(0970) Tympanic Isthmus Invasion Seems More Important Than Posterior Quadrant Expansion in Early Congenital Cholesteatoma Staging

Introduction: In early congenital cholesteatoma (CC) under intact ossicle chain, tympanic isthmus (TI) invasion from cochleariform process to stapes anterior arch, is challenging part of surgery, and this often causes residual cholesteatoma or ossicle removal. The study aims 1) to compare the clinical outcome of TI invasion, earlier stage I CC in the ASQ without TI invasion, and advanced CC with ossicle destruction, 2) to decide if ossicle removal is required if tymapanic isthmus invasion is positive in early CC.

Methods: Among our 2000 cases of consecutive CC series between 2009 and 2022, 188 cases showed tympanic isthmus invasion medial to intact ossicle chain and normal hearing.

Results: The mean age at the time of operation was 41.9 months (SD 14.4, range 14–86).  Extended tympanotomy flap elevation usually for earlier CC was not sufficient TI invasion, that additional scutum reduction and atticotomy was required to access the tymapnic isthmus from posterior side. Ossicle removal was required in 22.2% (38/171) to access the tympanic isthmus, usually when the anterior arch of stapes invasion was definite. TI invasion showed intermediate clinical outcome between stage I and advanced CC. Residual cholesteatoma was equivocal between ossicle preservation group 8.7% (13/150) vs. ossicle removal group 7.8% (3/38). The postoperative speech threshold of the MSA ossiculoplasty was 16 dB worse than the ossicle preservation group. The residual rate and hearing outcome of intact ossicle removal approach was not better than more advanced CC already with long process destruction.

Conclusions: Anterior tympanic isthmus invasion was a more objective criterion for stage II CC, than PSQ expansion.  Regarding normal hearing and an acceptable rate of residual cholesteatoma, we prefer a laser-assisted ossicle preservation approach first for anterior tympanic isthmus invasion of normal hearing CC. However, some might prefer the ossicle removal approach first if the cold technique shows frequent recurrence.