Retrospective case study of carbon dioxide laser stapedotomy with lens-based and mirror-based micromanipulators

Abstract

Most clinical studies on carbon dioxide (CO₂) (λ = 10.6.mm) laser stapedotomy have been carried out with the laser guided by a conventional lens-based micromanipulator, with the attendant risks of correct aiming (HeNe) and surgical (CO₂) beam misalignment. Hence, engineering advances have attempted to improve laser targeting as well as the spot size focus. The development of the mirror-based micromanipulator was a response to this need but no data concerning its use in stapes surgery is available. We performed a retrospective case-series review of patients treated for otosclerosis between 1992 and 2000. Primary laser stapedotomy was performed in 218 consecutive patients. In the first 78 procedures, the aiming beam (HeNe, λ = 632 nm) and surgical beam (CO₂) were guided with a conventional lens-based micromanipulator whereas in the subsequent 140 procedures, they were guided by using a mirror-based micromanipulator. Hearing was tested at six and 12 months. The mean (SD) air-bone gap was 5 dB (4.5) and 4.5 dB (3.9). The mean closure was 15 dB (9.9) and 14.4 dB (9.4). The mean change in the high-tone bone-conduction level was 5.5 dB (7.3) and 7.8 dB (7.5). Overheating of the facial canal produced transient facial paralysis in one case and was due to misalignment of the beams with the lens-based micromanipulator. Use of the mirror-based micromanipulator obviated the need to verify alignment. The light-weight and superior optical yield of this system made it possible to reduce the number of impacts on the footplate by the integral restitution of the energy source. This study demonstrated that the CO₂ laser is an effective method for performing stapedotomy. In addition, microtrauma to the labyrinth is reduced by its ability to perform calibrated footplate fenestration without mechanical or vibrational injury to the inner ear. The optical reflection micromanipulator simplified beam alignment and enhanced surgical comfort.