Influence of subjective visual vertical misperception on balance recovery after stroke

Background: Subjective visual vertical (SVV) perception can be perturbed after stroke, but its effect on balance recovery is not yet known. Aim: To evaluate the influence of SVV perturbations on balance recovery after stroke. Methods: 28 patients (14 with a right hemisphere lesion (RHL) and 14 with a left hemisphere lesion (LHL)) were included, 5 were lost to follow-up. SVV perception was initially tested within 3 months after stroke, then at 6 months, using a luminous line, which the patients adjusted to the vertical position in a dark room. Mean deviation (V) and uncertainty (U), defined as the standard deviation of the SVV, were calculated for eight trials. Balance was initially assessed by the Postural Assessment Scale for Stroke (PASS), and at 6 months by the PASS (PASS6), a force platform (lateral and sagittal stability limits (LSL6 and SSL6)), the Rivermead Mobility Index (RMI6) and gait velocity (v6). Functional outcome was also assessed by the Functional Independence Measure at 6 months (FIM6). Results: The scores for balance and for FIM6 were related to the initial V value: PASS6 (p = 0.01, tau = -0.38); RMI6 (p = 0.002, tau = -0.48), LSL6 (p = 0.06, tau = -0.29), SSL6 (p = 0.004, tau = -0.43), v6 (p = 0.01, tau = -0.36) and FIM6 (p = 0.001, -tau = -0.49), as well as to the initial U value: PASS6 (p = 0.03, tau = -0.32), RMI6 (p = 0.02, tau = -0.35), SSL6 (p = 0.005, tau = -0.43) and FIM6 (p = 0.01, tau = -0.38). Conclusions: Initial misperception of verticality was related to a poor score for balance after stroke. This relationship seems to be independent of motricity and neglect. Rehabilitation programmes should take into account verticality misperceptions, which could be an important factors influencing balance recovery after stroke.