Background: Surgery of the inner ear requires atraumatic techniques to preserve the sensory structures of the inner ear. With modern laser technology, surgery can be performed without mechanical contact, reducing the risk of direct mechanical trauma. However, energy transfer by laser light has the potential to induce damage by heating, pressure waves, or direct irradiation, depending on the properties of the laser and parameters of application.
Hypothesis: The application of laser systems in inner ear surgery may have an advantage over traditional techniques; the carbon dioxide laser in continuous mode with an automated scanning procedure and the erbium:yttrium-aluminum-garnet laser were compared with a mechanical technique, using a diamond drill.
Methods: A cochleostomy in the basal cochlear turn of guinea pigs was created. Thresholds in response to frequency-specific stimuli and clicks were established by recording compound action potentials, both before and after the procedure.
Results: The best results in terms of preservation of cochlear function were obtained with the diamond drill. However, a single ear had a complete loss after fracture of the cochlear wall. Mean threshold shifts observed with the carbon dioxide laser were slightly greater, showing mild high-frequency losses, although differences to the group of drilling were not statistically significant. Results with the erbium:yttrium-aluminum-garnet laser showed significantly higher degrees of hearing loss than the other two groups, predominantly in the high-frequency region.
Conclusions: Mechanical opening of the inner ear using a microdrill can be performed with minimal hearing loss; however, it carries the risk of direct trauma to the inner ear. The carbon dioxide laser with a new scanning technology as a noncontact procedure is shown to be effective and safe. It can be regarded as a useful tool in inner ear surgery. The erbium:yttrium-aluminum-garnet laser has a greater potential to cause damage.