Changes in Tissue Substance P Levels in Patients With Carpal Tunnel Syndrome

Abstract

Abstract BACKGROUND: Although carpal tunnel syndrome (CTS) is the most common entrapment neuropathy in adults, its etiology is not completely known. Chronic inflammation, fibrosis of the transverse carpal ligament (TCL), and altered sensory response contribute to the symptoms. OBJECTIVE: Because substance P (SP) is known to be involved in neuropathic pain, chronic inflammation, and fibrosis, the present study evaluated changes in SP levels in patients with CTS. METHODS: TCL, median nerve adventitia, and synovial connective tissue of the middle flexor digitorum superficialis tendon samples from patients (n = 42) with CTS and healthy control subjects (n = 13) who were operated on for hand wounds were obtained at surgery. A group of these patients with CTS (n = 9) had received meloxicam treatment for 10 days before surgery. A 2-step acetic acid extraction was used to determine changes in SP levels in free nerve endings (neuronal) and in nonneuronal cells. RESULTS: Changes in SP levels were observed in both neuronal and nonneuronal tissues. SP levels increased in extracts of the TCL and synovial connective tissue of the middle flexor digitorum superficialis tendon but not in the median nerve adventitia of patients with CTS. Meloxicam pretreatment increased SP levels in nonneuronal components of the TCL. CONCLUSION: These findings suggest that SP contributes to the pain and inflammation associated with CTS. Further studies are required to evaluate the therapeutic potentials of SP receptor (NK1R) antagonists in CTS.