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Electrocochleography for the Diagnosis of Ménière's Disease: The Wrong Stimulus.

To the Editor: We wish to comment on the recent article entitled ‘‘Click stimulus electrocochleography versus MRI with intratympanic contrast in Menière’s disease: A systematic review’’ by Ziylan et al. (1). The authors discussed four relevant articles (2–5). The three employing click stimulus electrocochleography (EcochG) (2–4) were used for their conclusion which was that ‘‘there is relative low sensitivity and negative predictive value for, click stimulus electrocochleography compared with MRI with intratympanic gadolinium administration for detecting endolymphatic hydrops in patients with Ménière’s disease.’’ It highlights the reasons for widespread scepticism of electrocochleography as a reliable test for Ménière’s disease (6). Three authors (2–4) have used a click SP/AP ratio of >0.33 which is not diagnostic for endolymphatic hydrops and which will have enhanced its apparent sensitivity. The sensitivity and specificity figures for tone-burst ECochG were not available from our data as we compared the two tests with a clinical diagnosis of Ménière’s disease, rather than using magnetic resonance imaging (MRI) as the ‘‘gold standard’’ of this condition. We have subsequently revised our data in this manner to compare tone-burst ECochG in our patients with an MRI scan demonstrating endolymphatic hydrops. Table 3 in (1) has been reproduced in Table 1 here to include our own results for click and tone burst stimuli with a diagnostic sensitivity for clicks of 28.6 and 92.9% for tone bursts. As is mentioned in our article, we think that tone burst ECochG may detect electrophysiologic changes from pathologic basilar membranes with more sensitivity than the degree of hydrops that can be detected currently with MRI scanning. That cochlear endolymphatic hydrops could be ascertained by electrophysiological testing arose from a publication by Gibson et al. (7) in 1977. Using transtympanic electrocochleography they claimed that an enlarged direct current component of the click stimulus action potential (AP) called the summating potential (SP) could be an indication of cochlear hydrops. This was confirmed by Coats et al. (8) which lead to numerous publications using an SP/AP ratio of 0.33 to 0.35, and to an eventual disenchantment as to the reliability of the test (6). It was further compounded by audiologists using remote eardrum or canal electrodes that give responses approximately one-tenth of the magnitude of those achieved by direct contact with the cochlea. Subsequently, Gibson (9) by comparing click response SP/AP ratios of Ménière’s ears with ears with comparable hearing instead of Ménière’s patient opposite ears, retracted this claim, unless the SP/AP ratio reaches a severe criterion of 0.5. Meanwhile, Gibson (9) had employed tone bursts as a stimulus , giving the test a significantly higher sensitivity and specificity, confirmed by others (5,10). It cannot yet be achieved using a remote eardrum or canal electrode. Nonetheless, click stimulus EcochG continues to be employed as a diagnostic test for Ménière’s disease despite the evidence that it should abandoned. The recent advent of MRI inner ear imaging to detect hydrops in Ménière’s disease (11) has predictably inspired studies comparing its sensitivity with that of electrocochleography (1). Images and conclusions from MRI inner ear imaging seem to be confounded by variables such as brand of scanner, head coil specifications, and the possibility that gadolinium entry may be uneven and favor the vestibule. Meanwhile, transtympanic tone burst electrocochleography remains the most simple, cheap, and sensitive test for detecting