Neuromodulation strategies tailored to facilitate SMA activity may be ineffective for the treatment of gait initiation impairment in people with PD and FOG.

Objective To examine the effects of cue timing, across three sensory modalities, on anticipatory postural adjustments (APAs) during gait initiation in people with Parkinson’s disease (PD). Design Observational study. Setting Biomechanics research laboratory. Participants Twenty-five individuals with idiopathic PD (11 with freezing of gait, FOG) were studied in the off-levodopa state (12-hour overnight withdrawal). Interventions Gait initiation was tested without cueing (self-initiated) and with three cue timing protocols: fixed delay (3 s), random delay (4–12 s) and countdown (3-2-1-go, 1 s intervals) across three sensory modalities (acoustic, visual and vibrotactile). Main Outcome Measures The incidence and spatiotemporal characteristics of APAs during gait initiation were analyzed, including vertical ground reaction forces and center of pressure. Results All cue timings and modalities increased the incidence and amplitude of APAs compared to self-initiated stepping. Acoustic and visual cues, but not vibrotactile stimulation, improved the timing of APAs. Fixed delay or countdown timing protocols were more effective at decreasing APA durations compared to random delay cues. Cue-evoked improvements in APA timing, but not amplitude, correlated with the level of impairment during self-initiated gait. Cues did not improve the late push-off phase in the FOG group. Conclusions External cueing improves gait initiation in PD regardless of cue timing, modality, or clinical phenotype (with and without FOG). Acoustic or visual cueing with predictive timing provided the greatest improvements in gait initiation thus these protocols may provide the best outcomes when applied by caregivers or devices.

Gait initiation involves a complex sequence of anticipatory postural adjustments (APAs) during the transition from steady state standing to forward locomotion. APAs have four core components that function to accelerate the center of mass forwards and towards the initial single-support stance limb. These components include loading of the initial step leg, unloading of the initial stance leg, and excursion of the center of pressure in the posterior and lateral (towards the stepping leg) directions. This study examined the incidence, magnitude, and timing of these components and how they change across the lifespan (ages 20–79). 157 individuals performed five trials of self-paced, non-cued gait initiation on a computerized walkway. At least one component of the APA was absent in 23% of all trials. The component most commonly absent was loading of the initial step leg (absent in 10% of all trials in isolation, absent in 10% of trials in conjunction with another missing component). Trials missing all four components were rare (1%) and were observed in both younger and older adults. There was no significant difference across decades in the incidence of trials without an APA, the number or type of APA components absent, or the magnitude or timing of the APA components. These data demonstrate that one or more components of the APA sequence are commonly absent in the general population and the spatiotemporal profile of the APA does not markedly change with ageing.

Background: Subtle gait deficits can be seen in people with idiopathic rapid eye movement (REM) sleep behavior disorder (RBD), a prodromal stage of Parkinson’s disease (PD) and related alpha-synucleinopathies. It is unknown if the presence and level of REM sleep without atonia (RSWA, the electromyographic hallmark of RBD) is related to the severity of gait disturbances in people with PD. Objective: We hypothesized that gait disturbances in people with mild to moderate PD would be greater in participants with RSWA compared to those without RSWA and matched controls, and that gait impairment would correlate with measures of RSWA. Methods: Spatiotemporal characteristics of gait were obtained from 41 people with PD and 21 age-matched controls. Overnight sleep studies were used to quantify muscle activity during REM sleep and group participants with PD into those with RSWA (PD-RSWA+, n = 22) and normal REM sleep muscle tone (PD-RSWA-, n = 19). Gait characteristics were compared between groups and correlated to RSWA. Results: The PD-RSWA+ group demonstrated significantly reduced gait speed and step lengths and increased stance and double support times compared to controls, and decreased speed and cadence and increased stride velocity variability compared to PD-RSWA- group. Larger RSWA scores were correlated with worse gait impairment in the PD group. Conclusion: The presence and level of muscle tone during REM sleep is associated with the severity of gait disturbances in PD. Pathophysiological processes contributing to disordered gait may occur earlier and/or progress more rapidly in people with PD and RBD.

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