anosognosia for hemiplegia (AHP) is characterised by poor insight or underestimation of hemiplegia after brain injury. Recent explanations of AHP have used an established ‘forward model’, which proposes that normal motor awareness involves comparing the predicted and actual sensory consequences of movements. These accounts propose that AHP patients may be able to form representations of their intended movements (i.e., motor representations), but fail to register discrepancy between intended and actual movements. A prediction arising from this proposal is that AHP patients are able to generate motor representations involving their hemiplegic limb(s). Our study provides the first direct examination of this prediction in patients with AHP. We used an existing ‘grip selection task’, which investigates motor representations by comparing how patients would grasp an object and how they actually grasp the same object. Eight right hemisphere stroke patients with AHP, 10 control patients (non-AHP), and 22 age-matched healthy volunteers (HVs) completed the task. Results showed that HVs outperformed both AHP and non-AHP patients in their motor representations for the hemiplegic limb; however, the performance of AHP and non-AHP patients did not differ significantly. Motor representations for the intact limb were lower than normal in AHP patients, whereas performance in non-AHP patients was midway between the AHP and HV groups. Findings suggested that the ability to form motor representations lie on a continuum, but that impaired motor representations for the paralysed limb cannot account for AHP. Distorted motor representations, in combination with other deficits, might contribute to the pathogenesis of AHP.     

Pontine anosognosia for hemiplegia.

Four patients had anosognosia for hemiplegia (AHP) as a manifestation of pontine infarction in the mediolateral region. Patients with AHP syndrome had no mental and neuropsychologic disturbances, and all had involvement of the medial or lateral part of the pons (medial or lateral pontine reticular nuclei). Brainstem lesions, which activate frontoparietosubcortical areas, may be a critical factor in the development of AHP syndrome.     

The pathogenesis of anosognosia for hemiplegia

We compared patients with unawareness of hemiplegia lasting more than 1 month after right hemisphere stroke with other patients with right hemisphere stroke who became aware of hemiplegia within a few days after onset. Patients with persistent unawareness invariably had severe left hemisensory loss and usually had severe left spatial neglect. They were almost always apathetic; their thought lacked direction, clarity, and flexibility, and they had at least moderate impairment of intellect and memory. Their right hemisphere strokes were large and always affected the central gyri or their thalamic connections and capsular pathways. In addition, there was evidence of at least mild left hemisphere damage, most commonly caused by age-associated atrophy. The pathogenesis of anosognosia for hemiplegia may involve failure to discover paralysis because proprioceptive mechanisms that ordinarily inform an individual about the position and movement of limbs are damaged, and the patient, because of additional cognitive defects, lacks the capacity to make the necessary observations and inferences to diagnose the paralysis. We discuss the implications of this "discovery" theory and contrast it with other explanations of anosognosia.     

Illusory limb movements in anosognosia for hemiplegia

To clarify the relation between anosognosia for hemiplegia and confabulation, 11 patients with acute right cerebral infarctions and left upper limb hemiparesis were assessed for anosognosia for hemiplegia, illusory limb movements (ILMs), hemispatial neglect, asomatognosia, and cognitive impairment. Five of 11 patients had unequivocal confabulation as evidenced by ILMs. The presence of ILMs was associated with the degree of anosognosia (p = 0.002), with hemispatial neglect (p<0.05), and with asomatognosia (p<0.01). The results confirm that a strong relation exists between anosognosia for hemiplegia and confabulations concerning the movement of the plegic limb. There is also a strong relation between ILMs and asomatognosia.     

A diagnostic formulation for anosognosia in Alzheimer's disease

Objective

To determine the earliest symptoms of anosognosia in people with Alzheimer''s disease and to validate a criteria‐guided strategy to diagnose anosognosia in dementia.

Methods

A consecutive series of 750 patients with very mild or probable Alzheimer''s disease attending a memory clinic, as well as their respective care givers, was assessed using a comprehensive psychiatric evaluation.

Results

The factors of anosognosia for (1) basic activities of daily living (bADL), (2) instrumental activities of daily living (iADL), (3) depression and (4) disinhibition were produced by a principal component analysis on the differential scores (ie, caregiver score minus patient score) on the anosognosia questionnaire for dementia. A discrepancy of two or more points in the anosognosia‐iADL factor was found to have a high sensitivity and specificity to identify clinically diagnosed anosognosia in people with Alzheimer''s disease. By logistic regression analysis, the severity of dementia and apathy were both shown to be noticeably associated with anosognosia in people with Alzheimer''s disease.

