Hoffmann reflex parameters as neurophysiological biomarkers for quantifying spasticity: A systematic review

Background: Spasticity is a common motor disorder observed after neurological injuries such as stroke, spinal cord injury (SCI), and cerebral palsy (CP), significantly impairing function and quality of life. Quantitative assessment of spasticity is crucial for targeted rehabilitation. The Hoffmann reflex (H-reflex) offers a neurophysiological measure of spinal motoneuron excitability and inhibitory control using various parameters. This review aims to synthesize evidence on the use of H-reflex parameters to quantify spasticity in these three neurological conditions. Method: A systematic literature search was conducted in PubMed and Google Scholar for studies published between 2016 and May 2025. Inclusion criteria targeted empirical studies assessing H-reflex in adults with stroke, SCI, or CP as an outcome measure of spasticity. Screening followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, with risk of bias assessed using the Cochrane tool. Data on study characteristics, H-reflex parameters, and correlations with clinical scales were extracted and analyzed. Results: Eleven studies met eligibility criteria and most of it demonstrated low risk of bias. Nearly, 298 patients involving conditions such as stroke, SCI, and CP were considered. H-reflex amplitude and Hmax/Mmax ratio were the most consistently measured parameters measured in at least eight of the studies. Latency was less frequently reported but indicated altered neural excitability and responsiveness post-intervention. Conclusion: H-reflex amplitude and Hmax/Mmax ratio serve as reliable neurophysiological biomarkers for spasticity quantification in stroke, SCI, and CP. The H amplitude and Hmax/Mmax ratio increases with spasticity and latency decreases. H-reflex serves as a valuable tool in both research and clinical practice for the assessment, monitoring, and neurophysiological understanding of spasticity.