Analysis of Standing Posture in Patients with Bilateral Loss of Labyrinthine Excitability

The forward-backward and right-left sways in the upright standing posture were examined using stabilometry and analysis with a 5-dimensional feedback model. The forward-backward sway was found to have a fast, hidden periodicity, composed of sways due to a loss of the labyrinthine righting reflex upon the head and interaction between the head and knee sways. Furthermore, on the basis of our previous investigation, the forward-backward sway was found to depend on the increased spinal reflexes caused by a loss of labyrinthine inhibitory control upon the antigravity muscles. The right-left sway is slow and irregular, being mainly produced by disturbance of the head righting reflex.