[Abstract Title]. - Society for Neuroscience

Program#/Poster#: 275.27/KK8
Topic: D.16.d. Kinematics and Muscle Activity
Title: The effect of early stage Parkinson‟ disease on dynamic postural stability during turning
activities
Authors: J. SONG 1 , *B. E. FISHER 1 , S. SIGWARD 1 , G. PETZINGER 2 , G. J. SALEM 1 ;
1 Biokinesiol & Physical Therapy, 2 Neurol., USC, Los Angeles, CA
Abstract: PURPOSE: Persons with early stage Parkinson‟s disease (EPD) typically show
minimal levels of impairment and disability, as quantified by scores of less than or equal to two
on the Hoehn and Yahr scale. Previous studies have found no differences in gait parameters
between healthy control (HC) participants and persons with EPD suggesting that more complex
tasks may be needed to discriminate between these groups. Turning tasks impose a greater
demand on postural stability as they require coordination of speed modulation with reorientation
of the body. Given this, evaluation of postural stability during turning may be more sensitive to
detect impairments due to EPD. Therefore, the purpose of this pilot study was to compare
measures of dynamic postural stability between persons with EPD and HC participants during
turning activities.
SUBJECTS: Two persons diagnosed with EPD and two HC subjects participated in the study.
MATERIALS AND METHODS: Subjects were instructed to walk 4 meters and perform a 90 0
turn at a designated location. Three-dimensional kinematics (8 camera, VICON Motion System,
60 Hz) and segment inertial parameters (Dempster, 1971) were used to calculate the whole body
center of mass (COM). Center of pressure (COP) was determined from force plate measures
during single and double limb stance (AMTI force plate 1.2m x 1.2m, 1560Hz). To account for
the effects of COM velocity on postural stability during turning, an extrapolated COM (eCOM)
was calculated using COM position and velocity as previously described by Hof et al., 2005.
Dynamic postural stability was defined as the distance from COP to the eCOM in the mediallateral
(ML) and anterior-posterior (AP) directions. RESULTS: When compared to HC
participants, both subjects with EPD demonstrated a greater AP distance during turning activities
indicating a greater threat to stability in the AP direction. In contrast, the subjects with EPD
exhibited a shorter ML distance indicating a smaller threat to stability in the ML direction.
CONCLUSION: Persons with EPD utilized different control strategies during turning tasks than
HC participants. These preliminary data suggest that measures of dynamic postural stability
during turning are sensitive enough to discriminate between persons with EPD and HC
participants. However, it remains unclear if the control strategies employed by persons with EPD
are associated with an inability to modulate COM velocity or position relative to COP. Dynamic
postural stability during turning may be an early predictor of fall risk in persons with PD.
Disclosures: J. Song, None; B.E. Fisher , None; S. Sigward, None; G. Petzinger, None; G.J.
Salem, None.