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The effect of idiopathic Parkinson's disease on seated trunk reactions Pauhl, Katherine Elizabeth

Abstract

A common symptom of Idiopathic Parkinson’s disease (IPD) is decreased trunk and balance control. These deficits in patients with IPD are not treatable, and their underlying mechanisms are not well understood. Additionally, it is not known to what extent decreased trunk control contributes to postural instability in patients with IPD. Previous work by Martin (1965) observed that patients with post-encephalitatic Parkinson’s disease would fall in the direction of the tilt when perturbed while seated. In order to better understand the underlying causes of these observed trunk deficits and attempt to replicate Martins findings, this study investigated postural corrective movement of the trunk while seated in patients with IPD and age-matched healthy controls. Participants’ range of motion (ROM) was tested actively and passively while lying supine, following which, bilateral electromyography (EMG) (rectus abdominis (RA), external oblique (EO), and erector spinae (EST9, L3)) and 3-D kinematic measures were recorded while participants were seated on a modified chair and received unexpected perturbations, 7° at 40°/sec, in four different directions (forward, backward, left, and right). EMG responses were normalized to participant’s maximum voluntary contractions. We observed patients with IPD to have decreased active and passive ROM only in the frontal plane relative to controls. Patterning of muscle responses to rotational perturbations did not vary between groups in any direction, except backward, and trends toward significantly greater EST9 activity were observed during backward and left tilts in patients with IPD. Despite this both patients with IPD and controls were able to make appropriate trunk corrective movements opposite the direction of the tilt. However, two patients, who were most severely affected, did make incorrect trunk movements in the direction of the tilt during left and right tilting perturbations which, upon visual inspection, appear to be due to improperly modulated and timed muscle responses. Thus, our data counters the findings of Martin, and suggests the trunk is posturally stable in IPD. Therefore, balance instabilities during stance are likely due to improper responses of the lower limbs. However, as disease severity increases, the contributing influence of an improperly responding trunk may add to their postural deficits.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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