Improving the clinical diagnosis of personal neglect: a reformulated comb and razor test

Implicit awareness in anosognosia for hemiplegia: unconscious interference without conscious re-representation

Some patients with anosognosia for hemiplegia, i.e. apparent unawareness of hemiplegia, have been clinically observed to show 'tacit' or 'implicit' awareness of their deficits. Here we have experimentally examined whether implicit and explicit responses to the same deficit-related material can dissociate. Fourteen stroke patients with right hemisphere lesions and contralesional paralysis were tested for implicit and explicit responses to brief sentences with deficit-related themes. These responses were elicited using: (i) a verbal inhibition test in which patients had to inhibit completing each sentence with an automatic response (implicit task) and (ii) a rating procedure in which patients rated the self-relevance of the same sentences (explicit task). A group of anosognosic hemiplegic patients was significantly slower than a control group of aware hemiplegic patients in performing the inhibition task with deficit-related sentences than with other emotionally negative themes (relative to neutral themes). This occurred despite their explicit denial of the self-relevance of the former sentences. Individual patient analysis showed that six of the seven anosognosic patients significantly differed from the control group in this dissociation. Using lesion mapping procedures, we found that the lesions of the anosognosic patients differed from those of the 'aware' controls mainly by involving the anterior parts of the insula, inferior motor areas, basal ganglia structures, limbic structures and deep white matter. In contrast, the anosognosic patient without implicit awareness had more cortical lesions, mostly in frontal areas, including lateral premotor regions, and also in the parietal and occipital lobes. These results provide strong experimental support for a specific dissociation between implicit and explicit awareness of deficits. More generally, the combination of our behavioural and neural findings suggests that an explicit, affectively personalized sensorimotor awareness requires the re-representation of sensorimotor information in the insular cortex, with possible involvement of limbic areas and basal ganglia circuits. The delusional features of anosognosia for hemiplegia can be explained as a failure of this re-representation.

Errors of somatosensory localisation in a patient with right-hemisphere stroke

Following a right-hemisphere stroke, Patient NG could detect somatosensory stimulation that she was unable to localise. With vision precluded, NG systematically mislocalized touch on the little and ring finger of her affected left hand, and reported feeling this touch on the neighbouring rightward finger. This pattern of mislocalization occurred not only when the Examiner administered touch but also when touch was self-administered. We manipulated the relative position of NG's two hands during sensory assessment of the affected hand. When NG's right hand was positioned to the left of her affected hand, NG exhibited improved localisation. Theoretical and clinical implications are discussed.

Is Visuospatial Hemineglect Longitudinally Associated with Postural Imbalance in the Postacute Phase of Stroke?

Introduction. The purpose of this study was to determine the longitudinal association of visuospatial hemineglect with postural imbalance in postacute stroke patients and to establish whether this relationship is confounded by other determinants. Methods. A prospective cohort study of 53 postacute stroke patients consecutively admitted for inpatient rehabilitation was conducted. Transfers and standing balance were assessed with the Berg Balance Scale (BBS) and walking balance with the Functional Ambulation Categories (FAC). Repeated measurements took place at baseline (36.6 ± 10.4 days after stroke) and after 6 and 12 weeks. Visuospatial hemineglect was assessed by an asymmetry index, derived from the Letter and Star Cancellation Tests. Random coefficient analysis was used to analyze the longitudinal impact of visuospatial hemineglect on the BBS and FAC. The association between hemineglect and outcome was corrected for the following potential confounders: age, severity of paresis of the lower leg, sensory deficits, and presence of hypertonia. A covariate was considered to be a confounder if the regression coefficient of hemineglect on outcome changed by >15%. Results. Visuospatial hemineglect was significantly associated with BBS and FAC. The relation between hemineglect and both BBS and FAC was confounded by severity of paresis of the lower limb. After controlling for severity of paresis, hemineglect remained independently associated with BBS, whereas the association with FAC lost significance. Conclusion. Visuospatial hemineglect is an independent covariate that is longitudinally associated with postural imbalance after stroke. These findings suggest that hemineglect is an important factor for controlling static and dynamic standing balance during the first months poststroke.

Reality monitoring in anosognosia for hemiplegia

Anosognosia for hemiplegia (AHP) is a lack of awareness about paralysis following stroke. Recent explanations use a 'forward model' of movement to suggest that AHP patients fail to register discrepancies between internally- and externally-generated sensory information. We predicted that this failure would impair the ability to recall from memory whether information is internally- or externally-generated (i.e., reality monitor). Two experiments examined this prediction. Experiment 1 demonstrated that AHP patients exhibit a reality monitoring deficit for non-motor information (i.e., perceived vs. imagined drawings), whilst hemiplegic controls without anosognosia (nonAHP) perform like age-matched healthy volunteers (HVs). Experiment 2 explored if this deficit occurs when AHP patients discriminate performed, imagined, or observed movement. Results showed impaired reality monitoring for movements in AHP and nonAHP patients relative to HVs. Findings suggest that reality monitoring processes not directly related to movement, together with a failure to reality monitor movements, contribute to the pathogenesis of AHP.

