This guide outlines how you can use wideband acoustic immittance (WAI or MEPA) for differential diagnosis of conductive hearing loss (CHL) in adults with an intact tympanic membrane and aerated middle-ear
According to a recent report funded by the NIH (Nakajima et al., 2012), CHL with an intact TM and aerated middle-ear can be associated with three conditions: ossicular fixation (usually from otosclerosis), ossicular discontinuity, and superior semicircular canal dehiscence (SCD). They are sometimes hard to differentially diagnose in the clinic, and may require surgery or expensive tests to fully investigate. Nakajima et al. showed how to use MEPA and an audiogram to aid in the differential diagnosis in an office setting.
This test is applicable to patients with CHL, defined as >10 dB air-bone gap (ABG) on pure-tone audiometry (averaged over either 500, 1000, 2000 Hz or 250, 500, 1000 Hz), and with an intact TM and aerated middle ear.
First, some definitions:
Fig 6B in Nakajima et al. (2012) illustrates how the 3 conditions tend to cluster when plotted as absorbance level difference against the ABG.
To aid in interpretation:
In Nakajima's study, sensitivity and specificity were good (from their Table 1), but they are based on a small number of subjects (N=31 ears), so caution should be used in applying these results:
|Semicircular canal dehiscence|
This research was published after HearID's release, so the ADL calculation isn't included in these versions. Subsequent versions of HearID will include the absorbance difference level relative to the specified mean norm. To make this calculation manually:
Nakajima, H. H., Pisano, D. V., Roosli, C., Hamade, M. A., Merchant, G. R., Mahfoud, L., Halpin, C. F., Rosowski, J. J., and Merchant, S. N. (2012). "Comparison of ear-canal reflectance and umbo velocity in patients with conductive hearing loss: a preliminary study," Ear Hear. 33, 35-43.
Rosowski, J. J., Nakajima, H. H., Hamade, M. A., Mahfoud, L., Merchant, G. R., Halpin, C. F., and Merchant, S. N. (2012). "Ear-canal reflectance, umbo velocity, and tympanometry in normal-hearing adults," Ear Hear. 33, 19-34.
conductive hearing loss, CHL, umbo velocity, middle-ear wideband reflectance, differential diagnosis, semicircular canal dehiscence, superior canal dehiscence syndrome, SCDS, stapedovestibular ankylosis, otosclerosis, stapedectomy.
This guide was compiled by Mimosa Acoustics from peer-reviewed scientific research (funded by the NIH) to assist clinicians in interpreting results from HearID and OtoStat. It will be updated as new research becomes available. HearID and OtoStat do not provide diagnoses. All diagnostic decisions are the responsibility of the clinician.
Version 1.1, 3 April 2015.
Prepared by Judi Lapsley Miller, PhD.
Version 1.0 was reviewed by John Rosowski, PhD, Professor of Otology and Laryngology, Massachusetts Eye and Ear Infirmary, 9 July 2013.