Conclusion

Anosognosia in those with Alzheimer''s disease is manifested as poor awareness of deficits in iADL and bADL, depressive changes and behavioural disinhibition. The frequency of anosognosia is found to increase considerably with the severity of dementia. The validity of a specific set of criteria to diagnose anosognosia in people with Alzheimer''s disease was shown, which may contribute to the early identification of this condition.Anosognosia (from the Greek “nosos” (illness) and “gnosis” (knowledge)) is a term coined by Babinski to refer to the phenomenon of denial of hemiplegia.¹ From an etymological perspective, the term anosognosia may be construed as the lack of knowledge or awareness of an illness. Anosognosia has also been reported among patients with Wernicke''s aphasia, who do not attempt to correct paraphasias and who may become irritable with others when their jargon‐loaded speech is not properly understood. Anton''s syndrome occurs in patients with cortical blindness, who deny being blind and confabulate responses when asked to recognise visually presented objects. In the context of people with Alzheimer''s disease, anosognosia was construed as the denial or lack of awareness of impairments in activities of daily living (ADL) or about neuropsychological deficits.^2,3 Different strategies have been used to assess anosognosia in Alzheimer''s disease, and these are briefly described as follows (see Clare^4,5 for a thorough review).     

Phenomenology and neural correlates of implicit and emergent motor awareness in patients with anosognosia for hemiplegia

Anosognosia for hemiplegia (AH) is characterized by a lack of awareness of motor disorders and appears associated with fronto-temporal-parietal damage. Neuropsychological evidence indicates that behavioral indices of residual forms of motor awareness may co-exist with explicit denial of impairment. Here we explore whether the attempt by AH patients to perform an action may disclose residual forms of motor awareness and whether such forms are underpinned by different neural structures. Twelve hemiplegic patients affected by AH were tested in tasks assessing: (i) implicit awareness (IA), indexed by discrepancies between verbal reports and actual motor behavior; (ii) emergent awareness (EA), indexed by increased verbal awareness induced by the attempt to perform actions. IA and EA were found in five and three patients, respectively. Lesion analysis indicates that while the lack of IA is associated with damage to subcortical white matter anterior to the basal ganglia, lack of EA is linked to damage to cortical regions including insulo-frontal, temporal and parietal structures. Our results indicate that deficits in explicit and implicit awareness are associated with lesions involving different cortico-subcortical structures. Moreover, the results show that the attempt to perform an action may ameliorate body awareness deficits and have implications for rehabilitation.     

Error-based training and emergent awareness in anosognosia for hemiplegia

Residual forms of awareness have recently been demonstrated in subjects affected by anosognosia for hemiplegia, but their potential effects in recovery of awareness remain to date unexplored. Emergent awareness refers to a specific facet of motor unawareness in which anosognosic subjects recognise their motor deficits only when they have been requested to perform an action and they realise their errors. Four participants in the chronic phase after a stroke with anosognosia for hemiplegia were recruited. They took part in an “error-full” or “analysis of error-based” rehabilitative training programme. They were asked to attempt to execute specific actions, analyse their own strategies and errors and discuss the reasons for their failures. Pre- and post-training and follow-up assessments showed that motor unawareness improved in all four patients. These results indicate that unsuccessful action attempts with concomitant error analysis may facilitate the recovery of emergent awareness and, sometimes, of more general aspects of awareness.     

The anatomy of anosognosia for hemiplegia: a meta-analysis

Anosognosia for hemiplegia is the denial of the contralesional motor deficits that may follow brain damage. Although this disturbance has been reported in the neurological literature since the beginning of the last century, only few longitudinal studies have addressed the issue of the anatomical substrate of the disorder. Here we present a comprehensive review of the literature on anosognosia for hemiplegia from 1938 to 2001, taking into account some of its clinical, epidemiological and anatomical aspects. In particular, an attempt has been made to identify the intra-hemispheric lesion locations most frequently associated to the denial behaviour. Our review shows that anosognosia for hemiplegia most frequently occurs in association to unilateral right-sided or bilateral lesions of different brain areas (cortical and/or subcortical). It seems to be equally frequent when the damage is confined to frontal, parietal or temporal cortical structures, and may also emerge as a consequence of subcortical lesions. Interestingly, the probability of occurrence of anosognosia is highest when the lesion involves parietal and frontal structures in combination, if compared to other combinations of lesioned areas. This pattern of lesions suggests the existence of a complex cortico-subcortical circuit underlying awareness of motor acts that, if damaged, can give raise to the anosognosic symptoms.     

Modular structure of awareness for sensorimotor disorders: evidence from anosognosia for hemiplegia and anosognosia for hemianaesthesia

In the present paper, we shall review clinical evidence and theoretical models related to anosognosia for sensorimotor impairments that may help in understanding the normal processing underlying conscious self-awareness. The dissociations between anosognosia for hemiplegia and anosognosia for hemianaesthesia are considered to give important clinical evidence supporting the hypothesis that awareness of sensory and motor deficits depends on the functioning of discrete self-monitoring processes. We shall also present clinical and anatomical data on four single case reports of patients selectively affected by anosognosia for hemianaesthesia. The differences in the anatomical localization of lesions causing anosognosia for hemiplegia and anosognosia for hemianaesthesia are taken as evidence that cerebral circuits subserving these monitoring processes are located in separate brain areas, which may be involved both in the execution of primary functions and the emergence of awareness related to the monitoring of the same functions. The implications of these findings for the structure of conscious processes shall be also discussed.     

