A perspective on the use of the CatWalk device to assess dynamic spasticity in rodent models.

Introduction: Spasticity is a hallmark of upper motor neuron syndrome and arises from complex neurophysiological and biomechanical alterations, including disinhibition of the stretch reflex and secondary changes in muscle properties. While rodent models are widely used to study spasticity, objective assessment of dynamic spasticity during locomotion remains challenging. The CatWalk (CW) system is a well-established tool for automated gait analysis; however, its specific utility in quantifying spasticity-related gait abnormalities has not been systematically evaluated. Methods: A focused literature review was conducted to identify studies employing the CatWalk system in rodent models with features of spasticity. These parameters were then evaluated conceptually as candidate surrogate markers of dynamic spasticity and current evidence supporting their use. Results: Only a limited number of studies have explicitly used the CW system to assess spasticity-related gait alterations. A wide range of parameters was reported, including print-related, spatiotemporal and coordination-related parameters. While many parameters are sensitive to functional impairment, some might lack specificity for spasticity. In contrast, dynamic gait parameters such as stand phase duration, relative paw placement emerge as candidate surrogate markers but currently lack validation against established measures of spasticity. Discussion: The CW system offers substantial potential for assessing dynamic aspects of spastic gait in rodent models; however, careful selection and interpretation of parameters are critical. We propose potential candidates for future validation rather than established markers of spasticity. Future studies should focus on standardizing outcome measures and validating parameter sets that accurately reflect the underlying pathophysiology of spasticity, thereby improving translational relevance.