2021 Volume 31 Issue 1 Pages 15-21
Thirty cases of auditory ossicular malformations focusing on the differential diagnosis of discontinuity and fixation of the ossicular chain have been reported. The preoperative diagnosis of ossicular discontinuity and fixation based only on audiograms often differs from that based on intraoperative surgical findings. Since tympanograms and the stapedial reflex are not very useful in the differential diagnosis of discontinuity and fixation of the ossicular chain and computed tomography cannot reveal the fixation of the stapes, the author established a quantitative index by assessing the preoperative hearing threshold level using the air-bone gap at 4 kHz and air conduction at 4 kHz.
By drawing receiver operating characteristic curves for each quantitative index, cut-off values of the hearing threshold level were defined to determine ossicular discontinuity and fixation. Accuracy rates of the diagnosis of ossicular discontinuity and fixation calculated by comparing the results of the intraoperative observation of the ossicles with the preoperative diagnosis using this index were >70%. Hence, the author recommends these quantitative indices as new criteria to diagnose ossicular discontinuity and fixation. Intraoperative observation led to the following diagnoses: absence of the incudo-stapedial joint was observed in 12 ears, absence of the stapedial crus in three ears, fixation between the tip of the malleus handle and bony external meatus (malleus bar) in one ear, fixation of the supra-structure of the stapes in two ears, fixation of the malleus and/or incus in four ears, fixation of the foot plate of the stapes in four ears, and absence of the oval window in four ears. According to the guidelines for reporting hearing results following middle ear and mastoid surgery proposed by the Japan Otological Society (2010), postoperative hearing improvement was achieved in 25 of 30 ears (83.3%).
