Objective: To investigate whether inertial sensor–derived metrics can objectively quantify axial symptoms in Parkinson’s disease (PD), focusing on posture and postural instability.

Background: Axial symptoms such as postural abnormalities and impaired balance are among the most disabling motor symptoms in PD and are strongly associated with an increased risk of falls. Their evaluation in clinical practice is mainly based on observational rating scales, which provide only subjective estimates of motor impairment. Wearable inertial sensors allow quantitative characterization of body motion through kinematic signals, enabling a more objective assessment of postural control and axial motor dysfunction.

Method: Forty PD patients (Hoehn and Yahr 2.5–4) were recruited across two Movement Disorders centers. Participants performed 60 s quiet standing tasks (eyes open, EO, and eyes closed, EC) and 360-degree turns, recorded using inertial sensors (Movit system, Captiks S.r.l., Italy) placed on the lower back and ankles. Relevant kinematic metrics were extracted from the inertial signals in both the time and frequency domains. Correlations between sensor-derived metrics and clinical scales assessing posture (MDS-UPDRS item 3.13) and postural stability (MDS-UPDRS item 3.12) were evaluated using Spearman’s ρ and the associated p-value, while differences between EO and EC standing conditions were assessed using the Wilcoxon test.

Results: The entropy computed from the ankle-mounted sensor was significantly higher in the EC task compared to EO (p < 0.001) and positively correlated with the clinical posture scale (ρ = 0.71, p < 0.001). In the turning task, a positive correlation was found between the range of vertical angular velocities of the trunk and the postural stability scale (ρ = 0.61, p < 0.001), as well as between the trunk entropy and the posture scale (ρ = 0.61, p < 0.001).

Conclusion: Inertial sensor–derived metrics can capture clinically relevant features of axial motor impairment in PD, showing significant associations with posture and postural stability scales. These findings support the potential of wearable inertial sensors as objective tools for the quantitative assessment of axial symptoms in PD.

References: This study was supported by “Objective monitoring of axial symptoms in Parkinson’s disease: quantitative assessment in daily life based on the use of wearables, video sensing and artificial intelligence (OMNIA-PARK)” project, funded by European Union – Next Generation EU within the PRIN 2022 PNRR program (D.D.1409 del 14/09/2022 Ministero dell’Università e della Ricerca).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/sensor-based-assessment-of-axial-symptoms-in-parkinsons-disease/