Characterizing a Joint Reflection-Distortion OAE Profile in Humans With Endolymphatic Hydrops

Area of Science:

• Otoacoustic Emissions (OAEs)
• Inner Ear Physiology
• Meniere Disease Pathophysiology

Background:

• Endolymphatic hydrops (EH) is characterized by increased endolymph volume, leading to distension of inner ear membranes.
• Otoacoustic emissions (OAEs) are sound emissions generated by the cochlea, reflecting its functional status.
• Joint OAE profiles, combining distortion- and reflection-class emissions, offer a comprehensive assessment of cochlear function.

Purpose of the Study:

• To characterize the joint otoacoustic emission (OAE) profile in individuals with endolymphatic hydrops (EH).
• To investigate the utility of joint OAE profiles for clinical assessment and monitoring of EH.
• To compare OAE characteristics between individuals with EH and normal hearing controls.

Main Methods:

• 16 adults with diagnosed EH and 18 age-matched normal hearing (N) adults participated.
• Cubic distortion product (DP) OAEs and stimulus-frequency (SF) OAEs were measured and analyzed as a joint OAE profile.
• OAE level, input/output functions, and phase-gradient delays were assessed in the apical cochlear region.

Main Results:

• Both EH and N groups showed reflection emissions higher than distortion emissions.
• OAE source strength and level were significantly reduced at low frequencies in the EH group, more so for distortion than reflection emissions.
• EH ears exhibited a steepened growth slope for reflection emissions and an elevated compression knee for distortion emissions.

Conclusions:

• Endolymphatic hydrops impacts both distortion and reflection OAE generation differently.
• Distortion-product OAEs (DPOAEs) were more affected by EH than stimulus-frequency OAEs (SFOAEs).
• A joint OAE approach is valuable for concurrently assessing intracochlear generation processes affected by hydrops.