Implementation and validation of a stride length estimation algorithm, using a single basic inertial sensor on healthy subjects and patients suffering from Parkinson’s disease

As low cost and highly portable sensors, inertial measurements units (IMU) have become increasingly used in gait analysis, embodying an efficient alternative to motion capture systems. Meanwhile, being able to compute reliably accurate spatial gait parameters using few sensors remains a relatively complex problematic. Providing a clinical oriented solution, our study presents a gyrometer and accelerometer based algorithm for stride length estimation. Compared to most of the numerous existing works where only an averaged stride length is computed from several IMU, or where the use of the magnetometer is incompatible with everyday use, our challenge here has been to extract each individual stride length in an easy-to-use algorithm requiring only one inertial sensor attached to the subject shank. Our results were validated on healthy subjects and patients suffering from Parkinson’s disease (PD). Estimated stride lengths were compared to GAITRite© walkway system data: the mean error over all the strides was less than 6% for healthy group and 10.3% for PD group. This method provides a reliable portable solution for monitoring the instantaneous stride length and opens the way to promising applications

Effects of Sensitive Electrical Stimulation-Based Somatosensory Cueing in Parkinson's Disease Gait and Freezing of Gait Assessment

International audienceThis study aims to investigate the effect of a somatosensory cueing on gait disorders in subjects with Parkinson's disease (PD). After having performed stepping in place and timed up and go assessing tasks, 13 participants with PD were equipped with an electrical stimulator and an inertial measurement unit (IMU) located under the lateral malleolus on the sagittal plane. Electrodes were positioned under the arch of the foot and electrical stimulation (ES) parameters (five 500 ms/phase charge-balanced biphasic pulses delivered at 200 Hz, repeated four times at 10 Hz) adjusted to deliver a sensitive signal. Online IMU signal was processed in order to trigger ES at heel off detection. Starting from a quiet standing posture, subjects were asked to walk at their preferred speed on a path including 5 m straight line, u-turn, and walk around tasks. Three situations were considered: no stimulation baseline precondition (C0), ES condition (C1), and no stimulation baseline post-condition (C0bis), for eliminating a learning effect possibility. In ES condition (C1) the time to execute the different tasks was globally decreased in all the subjects (n 5 13). Participants' results were then grouped regarding whether they experienced freezing of gait (FOG) or not during C0 no stimulation baseline precondition. In " freezer " subjects (n 5 9), the time to complete the entire path was reduced by 19%. FOG episodes occurrence was decreased by 12% compared to baseline conditions. This preliminary work showed a positive global effect on gait and FOG in PD by a somatosensory cueing based on sensitive electrical stimulation

Correlations between soluble alpha/beta forms of amyloid precursor protein and Abeta38, 40 and 42 in human cerebrospinal fluid

International audienceCerebrospinal fluid (CSF) biomarkers are now widely used for diagnosis of Alzheimer disease (AD) in atypical clinical forms, for differential and early diagnosis, or for stratification of patients in clinical trials. Among these biomarkers, different forms of amyloid peptides (Aβ) produced by the cleavage of a transmembrane precursor protein called APP (amyloid precursor protein) have a major role. Aβ peptides exist in different length the most common ones having 40 (Aβ40), 42 (Aβ42), or 38 (Aβ38) amino acids in length. APP processing by gamma-secretase releases also an amino-terminal secreted fragment called sAβPP-beta while an alternative nonamyloidogenic cleavage of APP, through an alpha-secretase, liberates another fragment called sAβPP-alpha. To decipher the molecular and pathological mechanisms leading to the production and the detection of these entities is essential for the comprehension and the prevention of AD. In this report, we present the results of the Keywords: Biomarkers CSF Soluble amyloid precursor proteins Aβ fragment peptides Alzheimer disease Dementi

