Triple semicircular canal occlusion in the guinea pig

Hearing preservation is possible with translabyrinthine procedures, but the optimal means of sealing the remaining labyrinth has not been determined. The purpose of this study was to compare the effects of mechanical and nonmechanical (CO2 laser-assisted) triple semicircular canal occlusion on hearing in the guinea pig. All three semicircular canals of 19 guinea pigs were treated with one of four techniques: fenestration without packing (control), fenestration with packing, CO2 laser coagulation of the membranous canal without packing, or laser coagulation with packing. Six weeks postoperatively, electrocochleographic thresholds were significantly elevated in one of five ears treated with packing alone, in one of five ears treated with laser and packing, in two of five ears treated with the laser alone, and in all four control ears. Thresholds were significantly elevated in control versus occluded ears (p < 0.05). There were no significant differences between the ears treated with laser or packing. These findings suggest that hearing can be preserved in triple canal occlusion by means of sealing the membranous labyrinth with either CO2 laser coagulation or mechanical packing. Further study on the feasibility of hearing preservation with complete labyrinthectomy is warranted.