[Nonsequential vector analysis of body sway in Menière's disease]

Body sway test which examines the vestibulo-spinal reflex is sensitive for evaluating vestibular dysfunction in patients with vertigo, dizziness or unsteadiness. Body sway is usually evaluated by measuring the length and area of traces on the force platform. However, it is not necessarily possible to evaluate abnormal body sway with these indicators because there is a discrepancy between sway length and area. In the present study, 8 directional vectro-posturography was developed and applied to the patients with Meniere's disease. Averaging of measurements at moving 3 points was used to eliminate high frequency noise over 4.92Hz. The subjects consisted of 66 patients with unilateral Meniere's disease and 31 normal controls. Eight directional vectrogram allowed measurement of shift area and directionality, simultaneously. The patient's group showed statistically significant body sway in the right forward and left backward direction with eyes open, in all the directions with eyes closed, when compared with the control's group. The effect of vision on postural stability was studied by obtaining 8 directional Romberg's quotients. The patients with Meniere's disease had significantly in forward-backward, and left-forward and right-backward direction when compared with controls. However, laterality of the affected side was not detected from the vectrogram. The effect of endolymphatic sac operation on postural stability was evaluated in the patients of unilateral Meniere's disease who showed progressive hearing loss and resisted conservative medication therapy. The results showed unstable body sway in the condition with eyes closed until at least 4 months after the operation. The patients with Meniere's disease presented pathological body sway, even during symptom free periods, when examined with 8 directional vector posturography. Power spectral analysis of body sway indicated that most energy was distributed at frequencies lower than 0.5Hz. Nevertheless, directional preponderance of body sway was characterized by higher frequency components. The findings infers that postural stability at the frequency range over 0.5Hz, may be governed by the input of vestibular organs.