Article

OBJECTIVE: To characterize preparation for compensatory stepping in people with
Parkinson's disease (PD) compared with healthy control subjects, and to determine
whether levodopa medication improves preparation or the execution phases of the
step. DESIGN: Observational study. SETTING: Outpatient neuroscience laboratory.
PARTICIPANTS: Nineteen participants with idiopathic PD tested both in the on and
off levodopa states and 17 healthy subjects. INTERVENTION: Moveable platform with
posterior translations of 24cm at 56cm/s. MAIN OUTCOME MEASURES: Compensatory
steps forward, in response to a backward surface translation (24cm amplitude at
56cm/s), were categorized according to the presence of an anticipatory postural
adjustment (APA) before stepping: no APA, single APA, or multiple APAs. The
following step parameters were calculated: step latency, step length, center of
mass (CoM) average velocity, and CoM displacement at the step initiation.
RESULTS: Lateral APAs were evident in 57% and 42% of trials for people with PD in
the off and on medication states, respectively, compared with only 10% of trials
for control subjects. Compared with subjects with PD who did not have APAs, those
subjects with PD who did make an APA prior to stepping had significantly later
(mean +/- SEM, 356+/-16ms vs 305+/-8ms) and shorter (mean +/- SEM, 251+/-27mm vs
300+/-16mm) steps, their CoM was significantly farther forward (185+/-7mm vs
171+/-5mm) at foot-off, and they took significantly more steps to regain
equilibrium. Levodopa did not affect the preparation or execution phase of
compensatory stepping. Poor axial scores and reports of freezing in the United
Parkinson's Disease Rating Scale were associated with use of 1 or more APAs
before compensatory stepping. CONCLUSIONS: Lateral postural preparation prior to
compensatory stepping in subjects with PD was associated with inefficient balance
recovery from external perturbations.

Langue : ANGLAIS