Cadavar brains reveal NIR laser penetrates skull, scalp

Although the cause of traumatic brain injury (TBI)–a bomb blast, traffic accident, or violent assault–remained as diverse as the millions of individuals afflicted by the ensuing symptoms–memory loss, confusion, and personality changes–the prognosis was considered fixed.

No treatment was effective for reversing damage deep within the brain.

Today, scientists are challenging this long held belief by testing a regenerative procedure that appears plucked from the pages of a science fiction novel.

Laser and LED light therapy–or Photobiomodulation (PBM)–is a revolutionary new technique for treating a host of neurological and pain-associated disorders–including TBI and stroke. Theoretically, PBM reverses damage in diseased brain tissue by flooding neurons with laser or LED generated photons that ramp up cellular energy production and stimulate healing.

Although scientists knew specific wavelengths of light interacted with human cells, it wasn’t until recently that scientists demonstrated near-infrared (NIR) laser light penetrates the human scalp and skull, tunneling deep into the brain

In light of this new evidence, will treatments for neurological diseases change?

What is photobiomodulation?

Cells rely on energy production to perform basic tasks for staying healthy and functional.  This energy (called ATP) is generated by tiny engine-like compartments located in nearly all human cells.

When cells are damaged or aged, an inhibitory molecule called nitric oxide (NO) builds up in the mitochondria binds to cytochrome c oxidase (CCO)–an enzyme in the ATP production assembly-line. This marriage essentially shuts down the cell’s power source, effectively halting metabolism, healing, and functioning.

PBM is a regenerative medicine technique that involves shining near-infrared (NIR) or red laser light on specific regions of the scalp to kick-start the mitochondria in damaged neurons.

Mitochondrial CCO absorb NIR photons. This energy transfer causes NO release and allows ATP production to resumes. Once freed, NO dilates surrounding blood vessels and the effect is two-fold: circulation and lymphatic drainage around the injured area increase allowing toxic debris and excess fluid to flood out of the region as nutrients and oxygen surge in, thereby reducing inflammation and freeing space for adult stem cells to differentiate and proliferate.

Can NIR light really penetrate the scalp and skull?

Scientists approached the profound implications of reversing neurodegeneration and stimulating healing with skepticism. Research in animal models, computer simulations, and multiple case series documenting the beneficial effects of brain PBM failed to sufficiently answer if a therapeutic dose of photons could pass through the human skull and scalp.

However, a study published in Lasers in Surgery and Medicine demonstrated beneficial quantities of light can reach brain tissue using rather atypical patients–human cadavers.

For the study, the authors recruited–or technically acquired–8 human cadavers to investigate the transmission of light at three different wavelengths–660, 808, and 940nm–through the intact scalp, skull, meninges, and brain.

The brains and bones of PBM

To assess the impact of structural differences between the top and sides of the head on depth of penetration, researchers sectioned four of the eight heads just above the ear and removed the calvaria–or skullcap containing the brain–from the facial bones. The remaining four heads were sectioned right down the middle–along with the midsagittal plane–splitting in half and exposing the occipital, parietal, and frontal lobes.

The cut side of each head was set on a transfer plate and secured into a cranial fixation ring, exposed brain tissue facing upward. The laser was placed flush against the skull and a sensor probe array equipped with a 9 point detector for measuring the radiant energy of the laser, was lowered into the naked brain tissue.

The researchers flipped a switch–killing the lights and plunging them into darkness. Now, confident stray photons wouldn’t interfere with the probe’s delicate readings, the experiment began.

The scientists switched on the laser and 808, 660, then 940 nm wavelength light streamed through the cadaver’s head–racing toward the sensor embedded 5mm on the opposite side.

The probe maintained its downward trajectory, pausing every 5 mm to record fresh data from each wavelength until it hit the dura mater–a thick, outer layer of the meninges that encases and separates the brain from the bone.

After analyzing 20 sites on eight cadavers, researchers concluded that 808 nm light outshined other wavelengths by tunneling through skull, scalp, meninges, and permeating 50 mm–roughly 2 inches–of brain tissue. These values experimentally confirm computational models that predict some wavelengths can, in fact, target recesses deep within the brain.

The future of PBM–can light make me smarter, better, faster, stronger?

Research is a continuous ebb and flow of supportive and contradictory evidence that washes away embellishments and flushes out holes in scientific hypotheses. Absent direct experience in research, interpreting published findings and determining their validity is difficult for anyone seeking online medical advice–particularly those pursuing alternatives treatments after learning there’s nothing modern medicine can do.

Clinical trials are underway to test the efficacy of PBM therapy for TBI, Alzheimer’s disease, dementia, tendinopathies, osteoarthritis, and pain management. Despite promising initial research, the treatment remains in its infancy and there is no definitive scientific conclusion regarding PBM.

Inexpensive devices advertising light therapy as a panacea–curing depression, boosting intelligence, and taking away your pain–because “science says it will” should be met, like all things, with a healthy degree of skepticism.


For more information:

Tedford, C. E., DeLapp, S. , Jacques, S. and Anders, J. (2015), Quantitative analysis of transcranial and intraparenchymal light penetration in human cadaver brain tissue. Lasers Surg. Med., 47: 312-322. doi:10.1002/lsm.22343

Hamblin, Michael R. “Photobiomodulation for traumatic brain injury and stroke.” Journal of neuroscience research 96.4 (2018): 731-743. doi:10.1002/jnr.24190

Saltmarche AE, Naeser MA, Ho KF, Hamblin MR, Lim L. Significant Improvement in Cognition in Mild to Moderately Severe Dementia Cases Treated with Transcranial Plus Intranasal Photobiomodulation: Case Series Report. Photomed Laser Surg. 2017 Aug;35(8):432-441. doi: 10.1089/pho.2016.4227. Epub 2017 Feb 10.

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