Body sway analysis by a feedback model and observation of patients with vestibular, central and peripheral equilibrium disturbances

Abstract

Disturbances of standing posture regulation in patients with vestibular, cerebellar, spinal and peripheral disorders were studies by a time series analysis with a 5-dimension feedback model.Sways of the head, shoulder, hip, knee and foot during upright standing were recorded with a position sensor system and stored in a PDP-11 computer. With the use of a 5-dimension feedback model the stored data were processed by a specially designed program.1) In a patient with bilateral loss of labyrinthine excitability and a forward-backward (F-B) sway in the statokinesigram, the determinant was 0.43 in F-B sway. The power spectrum and the correlograms indicated periodic components of about 0.4 Hz in F-B sway. The impulse responses to head movements converged with periodic sways against external disturbances. The transfer functions calculated with shoulder movement as input and head and knee movements as output indicated increases of the gain. The relative power contribution showed that the pro-portion of head movement increased during sway of the shoulder, hip and knee.2) In a patient with unilateral loss of labyrinthine excitability and a right-left (R-L) sway, the power spectrum and the correlograms indicated periodic components of about 0.3 Hz in R-L sway. The relative power contribution showed that the proportion of shoulder movement increased during the sway of the head, hip and knee in low frequency.3) In a patient with spino-cerebellar degenera tion and a diffuse, large sway, the determinant wa: 0.025 in F-B sway. The power spectrum and the correlograms indicated periodic components of about 0.3 Hz. The impulse responses were divergent The transfer functions indicated disorders of coordination.4) In a patient with an infarction of a cerebellar hemisphere and a small R-L sway, the determinants were from 0.57 to 0.77. The power spectrum and the correlograms indicated poor periodicity. The impulse responses were slightly divergent. The transfer functions and relative power contribution were similar to those in normal subjects.5) In a patient with Caisson disease and a large F-B sway, the determinant was 0.007 in F-B sway. The impulse responses were divergent. The transfer functions calculated with hip movement as input and head and knee movement as output indicated in-creases of the gain.6) In a patient with Friedreich's ataxia and an enlarged sway with the eyes closed, the determinants were from 0.31 to 0.74. The power spectrum and the correlograms indicated no periodicity. The transfer functions were similar to those in normal subjects. The relative power contribution showed that the propotion of the hip movement increased during sway of the head and knee.7) In a patient with Charcot-Marie-Tooth disease and an enlarged sway with the eyes closed, the determinants were from 0.73 to 0.95. The impulse responses were convergent. The transfer functions and the relative power contribution were similar to those in normal subjects.