A cohort study on longitudinal changes in postural balance during the first year after stroke

Does visuospatial neglect contribute to standing balance within the first 12 weeks post-stroke? A prospective longitudinal cohort study

BACKGROUND

Visuospatial neglect (VSN) has been suggested to limit standing balance improvement post-stroke. However, studies investigating this association longitudinally by means of repeated within-subject measurements early post-stroke are lacking. This prospective longitudinal cohort study evaluates the longitudinal association of egocentric and allocentric VSN severity with 1) standing balance independence and 2) postural control and weight-bearing asymmetry (WBA) during quiet standing, in the first 12 weeks post-stroke.

METHODS

Thirty-six hemiplegic individuals after a first-ever unilateral stroke were evaluated at weeks 3, 5, 8 and 12 post-stroke. Egocentric and allocentric VSN severity were evaluated using the Broken Hearts Test. The standing unperturbed item of the Berg Balance Scale (BBS-s) was used to clinically evaluate standing independence. Posturographic measures included measures of postural control (mediolateral (ML)/anteroposterior (AP) net center-of-pressure velocities (COPvel)) and WBA during quiet standing. A linear mixed model was used to examine longitudinal associations between egocentric and allocentric VSN, and BBS-s, COPvel-ML, COPvel-AP and WBA within the first 12 weeks post-stroke.

RESULTS

Egocentric (β = -0.08, 95%CI[-0.15;-0.01], P = .029) and allocentric VSN severity (β = -0.09, 95%CI[-0.15; -0.04], P = .002) were significant independent factors for BBS-s scores in the first 12 weeks post-stroke. Egocentric and allocentric VSN were no significant independent factors for COPvel-ML, COPvel-AP and WBA in the first 12 weeks post-stroke.

CONCLUSIONS

Allocentric and egocentric VSN severity were significantly associated with decreased standing independence, but not impaired postural control or greater asymmetric weight-bearing, in the early subacute post-stroke phase. This may involve traditional VSN measures being not sensitive enough to detect fine-grained VSN deficits due to a ceiling effect between 5 and 8 weeks post-stroke, once the individual regains standing ability. Future studies may require more sensitive VSN measurements to detect such deficits. Trial registration Clinicaltrials.gov. unique identifier NCT05060458.

Is a portable pressure plate an alternative to force plates for measuring postural stability and interlimb coordination of quiet standing balance control?

Introduction

Center-of-pressure (COP) synchronization and symmetry can inform adaptations in balance control following one-sided sensorimotor impairments (e.g., stroke). As established force plates are impossible to transport, we aimed to criterion validate a portable pressure plate for obtaining reliable COP synchronization and symmetry measures, next to conventional postural stability measures.

Methods

Twenty healthy adults participated. In a single session, three 40-s eyes-open and eyes-closed quiet stance trials were performed per plate-type, randomly ordered. Individual-limb COPs were measured to calculate between-limb synchronization (BLS) and dynamic control asymmetry (DCA). Net COP (i.e., limbs combined) area, amplitude, and velocity were used to describe anteroposterior (AP) and mediolateral (ML) postural stability. Criterion validity was evaluated using Spearman correlations (r) and Bland-Altman plots. Test-retest reliability was tested using intraclass correlation coefficients (ICC).

Results

Strong correlations (r > 0.75) and acceptable reliability (ICC > 0.80) were found regarding individual-limb COP velocity and DCA, net COP ML amplitude and AP and ML velocities. Bland-Altman plots yielded possible proportional bias; the pressure plate systematically underestimated COP scores by force plates and a larger error associated with a larger measurement.

Conclusions

Despite correlations between instruments and sufficient reliability for measuring postural stability and DCA, this technical note strongly suggests, due to a systematic deviation, using the same plate-type to accurately assess performance change within subjects longitudinally over time.