Postural response characterization in elderly patients with bilateral vestibular hypofunction

Hamlet Suarez, Gonzalo Sotta, Cecilia San Roman, Sofia Arocena, Enrique Ferreira, Dario Geisinger, Alejo Suarez & Juan Picerno

Abstract

Conclusions: The measurement of the energy consumption (EC) of the body’s center of pressure (COP) to maintain the upright stance position was higher in elderly patients with bilateral vestibular hypofunction (BVH) compared with a control group and may be a valid parameter in the assessment of balance disorders. Objective: The aim of the study was to evaluate the energy consumption of the COP in elderly patients with BVH. Methods: The COP was recorded on a force platform (FP) for eight elderly patients with BVH related to aging and eight normal control group subjects. The EC of the COP was calculated using the discrete wavelet transform. The two groups were tested in standing position on the FP in three sensory conditions:1, eyes open; 2, eyes closed; and 3, standing on a foam pad placed on the force platform. Wilcoxon’s rank test and multi-factor analysis of variance were used, with the level of significance set at 0.05. Results: BVH patients showed higher values of EC of the COP signal measured in arbitrary units compared with the control group (conditions 1 and 2). None of the BVH patients could perform the test in condition 3. BVH patients had increased EC in the frequency band between 0.1 and 0.78 Hz when the visual information was canceled (condition 2).

Keywords

Wavelets, posturography, postural control

Postural control and sensory perception in patient with Parkinson’s Disease

Suarez H, Geisinger D, Suarez A, Carrera X.

Acta Otolaryngol. 2009 Apr;129(4):354-60

Abstract

CONCLUSIONS: This study suggests that patients with Parkinson’s disease (PD), even in the early stages, have decreased body limits of stability (LOS) and changes in the visual input impair their postural control.

OBJECTIVE: To assess the LOS and the postural responses after changes in visual input in a group of PD patients in stage 1 of the Hoehn and Yahr classification.

SUBJECTS AND METHODS: Twenty PD patients in stage 1 and a group of 24 normal subjects as control were assessed in two tests: (1) the LOS and (2) measurement of the body center of pressure area (COP) 10 s before and after sudden change in visual flow velocity. We also investigated labeling of the COP trajectory in these two periods. The stimulation paradigm was a horizontal optokinetic stimulation (60 degrees /s and suddenly stopped) using a virtual reality system.

RESULTS: LOS showed significant decrease in PD patients as compared with the control group (p<0.001, Kruskal-Wallis and Wilcoxon ranked test). The COP values increased significantly (p<0.001, Wilcoxon signed rank test) after sudden changes in the visual flow velocity in relation to the control group. After the visual stop the PD patient showed a spatial ‘roaming’ approaching the limits of stability and therefore impairing the postural control.

Postural Adaptation in Elderly Patients with Instability and Risk of Falling after balance training using a Virtual Reality System.

Suarez H, Suarez A, Lavinsky L.

International Tinnitus Journal. 2006. 12:41-45.

Abstract. Our aim in this study was to assess postural control adaptation quantitatively in unsteady elderly patients at risk of falls in open spaces and givenbalance training with a virtual-reality system reproducing environmental stimulation. Using a balance rehabilitation unit based on a virtual-realitysystem that changes sensory information (visual, vestibular, and somatosensory), we treated 26 elderly, unsteady patients who were prone to falling(age range, 73-82 years) and who were enrolled in a customized vestibular rehabilitation program. We assessed postural responses by posturography before and after 6 weeks in the vestibular rehabilitation program under two conditions: (1) standing, eyes open, static visual field, and (2) standing, eyes open, dynamic visual field through virtual-reality goggles, generating horizontal optokinetic stimulation (70 degrees per second angular velocity). We recorded postural responses with a platform measuring the confidential ellipse of the center-of-pressure distribution area and sway velocity with a scalogram analyzing postural behavior by wavelets. After 6 weeks of treatment, postural response confidential ellipse and sway velocity values were lower, evincing decreased amplitudes and sway frequency contents in the scalogram by wavelet under both stimulation paradigm conditions. These findings suggest postural adaptation under the two perceptual conditions when patients had static and dynamic visual fields. The possibility of treatingelderly fallers with balance disorders using a virtual-reality environmental stimulation reproduction system is discussed.