Characteristics of Mid-Frequency Sensorineural Hearing Loss Progression.

OBJECTIVES: To characterize the progression of mid-frequency sensorineural hearing loss (MFSNHL) over time. METHODS: A retrospective chart review spanning 2012 to 2017 was performed at a tertiary care audiology and neurotology center. Our cohort included 37 patients met the criteria for MFSNHL also known as "cookie bite hearing loss." It was defined as having a 1, 2, and 4 kHz average pure tone audiometry greater than 10 dB in intensity compared with the average threshold at 500 Hz and 8 kHz. RESULTS: Average age at initial presentation was 11.8 years (range, 8 mo to 70 yr). Across all individuals, the average mid-frequency threshold was 47 dB, compared with 27 dB at 500 Hz and 8 kHz. Twenty-three patients (62%) had multiple audiograms with 4-year median follow up time. Average values across all frequencies (0.5, 1, 2, 4, 8 kHz) in the initial audiogram was 37 dB, compared with an average of 39 dB demonstrated on final audiogram. Of those with serial audiograms, only five patients demonstrated threshold changes of 10 dB or more. Of these five patients, only one was found to have clinical worsening of MFSNHL. CONCLUSIONS: MFSNHL is an uncommon audiometric finding with unspecified long-term outcomes. We demonstrated that most patients (96%) with MFSNHL do not experience clinical worsening of their hearing threshold over almost 4 years of follow up. Future prospective studies aimed at collecting longer-term data are warranted to further elucidate the long-term trajectory of MFSNHL patients.