Validity of spasticity related parameters obtained from manual clinical instrumented assessment in stroke patients

Spasticity is a common post-stroke impairment, yet current clinical scales fail to distinguish between neural and non-neural components. This study aims to evaluate the discriminative validity of the Instrumented Spasticity Assessment (ISA) tool in chronic stroke patients by comparing ISA-derived parameters between affected, nonaffected, and healthy control legs. This cross-sectional study included 18 chronic first-ever stroke patients and 28 age-matched controls. ISA measurements (EMG and torque) were collected during passive stretches at low (5s) and high (fast as possible) velocities. Changes in EMG and torque between velocities were analyzed to distinguish neural and non-neural spasticity components. The affected leg showed significantly higher rms-EMG HV-LV than healthy controls (p = 0.002, small effect), and higher rms-EMG HV-LV (%) than both the non-affected leg (p = 0.004, large effect) and healthy controls (p < 0.001, small effect). Torque HV-LV was significantly lower in the affected leg compared to the non-affected leg (p < 0.001, large effect) and healthy controls (p < 0.001, small effect). ISA-derived spasticity parameters showed discriminative validity between affected and non-affected legs in stroke patients and versus healthy controls. Significant differences highlight ISA’s potential to improve spasticity assessment and guide treatment in clinical practice.