Article

Impairment of postural control is a common consequence of Parkinson's disease
(PD). Increasing evidences demonstrate that the pathophysiology of postural
disorders in PD includes deficits in proprioceptive processing and integration.
However, the nature of these deficits has not been thoroughly examined. We
propose to establish a link between proprioceptive impairments and postural
deficits in PD using two different experimental approaches manipulating
proprioceptive information. In the first one, the subjects stood on a platform
that tilted slowly with oscillatory angular movements in the frontal or sagittal
planes. The amplitude and frequency of these movements were kept below the
semicircular canal perception threshold. Subjects were asked to maintain vertical
body posture with and without vision. The orientations of body segments were
analyzed. In the second one, the postural control was tested using the
tendon-vibration method, which is known to generate illusory movement sensations
and postural reactions. Vibrations were applied to ankle muscles. The subject's
whole-body motor responses were analyzed from center of pressure displacements.
In the first experiment, the parkinsonian patients (PP) were unable to maintain
the vertical trunk orientation without vision. Their performances with vision
improved, without fully reaching the level of control subjects (CS). In the
second experiment, the postural reactions of the PP were similar to those of the
CS at the beginning of the perturbation and increased drastically at the end of
the perturbation's period as compared to those of CS and could induce fall. These
results will bring new concepts to the sensorimotor postural control, to the
physiopathology of posture, equilibrium and falls in PD and to the role of basal
ganglia pathways in proprioception integration. Nevertheless, in order to assess
precisely the role played by sensorimotor integration deficits in postural
impairments in PD, further studies establishing the links between clinical
features and abnormalities are now required.
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Langue : ANGLAIS