Hearing evaluation
In this study, pure-tone average (PTA), calculated using 0.5-, 1-, 2-,
and 3-kHz air conduction thresholds, was used to evaluate the hearing
level of the patients. The 3-kHz threshold used in this study was
interpolated by averaging the thresholds at 2 and 4 kHz, because the
3-kHz threshold is not routinely tested in China. The postoperative
evaluation included three time points, at 6 months,12 months and 18
months postoperatively. Hearing deterioration or improvement was
assessed according to the A New Standardized Format for Reporting
Hearing Outcome in Clinical Trials 9. Hearing
deterioration was defined as a PTA elevating ≥10 dB when compared with
the hearing level preoperatively. The definition of stages was based on
the hearing levels of patients pre-operatively10. In
brief, a stage I corresponded to a PTA < 25 dB HL, stage II
corresponded to a PTA of 25 - 40 dB HL, stage III corresponded to a PTA
of 41-70 dB HL and stage IV corresponded to a PTA >70 dB HL. The word
recognition score cannot be reported in this study due to the variety of
dialects. It is difficult to acquire reliable scores using a single
standardization scale when evaluated patients speak different types of
dialects.