SP/AP Area Ratio in the Diagnosis of Ménière's Disease Conventional analysis of the click-evoked electrocochleogram includes measurement of the amplitudes of the cochlear summating potential (SP) and auditory nerve action potential (AP) to derive the SP/AP amplitude ratio. It is now well documented that an amplitude ratio where SP is elevated relative to AP may be a positive finding ... Clinical Focus: Grand Rounds
Clinical Focus: Grand Rounds  |   June 01, 1999
SP/AP Area Ratio in the Diagnosis of Ménière's Disease
 
Author Affiliations & Notes
  • John A. Ferraro, PhD
    Hearing and Speech Department, University of Kansas Medical Center, 39th and Rainbow Boulevard, Kansas City, KS 66160-7605
  • Richard P. Tibbils
    Hearing and Speech Department, University of Kansas Medical Center, 39th and Rainbow Boulevard, Kansas City, KS 66160-7605
  • Corresponding author: e-mail: jferraro@kumc.edu
Article Information
Hearing Disorders / Balance & Balance Disorders / Clinical Focus / Grand Rounds
Clinical Focus: Grand Rounds   |   June 01, 1999
SP/AP Area Ratio in the Diagnosis of Ménière's Disease
American Journal of Audiology, June 1999, Vol. 8, 21-28. doi:10.1044/1059-0889(1999/001)
History: Received November 18, 1997 , Accepted December 22, 1998
 
American Journal of Audiology, June 1999, Vol. 8, 21-28. doi:10.1044/1059-0889(1999/001)
History: Received November 18, 1997; Accepted December 22, 1998

Conventional analysis of the click-evoked electrocochleogram includes measurement of the amplitudes of the cochlear summating potential (SP) and auditory nerve action potential (AP) to derive the SP/AP amplitude ratio. It is now well documented that an amplitude ratio where SP is elevated relative to AP may be a positive finding for endolymphatic hydrops in patients suspected of having Meniere's disease (MD). However, the incidence of an elevated SP/AP amplitude ratio in the general MD population is only ≈60%. This relatively low value necessitates efforts to improve the diagnostic sensitivity of electrocochleography (ECochG) for MD. A review of early and more recent literature in this area indicates that consideration of both the amplitude and duration of ECochG components may help to achieve this goal. The present study combined these features to measure the "area" of the SPAP complex in normal and MD populations. A software routine was used to measure the amplitude x duration area of the SP-AP complex in (a) normally hearing adults with normal SP/AP amplitude ratios (Group 1), (b) confirmed MD patients with elevated SP/AP amplitude ratios (Group 2), and (c) probable MD patients with normal SP/AP amplitude ratios (Group 3). Ninety percent of the confirmed MD patients in Group 2 displayed elevated SP/AP area ratios relative to the normative value established from Group 1. In addition, almost half of the probable MD patients from Group 3 displayed elevated area ratios. These findings indicate that measurement of the SP/AP area ratio holds promise for improving the sensitivity of ECochG in the diagnosis of MD.

Acknowledgments
Portions of this study were presented at the 1997 Biennial Symposium of the International Electric Response Audiometry Study Group, Memphis, TN, in July 1997.
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