Testing of vibratory thresholds as a clinical examination for patients with unsteadiness due to somatosensory disorders

The somatosensory system is an important component for balance control. Disorders of this system are characterized by postural unsteadiness and could be assessed by vibratory sensation. However, the measurement of vibratory thresholds (VTs) has been rarely employed as a clinical test for patients with unsteadiness. This study aimed to evaluate the difference in vibratory thresholds between patients with somatosensory disorders and healthy volunteers, and to provide a means for evaluating somatosensory disorders in patients with balance problems. Using a vibrometer and a force-measuring platform, VTs and postural balance in 108 healthy volunteers (age, 17-79) and 19 patients with somatosensory disorders (age, 60-79) were examined. VTs of the plantar surface, as well as total length of the path and envelope area (ENV) of posturograms, in patients with somatosensory disorders were significantly larger than those in healthy volunteers. Regression analyses showed that VTs ≥ 28 dB (peak-to-peak amplitude, 24 μm) of the plantar surface at 125 Hz and ENV ≥ 10 cm² were significant indices for unsteadiness due to somatosensory disorders. VT testing of the plantar surface as well as posturography appears to be useful as a clinical examination for patients with unsteadiness.