New methods of posturographic data analysis may improve the diagnostic value of static posturography in multiple sclerosis

Abstract

Background: Early and accurate diagnosis of multiple sclerosis (MS) is crucial for its effective treatment. In MS diagnostic, neuronal networks that control posture and movement are of particular importance, which performance can be assessed using static posturography. Unfortunately, most of the commercially available posturographic platforms are not equipped with the appropriate procedures.

Methods: To solve this problem, the postural sway trajectories have been recorded in 55 MS patients while standing quiet with eyes open (EO), and then with eyes closed (EC). The trajectories were analyzed using our novel methods of postural sway parametrization, including sway stability vector (SV), anteroposterior and mediolateral sway indices (DIAP and DIML).

Results: The results exhibited unique postural sway patterns that may be attributed to MS. Our novel parametrization methods of postural sway showed pathology specific increase of the postural sway velocity in EC tests. Additionally, we documented the abnormal alterations of the anteroposterior (AP) and the mediolateral (ML) sway indices that were also uniquely dependent on visual input. In EC tests, patients exhibited a characteristic pattern of sway increase in both AP and ML directions that correlated with the advance of the disease as measured by the EDSS Kurtzke scale and Functional System Scores.

Conclusions: The applied in the present study our novel posturographic metrics give the assessment a diagnostic value. It allows us to recommend the static posturography test as a simple and safe supplementary clinical tool in the diagnosis of MS. In the assessment of MS pathology or the effects of its treatment, the impact of vision on the sway stability vector seems the most important factor.

Keywords: Directional indices; Multiple sclerosis; Postural control; Posturography; Stability vector.

Figure 1

Changes of mean anteroposterior AP COP velocity (panel A) and mediolateral ML COP velocity (panel B) in 3 groups of MS patients (G1-G3; for details see Table 1). Tests were performed with eyes opened (EO), and with eyes closed (EC). Reference values were computed from the age-matched, healthy control group (n = 36). Error bars represent standard deviation. NS – insignificant difference, ∗∗∗-p≤0.001.

Figure 2

Attributes of Stability Vector: amplitude - SVamp (panel A), and azimuth – Svaz (panel B) in 3 groups of MS patients (G1-G3; for details see Table 1). Posturographic tests were performed with eyes opened (EO), and with eyes closed (EC). Reference values were computed from the age-matched, healthy control group (n = 36). Error bars represent standard deviation. NS – insignificant difference, ∗∗∗-p≤0.001.

Figure 3

Changes of Directional Sway Indices: DIAP panel A, and DIML panel B) in 3 groups of MS patients (G1-G3; for details see Table 1). Standard posturographic tests were performed with eyes opened (EO), and with eyes closed (EC). Reference values were computed from the age-matched, healthy control group (n = 36). Error bars represent standard deviation. NS – insignificant difference, ∗∗- p ≤ 0.01 ∗∗∗-p≤0.001.