Transcranial photobiomodulation for stroke in animal models

Photobiomodulation (PBM) for ischemic stroke was the first application of PBM to undergo serious large-scale clinical trials NEST 1, NEST 2 and NEST 3. This chapter will cover the preclinical animal studies that were conducted in order to establish the protocols and dosimetry that were used in these trials. We have decided to group these studies according to the type of ischemic stroke model that was studied: (1) Models of middle cerebral artery occlusion or ligation; (2) rabbit small clot embolic model involving injection of autologous blood clots into the brain; (3) photothrombotic stroke involving injection of rose bengal dye into the bloodstream followed by transcranial laser irradiation. Investigators have mostly used NIR lasers onto the head within a defined time frame after the stroke (hours), and pulsed light was shown to be superior to CW. PBM could be combined with thrombolytic enzymes. For the time being, clinical trials have ceased after the failure of NEST 3, despite the marked success of the animal experiments. Perhaps it is time to start them again.