4 DISCUSSION
EC-LSC is a rarely encountered phenomenon in clinical practice. In this study, we reviewed the data of 156 patients and found that seven patients exhibited varying degrees of ossification (incidence, 4.5%). The osseous tissue may hinder the further expansion of the cholesteatoma from the attic to the aditus ad antrum. However, the osseous tissue often fuses with key anatomical structures such as the semicircular canals and ossicles that may obstruct the aditus ad antrum in severe cases. This increases the difficulty of identifying the aforementioned anatomical structures during surgery, which may elevate the probability of intraoperative damage to the semicircular canals or to the ossicles and the facial nerve in some cases.