Light therapy increases brain connectivity after injury, study finds

Low-level light therapy appears to affect brain healing in people who have suffered significant brain damage, according to a study published in Radiology.

Lights of different wavelengths have been studied for years for their healing properties. Researchers at Massachusetts General Hospital (MGH) performed low-level light therapy on 38 patients who had suffered moderate traumatic brain injury, a head injury severe enough to impair cognition and/or be visible on a brain scan. Patients received light therapy within 72 hours of their injuries using a helmet emitting near-infrared light.

“The skull is completely transparent to near-infrared light,” said study co-senior author Rajiv Gupta, MD, Ph.D., of the MGH Department of Radiology. “Once you put the helmet on, your whole brain is bathed in this light.”

Researchers used an imaging technique called functional MRI to evaluate the effects of light therapy. They focused on resting brain functional connectivity, the communication between brain regions that occurs when a person is at rest and not engaged in a specific task. The researchers compared MRI results during three phases of recovery: the acute phase one week after injury, the subacute phase two to three weeks after injury, and the late subacute phase three months after injury. injury.

Of the 38 patients participating in the trial, 21 did not receive light therapy while wearing the helmet. This was done to serve as a control to minimize bias due to patient characteristics and avoid potential placebo effects.

Patients who received low-intensity light therapy showed a greater change in resting-state connectivity in seven pairs of brain regions during the acute to subacute recovery phase compared to control participants.

“There was increased connectivity in those receiving light treatment, primarily in the first two weeks,” said study co-author Nathaniel Mercaldo, Ph.D., a statistician at MGH. “We were unable to detect any long-term connectivity differences between the two treatment groups. So while the treatment initially appears to increase brain connectivity, its long-term effects still need to be determined.”

The precise mechanism of light therapy’s effects on the brain also remains to be determined. Previous research has found impairment of an enzyme in the cell’s mitochondria (often called the “powerhouse” of a cell), Dr. Gupta said. This leads to increased production of adenosine triphosphate, a molecule that stores and transfers energy within cells. Light therapy has also been linked to blood vessel dilation and anti-inflammatory effects.

“Much work remains to be done to understand the exact physiological mechanism behind these effects,” said Suk-tak Chan, Ph.D., study co-author and biomedical engineer at MGH.

Although connectivity increased in light therapy-treated patients during the acute to subacute phases, there was no evidence of a difference in clinical outcomes between treated and control participants. Additional studies in larger patient cohorts and correlative imaging beyond three months may help determine the therapeutic role of light in head trauma.

Researchers expect the role of light therapy to expand as new study results come in. The 810 nanometer wavelength light used in the study is already used in various therapeutic applications. It is safe, easy to administer and does not require surgery or medication. The portability of the headset means it can be delivered outside of the hospital. According to Dr. Gupta, it could have applications in the treatment of many other neurological conditions.

“There are many connectivity disorders, primarily in psychiatry, in which this intervention may play a role,” he said. “PTSD, depression, autism: these are all promising areas for light therapy.”