Hearing Loss in Bacterial Meningitis Revisited-Evolution and Recovery

Abstract

Background: Hearing loss and deafness are well-known sequelae from bacterial meningitis (ABM) and may result in social dysfunction and learning difficulties. Yet, the timely development of hearing loss and restitution is poorly studied, especially among adults. Hearing loss was revisited using otoacoustic emissions (OAEs) to determine the occurrence, magnitude, and development of hearing loss among adults with ABM.

Methods: Distortion product OAEs were measured in patients with ABM the day of admission and days 2, 3, 5-7, and 10-14 and at follow-up 30-60 days after discharge. Frequencies were categorized as low (1, 1.5, 2 kHz), mid (3, 4, 5 kHz), mid-high (6, 7, 8 kHz), and high (9, 10 kHz). Audiometry was performed on discharge and 60 days after. Results were compared with 158 healthy controls.

Results: OAE was obtained in 32 patients. ABM was due to S. pneumoniae in 12 patients (38%). All patients were treated with dexamethasone. OAE emission threshold levels (ETLs) were significantly decreased upon admission and at follow-up in all frequencies compared with healthy controls. A substantial and significant decrease in ETLs was found in S. pneumoniae meningitis. Sensorineural hearing loss (SNHL) >20 dB was present in 13 of 23 (57%) at discharge and in 11 of 18 patients (61%) 60 days after discharge. Hearing recovery decreased from day 3.

Conclusions: Hearing loss in ABM still affects >60% of patients despite treatment with dexamethasone. In S. pneumoniae meningitis, SNHL is profound and permanent. A window of opportunity for systemic or local treatments aiming to preserve cochlear function is proposed.

Keywords: OAE; bacterial meningitis; cochlea; hearing loss; otoacoustic emissions.

Figure 1.

Emission threshold levels among healthy control group participants. Graph (A) shows ETLs among females, and graph (B) shows ETLs among males. The age groups are divided into decennials from 18 to 80+ years. Abbreviation: ETL, emission threshold level.

Figure 2.

Changes in ETLs from admission to follow-up showing the dB level of each frequency measured (1–10 kHz). The red line shows admission ETL; the blue line shows ETLs on day 3 (72 h after admission); the green line shows ETLs at final follow-up. The black dotted line shows the mean ETL level of age- and sex-matched controls. The gray scattered area at the bottom of each graph is the noise floor. The ETL level of detection was calculated from the noise floor with the addition of SNR +3 dB (low, mid, and mid-high frequencies) and +6 dB (high frequencies). A and B, A male (age 20) and female (age 18) with N. meningitidis meningitis. C and D, A male (age 50) and female (age 61) with S. pneumoniae meningitis. E and F, A male (age 65) and female (age 75) with H. influenzae meningitis. G and H, A male (age 71) and female (age 64) with other pathogens (S. aureus and E. coli, respectively). I and J, A female (age 67) and male (age 64) with meningitis with unidentified pathogens. Abbreviations: ETL, emission threshold level; SNR, signal-to-noise ratio.