A system and method of illuminating tissue, particularly within the cranial cavity, through the mouth or nose. The system includes a light source and a power source for powering the light source. Optics are included for directing light from the light source towards the cranial cavity when the apparatus is inserted into a cavity of the head. Light from the light source and output from the optic provides cellular interaction treatment toward a specified area of the head region. Providing illumination where there are already holes in the skull results in more efficient coupling of light to the cells.