Role of right posterior parietal cortex in maintaining attention to spatial locations over time

Recent models of human posterior parietal cortex (PPC) have variously emphasized its role in spatial perception, visuomotor control or directing attention. However, neuroimaging and lesion studies also suggest that the right PPC might play a special role in maintaining an alert state. Previously, assessments of right-hemisphere patients with hemispatial neglect have revealed significant overall deficits on vigilance tasks, but to date there has been no demonstration of a deterioration of performance over time--a vigilance decrement--considered by some to be a key index of a deficit in maintaining attention. Moreover, sustained attention deficits in neglect have not specifically been related to PPC lesions, and it remains unclear whether they interact with spatial impairments in this syndrome. Here we examined the ability of right-hemisphere patients with neglect to maintain attention, comparing them to stroke controls and healthy individuals. We found evidence of an overall deficit in sustaining attention associated with PPC lesions, even for a simple detection task with stimuli presented centrally. In a second experiment, we demonstrated a vigilance decrement in neglect patients specifically only when they were required to maintain attention to spatial locations, but not verbal material. Lesioned voxels in the right PPC spanning a region between the intraparietal sulcus and inferior parietal lobe were significantly associated with this deficit. Finally, we compared performance on a task that required attention to be maintained either to visual patterns or spatial locations, matched for task difficulty. Again, we found a vigilance decrement but only when attention had to be maintained on spatial information. We conclude that sustaining attention to spatial locations is a critical function of the human right PPC which needs to be incorporated into models of normal parietal function as well as those of the clinical syndrome of hemispatial neglect.

Is Visuospatial Hemineglect Really a Determinant of Postural Control Following Stroke? An Acute-Phase Study

Objective. The purpose of this study was to determine the independent contribution of visuospatial hemineglect to impaired postural control in the acute phase (<2 weeks) of stroke compared with other possible clinical and biological determinants. Methods. This study was conducted in 4 hospitals in the mid-east region of the Netherlands. A total of 78 consecutive patients with a first-ever acute supratentorial stroke was included. Functional balance was measured with the Trunk Impairment Scale, the Trunk Control Test, the Berg Balance Scale, and the Functional Ambulation Categories. Visuospatial hemineglect was assessed by means of an asymmetry index obtained from the Behavioral Inattention Test. The Motricity Index, vibration threshold, sustained attention, and the presence of hemianopia were registered as other possible clinical determinants. Stepwise backward multiple linear regression analysis was performed introducing all selected clinical determinants as well as age and poststroke time as possible biological determinants. Results. Hemineglect was present in 17 patients (21.8%). The groups with and without hemineglect were different for gender and the proportion of right hemisphere strokes, but not for age, type of stroke, or poststroke time. Neglect patients had on average lower scores on all functional balance tests as well as on the clinical assessments. Multivariate linear regression showed that, besides hemineglect, only muscle strength and age independently contributed to impaired balance explaining 65% to 72% of variance of the selected outcomes. Conclusion. This study showed that hemineglect independently contributes to impaired postural control in the acute phase of stroke.

Finger recognition and gesture imitation in Gerstmann's syndrome

We report the association between finger agnosia and gesture imitation deficits in a right-handed, right-hemisphere damaged patient with Gerstmann's syndrome (GS), a neuropsychological syndrome characterized by finger and toe agnosia, left-right disorientation and dyscalculia. No language deficits were found. The patient showed a gestural imitation deficit that specifically involved finger movements and postures. The association between finger recognition and imitation deficits suggests that both static and dynamic aspects of finger representations are impaired in GS. We suggest that GS is a disorder of body representation that involves hands and fingers, that is, the non-facial body parts most involved in social interactions.

Developing functional outcome measures for unilateral neglect: A pilot study

Stroke patients may develop personal neglect, peripersonal neglect or both. Four new measures were tested in a sample of 42 right-handed inpatients (25 male; 17 female, median age 72 years). Participants removed keys from a rack, identified grocery items, washed their face, and cleaned a tray. Prior to this, they were classified as: no neglect (15), personal neglect (8), peripersonal neglect (7), and both personal and peripersonal neglect (12). The sensitivity and specificity of each new measure was determined by agreement with the classification. Test-retest reliability was determined using weighted kappa statistics or limits of agreement. Four occupational therapists (OTs) rated videos of the face and tray measures, and software was developed to measure objectively time spent and area covered on Face and Tray. Keys and Grocery had high specificity, good reliability but poor sensitivity. For the OTs' video ratings, there was good and moderate inter-rater reliability on Tray and Face respectively for area covered, but not time spent. Intra-rater reliability was also better for area than time on Tray. However, the validity of Face and Tray themselves is currently inadequate. A longitudinal study is proposed to modify the measures, increase their sensitivity and evaluate their ability to monitor change over time.

Changes in spatial position of hands modify tactile extinction but not disownership of contralesional hand in two right brain-damaged patients

Somatic misperceptions and misrepresentations, like supernumerary phantom limb and denial of ownership of a given body part, have typically been reported following damage to the right side of the brain. These symptoms typically occur with personal or extrapersonal neglect and extinction of left-sided stimuli, suggesting that all these different symptoms may be linked to the same neural substrate. In the present research, we tested two right brain-damaged (RBD) patients to find out whether changing the position of the hands in space influences tactile extinction and denial of ownership to the same extent. Results showed that manipulation of the spatial position of the hands reduces tactile extinction but leaves denial of ownership of the left hand unaffected. Such a dissociation suggests that delusional misperceptions may be independent from somatic neglect and that representation of hands in space and attribution of ownership are dynamically mapped in at least partly separate neural substrates.