Positive behavioral improvement has been observed following transcranial near-infrared light therapy in humans with chronic traumatic brain injury and acute stroke. We first examined the effect of 808 nm laser diode irradiation on regional cerebral blood flow (rCBF) in mice. An 808 nm CW diode laser was applied to the hemisphere transcranially. Transcranial near-infrared laser irradiation increased rCBF by 30% compared to control value in mice. Near-infrared laser irradiation also provoked a significant increase in cerebral nitric oxide concentration. In the clinical setting, transcranial near-infrared lightemitting diode irradiation to the forehead in a patient with persistent vegetative state following head injury was done. rCBF showed focal increase of 20%, compared to the pre-treatment value. The patient showed some improvement in his neurological condition after light-emitting diode therapy. Transcranial near-infrared irradiation might increase rCBF with some improvement of neurological condition in patients. Further study is warranted.
