A Method for Automatic and Objective Scoring of Bradykinesia Using Orientation Sensors and Classification Algorithms

Abstract

Correct assessment of bradykinesia is a key element in the diagnosis and monitoring of Parkinson's disease. Its evaluation is based on a careful assessment of symptoms and it is quantified using rating scales, where the Movement Disorders Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) is the gold standard. Regardless of their importance, the bradykinesia-related items show low agreement between different evaluators. In this study, we design an applicable tool that provides an objective quantification of bradykinesia and that evaluates all characteristics described in the MDS-UPDRS. Twenty-five patients with Parkinson's disease performed three of the five bradykinesia-related items of the MDS-UPDRS. Their movements were assessed by four evaluators and were recorded with a nine degrees-of-freedom sensor. Sensor fusion was employed to obtain a 3-D representation of movements. Based on the resulting signals, a set of features related to the characteristics described in the MDS-UPDRS was defined. Feature selection methods were employed to determine the most important features to quantify bradykinesia. The features selected were used to train support vector machine classifiers to obtain an automatic score of the movements of each patient. The best results were obtained when seven features were included in the classifiers. The classification errors for finger tapping, diadochokinesis and toe tapping were 15-16.5%, 9.3-9.8%, and 18.2-20.2% smaller than the average interrater scoring error, respectively. The introduction of objective scoring in the assessment of bradykinesia might eliminate inconsistencies within evaluators and interrater assessment disagreements and might improve the monitoring of movement disorders.

Quantification of Finger-Tapping Angle Based on Wearable Sensors

“…In addition to analyzing the diversities of tapping patterns performed by the patients with motor impairments, our goal was to offer a minimal set of sensors and maximal information for clinicians. Several authors performed tapping assessment with only one sensor placed on the index finger and calculated the angle of the finger relative to the vertical axis [8,17,37,38] or, having the hand placed on a table, defined the zero-angle when the finger is down [39]. Although the majority of movement in finger tapping is performed by the index finger, we have found that it was important to also have a sensor on the thumb.…”

“…The tapping test has been widely used for assessment of ataxia [2], stroke recovery [3], Alzheimer’s disease [4], and of bradykinesia in Parkinson’s disease (PD) [5,6,7,8,9]. It is included in the Unified Parkinson’s disease rating scale (MDS-UPDRS test, [10]).…”

“…Systems with gyroscopes have been used for evaluating bradykinesia [5,8,15,16,28] by assessing the speed (or the angular velocity obtained from gyroscopes), rhythm (variation of the angular velocity), and amplitudes of movements (calculated angle excursions). Researchers have been placing inertial sensors on different finger and hand parts to assess bradykinesia and estimate the movement amplitudes.…”

“…Researchers have been placing inertial sensors on different finger and hand parts to assess bradykinesia and estimate the movement amplitudes. The tapping amplitudes can be quantified through angle excursions [8,15,16,27]. Using inertial sensors, the majority of finger-tapping parameters, such as tapping duration, and opening and closing velocities are relatively simple to be calculated.…”

“…Using inertial sensors, the majority of finger-tapping parameters, such as tapping duration, and opening and closing velocities are relatively simple to be calculated. The tapping amplitude, a spatial parameter describing the tapping performance, can be defined and estimated in different ways, e.g., as the absolute angle from the index finger to an axis [8], or the relative angle excursions the thumb and the index finger [15,16]. However, patients with motor impairments perform the finger-tapping task in very different manners, so that the relative 3D movements of fingers can be challenging to define, measure, and express as a single parameter.…”