A new measure of movement symmetry in early Parkinson's disease patients using symbolic processing of inertial sensor data

Abstract

Abstract-Movement asymmetry is one of the motor symptoms associated with Parkinson's disease (PD). Therefore, being able to detect and measure movement symmetry is important for monitoring the patient's condition. The present paper introduces a novel symbol based symmetry index calculated from inertial sensor data. The method is explained, evaluated, and compared to six other symmetry measures. These measures were used to determine the symmetry of both upper and lower limbs during walking of 11 early-to-mid-stage PD patients and 15 control subjects. The patients included in the study showed minimal motor abnormalities according to the unified Parkinson's disease rating scale (UPDRS). The symmetry indices were used to classify subjects into two different groups corresponding to PD or control. The proposed method presented high sensitivity and specificity with an area under the receiver operating characteristic (ROC) curve of 0.872, 9% greater than the second best method. The proposed method also showed an excellent intraclass correlation coefficient (ICC) of 0.949, 55% greater than the second best method. Results suggest that the proposed symmetry index is appropriate for this particular group of patients.

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

“…Therefore some studies have been focused on atypical motions, like drawing ability (17) and movement symmetry (18,19), which may become a supplementary basis for the early diagnosis of PD. A recent study suggested that a digital pen implanted with the Manus Platform (a novel sensor system) could discriminate early PD patients from control subjects who did not have PD but did have other impairments or PD-like symptoms (such as essential tremor) (17).…”

“…Also, early PD patients may exhibit very subtle asymmetrical gait and hand movements (19), which are hard to be observed and evaluated by naked eyes. Therefore, a novel symbol based symmetry index referred to as "SI symb ", which was derived from inertial sensor data, was developed to differentiate between early-to-mid-stage PD patients and healthy controls (18). This novel continuous symbolic symmetry index, SI symb , presented high sensitivity and specificity.…”

Assessment of Gait Symmetry and Gait Normality Using Inertial Sensors: In-Lab and In-Situ Evaluation

“…As a result, only the shape of the signal and not its relative temporal characteristics are taken into account. A symbolic method for estimating gait symmetry using accelerometers [24] or gyroscopes [25] has been suggested, which takes into account not only the shape but also the temporal characteristics of the signal. This symmetry measure is used in the present paper.…”

“…The symmetry measure used in this paper was presented in [25]. The sensor signal, accelerometer or gyroscope, was standardized to zero mean and unitary standard deviation, then segmented into N symbols.…”

“…The period between consecutive occurrences of the same symbol are calculated and stored in a period histogram [25]. Similarly, the period between symbol transitions of the same type may be stored in a transition histogram.…”