Tinnitus (TI) is held to be a symptom that is usually associated with hearing losses of various origin (Chaba, 1982). This notion was, at least partially, supported by Berlin. In a number of patients with Tl, who did not show hearing losses on discretefrequency audiometry, he demonstrated small circumscribed losses at between frequencies by means of Békésy audiometer with a continuous-frequency sweep. Berlin then proposed that in some other patients, in whom hearing losses are not evident, these may be located in the highfrequency region, beyond the reach of conventional audiometry, i.e., beyond 8 kHz.

The discovery of the presence of spontaneous mechanical activity within the cochlea has lead to speculation that this may be responsible for some forms of cochlear tinnitus. However, attempts in the present study, and also in other studies from the literature, to show a relationship between the measured spontaneous acoustical emissions in the external meatus and the subjective pitch matching of tonal tinnitus have not been very successful. In only two tinnitus patients out of 53 could an acoustic emission be detected which appeared to correlate with the subjective complaint.

A simple apparatus for the detection of acoustical emissions is described and the possible mechanisms for the generation of cochlear tinnitus are discussed.

Vestibular evoked responses to repetitive acceleration stimuli were recorded by skin electrodes in cats using filtering and averaging techniques. The response is made up of six—eight waves during the first 10 msec following the stimulus. Longer latency myogenic responses had large amplitude and disappeared following the paralysis of the animals. The neurogenic waves disappeared after the destruction of both inner ears or the excision of both eighth nerves and following death. Destruction of the inner ear, or excision of the VIIIth nerve on one side leads to response patterns of excitation vs. inhibition when appropriate excitatory and inhibitory acceleration stimuli are applied. The possible generators of the evoked responses are discussed in the light of the physiology of the vestibular pathways, and the results of the present experiments suggest that the generators of the first and second waves are the vestibular nerve and vestibular nucleus respectively. In addition, the vestibular evoked response seemed to be more sensitive to ischemia of the brain than the auditory brainstem evoked response and may therefore reflect better changes in brain function.

A few weeks ago I came across a very remarkable old book. I should like to tell you about it as a contribution to the history of medicine regarding the treatment of tinnitus.

Electrical stimulation of the auditory system results in auditory perception as well as auditory suppression. Historically, this is well documented. The recent application of advances of high technology and microsurgery of the ear have allowed basic science and clinical investigation to have access to electrical stimulation of the auditory system and its response. It is historically of great interest that such investigation in the past always involved attempts for evaluation and treatment for either auditory stimulation and/or auditory suppression. I believe the work of Aran (1981) reawakened recent interest in electrical stimulation of the auditory system for tinnitus suppression as well as auditory stimulation. Briefly, in his investigation of a deaf patient, he observed the following: (a) negative currents were more effective than positive currents for auditory stimulation; (b) positive current pulses reduced (suppressed) the intensity of tinnitus; (c) electrical stimulation in deaf patients by negative currents resulted in some sound perception. (In the congenitally deaf patients, it is difficult to evaluate the sensation produced); (d) the intensity of positive pulses necessary to suppress tinnitus is always higher than that of negative pulses resulting in auditory perception; (e) for positive pulses, the range between the threshold of tinnitus suppression and auditory perception when pulses of intermediate intensity are used, without inducing auditory perception, is wide enough to achieve total tinnitus suppression. (In other words, the current effective for electrical stimulation suppressing tinnitus is at a strength well below that producing auditory sensation); (f) negative electrical pulses can produce two different sounds-tinnitus and an auditory sensation; (g) electrical stimulation via the promontory and/or round window can be used both for auditory stimulation as well as for auditory suppression.

One of the first things one should do when trying to understand the origin of tinnitus (TI) is to take a look at signal transmission in the auditory system in general and at the coding mechanisms in particular.

The use of electrical stimulation of the ear for artificial auditory stimulation of the profoundly deaf, as well as for the suppression of tinnitus when it is exceedingly annoying (Cazals et al., 1978) has been extensively discussed here, but I would like to present now other possible clinical applications of electrical stimulation. These concern its use as a new tool in objective audiometry

The experience that I am going to describe now is inspired initially by observation of one patient who was being stimulated electrically in order to induce hearing. This was some years ago. Our attention to this problem was raised by chance when we asked him, in the simple original threshold tests that we were carrying out at the time, to raise his arm whenever he heard the sound. We were stimulating him and he kept raising his arm in fact whenever we were switching off. This was very irritating. We kept turning to our engineers and said ‘I am sure you must have switched it round’ and the apparatus was examined many times. It was only at the end of this that we realised that in fact what was happening was that we were suppressing his tinnitus in an acute manner.

Our early experience with the use of cochlear implants indicated that chronic electrical stimulation to the inner ear tends to help tinnitus. For this reason we have been investigating the use of electrical stimulation as a treatment for the symptom of tinnitus.

A non-invasive method of external electrical stimulation has been used in 13 patients in an attempt to control the subjec-tive tinnitus. This investigation has been part of an on-going project on electrical stimulation for tinnitus suppression-auditory stimulation by the Division of Otolaryngology—Center for Communica-tion Sciences, Downstate Medical Center, Brooklyn, New York.

The primary goals of the physician to be achieved for the tinnitus patient are: (a) Exclusion of disease entity(ies) benign and/ or malignant which may be the cause of tinnitus by performing a complete neuroto-logic examination, (b) Control/treatment of tinnitus based upon a classification of the tinnitus. In both cases, an attempt is made to objectivize the subjective symptom of tinnitus. Both classification and evaluation of tinnitus are fundamental for treatment.