[Application of cochlear microphonics combined with otoacoustic emission in early differential and localization diagnosis of auditory neuropathy].

Objective: The purpose of this study was to investigate the diagnostic value and clinical significance of cochlear microphonics (CM) combined with otoacoustic emission (OAE) in patients with auditory neuropathy (AN). Methods: The study included patients who were diagnosed with bilateral AN and had CM originating from both sides. The CM amplitude, latency, duration and intensity-amplitude (I/O) function curve were recorded by CM test. According to whether the distortion product otoacoustic emissions (DPOAE) passed through, the patients were divided into three groups: bilateral OAE passed group (OAEPP Group), bilateral OAE failed group (OAERR Group), and unilateral OAE passed through one side failed group (OAEPR Group). OAE was elicited by four or more frequencies of 750-8 000 Hz. The characteristics of CM and its related influencing factors were analyzed, and data were processed and analyzed by SPSS 26.0 software. Results: (1) A total of 256 patients (512 ears) with AN were enrolled, including 161 patients (322 ears) in OAEPP group, 32 patients (64 ears) in OAEPR group and 63 patients (126 ears) in OAERR group. OAE failed in 30.9% of patients with AN. (2) When the stimulation intensity was 100 dB nHL, the CM amplitude of OAE passing ear (OAEP+CMP group) in AN patients aged 3 years was 0.43±0.17μV, which was significantly higher than that of OAE not passing ear (OAER+CMP group) (0.29±0.15) μV (t=4.876，P<0.001). The CM duration of the OAEP+CMP group was (5.18±1.04) ms, which was longer than that of the OAER+CMP group at 4.60±1.12 ms (P=0.005). The I/O function curve of OAEP+CMP group showed a nonlinear trend, while, that of OAER+CMP group showed a linear trend. (3) In the OAEP+CMP group of AN patients, the amplitude of CM was negatively correlated with the onset age, test age, disease course, PTA, and ASSR threshold (P<0.001), with correlation coefficients of r=-0.475, r=-0.519, r=-0.367, r=-0.374, and r=-0.494, respectively. In the OAER+CMP group of AN patients, the amplitude of CM was negatively correlated with the onset age, test age, and ASSR threshold (P<0.05), with correlation coefficients of r=-0.271, r=-0.240, and r=-0.287, respectively. Conclusions: Excluding patients with high-frequency steeply sloping hearing loss, when ABR is absent or abnormal and OAE is absent, CM detection can reduce the rate of missed diagnosis of AN. The analysis of CM amplitude and I/O function curve is helpful to determine the lesion site of AN patients, which is convenient for early diagnosis and effective intervention.