Objective: To quantify differences in postural responses to perturbations in people with Parkinson disease (PD) with and without freezing of gait (FOG+, FOG-, resp.), using a manual perturbation and wireless inertial sensors.

Background: Clinically, postural responses in people with Parkinson disease (PD) are assessed with the ‘pull test’ (postural stability) from the motor section of the Unified Parkinson Disease Rating Scale (UPDRS). However the measure is subjective and does not specifically quantify the postural response. We developed a manual Push and Release test as an alternative to provide more sensitive reactive postural-response measures (Horak et al 2009, Smith et al 2014). More recently, we developed new algorithms to quantify the details of the Push and Release using inertial sensors that could be used in a clinical setting.

Methods: PD subjects were tested in functional OFF state, 15 PD FOG+ (Motor UPDRS = 50.5±18.8), 54 PD FOG- (UPDRS = 35.2±10.4), and 24 healthy, age-matched control subjects. Subjects wore six Opal triaxial inertial sensors (APDM, Portland, OR) on their chest, lumbar area, wrists, and feet. A reactive postural response was elicited by having subjects lean backward into the hands, placed at shoulder level, of the test administer. The administer leaned the subject backward until the subject’s center of mass position was outside of their base of support (posterior to the heels). After three seconds the administer let go of the subject, who attempted to recover balance by stepping. Push and Release measures are given in Table 1

Results: The mean postural stability subscore of UPDRS was 1.60±1.35 in PD FOG+ and 0.87±0.95 in PD FOG-. The PD FOG+ and FOG- took more steps to recover, had a shorter step length, and lower step height, compared to the Control group. [table1]

Conclusions: Postural responses to the Push and Release test can be quantified in a clinical setting using body-worn, inertial sensors and is sensitive to PD.

References: Horak, F., Frank, J., Wrisley, D., The Balance Evaluation Systems Test (BESTest to differenciate balance deficits. Physical Therapy, 89(5):484-98, 2009, PMCID: PMC2676433.

Smith, BA, Carlson-Kuhta, P, Horak, FB, Consistency in administration and response for the backward push and release test: A clinical assessment of postural responses, Physiotherapy Research International, 2016 21(1):36-46. [Epub] 2014, PMCID: PMC4447599.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/quantifying-postural-stability-differences-in-people-with-parkinsons-disease-with-and-without-freezing-of-gait-using-body-worn-sensors/