LASER LABYRINTHECTOMY

Concepts and methods of laser labyrinthectomy have been proposed based on experimental studies in which the macula utriculi was irradiated w ith an argon laser beam through the oval window. In our previous repor ts, a single application of the beam (1.5 W, 0.5 s) eradicated the gui nea pig macula within 5 weeks. The contour of the membranous labyrinth was normal and intact. The human macula utriculi was approached after stapedectomy and irradiated with an argon laser in a patient who deve loped persistent positional vertigo after closure of a perilymph fistu la. Laser singular neurectomy was also done. Hearing remained unchange d, and the patient's vertigo disappeared. The human macula sacculi, ho wever, cannot be irradiated, because of the presence of pigment in the saccular wall. In guinea pigs, the semicircular canals were irradiate d from the outside. The lateral and posterior canals were approached t hrough the middle ear, whereas the anterior canal was approached throu gh the posterior fossa. Argon laser irradiation (1-1.5 W, 0.5 s) to th e bony canal produced a charred area with or without perforation. The semicircular duct showed shrinkage and tearing of the trabecular meshw ork immediately after irradiation. Several weeks later, the canal had been obliterated by ossification. Although laser labyrinthectomy can d estroy the function of individual otolithic organs and eliminate dynam ic impulses of the semicircular canals, hearing can be preserved.