Unawareness of disease following lesions of the right hemisphere: anosognosia for hemiplegia and anosognosia for hemianopia

Unawareness of motor and visual-field defects was investigated in 97 right brain-damaged subjects. Both kinds of anosognosia were found to be double-dissociated from more elementary neurological disorders and from personal and extra-personal neglect. The relationships between anosognosia and unilateral neglect are discussed and allusion is made to the implications concerning the neurological organization of higher control functions.     

On-line anosognosia: unawareness for chorea in real time but not on videotape delay

In hemiplegics, anosognosia (unawareness of deficit) rests on a mismatch between expected and actual movement: a feedback hypothesis emphasizes sensory deficits or neglect, a feedforward hypothesis postulates impaired intention to move. Anosognosia for other problems is less studied. The authors report a man without sensory deficits who was unaware of choreiform movements, except on videotape delay. The authors believe that a feed-forward mechanism underlies his "on-line" unawareness.     

Recent trends in rehabilitation interventions for visual neglect and anosognosia for hemiplegia following right hemisphere stroke

This article highlights the most recent findings regarding the rehabilitation interventions for the syndromes of visual neglect and anosognosia for hemiplegia that occur following right hemisphere stroke. We review papers published in the past 4 years pertaining to therapeutic approaches for these two syndromes in order to identify the trends in the development of effective interventions. Overall, it appears well recognized that visual neglect syndromes and awareness syndromes frequently co-occur and both include complex, multifaceted impairments leading to significant difficulties in daily life functioning following stroke. Thus, the interventions for these syndromes must be multifaceted in order to address the complex interplay of cognitive-behavioral-emotional components. There appears to be a trend for using combination therapeutic interventions that address these components.     

VATA-L: visual-analogue test assessing anosognosia for language impairment

Lack of awareness (anosognosia) for one's own language impairments has rarely been investigated, despite hampering language rehabilitation. Assessment of anosognosia by means of self-report is particularly complex, as a patient's language difficulties may seriously prevent or bias the assessment. Other methods, such as measures of self-correction and error detection, have provided valuable information, although they are an indirect form of assessment of anosognosia and are not exempt from methodological criticisms. In this study we report on a new tool, the VATA-L (Visual-Analogue Test for Anosognosia for Language impairment), geared at assessing explicit anosognosia for aphasia. The VATA-L compares the patient's self-evaluation with caregivers' evaluations of the patient's verbal communication abilities in a series of common situations. By means of non-verbal support and a system of check questions, this test minimizes some of the methodological limitations of existing diagnostic tools (e.g., structured interviews), enhancing reliability, and enabling assessment of patients with aphasia. Finally, normative data provided in the study allow a clearer interpretation of the patient's performance and facilitate assessment of anosognosia.     

Development and validation of the computerized bilateral motor coordination test

The purpose of this study was to explore the validity of computerized scaling of bilateral, motor coordination in children 4–6 years of age. There were 623 children with an average age of 5, years and 2 months (standard deviation = 6 months) that participated. The 290 girls (46.5%) and 333, boys (53.5%) were from a purposive sample taken from public and private kindergartens in Taiwan. The computerized bilateral motor coordination test included two subtests, bilateral coordination, movements and projected actions. The motion analysis, with mark position and contour motion, was, used to collect important variables from the subtests. Using the judgments of the experts as the, criterion standards, the accuracy, sensitivity, and specificity of the tool were calculated to evaluate the, validity of the computerized bilateral motor coordination test. The accuracy, sensitivity, and, specificity of the bilateral coordination movement subtests were on average 83.9%, 86.4%, and 83.1%, respectively. The accuracy, sensitivity, and specificity of the projected action subtests were on average, 90.5%, 88.1%, and 90.4%, respectively. The computerized bilateral motor coordination tests showed, an average accuracy of 86.3%, a sensitivity of 87.0%, and a specificity of 85.8%. The computerized, bilateral motor coordination test could be a valuable tool when used to identify problems of bilateral, motor coordination and in permitting early intervention to remedy these problems.     

Physiological alterations of motor units in hemiplegia

Isometric contractions of single motor units in the first dorsal interosseous muscle were recorded with an intramuscular microstimulation technique in patients with short- or long-term hemiplegia and compared with controls. In the hemiplegic patients motor units could be classified as in controls, utilizing twitch contraction time and fatigue sensitivity, as FF (fast fatigable), FR (fast fatigue resistant) and S (slow fatigable). The mean twitch contraction time of fast-twitch but not slow-twitch units was slightly prolonged in patients with spastic hemiplegia and motor units, especially type S, tended to generate larger twitch tensions. A fourth type of motor unit, characterized by slow-twitch contraction times and increased fatigability (SF units), was recorded in long-term hemiplegia. The data demonstate that during long-term spastic hemiplegia in man some motor units develop increased fatigability and prolonged-twitch contraction times, reflecting the dynamic properties of muscle.