Objective: Distinguish biomechanical from neurological gait influences in people with PD.
Background: Hypokinetic walking in PD has been described by comparison to unimpaired controls. Walking speed, a powerful influence on gait, has not been controlled in most studies. The rapid and reversible response of patients with PD to DBS provides a means to separate biomechanical from neurological effects on walking.
Methods: We tested 5 subjects with PD that demonstrated marked clinical improvement in hypokinesia following bilateral subthalamic nucleus DBS (3M,2F; mean age 62ฯฎ6.6 yrs; mean body mass 89.6 kgฯฎ28.7 kg, DBS ี6 mo prior). 4 of 5 subjects with PD were tested in the drug-off state after overnight withdrawal of anti-PD medication. 5 matched Control subjects (CTRL) provided comparison data. All subjects walked on a treadmill at 0.36 m/s; two 30s trials for each condition. Subjects with PD were tested with DBS ON, then the DBS turned off and testing repeated 30 min later (DBS OFF). CTRL subjects were tested twice with 30 mins between sessions. Temporospatial gait parameters and sagittal ankle kinematics were captured with a computerized reflective marker system. Data from the most symptomatic leg (PD) were compared to the dominant leg of the CTRL group using MANOVA with pฯฝ0.05 followed by post-hoc Wilk's Lambda.
Results:
PD DBS ON PD DBS OFF
CTRL Sess 1 CTRL Sess 2
Step Length (cm)* 24.6 (6.5) 22.2 (6.0) 33.9 (3.1) 36.1 (1.9) Cadence (steps/min)* 96.3 (36.1) 101.5 (24.3) 65.4 (4.5) 62.9 (5.8) Initial Dbl Support (%) 22.1 (3.1) 21.7 (3.2) 23.0 (1.0) 21.3 (0.7) Dorsiflx @ Initial Contact 2.7 (5.2) 4.9 (4.4) -0.6 (3.0) -1.4 (5.6)
Avg Dorsiflx @ Single Leg Stance 8.9 (4.0) 9.8 (4.7) 7.4 (2.9) 7.0 (3.2)
Avg Dorsiflx @ Early Swing -0.2 (7.0) -0.7 (7.6) 1.2 (4.3) -0.4 (6.4) Avg Trunk Rotation 3.8 (2.5) 2.6 (1.2) 2.4 (1.1) 2.6 (1.6) Base of Support (cm) 12.7 (3.7) 10.1 (2.1) 12.0 (3.1) 10.8 (3.4) Mean (sd) *ฯญsignificant difference Step Length: PD-vs-CTRL, pี
0.02, DBS ON-vs-DBS OFF, pฯญ0.04 Cadence: PD-vs-CTRL, pี
0.009 only for DBS OFF-Session 2 Conclusion: The few differences between PD and CTRL imply a dominant biomechanical influence on slow walking. Differences between PD and CTRL subjects and effects of DBS were present only in Step Length and Cadence. Comparative studies of PD hypokinesia must consider the effects of walking speed.