Synchronization of the signal posturographic to optic-kinetic stimulus for the diagnosis and the rehabilitation of vestibular disorder with “VERTIGO STATIC PLATFORM”

Abstract

minimal acceleration [1]. In normal circumstances, this allows for the minimisation of the head acceleration with the consequent reduction of inertial loads and stabilisation of the optic flow. In patients with muscular myopathies causing impairments at trunk level, the ability to control upper body accelerations and ensure head stability is expected to be reduced. Aim of this study is to test the above hypothesis, as a paradigmic example, in subjects with facioscapulohumeral dystrophy. Methods: Twenty control healthy subjects (CS, 25 ± 6 years, 1.6 ± 0.1 m, 58 ± 8 kg) and 12 subjects with facioscapulohumeral dystrophy (DS, 38 ± 10 years, 1.8 ± 0.1 m, 85 ± 23 kg) participated in this study. They were asked to walk at their self-selected speed, and a 9-camera VICON MX was used to reconstruct the trajectories of 10 markers (anterior and posterior superior iliac spines, jugular notch, C7 spine process, front and back of the head, and heels). Head (H), upper trunk (T), and pelvis (P) movements were described using the trajectories of the midpoints between the head markers, between C7 and jugular notch, and the centroid of the iliac spines, respectively. The root mean square of the accelerations (aRMS) of H, T, and P were computed along the antero-posterior (AP), medio-lateral (ML) and vertical (V) directions. To investigate the differences between the two groups in the ability to attenuate the accelerations from pelvis to head level, the following coefficients were computed: cPT =( aRMSP − aRMST)/aRMSP, and cPH =( aRMSP − aRMSH)/aRMSP. The t-test was used for statistical analysis. Results: For the CS, at all levels, the aRMS was not correlated with the speed of progression. For the DS, a moderate, but not significant, inverse correlation between speed and head acceleration was found in the ML and AP directions. Both groups (figure) showed no significant aRMS attenuations along the V direction. In the CS, along the AP direction, pelvis acceleration was significantly higher (p < 0.01) than that at trunk and head levels. The DS, on the contrary, were less able to reduce the amplitude of the acceleration from pelvis to trunk and head levels, as shown by the lower (p < 0.01) attenuation coefficients. In the ML direction, finally, the head acceleration was attenuated with respect to the pelvis in the CS (p = 0.03), whereas it was higher (p < 0.01) than the pelvis acceleration in the DS, as shown by the negative cPT and cPH. Discussion: The ability to control head stability during walking is a characteristic of healthy adults, which is preserved in aging [2], but it was significantly compromised in the subjects with a myopathy. Along mediolateral direction, the head acceleration was even higher than that of the pelvis. A possible explanation for this result could be the adoption of a strategy to compensate for hip abductor weakness, but further studies are needed to validate this hypothesis.