Extended-high frequency (EHF) audiometry has been recommended for early identification and monitoring of cochlear damage. The main reason is that cochlear damage occurs at frequencies higher than 8000 Hz before the thresholds at conventional frequencies (250 Hz to 8000 Hz) are affected. Furthermore, hair cell damage at the frequencies higher than 8000 Hz cannot be detected using conventional audiometry. Thus, it is important that cochlear damage be detected earlier to reduce the progression of hearing loss. However, utilizing EHF audiometry for monitoring individuals at risk of developing cochlear damage is at present an inconsistent procedure, as it is not well established in standard clinical care. As the interest in EHF audiometry is increasing, it is important to determine to what extent EHF audiometry may be used for the early identification and monitoring of cochlear damage, as the clinical value of the procedure still has to be determined. The present systematic review was conducted to investigate existing evidence regarding the potential value of EHF audiometry for the early identification and monitoring of cochlear damage.
A systematic review was conducted using peer-reviewed literature in order to identify a large number of relevant publications that would assist in answering the research question. The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA-P) checklist was used as a guideline. Four electronic databases were utilised in this study to search for the relevant publications, namely Academic Search Complete (Ebscohost), Medline (Ebscohost), Scopus, and PubMed. A manual secondary search was conducted using the reference list of relevant reports already identified during the primary search. Reports were selected according to predefined inclusion and exclusion criteria and selection was followed by data extraction.
A total of 502 articles were identified and screened. Only 16 of the articles were compatible with the criteria and therefore included in the systematic review. These 16 articles included cross-sectional and cohort studies, which were evaluated using the Newcastle-Ottawa scale (NOS) for quality assessment. A factor that influenced the conclusions of the systematic review, is that all the studies were heterogeneous in nature. These differences had an influence on the practicability of comparing these studies. Due to a variety of equipment used to measure EHFs, no conclusion could be reached on preferred equipment. It is suggested that individuals should be tested with the same equipment over time for intra-monitoring of the EHFs to increase test-retest reliability. Despite the variations, the use of EHF audiometry was considered to be a valuable procedure for the early identification of cochlear damage by seven studies (43.75%). The other studies included in the systematic review suggested that the procedure would be useful when combined with conventional audiometry (six studies – 37.5%) or distortion product otoacoustic emission (DPOAE) testing (two studies – 12.5%), or both methods (one study – 6.25%).
Comparing EHF audiometry to conventional audiometry and DPOAE testing, the majority of the studies included in the systematic review (10 studies - 62.5%) found that EHF audiometry was the most sensitive procedure to identify cochlear damage. Many studies reported that the entire EHF threshold range was deteriorating in participants at risk for developing cochlear damage. The majority (seven) of the studies included, however, determined that 14 000 Hz and/or 16 000 Hz were the most sensitive to cochlear damage, especially in participants with NIHL. In conclusion, the systematic review demonstrated that EHF audiometry may be beneficial in the clinical assessment of cochlear damage both for early identification and for monitoring purposes. Including this procedure in clinical practice will allow practitioners to identify cochlear damage earlier and possibly preserve the hearing of these individuals at risk.
Dissertation (MA (Speech-Language Pathology and Audiology))--University of Pretoria, 2021.