Many of the treatments used to treat traumatic brain injuries attempt to resolve the symptoms experienced but do not provide means to heal or repair the injury. For instance, stimulants are used to improve alertness, attention, and cognitive processing; cognitive rehabilitation is implemented to help with concentration problems, executive dysfunction, and memory deficits; behavioural therapies help with aggression, social comprehension, and sleep disruptions. Although such remedies improve the patients’ quality of life and support their recovery, they fail to remedy the injury itself. This is why novel approaches are being developed in order to fill this gap. One such treatment is near-infrared light therapy.
What is near-infrared light therapy (NILT)?
Near-infrared light therapy takes advantage of the fact that near infrared light passes efficiently through the skull and thus it is able to reach the damaged brain regions. Near-infrared light of 800-900 nm wavelength light is typically used and it merges with the red spectrum of visible light (600 nm wavelength light). This light is passed to the brain using external low-power lasers or by light-emitting diode (LED) placed externally on the head with the light penetrating the skull and reaching brain matter. There is no standard delivery time yet, but in one clinical trial, NIR light was applied three times per week for 6 weeks on eleven brain sites for 10 minutes per site.
When using animal models to test its effectiveness, NILT led to the repair and recovery of damaged brain tissue. In human clinical trials, NILT improved cognitive function, particularly executive functioning and verbal memory, in chronic mild-TBI patients. It also helped improve psychological symptoms consistent with PTSD, anxiety, and depression. Sleep and mood improvements were also observed as well as a reduction in suicidal thoughts. These neurological and psychological benefits are not immediately observed following the treatment as it takes 1-4 weeks and multiple sessions to notice improvement.
How does it work?
The mechanism underlying the therapeutic benefits of NILT is not understood in full, but it involves the generation of adenosine triphosphate (ATP) which is the energy currency of the body. Near-infrared light is absorbed by cytochrome c oxidase in mitochondria which stimulates the generation of more ATP molecules, and thus more energy which can help repair the damaged neurons. NILT can also modulate other pathways that have anti-inflammatory properties, improve blood circulation, promote synaptogenesis (the creation of new synapses or connections between neurons) and neurogenesis (the birth of new neurons). All of these combined can trigger a regeneration cascade that repairs damaged brain regions due to the exposure of the near-infrared light.
Although promising, this type of treatment still requires more research. There are lingering questions regarding the optimal frequency of light delivery, wattage, brain regions to be targeted, and wavelength or combination of wavelengths to use. Pilot studies and animal models have provided very promising data regarding the healing properties of NILT for traumatic brain injuries that traditional treatments are failing to provide.
Written by Lea Farah
References
Henderson, T. (2016). Multi-watt near-infrared light therapy as a neuroregenerative treatment for traumatic brain injury. Neural Regeneration Research, 11(4), 563-565. https://doi.org/10.4103/1673-5374.180737
Morries, L. D., Cassano, P., & Henderson, T. A. (2015). Treatments for traumatic brain injury with emphasis on transcranial near-infrared laser phototherapy. Neuropsychiatric Disease and Treatment, 11, 2159-2175. https://doi.org/10.2147/NDT.S65809
Naeser, M. A., Zafonte, R., Krengel, M. H., Martin, P. I., Frazier, J., Hamblin, M. R., Knight, J. A., Meehan, W. P., & Baker, E. H. (2014). Significant improvements in cognitive performance post-transcranial, Red/Near-infrared light-emitting diode treatments in chronic, mild traumatic brain injury: Open-protocol study. Journal of Neurotrauma, 31(11), 18-1017. https://doi.org/10.1089/neu.2013.3244
Yao, X., Liu, C., Feng, D., Yin, J., & Chen, G. (2018). Transcranial near-infrared laser therapy in improving cognitive recovery of function following traumatic brain injury. Current Neuropharmacology, 16(9), 1320-1326. https://doi.org/10.2174/1570159X16666180321100439