Background and Purpose-Low-level laser therapy (LLLT) modulates various biological processes. In the present study,we assessed the hypothesis that LLLT after induction of stroke may have a beneficial effect on ischemic brain tissue. Methods-Two sets of experiments were performed. Stroke was induced in rats by (1) permanent occlusion of the middle cerebral artery through a craniotomy or (2) insertion of a filament. After induction of stroke, a battery of neurological and functional tests (neurological score, adhesive removal) was performed. Four and 24 hours poststroke, a Ga-As diode laser was used transcranially to illuminate the hemisphere contralateral to the stroke at a power density of 7.5 mW/cm 2 . Results-In both models of stroke, LLLT significantly reduced neurological deficits when applied 24 hours poststroke.Application of the laser at 4 hours poststroke did not affect the neurological outcome of the stroke-induced rats as compared with controls. There was no statistically significant difference in the stroke lesion area between control and laser-irradiated rats. The number of newly formed neuronal cells, assessed by double immunoreactivity to bromodeoxyuridine and tubulin isotype III as well as migrating cells (doublecortin immunoactivity), was significantly elevated in the subventricular zone of the hemisphere ipsilateral to the induction of stroke when treated by LLLT. Conclusions-Our data suggest that a noninvasive intervention of LLLT issued 24 hours after acute stroke may provide a significant functional benefit with an underlying mechanism possibly being induction of neurogenesis. (Stroke. 2006; 37:2620-2624.)

Background and Objective Low level light (or laser) therapy (LLLT) is a rapidly growing modality used in physical therapy, chiropractic, sports medicine and increasingly in mainstream medicine. LLLT is used to increase wound healing and tissue regeneration, to relieve pain and inflammation, to prevent tissue death, to mitigate degeneration in many neurological indications. While some agreement has emerged on the best wavelengths of light and a range of acceptable dosages to be used (irradiance and fluence), there is no agreement on whether continuous wave or pulsed light is best and on what factors govern the pulse parameters to be chosen. Study Design/Materials and Methods The published peer-reviewed literature was reviewed between 1970 and 2010. Results The basic molecular and cellular mechanisms of LLLT are discussed. The type of pulsed light sources available and the parameters that govern their pulse structure are outlined. Studies that have compared continuous wave and pulsed light in both animals and patients are reviewed. Frequencies used in other pulsed modalities used in physical therapy and biomedicine are compared to those used in LLLT. Conclusion There is some evidence that pulsed light does have effects that are different from those of continuous wave light. However further work is needed to define these effects for different disease conditions and pulse structures.

Transcranial laser therapy (TLT) was tested for efficacy in a mouse model of Alzheimer's disease (AD) using a near-infrared energy laser system. TLT is thought to stimulate ATP production, increase mitochondrial activity, and help maintain neuronal function. Studies were performed to determine the effect of TLT in an amyloid-β protein precursor (AβPP) transgenic mouse model. TLT was administered 3 times/week at various doses, starting at 3 months of age, and was compared to a control group (no laser treatment). Treatment was continued for a total of six months. Animals were examined for amyloid load, inflammatory markers, brain amyloid-β (Aβ) levels, plasma Aβ levels, cerebrospinal fluid Aβ levels, soluble AβPP (sAβPP) levels, and behavioral changes. The numbers of Aβ plaques were significantly reduced in the brain with administration of TLT in a dose-dependent fashion. Administration of TLT was associated with a dose-dependent reduction in amyloid load. All TLT doses mitigated the behavioral effects seen with advanced amyloid deposition and reduce the expression of inflammatory markers in the AβPP transgenic mice. All TLT doses produced an increase in sAβPPα and a decrease in CTFβ levels consistent with inhibition of the β-secretase activity. In addition, TLT showed an increase in ATP levels, mitochondrial function, and c-fos suggesting an overall improvement in neurological function. These studies suggest that TLT is a potential candidate for treatment of AD.

Low-level laser therapy (LLLT) has been evaluated in this study as a potential therapy for traumatic brain injury (TBI). LLLT has been found to modulate various biological processes. Following TBI in mice, we assessed the hypothesis that LLLT might have a beneficial effect on their neurobehavioral and histological outcome. TBI was induced by a weight-drop device, and motor function was assessed 1 h post-trauma using a neurological severity score (NSS). Mice were then divided into three groups of eight mice each: one control group that received a sham LLLT procedure and was not irradiated; and two groups that received LLLT at two different doses (10 and 20 mW/cm(2) ) transcranially. An 808-nm Ga-As diode laser was employed transcranially 4 h post-trauma to illuminate the entire cortex of the brain. Motor function was assessed up to 4 weeks, and lesion volume was measured. There were no significant changes in NSS at 24 and 48 h between the laser-treated and non-treated mice. Yet, from 5 days and up to 28 days, the NSS of the laser-treated mice were significantly lower (p < 0.05) than the traumatized control mice that were not treated with the laser. The lesion volume of the laser treated mice was significantly lower (1.4%) than the non-treated group (12.1%). Our data suggest that a non-invasive transcranial application of LLLT given 4 h following TBI provides a significant long-term functional neurological benefit. Further confirmatory trials are warranted.