Transcranial near-infrared laser therapy applied to promote clinical recovery in acute and chronic neurodegenerative diseases

Abstract

One of the most promising methods to treat neurodegeneration is noninvasive transcranial near-infrared laser therapy (NILT), which appears to promote acute neuroprotection by stimulating mitochondrial function, thereby increasing cellular energy production. NILT may also promote chronic neuronal function restoration via trophic factor-mediated plasticity changes or possibly neurogenesis. Clearly, NILT is a treatment that confers neuroprotection or neurorestoration using pleiotropic mechanisms. The most advanced application of NILT is for acute ischemic stroke based upon extensive preclinical and clinical studies. In laboratory settings, NILT is also being developed to treat traumatic brain injury, Alzheimer's disease and Parkinson's disease. There is some intriguing data in the literature that suggests that NILT may be a method to promote clinical improvement in neurodegenerative diseases where there is a common mechanistic component, mitochondrial dysfunction and energy impairment. This article will analyze and review data supporting the continued development of NILT to treat neurodegenerative diseases.

Figure 1. Preclinical laser device

(A) The figure shows the 2001 Photothera Inc. (previously Acculaser Inc.) research laser used in the original translational stroke studies [19,25,34]. The device is a Gallium–Aluminum–Arsenide (Ga-AI-As) diode laser with a wavelength of 808 ± 5 nm. The laser was coupled to a female SMA-905 adapted, 2-cm diameter probe via an OZ Optics Ltd. fiber optic (step index fiber with a 550-µm core diameter and a numerical aperture of 0.22). The probe utilized specially designed optics to generate a divergent, diffused, 5-mm diameter beam. (B) The figure shows the current 2011 Photothera Inc. translational multipulse wave mode research laser used in the translational development of noninvasive transcranial near-infrared laser therapy to treat stroke. The probe is also designed to generate a divergent, diffused, 5-mm diameter beam. The figure shows noninvasive transcranial near-infrared laser therapy treatment of a New Zealand white rabbit. Note the position of the laser probe central to the rabbit’s head positioned over the shaved pink area. Transmission studies in the rabbit demonstrated that when the laser probe is placed on the skin surface posterior to bregma on the midline [25], the laser beam covers the complete cortex. The laser was not turned on for this demonstration.

Figure 2. Clinical noninvasive transcranial near-infrared laser therapy treatment for stroke

The figure shows a Photothera Inc. clinical laser used in the NEST-1–3 clinical trials [12]. (A) Overall view including a Photothera Inc. continuous wave clinical laser. Essentially, the laser is similar to the device shown in Figure 1B but has been programmed for continuous wave delivery of 10 mW/cm² (1.2 J/cm²). (B) Close-up view of a patient with the wearable head apparatus receiving near-infrared laser therapy. Note the use of protective goggles during noninvasive transcranial near-infrared laser therapy treatment. Figure courtesy of C Tedford (Photothera Inc., Carlsbad, CA, USA).

Figure 3. Patient noninvasive transcranial near-infrared laser therapy treatment therapy headgear

The apparatus has positions for 20 independent 2-min applications of noninvasive transcranial near-infrared laser therapy treatment to cover the complete brain. The number system on the gear indicates all 20 treatment positions. Modified from [301].

Figure 4. Clinical noninvasive transcranial near-infrared laser therapy treatment (light emitting diode) for traumatic brain injury

The figure shows a MedX Health Corp. (Mississauga, ON, Canada) light emitting diode (LED). (A) The LED has one circular-shaped cluster head, with a diameter of 5.35 cm (2.1 inches). Treatment area coverage is 22.48 cm²; each cluster head contained 61 diodes (52 near-infrared 870-nm diodes and nine red 633-nm diodes, 12–15 mW each). Total optical output power was 500 mW (+20%) continuous wave; power density was 22.2 mW/cm² (+20%). (B) Close-up view of a patient receiving LED treatment to the left temporal lobe. Note the use of protective goggles during LED treatment. Photographs courtesy of M Hamblin, Harvard University (Boston, MA, USA).