SP/AP Area Ratio in the Diagnosis of Ménière's Disease

Abstract

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 Ménière's disease (MD). However, the incidence of an elevated SP/AP amplitude ratio in the general MD population is only approximately 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 SP-AP 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.

Amplitude and area ratios of summating potential/action potential (SP/AP) in Meniere's disease

“…The SP and AP areas were also measured referring to previous studies [8]. An image of a wave form of AP and SP complex was captured by an image scanner (ES 2200, Epson, Japan).…”

“…Therefore, a more sensitive diagnostic tool for MD and ELH has been anticipated. Recently, it was reported that the SP/AP area curve ratio in extratympanic ECochG significantly improved the diagnostic sensitivity of ELH in comparison with conventional SP/AP amplitude ratio in MD [8,9]. Ferraro and Tibbils [8] showed that the SP/AP area curve ratio was abnormally high in 44% of probable cases of MD (11/25) as well as in 90% of definite cases of MD (18/20).…”

“…Recently, it was reported that the SP/AP area curve ratio in extratympanic ECochG significantly improved the diagnostic sensitivity of ELH in comparison with conventional SP/AP amplitude ratio in MD [8,9]. Ferraro and Tibbils [8] showed that the SP/AP area curve ratio was abnormally high in 44% of probable cases of MD (11/25) as well as in 90% of definite cases of MD (18/20). Devaiah et al [9] compared SP/AP amplitude ratio and SP/AP area ratio in eight patients with possible MD, and showed that abnormally high values were observed in seven of the eight patients in the SP/AP area curve ratio, whereas they were observed in only four patients in the SP/AP amplitude ratio.…”

Avaliação dos potenciais evocados cocleares após lesão do utrículo por eletrocauterização

“…One might speculate that more-experienced surgeons will perform more precise, and involuntarily less traumatic, lesions. In our experiment, performed by the same surgeon with experience in this technique performed in a previous study 11 , we demonstrated that the sheep utricle is capable of withstanding surgical trauma without complete loss of cochlear function.…”

“…The analysis of the variable area was included in our study since it also represents a good parameter of interpretation of nerve conduction studies. The calculation of the SP/AP area ratio, described in some studies 11,12 and used in the present study, stands out as a very sensitive test to assess cochlear response to hearing stimulus in Ménière's disease, as well as in situations in which the cochlea is at risk due to surgical injury 13 . Since SP/AP area ratio is the integral of a function of the combination between amplitude and duration of action potential, Riemann integral reflects the number and synchronism of activated nerve fibers.…”