Changes in extended high frequency hearing following middle ear surgery.

Abstract

Middle ear surgery is frequently performed to eradicate disease and improve hearing. It is reported that thresholds in the extended high frequency (EHF) range (8 – 16 kHz) frequently deteriorate following middle ear surgery, despite improvements to air conduction thresholds and low rates of sensorineural hearing loss to conventional frequency (CF) range (0.25 – 8 kHz) thresholds. Currently, there is a lack of data exploring the nature of post-operative EHF hearing loss, and whether changes are transient or longstanding.

A TEAC HP-F100 bone conduction transducer capable of measuring EHF thresholds was modified and calibrated on 23 normal hearing participants using the real-ear calibration technique. EHF bone conduction data was measured in participants undertaking stapedotomy, ossiculoplasty and tympanoplasty surgeries. Air and bone conduction pure tone audiometry was assessed in four participants from 0.25 - 16 kHz prior to middle ear surgery and at approximately one week, one month and three months following surgery. EHF hearing impairment was evident in all four cases, demonstrating that elements of both sensorineural and conductive hearing loss can occur following middle ear surgeries. EHF sensorineural hearing loss, which partially recovered after three months, was demonstrated in the two stapes participants, whereas conductive hearing loss was more evident in the ossiculoplasty and tympanoplasty participants. Post-operative EHF hearing loss was indicative of potential intra-operative cochlear trauma or changes to the transmission mechanisms of the middle ear.

To assess long-term changes to EHF air conduction thresholds, pure-tone EHF audiometry was performed in two participants who had undertaken stapes surgeries previously, and who had formerly documented EHF hearing impairment. EHF bone conduction thresholds were also established in these two cases for the first time, revealing an EHF hearing loss which contained both sensorineural and conductive components in both cases. Assessing EHF threshold measurements over time in participants undergoing middle ear surgery may be a useful tool to monitor the long-term impacts of surgical factors on hearing outcomes.