A recent study published in the journal Radiology provides new insights into the potential benefits of low-level light therapy for individuals who have suffered significant brain injuries. The research found that patients receiving low-level light therapy showed greater changes in brain connectivity during their recovery compared to those who did not receive the treatment.
Traumatic brain injury (TBI) is a major global health issue, often resulting in long-term disability or death. Traditional treatments for TBI focus on pharmacological interventions, but there is growing interest in non-drug therapies. One such promising approach is low-level light therapy, also known as photobiomodulation. This therapy involves delivering near-infrared light to the brain through the scalp or nasal passages.
Previous studies have suggested that low-level light therapy can reduce cell death, inflammation, and other harmful processes in the brain. However, most of these studies have been small and lacked robust controls. This new study aimed to explore how low-level light therapy affects brain function in the early stages of recovery from moderate TBI.
For their new study, the researchers conducted a double-blinded, sham-controlled trial, meaning neither the participants nor the researchers knew who received the actual treatment and who received a placebo. The study involved 68 patients with moderate TBI, defined by specific scores on the Glasgow Coma Scale and the presence of abnormalities on head CT scans.
These patients were recruited from Massachusetts General Hospital between November 2015 and July 2019. They were randomly assigned to either the low-level light therapy group or the sham treatment group, which received a similar procedure without the active light therapy.
Participants in the low-level light therapy group wore a helmet that emitted near-infrared light. “The skull is quite transparent to near-infrared light,” explained study co-lead author Rajiv Gupta from the Department of Radiology at Massachusetts General Hospital. “Once you put the helmet on, your whole brain is bathing in this light.”
This treatment was given within 72 hours of their injury and repeated twice more over the next few days. Each session lasted about 20 minutes. The sham group underwent the same procedures, but their helmets did not emit light.
Both groups underwent a series of functional MRI (fMRI) scans to assess changes in brain connectivity. These scans were done at three time points: within the first week after injury (acute phase), 2-3 weeks later (subacute phase), and three months after the injury (late-subacute phase). A control group of 23 healthy individuals also underwent fMRI scanning, though only once, as their brain connectivity was not expected to change significantly over time.
The study found that low-level light therapy was associated with greater changes in resting-state functional connectivity (RSFC) between certain pairs of brain regions compared to the sham treatment. RSFC refers to the synchronization of brain activity between different regions while a person is at rest, which can provide insights into the brain’s functional networks.
From the acute phase to the subacute phase, seven pairs of brain regions showed greater increases in connectivity in the low-level light therapy group compared to the sham group. These regions included areas involved in sensory processing, motor control, and cognitive functions. Additionally, the low-level light therapy group demonstrated increased connectivity between the left temporal pole and various regions in the opposite hemisphere, such as the temporal, parietal, and occipital lobes.
Interestingly, while the low-level light therapy group showed increased connectivity, the sham group experienced decreased connectivity between certain brain regions during the same period. However, from the subacute to late-subacute phases, both groups exhibited increases in connectivity, suggesting a natural healing process occurring in both sets of patients.
“There was increased connectivity in those receiving light treatment, primarily within the first two weeks,” said study coauthor Nathaniel Mercaldo, a statistician with Massachusetts General Hospital. “We were unable to detect differences in connectivity between the two treatment groups long term, so although the treatment appears to increase the brain connectivity initially, its long-term effects are still to be determined.”
Despite its promising findings, the study has several limitations. Firstly, it was originally designed to assess structural connectivity, with functional connectivity as a secondary outcome. This means the sample size and study design may not have been optimal for detecting all relevant differences in brain function.
Secondly, the high attrition rate — where many participants dropped out before completing all follow-up visits — could have affected the results. Reasons for dropping out included physical conditions, scheduling conflicts, and loss of interest.
Another limitation is that the study used only self-reported measures of symptoms, which may not fully capture the clinical impact of low-level light therapy. Future research should include more comprehensive clinical assessments and consider factors such as hair characteristics, age, handedness, and substance use, which could influence the effects of light therapy.
The study provides preliminary evidence that low-level light therapy can enhance brain connectivity in the early stages of recovery from moderate traumatic brain injury. The findings suggest that low-level light therapy may support the brain’s natural healing processes by promoting functional connections between key regions. However, the clinical significance of these changes remains unclear, and further research with larger samples and longer follow-up periods is needed to establish the therapeutic potential of low-level light therapy.
“There is still a lot of work to be done to understand the exact physiological mechanism behind these effects,” said study coauthor Suk-tak Chan, a biomedical engineer at Massachusetts General Hospital.
The study, “Effects of Low-Level Light Therapy on Resting-State Connectivity Following Moderate Traumatic Brain Injury: Secondary Analyses of a Double-blinded Placebo-controlled Study,” was authored by Suk-tak Chan, Nathaniel Mercaldo, Maria G. Figueiro Longo, Jonathan Welt, Arman Avesta, Jarone Lee, Michael H. Lev, Eva-Maria Ratai, Michael R. Wenke, Blair A. Parry, Lynn Drake, Richard R. Anderson, Terry Rauch, Ramon Diaz-Arrastia, Kenneth K. Kwong, Michael Hamblin, Benjamin J. Vakoc, and Rajiv Gupta.
