Visuospatial asymmetry in dual-task performance after subacute stroke.

Various authors have referred to an association between neglect and non-spatial components of attention. It has been suggested that an increase in attentional load could exacerbate neglect symptoms and reveal subtle, well-compensated neglect. In the present study, 21 RH and 22 LH subacute stroke patients and 20 controls performed a computerized single-detection task (CVRT) and a dual task (CVRT-D) combining the detection task with a driving simulation task. Omissions, reaction times (RTs) and RT asymmetries were analysed to investigate the influence of increasing attentional load on neglect symptoms. RT asymmetries were most pronounced in RH patients. Although a clear increase in RT asymmetries between CVRT and CVRT-D was observed, the amount of increase did not differ between both patient groups. Within both patient groups, correlations between RT asymmetries and ipsilesional RTs as a measure of general attention were significant in the single task but not in the dual task, indicating that increased attentional load may result in different degrees of lateralized and general attentional problems. Half of the patients with neglect on the BIT (Behavioural Inattention Test) showed increased RT asymmetries from CVRT to CVRT-D. Moreover, two LH and RH patients without neglect symptoms on the BIT and CVRT showed distinctively increased asymmetries in the CVRT-D, fostering the idea of an emergence of subtle neglect under increased attentional load. Dual-task performance may draw attention towards patients who, without obvious signs of neglect, may show visuospatial attention deficits in complex situations.

Visuospatial asymmetry and non-spatial attention in subacute stroke patients with and without neglect.

Asymmetry in performance and an association with non-lateralized attention are often mentioned as two important aspects of the clinical manifestation of visuospatial neglect. Both these aspects were investigated in 21 left (LH) and 24 right hemisphere (RH) stroke patients and in 20 healthy subjects. The letter and star cancellation subtests of the Behavioural Inattention Task (BIT) and a computerized visual reaction time task (CVRT) with stimuli presented either left, central or right in extrapersonal space were administered. In LH patients, the calculation of BIT asymmetry scores allowed a better distinction between patients with and without neglect than raw omission scores. However, in RH patients, raw and asymmetry scores led to similar classifications. In the CVRT, raw and asymmetry scores for the number of omissions also produced identical classifications. Thus, the computation of asymmetry scores for omissions did not substantially refine the diagnosis of neglect. On the other hand, more patients were classified as neglect patients by using CVRT reaction time (RT) asymmetry scores than by using BIT or CVRT omission scores. Ipsilesional RT's were chosen as a measure of general, non-lateralized attention. The ipsilesional RT's of the LH and RH patients did not differ from the healthy subjects' lateral RT's. However, within the RH group, patients with both RT asymmetries and BIT scores above cut-off level showed longer ipsilesional RT's than patients with defective RT asymmetries but normal BIT scores. This supports the idea of an interaction between lateralized and non-lateralized attentional components in neglect, in which the presence of general attentional deficits exacerbates the severity of neglect symptoms. RT tasks may contribute to the detection of asymmetries in visuospatial attention in patients with subclinical neglect symptoms, who might compensate for their lateralized deficit in paper-and-pencil tasks employing intact general attention.

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.