Assessment and Management of Muscle Overactivity in People with Stroke : Long Term Functional and Biomechanical implications

Muscle overactivity, of which spasticity is one of the most disabling components, is a frequent consequence after a stroke. It interferes with voluntary movements and often causes significant walking impairment. Beyond functional limitations, spasticity has a substantial impact on quality of life, independence, and social participation. In this thesis, we pursued two main objectives: to improve the assessment of muscle overactivity and to investigate the effects of botulinum toxin treatment on gait function in people with stroke. Clinical assessment relies mainly on scales such as the Ashworth or Tardieu scales, which do not allow a precise distinction between the neural (nervous system–related) and non-neural (soft tissue–related) components of muscle overactivity. To address this, we validated an innovative instrumental method for quantifying muscle stiffness, providing objective and reproducible measurements. This method demonstrated good reliability in post-stroke spastic individuals and paves the way for a more precise description of the neural and non-neural components of muscle overactivity. This distinction is important for optimizing therapeutic choices, as approaches such as botulinum toxin primarily target the neural components and should be combined with techniques that also address non-neural components (such as rehabilitation or surgery) when patients present with a mixed profile. Thus, our work strengthens the link between detailed assessment, personalized treatment, and functional improvement. In parallel, we conducted a clinical study evaluating the effects of three cycles of progressively increasing doses of botulinum toxin in individuals with multifocal post-stroke spasticity. Botulinum toxin is standard of care for focal spasticity reduction, but its effects on gait remain conflictive, particularly after a single injection cycle. Our results show that repeated injections with sufficiently high doses, can lead to significant improvements in walking capacity (evaluated in a controlled setting). These findings support the importance of administering sufficiently high doses and allowing at least three cycles before expecting measurable effects on walking capacity. In conclusion, this thesis highlights the importance of combining objective assessment with tailored therapeutic strategies to optimize gait improvement after stroke. These results can inform clinical practice and inspire further research aimed at optimizing spasticity management, with the ultimate goal of enhancing walking performance (what individuals actually do in their own environment) and thereby improving autonomy and participation for people living with the aftermath of stroke.