Risk factors for bacterial infection to cause sensorineural hearing loss in eosinophilic otitis media.

Objective: Eosinophilic otitis media (EOM) is an intractable type of otitis media in which sensorineural hearing loss (SNHL) progresses over time. Clinically, bacterial infection complicates the course of EOM, making it challenging to control otorrhea/middle ear effusion (MEE) from infected ears, and accelerates the progression of SNHL. In this study, we focused on infection, one of the risk factors for SNHL in EOM, and analyzed factors associated with it.

Methods: In this cohort study, we evaluated 144 ears of 72 patients diagnosed with bilateral EOM. Patients visited our hospital once every 1-3 months and received intratympanic or systematic administration of steroids when otorrhea/MEE was observed. Several investigations, including blood tests, otorrhea/MEE cytology, bacterial culture tests, and respiratory function tests, were performed. In the otorrhea/MEE cytology, the leukocyte fraction was measured.

Results: Two risk factors for SNHL in EOM were middle ear mucosal thickening (p <0.01) and infection (p <0.05). Compared to the group with <40% neutrophils in otorrhea/MEE samples, groups with 40-70% and ≥70% neutrophils had a significantly higher bone conduction hearing level (p <0.01, p <0.05, respectively). Two risk factors associated with the occurrence of infection in EOM were tympanic membrane (TM) perforation (p <0.01) and the coincidence of otorrhea/MEE and rhinorrhea in bacterial culture test results (p <0.001). A positive correlation was observed between TM perforation and infection (p <0.001). Our analysis of the relationship between the frequency of intratympanic corticosteroids administration and the time-period until the occurrence of TM perforation showed that >4 intratympanic administrations/year significantly increased the risk of perforation (p<0.001). Pseudomonas aeruginosa was isolated from otorrhea/MEE samples, while Pseudomonas aeruginosa and fungi, detected in cultures of rhinorrhea samples, were significantly related to the deterioration of bone conduction hearing levels.

Conclusion: The risk factors associated with the occurrence of infection in patients with EOM were TM perforation and the coincidence of otorrhea/MEE and rhinorrhea in bacterial culture test results. Since TM perforation is likely to occur even due to intratympanic corticosteroids administration, it is necessary to confirm whether the frequency of treatment is appropriate and try a less invasive technique of administration. Furthermore, Pseudomonas aeruginosa infection poses a high risk for the development of SNHL, and clinicians should be alert to this possibility, even if the bacteria were identified only in cultures of rhinorrhea samples.