A 35-year-old man undergoes canal-wall-up mastoidectomy for primary acquired cholesteatoma with ossicular erosion. Pure-tone audiometry performed 6 weeks postoperatively shows an air-bone gap of 25 dB with bone conduction thresholds elevated by 15 dB compared to preoperative baseline. The audiogram pattern marked **B** in the diagram is observed. Which of the following best explains the postoperative hearing loss pattern?
A. Labyrinthine fistula with purely sensorineural hearing loss from lateral semicircular canal erosion
B. Complete ossicular chain reconstruction with normal bone conduction thresholds and conductive loss alone
C. Persistent ossicular discontinuity from incomplete reconstruction combined with sensorineural hearing loss from labyrinthine inflammation and surgical trauma
D. Tympanic membrane perforation causing conductive loss without any inner ear involvement
Explanation
Why "Persistent ossicular discontinuity from incomplete reconstruction combined with sensorineural hearing loss from labyrinthine inflammation and surgical trauma" is right
The pattern marked B in the diagram represents mixed conductive and sensorineural loss after mastoidectomy. In this patient, the preoperative ossicular erosion from cholesteatoma bone-resorbing enzymes (collagenase, RANKL-driven osteoclast activation) persists postoperatively despite surgery. The air-bone gap of 25 dB reflects the conductive component from ongoing ossicular discontinuity. The elevation of bone conduction thresholds by 15 dB compared to baseline indicates new sensorineural hearing loss, which occurs from labyrinthine inflammation triggered by cholesteatoma erosion and surgical manipulation during mastoidectomy. This mixed pattern is the expected postoperative outcome in canal-wall-up surgery when ossiculoplasty is not performed or incompletely reconstructed, and is consistent with EAONO/JOS 2017 guidelines and Cummings Otolaryngology 7e Ch. 142.
Why each distractor is wrong
Complete ossicular chain reconstruction with normal bone conduction thresholds and conductive loss alone: This would result in purely conductive loss (pattern D), not mixed loss. The elevated bone conduction thresholds in this case prove sensorineural involvement, which is not explained by ossicular reconstruction alone.
Labyrinthine fistula with purely sensorineural hearing loss from lateral semicircular canal erosion: A labyrinthine fistula would produce purely sensorineural hearing loss (pattern C), not mixed loss. While fistula can occur with cholesteatoma erosion of the lateral semicircular canal, the presence of an air-bone gap indicates a conductive component that fistula alone cannot explain.
Tympanic membrane perforation causing conductive loss without any inner ear involvement: Perforation alone causes conductive loss (pattern D), not mixed loss. Furthermore, the elevated bone conduction thresholds prove inner ear involvement, contradicting the premise of no inner ear pathology.
High-YieldNEET PG
Postoperative mixed hearing loss after cholesteatoma surgery = persistent ossicular damage + labyrinthine inflammation; ossiculoplasty or staged reconstruction may improve the conductive component.
Cummings Otolaryngology 7e Ch. 142; EAONO/JOS 2017
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