Miniaturized instrumented measurement of resistance to passive motion: the Smart Assessment of Spasticity (SAS) project

Spasticity is a major neurological condition that negatively affects movement generation and quality of life of people who experience it. The current work, being part of the Innovative Doctorates by the MUR (PON Project 2014-2020) is the product of a three-year doctoral program that sought to characterize various patterns of spasticity. The present dissertation would frame the topic of spasticity in three main chapters. Chapter 1 presents a general pathophysiology overview, assessment, and management of spasticity in neurological disorders. Chapter 2 describes two experimental pilot studies aimed to characterize spasticity in multiple sclerosis (MS), to identify its neural and biomechanical manifestations and responses to potential rehabilitation treatments. The first study depicts the effects of an isokinetic eccentric training targeting the hypertonic elbow flexors and shows that lengthening contractions increased the active and passive range of motion, also reducing the patient-rated burden of spasticity. The second study focused on the implementation of an isokinetic concentric training of spastic ankle plantarflexors. The protocol proposed significantly reduced resistance to passive motion in the absence of changes in electromyographic activity from hypertonic muscles, suggesting that this training may positively impact muscle architecture with no modulation of hypertonia. Chapter 3 introduces the final project, "SAS, Smart Assessment of Spasticity," which aimed to create a new quantitative tool for measuring spasticity-related resistance to passive motion in a cohort of individuals with MS. The main finding of this pilot study was that measurements of resistance to passive motion obtained by this newly introduced device are highly reliable and accurate and can also capture even subtle changes induced by acute interventions, thus proving a sensitive measuring system that can complement the subjective, clinical assessment of the manifestations of spasticity.