Immediateeffectsofhigh-intensitylasertherapyfornonspecificneckpain:adouble-blindrandomizedcontrolledtrial

Nonspecific neck pain (NNP) is a common condition affecting 21 to 50% of adults, with more than half of patients experiencing relapse within a year. It causes soft tissue pain, stiffness, sensory-motor dysfunction, and significant psychosocial burden including anxiety and depression. Current treatments include medication, exercise, and physical agents, but each has limitations: medications carry risks of gastrointestinal bleeding and cardiovascular problems with long-term use, while patient adherence to repetitive exercise therapy is often poor. High-intensity laser therapy (HILT) has emerged as a non-invasive treatment that may offer immediate pain relief through photochemical effects (promoting cellular energy production and reducing inflammation) and photothermal effects (improving blood circulation and reducing pain signaling).

However, few studies have examined whether a single session of HILT can produce immediate benefits for NNP patients, making this an important gap in clinical knowledge.

The researchers conducted a double-blind, placebo-controlled randomized trial at a single rehabilitation center in China. They recruited 28 adults with acute nonspecific neck pain (less than 30 days duration) who had not received treatment in the previous month. Participants were randomly assigned to either the HILT group (14 participants) or the placebo group (14 participants) using computer-generated randomization with sealed envelopes. Both groups received identical cranio-cervical exercises lasting approximately 30 minutes after their laser treatment.

The HILT group received active high-intensity laser therapy using a Class IV laser device with wavelengths of 980/810 nm, applied to trigger points and cervical regions with specific scanning protocols. The placebo group underwent identical procedures with the laser output turned off. Neither the patients nor the outcome assessors knew which treatment was being delivered, though treating therapists were aware of group assignment but blinded to specific laser parameters. Outcomes were measured immediately before treatment and 2 hours after treatment, chosen based on the peak action window of HILT photobiomodulation.

The primary outcome was pain intensity measured on a 0-100 mm visual analogue scale (VAS). Secondary outcomes included cervical active range of motion (flexion, extension, lateral flexion, and rotation), neck tissue stiffness measured with shear wave elastography (for splenius capitis, semispinalis capitis, and neck fascia), and functional disability assessed with the neck disability index (NDI).

Both groups improved significantly from baseline on all measures (p < 0.05), but the HILT group showed greater benefits than placebo on several key outcomes. For pain intensity, the HILT group achieved a mean VAS score of 29.64 ± 8.43 mm compared to 43.57 ± 10.08 mm in the placebo group, a statistically significant difference (p = 0.001) that exceeded the minimum clinically important difference of 10 mm. For cervical lateral flexion, the HILT group achieved 22.46 ± 3.62° on the right (p = 0.011 versus placebo) and 22.34 ± 2.74° on the left (p = 0.034 versus placebo). For neck muscle stiffness measured by shear wave elastography, the HILT group showed lower shear modulus values in the splenius capitis muscle (22.48 ± 4.03 kPa, p = 0.001) and semispinalis capitis muscle (23.50 ± 5.59 kPa, p = 0.028), indicating reduced stiffness.

However, no significant between-group differences were found for cervical flexion, extension, rotation, neck fascia stiffness, or NDI scores (all p > 0.05). No adverse effects were reported in either group during the trial.

This study provides evidence that a single session of high-intensity laser therapy combined with exercise can produce immediate improvements in pain, lateral neck movement, and superficial neck muscle stiffness for patients with acute nonspecific neck pain. The findings suggest HILT may be a useful adjunct to exercise for rapid pain relief in clinical practice, particularly when patients need immediate functional improvement. However, the lack of significant effects on overall cervical range of motion in other directions, neck fascia stiffness, and functional disability indicates that HILT alone is not sufficient for comprehensive rehabilitation. The researchers noted that deeper neck muscles may not receive adequate laser energy due to tissue depth, and that functional recovery likely requires sustained exercise programs rather than single sessions.

Clinicians should consider HILT as one component of a multimodal approach, with realistic expectations about its immediate versus long-term benefits. Patients should understand that while HILT may help with quick pain relief and some mobility gains, ongoing exercise and possibly repeated laser sessions are likely needed for lasting functional improvement.