Kinematic analysis of tremor - biomed 2010

Tremor, defined as a rhythmic and involuntary oscillation of a body part, is considered one of the most common disturbances of movement. The most frequent pathological forms, mainly affecting elderly people, are the essential tremor, the Parkinson's disease tremor and the physiological tremor. In order to examine the characteristics of a tremor, methods based on accelerometry and electromyography measures and more recently spirometry test, based on a digital acquisition of hand movements drawing an Archimedes' spiral, have been used. Though the quantification of tremors is the object of study for several researchers, today a standard method does not exist yet [1]. The most common techniques examine the frequency of tremors, however there is no consensus in literature on its value among the various pathological forms. As for handwriting, characteristics of tremors can be investigated from a kinematic point of view. For this aim, in this paper new quantitative kinematic parameters are proposed and their potential is evaluated on three groups of subjects (two with pathological tremors and a control group). Each subject underwent a set of four graphical tests (Horizontal Rows, Archimedes' Spiral, Triangle and Square) and the kinematic parameters calculated on the recordings were examined in order to establish which test and parameters are more sensitive to tremor differences and appropriate for pathologies identification. Significant differences were found for the number of strokes (being the stroke the base element of each hand movement), the number of ascending / descending tracts, the zero-crossing of velocity and acceleration profiles, the line curvature, the angular velocity and the dominant frequencies values extracted from FFT analysis of velocities, especially in relation with the Rows and Spiral tests. Depending on the test, some other significant differences were found in the velocity and acceleration mean values as well as in the number of components and pen-lift intervals. The results support the hypothesis that kinematic analysis can be useful in tremor studies and when used with suitable tests it can differentiate among pathological and normal subjects.