Lasers in neurosurgery: a historical overview.

This contribution to the history of laser applications to neurosurgical patients gives the background against which the subsequent developments took place. It covers the important facts regarding the theoretical formulations that led to the invention of the world's first laser in 1960. This was a pulsed ruby laser, which proved lacking in desirable surgical procedures, and at high powers was shown to be damaging to vital organs, such as the brain. It could be lethal to small animals. These very early tests of laser tissue and organ interaction included studies on protein in solution, cultured cells, brain, spinal cord and their surrounding tissues, and transplantable melanomas, as well as ependymoblastomas in mice. Fortunately, the continuous wave CO 2 laser came along in 1967 to replace both the pulsed ruby and neodymium-in-glass lasers. The CO 2 laser was quickly seen to possess surgical properties, namely, vaporization, cutting, hemostasis, and sterilization, without additional damage at a distance or remotely in time. Research studies on normal and pathologic tissues in and around the brain and spinal cord quickly and dramatically showed the potential for benefit to animal and human patients with experimental and naturally occurring neoplasms, burns, and decubitus ulcers. Lasers in neurosurgery are used largely for benign and malignant brain and spinal neoplasms. For benign tumors, debulking of tumor mass, and ablation of unwanted neoplasm without damaging adjacent, vital, functioning neural tissue, the laser adds another therapeutic adjunct and will, at times, aid in complete tumor removal. For malignant vascular growths, the laser will aid greatly in the safest possible excision with maximum hemostasis. Studies around the world, ongoing or planned, will surely extend the uses of lasers for neurosurgery into vascular, infectious, and reconstructive fields, particularly with the proliferation of laser instruments that exploit additional wavelengths into the larger infrared levels and even the shorter ultraviolet region. Experimental and, to some extent, clinical applications are testing the value of Nd:YAG, holmium:YAG, and erbium:YAG lasers in various surgical fields.