Abstract
Before 1964, electrocochleography (ECochG) was a surgical procedure carried out in the operating theatre. Currently, the newest application is also an intra-operative one, often carried out in conjunction with cochlear implant surgery. Starting in 1967, the recording methods became either minimal- or not-invasive, i.e., trans-tympanic (TT) or extra tympanic (ET), and included extensive studies of the arguments pro and con. I will review several valuable applications of ECochG, from a historical point of view, but covering all 75 years if applicable. The main topics will be: (1) comparing human and animal cochlear electrophysiology; (2) the use in objective audiometry involving tone pip stimulation—currently mostly pre cochlear implantation but otherwise replaced by auditory brainstem response (ABR) recordings; (3) attempts to diagnose Ménière’s disease and the role of the summating potential (SP); (4) early use in diagnosing vestibular schwannomas—now taken over by ABR screening and MRI confirmation; (5) relating human electrophysiology to the effects of genes as in auditory neuropathy; and (6) intracochlear recording using the cochlear implant electrodes. The last two applications are the most recently added ones. The “historical aspects” of this review article will highlight the founding years prior to 1980 when relevant. A survey of articles on Pubmed shows several ups and downs in the clinical interest as reflected in the publication counts over the last 75 years.
Highlights
Electrocochleography (ECochG) is a technique for recording sound-evoked cochlear and auditory nerve population responses from the round window, the cochlear wall, eardrum and external ear canal
Hearing improvement induced by the glycerol test did not produce a change in the summating potential (SP)/AP ratio—likely because both SP and AP increased or decreased together—and there was no significant difference between the glycerol test results and the incidence of an enhanced SP
auditory brainstem response (ABR) were recorded in response to electrical stimulation in five of six subjects, whereas no evoked CAP (eCAP) was evoked from the auditory nerve through the cochlear implant
Summary
Electrocochleography (ECochG) is a technique for recording sound-evoked cochlear and auditory nerve population responses from the round window, the cochlear wall (promontory), eardrum and external ear canal. Of relevance for diagnostics of Ménière’s disease, to be reviewed later, is FIGURE 4 | ECochG recordings obtained from three representative ears showing normal CAP threshold, elevated CAP threshold and the absence of neural response at maximum stimulation intensity (clicks, 120 dB p.e. SPL). This shows a series of typical input-output curves for Ménière ears with the median curve obtained in 20 normal ears. Much attention was paid on the so-called low- and high-amplitude and latency functions with a cross-over point at the bifurcating CAP waveform (see Figure 5) These typical waveforms and their presumed reflection of the underlying disturbances in the peripheral hearing organ can be studied more insightfully by using the narrow-band response derivation. Similarity of the CAP waveforms for the Ménière ear and the neuroma ear is completely removed when looking at the narrow band responses
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