Spectral Analysis of Handwriting Kinetic Tremor in Elderly Parkinsonian Patients

Abstract

Tremor is one of the motor impairments of Parkinson’s disease (PD) and manifests as different types, i.e. rest, kinetic and postural. To date, kinetic tremor in PD is barely examined and there is no agreed methodology to test and analyse it. In this exploratory and preliminary study, we aimed at characterizing handwriting-related kinetic tremor in PD during Archimedes’ Spiral and overlapped Circles drawing execution using a digitizing tablet. To achieve this, we integrated classical kinematic analysis with spectral analysis to establish the set of parameters better suited to discriminate PD patients from healthy controls. 15 PD patients and 11 elderly healthy control subjects were enrolled in the trial.

The results reveal that there are significant differences between PD patients and control subjects, especially at the level of spectral features. PD tremor produces higher Spectral Power and a clear peak in the band of involuntary movements, while Spectral Power of enhanced physiological tremor in controls is lower and randomly distributed over the frequencies. We conclude that spectral analysis and features extracted from the band of involuntary movements can be used to characterize parkinsonian handwriting kinetic tremor. The findings support the theory that the kinetic tremor in PD patients can be distinguished from the involuntary movement of the elderly caused by physiological age-related deterioration of the neuromuscular system’s functional capacity.