Background: Parkinson’s disease is characterized by three main symptoms: tremor, slow movement, and rigidity (stiff muscles). Over 89% of people with Parkinson’s disease experience rigidity rendering them stiff and making movement strenuous. It is one of the most responsive symptoms to treatment and can be used to deduce therapeutic efficacy. Under clinical evaluation, rigidity is defined as resistance to passive movement. Measurement of rigidity commonly relies on ordinal rating scales, which suffers issues with scaling (integer rating) and inter-rater reliability. Here, we present a novel palm-worn instrument to objectively quantify rigidity on a continuous scale. The device employs a miniature motor to flex the third digit of the hand whilst transducers record flexion and extension forces.
Objectives: We aim to determine congruence with the standard clinical rating scales, investigate sensitivity to the impact of deep brain stimulation (DBS) and contralateral movement, and make comparisons with healthy individuals.
Methods: Eight participants with Parkinson’s disease underwent evaluation during conditions: on and off DBS, and with and without contralateral limb movement to activate rigidity. During each DBS condition, wash-in/out effects were tracked using both our instrument and two blinded clinical raters. Sixteen healthy volunteers served as controls. A stepwise linear regression model predicted clinical ratings using objective data from our device.
Results: Rigidity measured using our instrument had moderate agreement (R = 0.68) with clinical ratings and showed differences between therapeutic state (p < 0.001), activation conditions (p = 0.011), and disease/healthy cohorts (p < 0.001). Rigidity gradually worsened over a one-hour period after DBS cessation, but improved much more rapidly with DBS resumption.
Conclusions: Given its ability to track changes in rigidity due to therapeutic intervention, our technique could have applications where continuous measurement is required or where a suitably qualified rater is absent.
Speaker Biography: Dr Thushara Perera has a Bachelor in Electronic Engineering (Hons) and a Masters in Biomedical Engineering from La Trobe University (Melbourne, Australia), where he won the Tad Szental Prize for best graduating engineer and the Hooper Memorial Prize for best final-year project. Dr Perera completed his PhD in neuroscience and joined the Bionics Institute as a Postdoctoral Research Fellow in 2012. Here, he worked as part of the Bionic Vision team to successfully trial Australia’s first bionic eye. At present, his research focusses on cutting-edge therapies for neurological disorders such as Parkinson’s disease. Dr Perera’s role in innovation was recognised in 2016 with a prestigious veski Victoria Fellowship.