Photobiomodulation for Median Nerve Neuroplasticity in Carpal Tunnel Syndrome: A Randomized Controlled Trial

Official title

Therapeutic Effects of Photobiomodulation (Low Level Laser Therapy) on Median Nerve Neuroplasticity in Patients With Carpal Tunnel Syndrome

Overview

Carpal Tunnel Syndrome (CTS) is the most common peripheral entrapment neuropathy, causing pain, paresthesia, and hand dysfunction due to median nerve compression at the wrist. While physiotherapy provides symptom relief, it does not effectively address the underlying neuroplastic deficits of the median nerve. Photobiomodulation (PBM), delivered at 830 nm near-infrared wavelength, has shown potential to enhance peripheral nerve regeneration via cytochrome c oxidase activation, ATP synthesis, and upregulation of neurotrophic factors including brain-derived neurotrophic factor (BDNF). This randomized controlled trial will evaluate whether 830 nm PBM (200 mW, 4 J/cm², 12 sessions over 4 weeks) combined with routine physiotherapy produces significantly greater neuroplastic recovery of the median nerve - assessed by high-resolution ultrasound (HRUS) measurement of median nerve cross-sectional area (CSA), nerve conduction study parameters and serum BDNF - compared to sham PBM combined with identical physiotherapy in adults with mild-to-moderate CTS. Neuroplasticity was operationalised as a multimodal construct comprising: (1) functional recovery, indexed by nerve conduction study parameters; (2) structural remodelling, indexed by median nerve cross-sectional area on high-resolution ultrasound; and (3) molecular neuroplastic signalling, indexed by serum BDNF. This multimodal approach was adopted because no single measure captures the full construct of peripheral nerve neuroplasticity (Padua et al., 2020).

Detailed description

Carpal tunnel syndrome is a compressive neuropathy of the median nerve associated with focal demyelination, impaired axonal transport, intraneural oedema, pain, sensory disturbance and functional limitation. Although conservative treatments can reduce symptoms, the physiological and structural processes accompanying median nerve recovery remain insufficiently characterized.

Photobiomodulation delivers non-thermal red or near-infrared light to biological tissue. Its proposed effects include modulation of mitochondrial activity, cellular energy production, oxidative signalling and inflammatory responses. Experimental evidence also suggests potential effects on Schwann-cell activity, axonal repair and neurotrophic signalling. However, clinical studies of photobiomodulation for carpal tunnel syndrome have generally been limited by small samples, heterogeneous treatment parameters and reliance on symptomatic outcomes without integrated assessment of nerve physiology, morphology and molecular responses.

This study will investigate whether adjunctive 830-nm photobiomodulation produces greater median nerve recovery than sham photobiomodulation when both groups receive the same routine physiotherapy. The primary hypothesis is that active photobiomodulation will produce greater improvement in median nerve sensory conduction velocity at the end of the four-week intervention. Follow-up assessment will examine whether any observed effect is maintained after treatment completion.

Electrophysiological testing will characterize changes in median nerve function, while high-resolution ultrasonography will assess structural changes in the nerve. Serum brain-derived neurotrophic factor will be evaluated as an exploratory circulating biomarker and will not be interpreted as a specific standalone measure of median nerve neuroplasticity. Patient-reported symptoms, functional status, pain and hand strength will be assessed to determine the clinical relevance of any physiological or structural changes.

By integrating electrophysiological, ultrasonographic, clinical and exploratory molecular measurements, the study aims to clarify whether the symptomatic effects of photobiomodulation are accompanied by objective evidence of median nerve recovery. The findings may help refine outcome selection and treatment parameters for future confirmatory trials.