BeatWalk: Personalized Music-Based Gait Rehabilitation in Parkinson’s Disease

Taking regular walks when living with Parkinson’s disease (PD) has beneficial effects on movement and quality of life. Yet, patients usually show reduced physical activity compared to healthy older adults. Using auditory stimulation such as music can facilitate walking but patients vary significantly in their response. An individualized approach adapting musical tempo to patients’ gait cadence, and capitalizing on these individual differences, is likely to provide a rewarding experience, increasing motivation for walk-in PD. We aim to evaluate the observance, safety, tolerance, usability, and enjoyment of a new smartphone application. It was coupled with wearable sensors (BeatWalk) and delivered individualized musical stimulation for gait auto-rehabilitation at home. Forty-five patients with PD underwent a 1-month, outdoor, uncontrolled gait rehabilitation program, using the BeatWalk application (30 min/day, 5 days/week). The music tempo was being aligned in real-time to patients’ gait cadence in a way that could foster an increase up to +10% of their spontaneous cadence. Open-label evaluation was based on BeatWalk use measures, questionnaires, and a six-minute walk test. Patients used the application 78.8% (±28.2) of the prescribed duration and enjoyed it throughout the program. The application was considered “easy to use” by 75% of the patients. Pain, fatigue, and falls did not increase. Fear of falling decreased and quality of life improved. After the program, patients improved their gait parameters in the six-minute walk test without musical stimulation. BeatWalk is an easy to use, safe, and enjoyable musical application for individualized gait rehabilitation in PD. It increases “walk for exercise” duration thanks to high observance.This research was supported by a European grant: BeatHealth: Health and Wellness on the Beat for VC, DD, CL, AGi, VD, RV, EH, ED, ML, BB, and SB (EU FP7-ICT contract #610633)

Tremor attenuation using FES-based joint stiffness control

International audienceIn this paper, a strategy to attenuate tremor based on co-contraction of antagonist muscles using Functional Electrical Stimulation (FES) is fully presented. Both methods to track tremor features in real-time, while filtering voluntary motion, and to identify a suitable joint model are described. Using this information, the stimulation controller modulates joint stiffness based on tremor intensity, while preventing the generation of undesirable joint torque. An experimental evaluation of the system, which confirmed the effectiveness of the approach, is also presented

Filtering Voluntary Motion for Pathological Tremor Compensation

International audienceThis paper describes an algorithm to estimate tremor and voluntary motion from measured motion data. Estimation is performed by means of an extended Kalman filter (EKF), which also estimates tremor parameters. Comparison of the proposed method with techniques described in the literature are conducted with two experimental data sets from tremor patients performing the same task, drawing a spiral. The presented algorithm may be directly applied in real-time pathological tremor compensation systems

Pathological Tremor and Voluntary Motion Modeling and Online Estimation for Active Compensation

International audienceThis paper presents an algorithm to perform online tremor characterization from motion sensors measurements, while filtering the voluntary motion performed by the patient. In order to estimate simultaneously both nonstationary signals in a stochastic filtering framework, pathological tremor was repre- sented by a time-varying harmonic model and voluntary motion was modeled as an auto-regressive moving-average (ARMA) model. Since it is a nonlinear problem, an extended Kalman filter (EKF) was used. The developed solution was evaluated with sim- ulated signals and experimental data from patients with different pathologies. Also, the results were comprehensively compared with alternative techniques proposed in the literature, evidencing the better performance of the proposed method. The algorithm presented in this paper may be an important tool in the design of active tremor compensation systems

Pathological tremor and voluntary motion modeling and online estimation for active compensation

This paper presents an algorithm to perform online tremor characterization from motion sensors measurements, while filtering the voluntary motion performed by the patient. In order to estimate simultaneously both nonstationary signals in a stochastic filtering framework, pathological tremor was represented by a time-varying harmonic model and voluntary motion was modeled as an auto-regressive moving-average (ARMA) model. Since it is a nonlinear problem, an extended Kalman filter (EKF) was used. The developed solution was evaluated with simulated signals and experimental data from patients with different pathologies. Also, the results were comprehensively compared with alternative techniques proposed in the literature, evidencing the better performance of the proposed method. The algorithm presented in this paper may be an important tool in the design of active tremor compensation systems

IMU Based Detection of Freezing of Gait and Festination in Parkinson's Disease

International audienceFreezing of gait (FOG) and festination are common symptoms in Parkinson Disease. They affect gait pattern and are associated to fall risks. We aim at early detection of FOG and festination episodes in order to trigger FES assistance. In this paper we present preliminary experimental results of FOG and festination detection including frequency analysis and gait parameters changes. The proposed solution is based on one wireless inertial sensor placed on the patient shank

Tremor attenuation based on joint impedance modulation using FES

International audienceIn this work we describe experiments to validate an alternative method to attenuate the effects of pathological tremor using FES. The method is based on co-contracting antagonist muscles in order to increase joint impedance and hence improve the joint stability for trembling movements. Both open-loop and closed-loop trials involving tremor patients and healthy subjects were conducted, and the results indicate that an effective functional benefit may be obtained