Research and development of a portable device to quantify muscle tone in patients with Parkinsons disease

Parkinson´s disease (PD) is a progressive, degenerative condition that is characterised by tremor, bradykinesia, cogwheel rigidity and postural instability. Currently, only subjective tests are employed and we aim to develop a portable device to quantify muscle tone in patients with movement disorders, in particular, Parkinson´s disease. A servo-motor robotic arm was developed to rhythmically flex and extend the subjects arm and their response was measured using continuous electromyography (EMG) sampled at 4kHz. Surface electrodes were attached over the biceps of the more severely affected arm and a reference electrode attached to the back of the contra-lateral hand. EMG data was normalized using the rest mean EMG level and then segmented into epochs according to the position data. EMG recorded from normal subjects remained flat throughout the trial with only very small fluctuations in amplitude about the mean. In contrast, biceps activity in parkinsonian patients tended to increase with flexion and as expected there were large variations in amplitude about the baseline activity. A fast fourier transform was also performed and spectra obtained from a typical Parkinsonian patient showed two peaks at approximately 6 Hz and 8 Hz, consistent with previously published data. In conclusion, the results clearly differentiate between normal and parkinsonian cases and to some extent severity. Quantification of disease severity might be possible given a broader range and greater number of patients.