A Comparison of the Accuracy of Objective Physiological Measuring Techniques for Rigidity in Parkinson’s Disease – A Systemic Review

Abstract

Background and Aim: Parkinson’s disease (PD), a common neurodegenerative disorder, often presents with debilitating rigidity. Despite its significance, rigidity assessment is qualitative, subjective and reliant on the examiner’s interpretation. This study aimed at comparing the reliability and applicability of objective methods for rigidity assessment in PD patients.

Methods: A systematic search in 4 bibliographic databases. Primary outcome was an objective assessment method of rigidity in PD, where reliability and correlation with UPDRS rigidity were reported. The secondary outcome was applicability of the method in a clinical setting.

Results: The study revealed the following rigidity assessment methods: isokinetic techniques, surface electromyography (sEMG), acoustic myography (AMG), myotonometry, and setup of devices based on force, inertia and mechanomyography sensors (FIM). Among 21 relevant studies, isokinetic techniques, while highly reliable, presented challenges in daily settings. Combining isokinetic assessment with sEMG gave insights into the neurophysiological origins of rigidity. Myotonometry exhibited ease of use and reliability but lacked a sufficiently high correlation with UPDRS rigidity scores. AMG emerged as highly reliable, with strong correlations to UPDRS assessments, and easy interpretation of data. sEMG recordings, while providing insights into muscle activity, posed challenges in signal interpretation. FIM showed promising outcomes with high reliability, applicability and correlation to UPDRS rigidity score.

Conclusion: AMG and FIM appear promising for rigidity assessment in PD. Both methods are easily applicable in the clinic, but only limited number of studies using these methods have been carried out so far.