The bone conduction threshold pattern may help to estimate the pathology underlying conductive hearing loss

Air conduction and bone conduction thresholds in audiograms provide clinically useful information. However, whether bone conduction audiograms can help distinguish between different conductive hearing disorders remains unestablished. This retrospective case-control study included patients with hearing loss (surgically-confirmed ossicular sclerosis, ossicular discontinuity or tympanic membrane perforation) and a group of people with normal hearing (Jikei University School of Medicine, Tokyo, Japan). Data were collected between November 30, 2017 and December 30, 2022. Bone conduction threshold patterns (pure tone audiometry) were compared between groups. All experiments were performed in accordance with the relevant guidelines and regulations. Ossicular fixation was associated with a dip at 2 kHz (57.8% of cases) in the bone conduction thresholds, whereas ossicular discontinuity showed a steep downslope of > 10 dB HL from 1 kHz to 3 kHz (75.0% of cases) with a tendency for a dip at 3 kHz (56.3% of cases). For patients with ossicular fixation, the probability of malleus or incus fixation was higher when the bone conduction thresholds at low frequencies (≤ 1 kHz) exhibited an upslope, whereas the probability of stapes fixation was higher when the pattern was a downslope (likelihood ratio = 4.9, P < 0.001). For patients with ossicular discontinuity, the probability of incomplete discontinuity was higher when the low-frequency bone conduction thresholds sloped upward, whereas a downslope was associated with a higher probability of complete discontinuity (likelihood ratio = 6.6, P = 0.018). Analysis of the pattern of the bone conduction thresholds might facilitate the preoperative diagnosis of ossicular sclerosis or ossicular discontinuity in patients with conductive hearing loss.