Interventions

• Device Photobiomodulation (Low-Level Laser Therapy)
  Photobiomodulation (PBM) delivered using a 46-diode cluster probe at 830 nm wavelength, 200 mW optical output power, continuous wave mode, 4 J/cm² energy density, applied in static contact technique over the carpal tunnel (volar wrist surface, 3-5 cm proximal to distal wrist crease). Application time per session: approximately 200 seconds (\~3.3 minutes). Treatment schedule: 3 sessions per week for 4 consecutive weeks (12 sessions total). Sham device output confirmed \<1 mW by calibrated photodi
• Device Sham Photobiomodulation
  Deactivated PBM device identical in external appearance to the active device. Applied using the same 46-diode cluster probe, contact technique, and duration (approximately 200 seconds) as the active arm. Output power confirmed \<1 mW by calibrated photodiode power meter (LaserCheck or equivalent) at baseline, session 6, and session 12 for the first five enrolled participants. No therapeutic light emission occurs.
• Other Routine Physiotherapy Programme
  Participants will receive an 4-week routine physiotherapy programme comprising median nerve mobilization, night splinting, and tendon-gliding exercises. Median nerve mobilization will use six sequential positions progressing from wrist-neutral finger/thumb flexion to finger, wrist, and thumb extension, forearm supination, and assisted thumb stretching. Each position will be held for 5 seconds; the sequence will be repeated 10 times, three times daily. A neutral volar wrist splint allowing free f

Primary outcome measures

• Change From Baseline in Median Nerve Sensory Conduction Velocity at Week 4 and week 8 [Time frame: Baseline, Week 4 and week 8]

Secondary outcome measures (8)

• Change From Baseline in Median Nerve Distal Motor Latency [Time frame: Baseline, Week 4 and Week 8]
• Change From Baseline in Median Nerve Sensory Nerve Action Potential Amplitude [Time frame: Baseline, Week 4 and Week 8]
• Change From Baseline in Median Nerve Cross-Sectional Area [Time frame: Baseline, Week 4 and Week 8]
• Change From Baseline in Boston Carpal Tunnel Questionnaire Symptom Severity Scale Score [Time frame: Baseline, Week 4 and Week 8]
• Change From Baseline in Boston Carpal Tunnel Questionnaire Functional Status Scale Score [Time frame: Baseline, Week 4 and Week 8]
• Change From Baseline in Pain Intensity Measured Using the Visual Analogue Scale [Time frame: Baseline, Week 4 and Week 8]
• Change From Baseline in Handgrip Strength [Time frame: Baseline, Week 4 and Week 8]
• Number of Participants With Treatment-Emergent Adverse Events [Time frame: From the first intervention session through Week 8]

Eligibility criteria

Inclusion criteria

• Age 18-60 years
• Clinical diagnosis of unilateral mild-to-moderate carpal tunnel syndrome based on positive Phalen test and/or Tinel sign
• Electrophysiological confirmation of CTS via nerve conduction study (NCS) meeting AANEM 2012 diagnostic criteria for mild-to-moderate CTS
• No prior photobiomodulation or laser therapy to the affected wrist within the preceding 3 months
• Ability to attend 3 treatment sessions per week for 4 consecutive weeks
• Able and willing to provide written informed consent (in Urdu or English)

Exclusion criteria

• Bilateral carpal tunnel syndrome
• Previous surgical release of the carpal tunnel on the affected side
• Systemic peripheral neuropathy (e.g., diabetes mellitus, hypothyroidism, Charcot-Marie-Tooth disease)
• Pregnancy or breastfeeding
• Implanted cardiac pacemaker, defibrillator, or other active electronic implant
• Active malignancy at or near the treatment site
• Current use of photosensitising medications (e.g., tetracyclines, amiodarone, psoralens)
• Corticosteroid injection into the carpal tunnel within the preceding 3 months
• Rheumatoid arthritis or other inflammatory joint disease affecting the wrist
• Open wounds, acute skin infection, or tattooed skin at the treatment site
• Inability to attend 3 sessions per week for 4 weeks
• Severe CTS confirmed by NCS (complete sensory or motor axon loss)

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Double blind

Primary purpose

Treatment

Study locations

Pakistan · 1 center

• University of Lahore Hospital — Lahore

Identifiers

NCT: NCT07714720 · REC/019/25/6332

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