Correlation of balance posturographic parameters during quiet standing with the berg balance scale in patients with parkinson's disease

Abstract

Background: Parkinson's disease (PD) is often clinically associated with posture instability and more easily falling. The Berg balance scale is a clinical indicator commonly used to subjectively evaluate a patient's balance ability. Meanwhile, computerized force platforms have been used in research on postural control. The various parameters obtained from posturography are interpreted to assess balance ability. The present study aims to explore the correlations between posturographic variables and the BBS, and furthermore to efficiently evaluate postural instability and fall risk of early and moderate PD patients.

Methods: A total of 46 PD patients were involved in the experiment. Patients were asked to perform BBS tests and force platform tests under eye open (EO) and eye closed (EC) conditions. The recorded COP signal was analyzed with the time domain statistical method, the frequency domain method of Power Spectral Density (PSD), and structural methods of Stabilogram Diffusion Analysis (SDA), Sway Density Plot (SDP) to retrieve different posturographic variables. The correlation between posturographic variables under EO and EC conditions with BBS was compared statistically. The significantly correlated posturographic parameters were then applied to analyze posturographic differences between different groups: faller vs. non-faller (patients with/without a history of falls in the past 12 months).

Results: Among the different posturographic parameters, the prediction ellipse area, the slope of the regression line at a high-frequency band of PSD in the medial-lateral (ML) direction, the crossover point of the regression lines of SDA in the anterior-posterior (AP) direction, and the distance between successive peaks of SDP had significant correlations with BBS. These selected BBS-related parameters also showed significant differences between faller and non-faller. The selected posturographic parameters can be used as effective indicators to evaluate the balance ability of Parkinson's disease patients.

Keywords: Balance control; Berg Balance Scale; Center of pressure (COP); Parkinson’s disease (PD); Posturography.

Fig. 1

A barefoot patient standing still on a force platform, (A) EO state, (B) EC state. EO = Eye Open, EC = Eye Close, X = ML direction, Y = AP direction

Fig. 2

PSD analysis diagram of a sample PD patient’s COP signal at the EO state: (A) in the ML direction; (B) in the AP direction. PSD = Power Spectral Density, ML = medial-lateral, AP = anterior-posterior, x = ML, y = AP.

Fig. 3

Logarithmic diffusion diagrams generated by SDA analysis of a PD patient’s COP signal at the EO: (A) in the ML direction; (B) in the AP direction. SDA = Stabilogram Diffusion Analysis, ML = medial-lateral, AP = anterior-posterior, x = ML, y = AP.

Fig. 4

Typical SDP of a PD patient’s COP signal: (A) PD patient’s stabilogram; (B) PD patient’s sway density curve. In (A), R (3 mm) was the given radius within which the COP trajectory could fall instantaneously at each time interval. SDP = sway density plot, EO = Eye Open, ML = medial-lateral, AP = anterior-posterior, x = ML, y = AP, COP = center of pressure

Fig. 5

Statistic assessment of the four posturographic parameters between faller and non-faller: (A) COP_PEA; (B) PSD_HSlope_x ; (C) SDA_CP_y ; (D) SDP_MD. EO = Eye Open; COP = center of pressure, PEA = he prediction ellipse area, SDP = sway density plot, SDA = Stabilogram Diffusion Analysis, PSD = Power Spectral Density