Trunk accelerometry reveals postural instability in untreated Parkinson’s disease

Abstract

While several studies have shown that subjects with advanced Parkinson's disease (PD) exhibit abnormalities in sway parameters during quiet standing, abnormalities of postural sway associated with untreated PD have not been reported. Although not clinically apparent, we hypothesized that spontaneous sway in quiet stance is abnormal in people with untreated PD. We examined 13 subjects, recently diagnosed with PD, who were not yet taking any anti-parkinsonian medications and 12 healthy, age-matched control subjects. Postural sway was measured with a linear accelerometer on the posterior trunk (L5 level) and compared with traditional forceplate measures of sway. Subjects stood for two minutes under two conditions: eyes open (EO) and eyes closed (EC). One of the most discriminative measures of postural changes in subjects with untreated PD was the increased ‘JERK’ of lower trunk in the EO condition, measured with the accelerometer. Root mean square and the frequency dispersion of postural sway in the EO condition also discriminated sway in untreated PD subjects compared to controls subjects. We conclude that accelerometer-based sway metrics could be used as objective measures of postural instability in untreated PD. Accelerometer-based analysis of spontaneous sway may provide a powerful tool for early clinical trials and for monitoring the effects of treatment of balance disorders in subjects with PD.

The within-day and between-day reliability of using sacral accelerations to quantify balance performance

“…This location was chosen as it is close to the centre of mass of the human body (Mancini et al, 2011;Whitney et al, 2011;Kim et al, 2013). All participants wore self-selected training shoes throughout as this reflects function and clinical practice.…”

“…This can be overcome by registering the degree of tilt of the sensor and using this to remove the gravity component of the sensor output. This method has been successfully applied in previous research involving accelerometers (Moe-Nilssen 1998a;Morgado-Ramirez et al, 2013;Williams & Cuesta-Vargas 2014) and accelerometers have successfully been used to quantify balance in older persons who fall (Doheny et al, 2012), children with dyslexia (Moe-Nilssen et al, 2003) and those with Huntington's disease (Dalton et al, 2013), Parkinson's disease (Mancini et al, 2011) and Vestibular disorders (Marchetti et al, 2013).…”

Objective and quantitative assessment of motor function in Parkinson’s disease—from the perspective of practical applications

“…It is generally accepted that mild motor dysfunction has started before the appearance of motor symptoms of PD, therefore inertial sensors can provide an advantage over the naked eye due to its sensitivity. In another study, a single sensor was attached on the lower back of the participant (often L5, near the body center of mass), and participants were asked to maintain an upright standing position with arms crossed on the chest, in both an eyes open (EO) and an eyes closed (EC) state (9,10). A number of features related to postural stability were collected and taken into analysis.…”

Objective and subjective measures reflect different aspects of balance in multiple sclerosis

“…For the present study, we used the composite score from the Sensory Organization Test (SOT) as generated by commercially available posturography devices and we extracted the raw center of pressure signal from each trial of the SOT and calculated root mean square (RMS), range, total sway area, and mean velocity for the resultant sway path. Analyses of these center of pressure variables have been shown to most effectively characterize different aspects of postural sway [14][15]. For example, sway area reflects the effectiveness of, or the stability achieved by, the postural control system and mean velocity reflects the amount of regulatory activity associated with this level of stability [15][16].…”

“…Analyses of these center of pressure variables have been shown to most effectively characterize different aspects of postural sway [14][15]. For example, sway area reflects the effectiveness of, or the stability achieved by, the postural control system and mean velocity reflects the amount of regulatory activity associated with this level of stability [15][16].…”