Ultrasound Shear Wave Elastography for Assessing Muscle Stiffness in Parkinson's Disease Patients

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor symptoms like tremors, bradykinesia, muscle rigidity, and postural instability, as well as various non-motor symptoms . While the exact cause of Parkinson's disease is not fully understood, it is thought to result from a combination of genetic and environmental factors, leading to the degeneration of dopamine-producing neurons in the brain . PD is the second most common neurodegenerative disorder after Alzheimer's disease, primarily affecting those over 60, with a higher prevalence in men . The disease significantly impacts quality of life due to progressive motor and non-motor disabilities, and while treatments can alleviate symptoms, there is currently no cure . Disease progression and prognosis vary, with advanced stages often leading to severe disability and reduced life expectancy .

Muscle rigidity, one of the major motor symptoms, refers to the increased resistance when muscles are passively stretched . Accurate assessment of muscle stiffness is essential for monitoring disease progression and evaluating therapeutic interventions .

Traditionally, clinical assessment tools like the Unified Parkinson's Disease Rating Scale (UPDRS), part III, are used to evaluate rigidity severity in PD patients . These assessments, involving manual joint movement and muscle palpation by professionals, are subjective and prone to error . Thus, there is a growing need for noninvasive, quantitative tools to assess muscle stiffness in PD patients .

Tools like electromyography (EMG) and myotonometry offer quantitative measurements . Ultrasound shear wave elastography (SWE) is another non-invasive technique that measures tissue stiffness by analyzing shear wave propagation. While SWE shows promise for various conditions, its application in PD-related muscle rigidity remains relatively unexplored .