Validation of Paw Skin Hyperspectral Imaging for Assessing Neuropathic Pain Severity in a Chronic Constriction Injury Model.

Neuropathic pain is a debilitating condition lacking objective and quantitative assessment tools, as current evaluations rely largely on subjective reports. Hyperspectral imaging (HSI) is a non-invasive technology that quantifies spatial and spectral tissue characteristics and has been applied in rheumatologic and metabolic disorders. This study investigated whether HSI-detected paw skin alterations correlate with graded nerve injury severity in a chronic constriction injury (CCI) model. Sprague-Dawley rats were assigned to sham or CCI groups with one to four sciatic nerve ligatures. Behavioral assessments (CatWalk XT gait analysis, thermal hyperalgesia, and mechanical allodynia) and paw HSI measurements were performed longitudinally. Histological and molecular analyses were conducted from paw skin to dorsal spinal cord tissues. At 1100 nm, HSI demonstrated progressive and significant spectral deviations proportional to injury severity across all CCI groups, whereas 1300 nm changes were only detected in severe injuries. Histology revealed increased fibrosis, NGF, TNF-α, synaptophysin, and microglial activation with greater injury severity, alongside reduced PGP9.5, neurofilament, AChR, Desmin, GAP-43, Pax3, and BDNF expression. These molecular findings were supported by electrophysiological and behavioral impairments, which correlated with injury grade by HSI. In conclusion, HSI at 1100 nm provides a sensitive and objective indicator of neuropathic pain severity and holds promise as a quantitative translational tool.