High-intensity and low-level laser therapy for cervical nerve root function: A narrative review of current evidence and knowledge gaps

Cervical radiculopathy is a neurological disorder associated with neck pain, radiating upper-extremity symptoms, and impaired nerve root function. High-intensity laser therapy (HILT) and low-level laser therapy (LLLT) have emerged as promising conservative interventions; however, their comparative effects on cervical nerve root function remain unclear. This narrative review examined current evidence regarding the biological mechanisms, clinical outcomes, and electrophysiological effects of HILT and LLLT in cervical radiculopathy. PubMed/MEDLINE and Scopus were searched, with Google Scholar used to identify additional studies. Randomized controlled trials, systematic reviews, and meta-analyses were considered, and evidence was synthesized to identify clinical findings and research gaps. Current evidence suggests that HILT and LLLT may improve pain, disability, and cervical range of motion in cervical radiculopathy and related cervical disorders. Experimental studies provide indirect mechanistic evidence that photobiomodulation may modulate inflammation, enhance mitochondrial function, promote tissue repair, and support biological processes associated with neural recovery. However, heterogeneity in laser treatment parameters and limited use of objective neurophysiological assessments preclude definitive conclusions regarding whether clinical improvements are accompanied by measurable cervical nerve-root recovery. Both HILT and LLLT appear safe and potentially effective as adjunctive interventions, but current evidence is insufficient to establish the superiority of either modality. Future randomized controlled trials incorporating standardized laser dosimetry and objective neurophysiological outcomes are needed to determine whether clinical improvements are accompanied by measurable cervical nerve-root recovery.