This meeting was conceived as a means of presenting the information to SIT—in a comprehensive, holistic manner. A joining of the aspects of basic sciences and clinical disciplines, as related to SIT. The purpose of the meeting is to provide a practical application of the presentations for the evaluation, treatment, and control of SIT. The goals of our meeting are:

(a) to establish standards for the evaluation and treatment of SIT;

(b) to present recent clinical advances in the diagnosis and treatment of SIT;

(c) to reduce and/or eliminate confusion in the site of lesion diagnosis and the symptom of SIT;

(d) to separate by evaluation the medical diagnosis that is etiology from the symptom and site of lesion of SIT to consider SIT as a separate entity;

(e) to control SIT—to conserve hearing.

As introduction to this meeting I am presenting an overview of the subject of SIT. I hope to emphasize the concepts of epidemiology; theories of mechanisms of SIT; basis science investigations relating to SIT; the state of the art, present and future, relating to SIT. Throughout our meeting stress will be placed upon correlating the basic sciences and the clinical sympton of subjective idiopathic tinnitus.

Tinnitus may be associated with lesions in the auditory system from the external auditory canal to the auditory cortex. So let's begin briefly, at first with the external auditory canal and move centrally. The external auditory canal has a slightly curved course. As one looks in, it is a course directed posteriorly and superiorly, then medially and finally anteriorly and inferiorly. The canal is oval in cross-section, with the long axis of this oval extending from anterior/superior to posterior/inferior. In the adult it averages 27 mm. in length. The outer 1/3 has a cartilaginous skeleton and the inner 2/3 has a bony skeleton. The bony canal wall is convexed anteriorly and inferiorly and this convexity obscures the anterior, inferior portion of the tympanic membrane. There are sebaceous glands and hair in the outer 1/3. The cartilaginous portion of the canal has transverse fissures in the anterior- inferior portion that are the fissures of Santorini.

There are various sources of tinnitus and the generation of the tinnitus is not at all obvious except in the two cases of objective tinnitus, muscular and vascular in origin. I’d like to offer you today an attempt to explain one particular kind of tinnitus. The tinnitus I’m talking about is the one which we usually see associated with an auditory sensitivity loss and with a threshold shift. We find this typically after sound exposure, either TTS or PTS, during the attacks of fluctuant hearing loss, and in the early stages of antibiotic intoxication.

Up until fairly recently, that is maybe 10-15 years ago, our only concern was whether hair cells were present or absent. And then, of course, it was clear that absent hair cells cannot function. There was one early exception and that was the demonstration by Wuestenfeld and Spranger and by Beck and Micheler in Germany, of so-called swollen nuclei.

Perhaps our greatest difficulty in dealing with tinnitus is that our understanding of how sound energy is transformed into neural impulses is still rather theoretical. The transduction process of the hair-cell receptor is still not entirely understood. Nevertheless, Davis’ (1961, 1965) principles of sensory action and his model of the hair-cell transduction process (1965) have provided a useful framework for our thinking and have helped to guide investigations into the sensory physiology of hearing. I would like to review some of these principles in a vein similar to that of Tonndorf (1975). In so doing, I can reveal the strengths and weaknesses of our knowledge of how the ‘ear’ works.

Figure 1 illustrates some of the sailient features of sensory systems in general. Several electrical events are elicited upon stimulation: a receptor potential, a generator potential, and spike-action potentials. The relation of the receptor and generator potentials to the stimulus waveform and to one another depends upon the specific method of coupling the stimulus energy to the receptor, and the characteristics of the connection between the receptor and the sensory neuron.

Medical audiologic evaluation of the patient presenting the primary symptom of tinnitus is an attempt to objectivize the subjective complaint. Tinnitus classification depends upon diagnostic information obtained from the medical-audiologic assessment and includes multi-disciplinary inter- pretation of these data by the audiologist and the otologist working as a team.

Test data obtained from 112 cases, 64 males with a mean age of 56.0 and 58 females with a mean age of 48.9 years, referred for medical-audiologic assessment with the chief complaint of tinnitus, indicate that site of lesion obtained audiologically, site of lesion obtained otologically, and site of lesion of the tinnitus need not necessarily be identical (Table I). In our clinic, medical-audiologic assessment for the complaint of tinnitus consists of cochleo-vestibular evaluation and tinnitus evaluation.

