Neuropathic pain and sarcopenia based on skeletal muscle mass assessment following lumbar spinal stenosis surgery: a prospective observational study in Japan

Study Design: Prospective cohort study. Purpose: To investigate the relationship between neuropathic pain (NeP) and skeletal muscle mass following lumbar spinal stenosis (LSS) surgery. Overview of Literature: Sarcopenia generally worsens clinical outcomes in degenerative diseases. Although a high prevalence of sarcopenia is observed in patients with LSS, it is reported that sarcopenia does not significantly affect the clinical symptoms of lumbar degenerative diseases; thus, its role must be reconsidered in LSS alongside other factors such as spinal alignment and degree of stenosis. Methods: We prospectively evaluated improvements in leg pain and lower limb skeletal muscle mass in 421 patients who underwent surgical treatment for LSS. Bilateral limb muscle mass was compared in 260 patients with unilateral leg pain. The association between postoperative muscle mass increase and improvement in leg pain (Visual Analog Scale [VAS] score <3) was assessed using multivariate logistic regression analysis. Results: Preoperatively, the affected limb exhibited significantly reduced muscle mass compared to the unaffected limb. Postoperatively, the affected side gained muscle mass, which was significantly greater than the unaffected side. Leg pain VAS score <3 and the epidural sac area were significantly associated with increased muscle mass postoperatively. Patients with postoperative improvement in leg pain showed a significant increase in muscle mass compared to those without improvement. Conclusions: In unilateral LSS, the affected limb undergoes significant muscle mass loss, which improves postoperatively with rehabilitation. The increase in muscle mass correlates with improvements in leg pain, indicating a potential relationship between NeP and sarcopenia.