Third Window Phenomenon in Advanced Otosclerosis: The Critical Role of Preoperative CT Imaging

Objective: To describe a case of advanced otosclerosis complicated by third window phenomenon and emphasize the importance of preoperative CT imaging in advanced or revision otosclerosis, not only for assessing ossicular status and superior semicircular canal dehiscence (SSCD) but also for detecting abnormal otic capsule demineralization that may contribute to third window pathology. Patients: A 52-year-old male with bilateral otosclerosis, mixed hearing loss, and multiple prior ear surgeries, including a right-sided bone-anchored hearing aid (BAHA), presented for revision surgery. Intervention(s): The patient underwent right-sided BAHA abutment removal with ossicular reconstruction using a Lippy bucket-handle prosthesis and left-sided revision stapedotomy with a new prosthesis and cartilage graft. Main Outcome Measure(s): Postoperative hearing outcomes were assessed via audiograms, with CT imaging used to evaluate persistent hearing loss in the left ear. Results: Right ear revision surgery improved hearing by 50-dB at 250 to 500-Hz, closing air-bone gaps. Left ear surgery resulted in a 10-dB worsening in the 3 to 6-kHz range. CT imaging revealed fenestral and retrofenestral otospongiosis with cochlear-perilymphatic continuity, indicating a third window phenomenon contributing to persistent hearing loss. Conclusions: In cases of persistent conductive hearing loss, third window phenomenon due to otospongiosis should be considered despite proper prosthesis placement and absence of SSCD or perilymph fistula.