Studies on Labyrinthine Equilibrium Disturbance

Abstract

Peculiarities of labyrinthine equilibrium disturbance were studied.
1) Long-term observation of equilibrium disturbance in patients with bilateral loss of labyrinthine excitability indicated that equilibrium disturbances continuing more than 5 years after the incidence of the loss of labyrinthine excitability were disturbances of body balance in standing and walking in the dark and disturbances in visual fixation during walking and running (jumbling phenomenon). The results indicated that the most important role of the vestibulo-spinal reflexes is the righting reflexes which aid in maintaining standing posture and that the vestibulo-ocular reflexes in humans play an active part in visual fixation during movements with periodic head motion. From this point of view, we attempted to analyse the body sway appearing in the upright standing posture of these patients and to study the transfer function of the vestibulo-ocular system in humans.
2) The feature of the standing sway in these patients was forward and backward sway consisting of about 0.4Hz and a component faster than 0.4Hz. We considered that the sway was induced because of the increase in the spinal reflexes caused by the loss of labyrinthine control of the antigravity muscular tonus and due to loss of labyrinthine head-righting movement which indicates a frequency-dependent gain enhancement.
3) The Bode plots of the transfer function of the vestibulo-ocular system obtained from a pendular rotation test in the dark showed frequency-dependent gain enhancement at the rate of 5dB/decade in a frequency range of 0.3 to 5Hz. This indicates that the vestibulo-ocular system plays an important role in visual fixation during rapid head movement. We considered that the deficit of this vestibulo-ocular function causes the jumbling phenomenon.