Laser labyrinthectomy.
Concepts and methods of laser labyrinthectomy have been proposed based on experimental studies in which the macula utriculi was irradiated with an argon laser beam through the oval window. In our previous reports, a single application of the beam (1.5 W, 0.5 s) eradicated the guinea 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 developed persistent positional vertigo after closure of a perilymph fistula. Laser singular neurectomy was also done. Hearing remained unchanged, and the patient's vertigo disappeared. The human macula sacculi, however, cannot be irradiated, because of the presence of pigment in the saccular wall. In guinea pigs, the semicircular canals were irradiated from the outside. The lateral and posterior canals were approached through the middle ear, whereas the anterior canal was approached through the posterior fossa. Argon laser irradiation (1-1.5 W, 0.5 s) to the bony canal produced a charred area with or without perforation. The semicircular duct showed shrinkage and tearing of the trabecular meshwork immediately after irradiation. Several weeks later, the canal had been obliterated by ossification. Although laser labyrinthectomy can destroy the function of individual otolithic organs and eliminate dynamic impulses of the semicircular canals, hearing can be preserved.