Effects of high-frequency rTMS targeting the primary motor cortex on pain, function, and brain network connectivity in patients with chronic nonspecific low back pain: an exploratory fNIRS analysis of a randomized sham-controlled trial

This study evaluated the effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) on pain and functional outcomes in patients with chronic nonspecific low back pain (NSLBP) and explored intervention-related changes in resting-state brain functional connectivity (FC). From May 2023 to June 2024, 60 patients with chronic NSLBP were recruited from the Departments of Rehabilitation Medicine, Orthopedics, and Pain Medicine at the Affiliated Hospital of North Sichuan Medical College. Participants were randomly assigned to two groups. The experimental group received high-frequency rTMS combined with conventional rehabilitation, whereas the control group received sham stimulation combined with the same rehabilitation program. Both groups underwent treatment five times per week for 2 weeks. rTMS was delivered using a Magneuro60 transcranial magnetic stimulator. Stimulation targeted the abductor pollicis brevis motor hotspot within the primary motor cortex (M1) contralateral to the painful side. The resting motor threshold was determined using surface electromyography, and all procedures followed established TMS safety guidelines. Before and after the intervention, all participants were assessed using the visual analogue scale (VAS), Oswestry Disability Index (ODI), Roland–Morris Disability Questionnaire (RMDQ), and functional near-infrared spectroscopy (fNIRS). Complete fNIRS data meeting quality-control criteria were available for 40 participants and were included in the exploratory FC analysis. VAS, ODI, and RMDQ scores improved substantially after treatment in both groups. A statistically significant group-by-time interaction was observed for VAS (F = 4.862, P = 0.031). However, the mean improvement in the experimental group exceeded that in the control group by only 0.65 points, below the prespecified clinical importance threshold of 2.0 points. No statistically significant group-by-time interactions were found for ODI or RMDQ ( P = 0.172 and P = 0.198, respectively). The exploratory fNIRS analysis identified no between-group differences in FC that remained significant after correction for multiple comparisons. Adding high-frequency M1-rTMS to standardized rehabilitation did not provide clear additional clinical benefit after 2 weeks. The point estimates for between-group differences in improvement in VAS, ODI, and RMDQ scores were all below the corresponding minimal clinically important difference (MCID) thresholds used in this study. The exploratory fNIRS analysis likewise showed no robust between-group differences in FC after correction for multiple comparisons. Trial Registration : Chinese Clinical Trial Registry, ChiCTR2300073873.