The effect of transcranial near-infrared laser therapy on chronic ischemic stroke patients: a randomized, single-blind, sham-controlled trial

Background: Transcranial photobiomodulation (TPBM) using near-infrared (NIR) light is a novel, non-invasive neuromodulation strategy with potential to enhance neurorecovery. While preclinical studies are promising, clinical evidence in chronic stroke remains limited and inconsistent. Objective: To evaluate the efficacy and safety of 980 nm transcranial NIR laser therapy as an adjunct to standard rehabilitation in improving neurological function in patients with chronic ischemic stroke. Methods: In this randomized, single-blind, sham-controlled trial, 40 chronic ischemic stroke patients (>6 months post-onset, NIHSS 7-22) were allocated to active treatment (n=20) or sham control (n=20). The active group received 980 nm laser therapy (6W, 20 minutes/session, 3 sessions/week for 8 weeks) applied to the forehead. The sham group underwent identical procedures with the laser inactivated. Both groups received concurrent standard rehabilitation. The primary outcome was the change in National Institutes of Health Stroke Scale (NIHSS) score from baseline to one-week post-treatment. Secondary outcomes included the Modified Rankin Scale (mRS), Barthel Index (BI), and Mini-Mental State Examination (MMSE). The trial was registered with the Cairo University Postgraduate Office (NILES-MAL-CU 24/05/21), no AI or large language model tools were used in the preparation of this manuscript. Results: No statistically significant between-group differences were observed in post-treatment NIHSS scores. After adjusting for baseline NIHSS scores using ANCOVA, the adjusted mean difference between groups was 0.6 points (95% CI: −1.8 to 3.0, p = 0.620; Cohen's d = 0.15). Both groups showed minimal, equivalent improvements from baseline (active: −0.6 ± 2.1 vs. sham: −0.6 ± 1.9; p = 1.000). Secondary outcomes (mRS, BI, MMSE) also revealed no significant differences. Post-hoc power analysis indicated the study was underpowered (12%) for the observed small effect size. No intervention-related adverse events were reported. Conclusion: Transcranial 980 nm NIR laser therapy did not demonstrate superior efficacy over sham treatment when added to standard rehabilitation for chronic ischemic stroke recovery. The intervention was safe and well-tolerated but provided no additional clinical benefit. These findings do not support the clinical use of this specific TPBM protocol in chronic stroke populations, though results are specific to the 980 nm wavelength and chronic phase, and should not be extrapolated to other parameters or acute stroke