The Distribution Of Cochlear Dead Region In The Cochlear With Different Degrees Of SNHL, And The Effects On Speech Discrimination In Mandarin

Objective In my research, by using threshold equalizing noise test (TEN test) to study the distribution of cochlear dead region in the cochlear with different degrees of sensorineural hearing loss (SNHL), and combining with speech discrimination score (SDS) and Quick Speech-in-Noise (Quick SIN) tests to investigate the effects of cochlear dead region on speech discrimination in Mandarin.Methods 43 SNHL patients (86 ears, classifying by ear) were divided into mild (7 patients,11 ears), moderate (20 patients,31 ears), severe (24 patients,38 ears) and profound (5 patients,6 ears) SNHL groups according to the degree of hearing loss. Then using TEN test, each group was divided into cochlear dead region group and no cochlear dead region group. And to analyze the distribution of cochlear dead region in the cochlear with different degrees of SNHL. And combining with SDS and Quick SIN tests to investigate the effects of cochlear dead region on speech discrimination in Mandarin. P value of <0.05 was considered statistically significant. Results Classifying by ear, following the distribution of cochlear dead region in the cochlear with different degrees of SNHL, there was no cochlear dead region in mild SNHL group (0/11), 22.6%(7/31) cochlear dead region were in moderate SNHL and the absolute threshold was above 55.18±5.75 dB,63.2%(24/38) cochlear dead region were in severe SNHL and the absolute threshold was above 69.84±5.68 dB,66.7%(4/6) cochlear dead region were in profound SNHL and the absolute threshold was above 83.75±3.06 dB. The results of cochlear dead region also showed,57.1% were high frequency cochlear dead region,28.6% were low frequency cochlear dead region, and 14.3% were mixed frequency cochlear dead region in moderate hearing loss. And 50% were high frequency cochlear dead region,20.8% were low frequency cochlear dead region, and 29.2% were mixed frequency cochlear dead region in severe hearing loss. The SDS of the subject with cochlear dead region was then compared to the SNHL subject with no cochlear dead region. The results showed a significant (p<0.05) reduction of SDS in the subject with cochlear dead region, and the reduction was significantly (p<0.05) decreased if the dead region is more than 3 frequencies in the quiet environment. In noisy environment, with the number of cochlear dead region increased, the bigger the SNR loss was, the worse the SDS was (p<0.05). Compared to high frequency cochlear dead region with low frequency cochlear dead region, it showed that there was no significant reduction of SDS. And the reduction was significantly decreased when the both with no cochlear dead region to compare.Conclusion With the above findings, we concluded that the cochlear dead region was related to the degree of hearing loss, the more serious the hearing loss was, the more likely the cochlear dead region appeared. And the dead region appeared more in the high frequency than low frequency. And the cochlear dead region also significantly reduced speech intelligibility in Mandarin, especially in noisy environment.