Study finds low-level light therapy results in increased brain connectivity within the first 2-3 weeks of moderate traumatic brain injury
By Fadhil Hussain. This article was initially published in the 6/13/24 edition of our Concussion Update newsletter; please consider subscribing.
A study published in Radiology discovered that low-level light therapy (LLLT) administered within 72 hours of a moderate traumatic brain injury (TBI) showed increased resting-state functional connectivity in the brains of participants during the early recovery stages. While still in the preliminary research phase, light therapy could be a highly accessible rehabilitation method due to its safety, non-invasiveness, ease of administration, and suitability for use outside hospital settings. This study contributes to a growing body of evidence that light therapy could be used in disorders that impact brain connectivity. According to a news release from the Radiological Society of North America, the study’s co-lead author, Dr. Rajiv Gupta, MD, PhD, said, “There are lots of disorders of connectivity…where this intervention may have a role. PTSD, depression, autism: these are all promising areas for light therapy.” While this study focuses on moderate TBI, photobiomodulation (LLLT) is also being researched as a treatment for mild TBI.
In the prospective study, researchers at Massachusetts General Hospital investigated whether LLLT altered resting state functional connectivity in patients with moderate TBI. Moderate traumatic brain injury, as defined by the US Veterans Affairs/Department of Defense, is a traumatic brain injury that results in a loss of consciousness for 30 minutes to 24 hours, accompanied by between 1 and 7 days of post-traumatic amnesia. The study included 38 participants who had suffered a moderate traumatic brain injury, with 17 participants in the LLLT group and 21 participants in the sham group. Additionally, there were 23 participants in a healthy control group. The LLLT group received low-level near-infrared light therapy, delivered by a Photomedex helmet, in three 20-minute sessions within 72 hours of their injuries. The sham group received the same procedure; however, the light-emitting diodes in the helmet were turned off. The control group did not receive LLLT or sham procedures. The participants’ functional MRI (fMRI) results were then compared at three time points: acute (within one week of injury), subacute (2-3 weeks), and late subacute (3 months).
Between the acute and subacute time points, the LLLT group showed increased resting state connectivity in 14 of 82 brain region pairs analyzed, with 7 of these region pairs showing significantly greater (positive) changes when compared to the sham group. Interestingly, connectivity continued to change between the subacute and late-subacute time points, although the researchers found no significant differences between connectivity changes experienced by the LLLT and sham treatment groups during this time. The researchers postulate that the continued changes “may suggest a natural healing process.”
These results add to a growing body of evidence that LLLT can modulate brain activities at rest. However, the cause and mechanism of the therapy are unclear. In the news release, Dr. Gupta stated that light therapy may alter an enzyme in cells’ mitochondria, which “leads to more production of adenosine triphosphate, a molecule that stores and transfers energy in the cells. Light therapy has also been linked with blood vessel dilation and anti-inflammatory effects.”
Despite the changes in brain connectivity, there were no observed differences in clinical outcomes between control participants and those in the LLLT- or sham-treated groups. The researchers stated that “as major improvement in life functioning can occur between 2 weeks and 12 months of natural recovery…it is too early to define the therapeutic role, if any, of LLLT.” Future research could explore how the connectivity changes observed in the present study compare with larger sample sizes, other imaging results, and clinical outcomes to help surmise the therapeutic role of LLLT in moderate TBI.
We have covered studies for photobiomodulation for mild TBI (here, here, here, and here) and a set of case studies of photobiomodulation for suspected CTE (preliminary results here and a synopsis of published results here.)
