About 50 to 60 % of patients who suffer from COM face > 30 dB of hearing loss [1,2]. One of the causes of hearing loss in these patients is erosion or discontinuity in the OC [3]. Although the most reliable indicator for OC status is intraoperative evaluation, preoperative audiometric tests predict either an incomplete or a complete ossicular discontinuity [3].

Zhu et al. [4] evaluated 176 ears and found an association between OC erosion and AC threshold > 55 dB and ABG > 40 dB. Furthermore, they revealed that the OC was normal in the patients who had AC threshold < 40 dB and ABG of 30 dB. Dinç et al. [1] revealed the comparison of preoperative audiometric variables with the intra-operative findings in 159 ears with COM. They concluded that hearing loss was greater in the lower frequencies and the least hearing loss was in ears with both intact and fixed OCs at 2000 Hz. Hearing loss was also detected in all frequencies while the better hearing was at 2000 Hz in patients with OC discontinuity.

The Carhart notch, another preoperative predictor in audiograms, is a deceptive depression in bone conduction (BC) thresholds that appears without a corresponding decline in air conduction (AC) thresholds. This notch is often detected in cases of stapes fixation due to otosclerosis, malleus or incus fixation, and otitis media with effusion. Despite the observed decrease in BC thresholds, the underlying mechanisms do not represent true conductive hearing loss, making the Carhart notch a misleading indicator in these conditions [[5], [6], [7]].

The high-frequency conductive hearing loss (HfCHL) test is a highly effective method for predicting incomplete ossicular discontinuity in COM patients without cholesteatoma [3]. A study by Sim et al. [8] on 14 patients showed that fluctuating hearing loss, HfCHL, and enhancement of hearing after the Valsalva maneuver correlated with ossicular discontinuity. A few studies with limited sample sizes [3,8,9] suggested the HfCHL test as a hallmark of OC discontinuity in ears without cholesteatoma. However, they didn't evaluate the OC status in different types of middle ear pathology. Ears with OC discontinuity, more effectively transmitted low-frequency sounds than high-frequency ones, leading to a larger ABG in high frequencies and an almost unusual pattern of a downslope audiogram with preserved BC.