Objectives:To quantify the progression of otosclerosis in the unoperated ear between two stapedotomy procedures for patients with bilateral otosclerosis which can help to determine whether a HRCT scan should be re-performed before the second surgery for patients who already received HRCT imaging before the initial surgery.Methods:35 patients who underwent bilateral stapedotomy were included.Two rounds of HRCT ex-amination and audiometry were performed at the time of the first surgery and second surgery on the ear that was not operated on during the initial surgery.The relationship between the changes in HRCT densitometry and audiometry over time was analyzed.Results:The second round of HRCT did not add significant information about the changes to the otosclerosis lesions in either the imaging diagnosis or the HRCT density values except for small changes in the HRCT densitometry readings at the area anterior to the inner auditory (P =0.01).While the changes in HRCT manifestation are small,changes near the fissula ante fenestram (FAF) were still positively correlated with the air bone gap (ABG) of patients (p =0.031,r =0.388).Conclusions:The progression of lesions in otosclerosis is slow resulting in small and insignificant changes to the HRCT features.Therefore,a repeat HRCT evaluations prior to surgery is not necessary for patients who have had a previous HRCT evaluation within 2 years of the operation.The small changes in HRCT manifestation near the FAF were still correlated with negative effects on the ABG which could cause worsened hearing thresholds over this timeframe.