Idiopathic Sudden Sensorineural Hearing Loss: Should Otoacoustic Emissions Be Added to the Monitoring Protocol? A Systematic Review

Idiopathic sudden sensorineural hearing loss (ISSNHL) refers to a loss of hearing, most commonly unilateral, that occurs suddenly (<= 72 h) with no identifiable cause or etiology. To date, there is no standard protocol to predict prognosis (hearing recovery) for patients with ISSNHL. However, studies have shown that changes in otoacoustic emissions (OAEs) often occur prior to changes in audiometric hearing thresholds. OAEs originate from the electrochemical motility of the outer hair cells (OHC) and reflect the integrity of the inner ear, specifically the cochlear amplifier. Therefore, OAEs may be useful as a prognostic predictive factor in patients with ISSNHL from the initial onset of symptoms through recovery. A systematic review of the literature was undertaken to assess the relationship between pure tone thresholds, OAEs, and subjective hearing improvement and/or recovery. Fourteen studies were identified for inclusion, and they overwhelmingly support the inclusion of OAEs in the protocol to monitor ISSNHL recovery. This finding supports the development of a standard diagnostic protocol that includes OAEs to predict patient hearing outcomes.