THE EFFECT OF LOW FREQUENCY SOUND ON POSTURAL STABILITY IN PATIENTS WITH VERTIGO CAUSED BY INNER EAR DYSFUNCTION.

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The effect of low frequency sound on postural stability was studied in patients with different type inner ear pathology. The low frequency sound level ranged from 130 to 132 dB and were delivered at the frequencies 4,8,16,25,50,63Hz. The postural response were measured with a force platform and the sway velocity of the center point of force was determined. In the healthy subjects, the low frequency sound stimulation did not increase body sway velocity. The subjects showed slight improvement of their postural stability during the stimulation period, probably due to alerting response generated by the low frequency sound stimulation. The mean responses of patients with Meniere's disease, with chronic otitis media with vertigo and with vertigo of peripheral origin showed increased body sway during stimulation. In the individual response 26% of the patients with Meniere's disease, 40% with chronic otitis media with vertigo, 26% with vertigo of peripheral origin experienced significant postural instability during the stimulation of low frequency sound. All patients with perilymphatic fistula showed significantly altered postural stability during low frequency stimulation. The result demonstrate that in subjects with different types inner ear disease the vestibular system starts to respond to low frequency sound. The activation of vestibulospinal responses by low frequency sound seems to be an expression the Tullio phenomenon. A long term effect on smoking on postural stability was examined on 80 subjects randomly selected from a population of professional forest workers. Age and smoking had significant simple correlation coefficients to sway velocity but hours of exposure to noise did not. The mean sway velocity increased with increase the dose of smoking. Smokers exhibited more unstable posturographic results than non-smokers. Smoking was suggested to have long term effect on the postural control system.