Systematic review of 41 studies evaluating single-point lower-trunk magneto-inertial sensors for gait and TUG assessment in Parkinson's and parkinsonisms found moderate-quality evidence (12% high-quality), good reporting of technical aspects but poor clinical characterization and protocol…

The paper supports single-point mIMUs as a promising, low-cost digital biomarker for monitoring mobility, stratifying patients, and serving as trial endpoints in PD, but emphasizes that standardization and better clinical reporting are needed before wide adoption for therapeutic development.

INTRODUCTION: Gait and balance impairments are among the most disabling motor symptoms of Parkinson's disease (PD) and parkinsonisms. Traditional clinical assessments are practical but often lack sensitivity to detect subtle functional changes and to monitor disease progression. Wearable magneto-inertial measurement units (mIMUs) offer an objective, portable, and low-cost alternative. Single-point mIMUs, positioned over the lower trunk, are particularly promising for clinical integration due to their simplicity. This systematic review critically evaluates how single-point mIMUs are used to assess functional mobility in PD and atypical parkinsonisms, and examines the quality and clinical transferability of current evidence. METHODS: Following PRISMA 2020 guidelines, a systematic search was conducted in Medline, CINAHL, Embase, and Scopus (January 2025). Eligible studies included adults with PD or atypical parkinsonisms assessed with a single wearable sensor during straight-line walking and/or the Timed Up and Go test. Data extraction included clinical characteristics, assessment protocols, sensor specifications, and computed parameters. A customized critical appraisal tool evaluated five domains: methodology, clinical aspects, assessment protocol, technical aspects, and clinical transferability. Studies were classified as high-, medium-, or low-quality. RESULTS: From 3,812 records, 41 studies met inclusion criteria, involving 395 participants (mean age 66 ± 5.9 years). Fourteen studies used the instrumented TUG, and 27 evaluated straight-line walking. Most studies were observational (90%). Only 12% achieved a high-quality rating, while 80% were medium-quality. "Technical aspects" was the best-rated domain, whereas "clinical aspects" and "assessment protocol" scored lowest, mainly due to incomplete reporting of sensor placement, acquisition conditions, computational methods, and clinical characterization of participants. Frequently reported outcomes included gait speed, step length, cadence, and TUG duration; however, methodological heterogeneity hindered cross-study comparability. DISCUSSION: Single-point mIMUs can detect clinically relevant gait and mobility impairments and hold potential for monitoring disease progression, evaluating treatment effects, and distinguishing patient subgroups. Nevertheless, the overall quality of evidence is moderate, and insufficient methodological transparency currently limits clinical translation. Standardization of sensor placement, task instructions, data processing, and reporting-along with clearer clinical rationale and sample characterization-is needed to support reproducibility and facilitate adoption in routine practice. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251025333.