| Objective:To analyze characteristices of hearing loss in perforations of the tympanic membrane.To determine whether chronic suppurative otitis media (CSOM)may cause sensorineural hearing loss(SNHL)and discuss the influence of the duration of disease,presence of cholesteatoma and ossicular erosion on the development of SNHL.Methods:The records of 80 patients with CSOM were reviewed in a retrospective study.1.There are 33 patients with the simple type of CSOM. Differences between ears of different size or location of perforation in air conduction threshold were analysed by one-way ANOVA over every frequencies (0.25kHz,0.5kHz,1kHz,2kHz,4kHz,8kHz).Linear regression models were used to clarify the relationships between duration and size of perforation.2. There are 55 patients with unilateral CSOM.Bone conduction threshold averages were calculated over the speech frequencies(0.5kHz,1kHz,2kHz). Differences between diseased and control ears in bone conduction thresholds were analysed by the paired student's t-test over the four frequencies(0.5kHz, 1kHz,2kHz,4kHz)and speech frequencies.The effect of the presence of cholesteatoma and ossicular erosion on SNHL over frequencies,2kHz and 4kHz were analysed by one-way ANOVA.Linear regression models were used to clarify the relationships between SNHL and CSOM. Results:1.There are 33 patients with the simple type of CSOM. Thirty-four(77.27%)TM perforations were of a size greater than 25%, whereas 10(22.73%)TM perforations were less than 25%in size.41.4%of the TM perforations of the patients with bilateral perforations were large.In the unilateral-perforation ones,6.7%of the TM perforations were large.The differences in size of perforation between patients with bilateral perforations and unilateral-perforation ones were statistically significant by 2 Independent Samples Tests.The average of air conduction threshold was maximum as the frequencies decline at 4 frequencies(0.25kHz,0.5kHz,1kHz,2kHz),and it was greatest(52.50dB HL)at frequency of 0.25kHz.The average of air conduction threshold of large-perforation ears was greater than middle-perforation ears or small-perforation ears at all frequencies(0.25kHz, 0.5kHz,1kHz,2kHz,4kHz).The differences between large-perforation ears and small-perforation ears were statistically significant at all frequencies(0.25kHz, 0.5kHz,1kHz,2kHz,4kHz)and speech frequencies(0.5 kHz,1kHz,2kHz). And it did the same between large-perforation ears and middle-perforation ears but at one frequency(0.25kHz).The average of air conduction threshold of large-perforation ears was more than 45dB HL at speech frequencies.The average of air conduction threshold of posterior-perforation ears was greater than anterior-perforation ears at all frequencies(0.25kHz,0.5kHz,1kHz,2kHz, 4kHz).The differences between them were statistically significant at three frequencies(0.25kHz,0.5kHz,4kHz).2.The average of bone conduction threshold of diseased ears was greater than control ears at all frequencies (0.25kHz,0.5kHz,1kHz,2kHz,4kHz).The differences between them were statistically significant at two frequencies(2kHz,4kHz).Bone conduction threshold shift at speech frequency and 4kHz was not associated with the duration or age.The presence of cholesteatoma and ossicular erosion was not associated with a significantly increased risk of SNHL.Conclusion:1)It was noted that the patients with bilateral TM perforations had comparatively larger perforations(more than 75%),whereas the patients with unilateral perforations were mainly less than 75%;2)The hearing loss is frequency dependent with the greatest loss occurring at the lowest sound frequencies,and it is maximum as the frequencies decline;3)The hearing loss of ears with large perforation is more obvious than ears with middle perforation or small perforation.The air conduction threshold of large-perforation ears is more than 45dB HL;4)The posterior-central perforations cause more hearing loss than anterior-central ones.5)CSOM can result in SNHL.It is occurring obviously at high frequencies.
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