Audiometric and electrophysiological correlations in sudden deafness

Electrophysiological measures were collected over 3 years in 61 cases of sudden deafness. Electrocochleography (ECochG) and Auditory Brainstem Responses (ABR) using click stimuli were recorded down to threshold and compared with pure-tone and speech audiometry data. This study was intended to precise 1) localization of the disorder, 2) prognosis, 3) analysis of the contribution of different frequencies in click-evoked responses. The following results are: 1) In most cases the observations indicated that the inner ear was affected. 2) However, in 19 cases electrophysiological measures revealed a retrocochlear involvement. Four acoustic neuromas were evidenced by CT scan. In 3 of these, audiometric and electrophysiological thresholds returned merely to normal levels after medical treatment, while brainstem responses remained delayed. Thus in these cases recovery would seem to be related to release of vascular compression in the auditory internal meatus. 3) When the latencies of the VII nerve potential (N1) and wave V (PV) were short, and the therapy undertaken early, a good recovery was often obtained. 4) When recovery occurred on low frequencies only, the electrophysiological responses to the click showed slight latency increases.

The etiology and pathogenesis of otitis media with effusion. A review

Otitis media with effusion (OME) has been well known for many years. Thus Politzer described this condition as early as 1878 and used a transtympanic grommet in its treatment. Nevertheless, this disease entity fell into oblivion during the first half of the present century.

Electrical stimulation of the ear: experimental studies

The possibility of stimulating the ear by way of an electrode on the round window in order to relieve tinnitus or to produce auditory sensations has been investigated experimentally in guinea pigs. The deleterious effects of DC currents applied to a normal cochlea clearly demonstrate that this means is unsuitable for use in relieving tinnitus in hearing patients. Although AC currents do not cause further damage in ears with the organ of Corti already destroyed by aminoglycosides, the effects of DC currents in such cases have still to be investigated before they can be recommended for the relief of tinnitus in totally deaf patients. Electrical stimulation of the round window combined with masking has made it possible to record responses of auditory neural elements from the eighth nerve to the auditory cortex. This technique could be promising for the basic study of the central auditory nervous system, both experimentally and clinically, and could lead to a more accurate evaluation of candidates for cochlear prostheses.

Electrical stimulation of the ear: clinical applications

Electrical stimulation of the ear in humans was performed with an extracochlear electrode on the round window. With positive currents, suppression of tinnitus could be induced. With negative currents, auditory sensations were evoked. Since electrical stimulation with DC currents may be hazardous in the long term, it cannot yet be proposed for the suppression of tinnitus. However, electrically evoked hearing sensations with AC currents seem to be of definite interest for some totally deaf patients.

Electrocochleographic measures of cochlear frequency selectivity in hearing loss of cochlear origin

One of the basic functions of the cochlea is to separate out the frequency components which are present in complex sounds. This frequency selectivity can be measured objectively in the clinic from the compound action potential (AP) during transtympanic electrocochleography, using a two-tone masking paradigm. An AP is evoked by a test tone near to threshold, and a measure is made of the frequency bandwidth over which this AP can be suppressed by a continuous pure tone masker. In normal-hearing subjects, this frequency range is 0.17-0.39 octaves (test tone pip at 4 or 8 kHz). In patients with cochlear deafness, this bandwidth is greatly enlarged, ranging from 0.42-2.2 octaves. Some observations suggest that a deterioration in frequency selectivity can occur before any important threshold elevation. The early detection of this could be a warning sign of potential cochlear susceptibility. In the clinic the measure is already of use: a deterioration is a positive indication of cochlear involvement in a hearing loss.

Transtympanic and surface recordings in the diagnosis of retrocochlear disorders

A series of patients presenting with subsequently surgically confirmed central tumour involving the auditory pathways were investigated using both transtympanic electrocochleography (TT ECochG) and surface recordings of brainstem evoked responses (BER). While ECochG allows a detailed study of peripheral function, BER allow the investigation of neural conduction up to the level of the inferior colliculus. Valuable information can be obtained from: (1) comparison of the amplitudes of the sensory and neural components of the ECochG; (2) comparison of ECochG, BER and auditory thresholds; (3) time interval measurements between the auditory nerve response (N1 on the ECochG) and the inferior colliculus (wave P4-5 on BER); (4) contralateral comparisons. Similar measurements performed in pure cochlear pathologies, mainly in Meniere's disease, yielded very significant differences.

Temporary tinnitus suppression in man through electrical stimulation of the cochlea

While investigating the possibilities of electrically induced hearing in cases of profound deafness, we observed that very often an appropriate stimulation of the cochlea could result in tinnitus cancellation. We present here a progress report on that phenomenon, including 15 subjects. Such a cancellation was restricted to tinnitus subjectively localized in the ear under test, we observed no effect on noises localized in the other ear, or centrally. This suppression occurred so long as the cochlea was stimulated and stopped when the stimulation ceased. This phenomenon was very reproducible and did not seem to affect simultaneous normal acoustic hearing. It is hypothesized that this phenomenon acts through an inhibition of abnormal activity of sensorineural elements of the electrically stimulated cochlea.