Experimental studies on the suitability of the erbium laser for stapedotomy in an animal model

Animal experiments in mature guinea pigs were devised to determine whether and to what extent inner ear damage can be caused by in vivo use of the erbium laser for stapedotomy. The present study examined the laser effect in connection with perforation of the basal convolution of the cochlea and subsequent application in the opened cochlea. Acoustic evoked potentials as compound action potentials (CAP) were recorded for changes in inner ear function. Findings demonstrated that five applications of the erbium:YSGG (yttrium-scandium-gallium-garnet) laser (energy, 85 mJ/pulse; energy density, 36 J/cm2) were needed to create a footplate perforation of 500-600 microns and did not lead to CAP alteration in any animal (n = 20). An increase of the repetition rate from 1 to 5 Hz likewise caused no CAP alteration (n = 17). Application of high total energies in the open cochlea (n = 5) to determine the safety of the laser system for stapedotomy revealed that a 10-fold increase in the total energy required for adequate perforation led to irreversible CAP alterations and no CAP could be recorded at a 15-fold increase in total energy. In contrast, a 5-fold maximum increase in total energy caused no CAP alterations. These results demonstrate the safety of the Er:YSGG laser comparable to that of the CO2 laser for stapedotomy, supporting its utility as an alternative method for surgery.