The Application of Otoacoustic Emissions in Detecting Carriers of Autosomal Recessive Non-Syndromic Hearing Loss
Level: Intermediate
Number of slides: 22
Abstract:
Oral presentation from the 2004 IAPA meeting:
Objectives: To determine whether sub-clinical auditory anomalies are present in carriers of autosomal recessive Non-Syndromic hearing loss (ARNSHL) and whether such changes can be detected using otoacoustic emissions (OAEs), a test of outer hair cell integrity. The possible association of any OAEs abnormalities and the presence of mutations in the GJB2 gene (Cx26) will be explored.
Methods: The study was designed as a case-control study. OAEs were recorded in 10 obligate carrier parents who were positive for mutations of the Cx26 gene and 10 presumed carrier parents from families who satisfied criteria of ARNSHL but did not screen positive for the GJB2 gene. These were compared to 10 age and sex matched controls. In all subjects OAEs, including transient OAEs, distortion product OAEs, and a test of medial olivocochlear (MOCB) efferent suppression, were carried out.
Results: OAEs abnormalities were detected for both carrier groups. TEOAE anomalies were more predominant in those parents that did not carry mutations for the Cx26 gene. Of particular note is the finding of high prevalence of absent TEOAE responses for the mid and high spectral bands for both carrier subgroups. DPOAE data again showed greater significant reductions for the Cx 26 -ve carriers especially in the mid and high frequency spectral bands. Finally, the MOCB efferent test detected significant reduced suppressions only for those parents that did not carry mutations in the GJB2 gene.
Conclusions: The study provides further evidence for the value of OAEs measurements in unveiling subclinical cochlear dysfunction in autosomal recessive carriers of hearing loss. The feature of high OAEs absent responses at 2.0 and 4.0 kHz shows susceptibility of the mid and high frequency regions. Further evidence of genetic heterogeneity for those carriers that carried no mutations for the GJB2 gene, was shown by the finding of reduced MOCB efferent suppression test in these carriers only.