Background: Carbon dioxide (CO2) laser stapedotomy is now one of the standard surgical treatments for otosclerosis. However, there are little normative data of the course of postoperative hearing acuity and the course of postsurgical depression of cochlear function of this technique.
Objective: To compare the hearing outcomes between early (between 1 to 3 months) and late (more than 1 year) postoperative periods in otosclerotic patients who underwent CO2 laser stapedotomy.
Material and Method: The charts of 73 primary CO2 laser stapedotomy procedures performed at Bangkok Metropolitan Administration Medical College and Vajira Hospital between 1997 and 2005 were reviewed. Only patients with early postoperative audiometric data between 1 to 3 months and with long-term postoperative audiometric data more than 1 year were selected for inclusion in the present study. Any patients who underwent CO2 laser stapedotomy for diseases other than otosclerosis and those who had revision surgery were excluded from the present study. The early and the late postoperative hearing outcomes were compared using postoperative closure of air-bone gaps and postoperative sensorineural hearing loss at pure-tone average and different frequencies.
Results: A group of 26 patients who underwent 30 CO2 laser stapedotomies met the criteria for analysis. The hearing outcomes were followed at the early and the late postoperative periods for an average of 1.8 and 36.2 months, respectively. The present study indicated that closure of air-bone gaps at pure-tone average and individual frequencies began in the early postoperative period and continued to improve through the late postoperative period. Bone conduction hearing thresholds were stable even in the early postoperative followup and the improvement in bone conduction hearing thresholds at 1 and 2 kHz and worsening at 4 kHz were seen.
Conclusion: After CO2 laser stapedotomy, the stability of cochlear function begins in the early postoperative period and remains stable through the late postoperative period. The conductive component of hearing thresholds continues to improve through the late postoperative period. Thus, the early postoperative hearing outcomes reflect a side effect of postsurgical sensorineural hearing loss and the long-term postoperative hearing outcomes determine the efficacy of this procedure.

Keywords: Laser, Stapedotomy, Hearing, Otosclerosis