Alternate Trains of Postural Muscle Vibration Promote Cyclic Body Displacement in Standing Parkinsonian Patients.

Patients suffering from Parkinson’s disease (PD)
have difficulties with control of stance, postural changes,
and walking, seemingly depending on problems in central
integration of proprioceptive information. We tested the
hypothesis that alternate vibration of postural muscles can
induce cyclic medio-lateral or antero-posterior sway in PD,
mimicking that accompanying body progression during
walking, thereby favoring the production of locomotor tasks.
In 12 standing PD patients and 11 healthy subjects, we
applied trains of vibratory stimuli, bilaterally in an alternating
paradigm to soleus, tibialis anterior, or paravertebral
muscles. The trains of stimuli were delivered at frequencies
selected to be above, near, and below the normal walking
rhythm. The displacement of the center of foot pressure
(CoP) was recorded. In PD, sway area during unperturbed
stance was just larger than in healthy subjects; shifts in CoP
in response to vibration were preserved, regardless of the
vibrated muscle pair; CoP oscillations along medio-lateral,
but not antero-posterior direction, were coupled to the vibration
trains; time to initiate and terminate the postural
responses was normal. PD patients correctly integrate and
exploit the vibration-induced proprioceptive inflow to produce
body oscillations comparable to those occurring during
walking. Vibratory stimulation can be safely and easily
employed to provoke rhythmic postural changes in
PD.