Postural behavior and Parkinson's disease severity

Progression of Parkinson disease (PD) increases severe motor symptoms such as bradykinesia, tremor, gait disturbance and postural instability, interfering with patients' daily life autonomy. Clinical evaluation is based on specific Scales like Hoehn & Yahr (H&Y) or UPDRS scales. The main goal of the study was to identify motor changes in the kinematic parameters related to different stages of Parkinson's disease progression according to H&Y scale. A secondary goal was to determine more objectively the stage of the disease reducing the discomfort of scales subjectivity. Our sample integrated 103 patients (45 female and 58 male, 70.5±8.4 years) diagnosed with PD by neurologists specialized in movement disorders. Postural Behavior was evaluated using Computerized Dynamic Posturography equipment (Balance Master System). Postural behavior was based on posturographic analysis of the center of pressure (CoP) time series (corresponding to the vertical projection of the center of gravity) to determine kinematic parameter(s) considered suitable to identify postural behavior modification. The posturographic tests applied were: 1) modified Clinical Test of Sensory Interaction on Balance (mCTSIB); 2) Limits of Stability (LOS); 3) Rhythmic Weight Shift (RWS). The results, concerning four stages of the H&Y scale (I-IV), showed significant differences between groups/stages. Static balance parameters like velocity, total distance, amplitude and frequency of CoP sway, increase with disease severity. In early to medium stages (I-II) of the disease, CoP presents a projection backwards, while in stage IV, this projection showed a trend to change forwards. Concerning dynamic balance, LOS presents a reduction mainly in the forward direction in all stages. The directional control in anterior-posterior RWS decreases with disease progression.