The brain can suffer from a variety of different disorders that can be classed into 3 broad groupings: Traumatic events such as traumatic brain injury, global ischemia, and stroke; Degenerative diseases such a Parkinson’s, Alzheimer’s, and dementia; and Psychiatric disorders such as PTSD, depression, and anxiety. All of these diverse conditions have evidence suggesting they can be beneficially affected by applying to the head, and the possibility that PBM may be used for cognitive enhancement in normal healthy individuals.
Transcranial photobiomodulation application, near infrared light is often applied to the forehead due to the possibility of better penetration without hair barrier and longer wavelengths. In the past laser have been used, recent introduction of inexpensive light emitting diode arrays has allowed for development of light emitting helmets, brain caps, and hand held devices to be used.
Photobiomodulation was discovered in 1967 by accident when Hungary’s Endre Mester attempted to repeat experiments published by McGudd in Boston using beams from recently discovered ruby laser experiments destroying cancerous tumors in laboratory animals. The ruby laser designed for Mester was only a fraction of the power the laser McGuff used, instead of curing experimental tumors Mester succeeded in stimulating hair regrowth and wound healing in the animals in the tumor sites leading to a series of papers called laser biostimulation which soon became known as low level laser therapy.
Low level laser therapy was initially studied for stimulation of wound healing, reduction of pain, and inflammation in various orthopedic conditions including carpal tunnel syndrome, tendonitis, and neck pain. Advent of light emitting diodes led to low level laser therapy being renamed low level light therapy as the use of coherent lasers became more accepted as not being absolutely necessary; recently a second occurred and the term photobiomodulation was adopted due to certain uncertainties in the exact meaning of low level.
Mechanisms of action of PBM centers around cytochrome c oxidase which is responsible for the final reduction of oxygen to water using electrons generated from glucose. Theory is that CCO enzyme activity may be inhibited by NO which can be dissociated by photons of light absorbed by CCO, absorption peaks are mainly in the red and near infrared spectral regions; when NO is dissociated mitochondrial membrane potential is increased, more oxygen is consumed, more glucose is metabolized, and more ATP is produced by mitochondria.
Brief increases in ROS produced in mitochondria has been shown. Bursts of ROS may trigger some mitochondrial signalling pathways leading to cytoprotective, anti-apoptotic, and anti-oxidant effects in the cells. NO released by photodissociation acts as vasodilator as well as dilator of lymphatic flow; No is a potent signalling molecule that can activate a number of beneficial cellular pathways.
Changes in intracellular calcium can be observed which may be explained by light mediated opening of calcium ion channels such as members of the TRP super family channels involved in heat sensing and thermoregulation. Beneficial impacts on the brain may be explained by increases in cerebral blood flow, greater oxygen availability and consumption, improved ATP production, and improved mitochondrial activity. Review of PBM on stimulating mitochondrial activity and blood flow has listed no less than 14 different transcription factors and signalling mediators reported to be activated after exposure.
Wide array of different light sources have been used in tPBM, one of the most controversial questions that remains to be answered conclusively is whether coherent monochromatic laser is superior to non-coherent LEDs.
There have been several studies on the effects of tPBM for brain disorders, acute stroke, chronic stroke, brain injury, TBI, Alzheimer’s disease, Parkinson’s disease, psychiatric disorders, and cognitive enhancement in both human and animal studies yielding promising results, with many of the investigators believing that PBM will become an important medical application fo light therapy in the coming years.
Despite best effort by big pharma most prescription brain disorder drugs are not generally highly regarded in today’s society, and many drugs have major side effects. The overall ageing population combined with lengthening life spans may suggest that dementia, Parkinson’s and Alzheimer’s disease will become even bigger global health problems, that after many years of research have yet to develop a drug to benefit these neurodegenerative disorders, and there is a similar state for drugs in regards to stroke and TBI. New research has indication for tPBM such as global ischemia, post operative cognitive dysfunction, and neurodevelopmental disorders including autism spectrum disorder may well emerge in the near future. Should inexpensive LED helmets be developed and successfully marketed as at home use devices, a number of patients would be in potential position to be of benefit, especially given the advent of the Interwebs making it easier to gain knowledge about this kind of treatment spreading, that may even be able to be ordered and delivered direct bypassing big pharma.
