The apparent effect of superior semicircular canal dehiscence (SSCD) on middle ear- and cochlear impedance has led researchers to investigate the use of wideband acoustic immittance as a screening tool when SSCD is suspected. The purpose of the study was to describe the absorbance characteristics and tympanometric values of ears with confirmed SSCD measured at tympanometric peak pressure (TPP) and at ambient pressure. Wideband Acoustic Immittance was performed at ambient pressure and at TPP on ten participants (12 ears) with confirmed SSCD, as well as on an age- and gender matched control group (12 ears). Inferential statistics were used to determine whether statistical differences existed for the absorbance values at each of the averaged frequencies, the resonance frequency (RF) and tympanometric data between the SSCD and control groups. The mean absorbance of the SSCD group reached a maximum at 890.9 Hz and a minimum at 6349.6 Hz. When testing absorbance at TPP, a statistically significant increase/peak in the absorbance values of the SSCD group (compared to those of the control group) was found from 630 to 890.9 Hz and a decrease from 4489.8 to 6349.6 Hz. Similar patterns were observed for absorbance at ambient pressure. A lower mean RF for ears with SSCD as well as an increased mean admittance magnitude (AM) value at RF was found compared to those of the control group. The peak in absorbance around 890 Hz that was found on SSCD ears in the current study is similar to findings from earlier studies that found a peak in absorbance/notch in reflectance around 1000 Hz, reiterating its use as a screening tool when SSCD is suspected. No significant difference was found between absorbance measured at ambient pressure and at TPP in the current study; however, the stringent inclusion criteria with regard to TPP most likely affected this outcome. As a result of the significant difference in RF of SSCD ears compared to the RF of the control group, the potential value of measuring the RF of the middle ear as well as AM at the RF, to differentiate between mass-and stiffness dominated pathologies, was also illustrated. Further research measuring the AM at RF in normal and pathological ears was suggested for comparison to the current study and to determine its clinical value.
Dissertation (MA (Audiology))--University of Pretoria, 2020.