Briefly, cochleo-evaluation consists of pure-tone audiometry; speech audiometry, including speech reception threshold and speech discrimination testing; tone-decay testing; short-increment sensitivity index; impedance audiometry consisting of tympanometry, acoustic reflexes (contralateral and ipsilateral) reflex-decay testing, and the Metz test for recruitment.

This paper concerns the results of 200 patients with tinnitus as a primary symptom. Sixty-nine patients formed a pilot study and are not discussed here. Full data are available on 131. The object was to examine each patient in as great detail as possible to see if any significant correlation could be found between different factors involved in their tinnitus. A previous study by Reed (1960) failed to show significant correlation between the variables analysed.

All data were recorded on specially prepared questionnaires. The first involved details of occupation, noise exposure, previous illness, family history of deafness or tinnitus, exposure to ototoxic drugs, details of previous ear disease, hearing aid experience, hearing problems and the incidence of problems at home and at work. The second questionnaire asked specific questions about the tinnitus, particularly its subjective loud- ness rating, variability and factors affecting it. The third questionnaire was used for recording details of otological and audiometric assessment, including the subjective synthesis.

The typical workup for tinnitus patients includes a medical examination, an audiometric assessment, a tinnitus evaluation and finally management of the patient. The means of managing the patient can involve drug therapy, biofeedback or masking. However, regardless of the treatment of choice, most patients undergo, at least to some degree, parts of the three initial evaluations. Our task is to describe, in part, the use of the audiogram in managing the tinnitus patient.

The audiometric work-up for the tinnitus patient does not differ greatly from the typical audiometric assessment performed for diagnostic purposes or a hearing aid evaluation. This procedure includes pure tone testing (air conduction and bone conduction), impedance audiometry and speech testing. Special auditory tests are performed only when additional diagnostic information is indicated. The only major difference in the procedure involves presenting pressure through the probe tip without the accompanying probe tone. This gives the clinician an indication as to whether or not atmospheric pressure changes might affect the patient's tinnitus.

A patient presenting a chief complaint of tinnitus poses an interesting problem to the clinician. Since tinnitus is a symptom and not a disease, our job as diagnosticians is to determine if the tinnitus is associated with hearing loss and to screen for retrocochlear involvement. At Temple Hospital, a patient with tinnitus is examined like any other patient. A thorough history is taken and a complete audiologic and otologic evaluation is done. Patients are then referred for brain-stem-evoked response audiometry (BSERA) according to the protocol shown in Table I. Patients are referred if they have unilateral hearing loss, unilateral or bilateral tinnitus, tinnitus uncorre- lated with hearing loss, vestibular complaints, asymmetric hearing loss, and progressive hearing loss. In addition, screening X-rays and/or blood tests might be ordered. Plesiotomograms of the temporal bone are taken to screen for the presence of a space-occupying lesion in or around the internal auditory meatus.

Masking in psychoacoustic experiments means that the perception of one acoustic stimulus, the signal, is over-ruled by the introduction of another acoustic stimulus, the masker. Signal and masker will compete with each other in a predictable way, as noted by Wegel and Lane (1924), and by Zwicker and Feldtkeller (1967), among others.

The interaction of signal and masker is described by masking curves, which can be thought of as a contour-line of the neural elements involved in processing signal and masker. Thus the masking curves reveal some of the parameters of the signal. Therefore masking experiments can be used to analyse signals otherwise not easily investigated. This was my purpose in studying the masking of tinnitus.

Three main features turned out to be of special interest:

1. the influence of frequency, spectrum and intensity, both of the tinnitus and of the masking stimuli;

2. the temporal pattern of the masking process;

3. binaural masking effects.

Various forms of sensorineural hearing loss today represent our greatest unsolved challenge. The cochlear implant, brainstem-evoked response audiometry, improved forms of electro-acoustic amplification, audiologic rehabilitation, better ways of delivering comprehensive services to the public, and, of course, the tinnitus masker, are significant developments.

Thirty years of experience with the hearing impaired has convinced me that tinnitus causes as much suffering and anguish, if not more, than hearing loss itself. Who among us has not been frustrated by our inability to provide relief to the tinnitus sufferer? How often have we told our patients that they must learn to live with this problem, that we have nothing specific to offer them, that we do not even know whether a successful stapedectomy will provide amelioration of this aspect of the problem? And how often has the patient told us in one way or another that those of us who do not suffer from this condition cannot understand what it is to live with this problem for months, years, or a lifetime.

