Power spectral analysis of postural sway during foam posturography in patients with peripheral vestibular dysfunction.

Objective: To assess the frequency-domain characteristics of postural instability caused by peripheral vestibular dysfunction by performing a power spectral analysis of the center of pressure (COP) sway during foam posturography.

Methods: Data were obtained from 78 patients and 163 controls. Two-legged stance tasks were performed in 4 conditions: eyes open with and without foam rubber, and eyes closed with and without foam rubber. We estimated the power spectrum of the acceleration signal using the maximum entropy method. The areas under the curve (AUCs) of power spectral density of the COP were calculated across low-frequency (0.02 to 0.1 Hz, LF-AUC), middle-frequency (0.1 to 1Hz, MF-AUC), and high-frequency (1 to 10 Hz, HF-AUC) ranges. We performed binomial logistic regression analyses to see whether the AUCs of selected bandwidths of COP have a stronger association with the presence of peripheral vestibular dysfunction in comparison with the velocity and area in the eyes closed/foam rubber condition.

Results: In both the controls and patients, the MF-AUC was significantly larger than the LF-AUC or HF-AUC in the eyes closed/foam rubber condition. In this condition, the presence of peripheral vestibular dysfunction had a significantly positive relationship with MF-AUC and HF-AUC (p < 0.05) and the MF-AUC of the anterior-posterior axis showed a stronger association with the presence of peripheral vestibular dysfunction than area.

Conclusion: An increase in activity at middle frequency movements could be characteristic of peripheral vestibular dysfunction when standing on foam rubber with the eyes closed.