The history of masking as applied to tinnitus must not be confused with the history of masking. Masking, defined as an interference of external sounds upon external sounds, has a long and well established history but the laws and principles which have evolved from those studies do not apply to the masking of tinnitus. Indeed, the masking of tinnitus is sufficiently unique that the term masking is incorrect. Unfortunately, it is too late to change the term now, but it is important that all realize that masking of tinnitus is entirely different from ordinary masking.

The use of masking for relief of tinnitus has been known for a long time. Perhaps the earliest written record is that of Hippocrates, who in 400 B.C. said: ‘Why is it that the buzzing in the ears ceases if one makes a sound? Is it because the greater sound drives out the less?’ (Book 32, paragraph 961-A). Clearly, Hippocrates had tinnitus (we would even guess that he had a noise-type tinnitus of a medium to low pitch) and clearly, he had experienced what we call masking of tinnitus.

Much work has been done on the concept of an ear level masker by Vernon (1977) and others in the U.S.A. The purpose of our small study in the U.K. was to see whether a low priced ‘Universal’ masking instrument would be-of value.

The maskers were manufactured by George Williams Engineering Ltd and distributed through the Royal National Institute for the Deaf at cost price (Hazell, 1977). The R.N.I.D. already supplies a number of environmental aids for hearing impaired people (such as flashing light door bells, baby alarms, etc) and it was not too difficult to add the prototype ear level masker to this list. The maskers retailed at £25. If the masker proved ineffective a full refund was made on return of the masker. Fitting was carried out in some cases at the Tinnitus Clinic held at University College Hospital, London, and in others by regional Audiology Centres. In all cases the names and addresses of those who purchased maskers were retained and all were circulated with questionnaires some three months after purchase of the masker.

I plan to make a slight alteration in the topic listed on your program today and the reason for this is that lately I have seen very clearly the ease with which tinnitus has been considered as only a local ear disorder. No-one can deny, or even dare to deny, that medical and psychologic factors in a patient's personal make-up greatly effect the severity of the tinnitus and his response to it. And yet, I’ve repeatedly heard over the course of the past month the complaint of non-physicians who have said: ‘Why do you require an otologic evaluation at the University of Oregon; we’re just as qualified to see this patient as anyone else’. I think the reason is clear and irrefutable; that tinnitus is a medical disorder and the evaluation of tinnitus without a medical evaluation is poor medicine. The subtleties of diabetes, and thyroid disease and hyperlipidemia, and hypertension and drug reaction and allergies, are all easily enough overlooked by a physician, not to say how frequently they might be overlooked by others.

A clinical classification of subjective idiopathic tinnitus is presented today as an aid to the clinician in the understanding of the tinnitus complaint; to establish the site of lesion of the tinnitus complaint; and to provide a logical basis for the treatment of subjective idiopathic tinnitus. The problem of subjective idiopathic tinnitus is multi-faceted.

An up-to-date, modern classification of subjective idiopathic tinnitus must be multi-faceted—one based on the relationship of subjective idiopathic tinnitus to:

(a) Parameters of external sound stimulation—objective and subjective, i.e. frequency, intensity, duration, pitch, loudness.

(b) Response of the auditory system to pure tone and masking stimulation.

(c) Correlation of findings of the cochleo-vestibular evaluation.

(d) Evoked response audiometry for early, middle, and late responses.

The classification of subjective idiopathic tinnitus must be a dynamic, expanding one of increasing complexity relating to the advances of the basic sciences; and one in which the clinician plays a vital role.

My interest in tinnitus is very long. It stems, I think, from an interest in the sensory nature of Medicine, if you like in the cultural aspect of it. Imagine my horror when I discovered, starting my training, that I had to do some millions of tonsillectomies and adenoidectomies and submucous resections of the septum, always aiming for an attempt at studying the senses. And, in fact, more than ten years ago, I decided that tinnitus was possibly the one that I could study then. The reason was that I was a very genial person, that we had little equipment available and that not very much was known about that subject; and I felt that if I’d say something, then maybe it would be of note. And here I am. Now the position, as I found it there, was the following: modern medicine is based on a comparison of symptomatology with pathological knowledge.