Fortnightly review: tinnitus—investigation and management

Introduction

Tinnitus (from the Latin tinnire, which means to ring or to tinkle) describes the sensation of any sound perceived in the head or in the ears without an evident external stimulus. Though tinnitus is subjective, for clinical purposes it is subdivided into subjective and objective tinnitus, the latter describing those few incidents in which the sound is detected or potentially detectable by another observer. Tinnitus is a manifestation of malfunction in the processing of auditory signals involving both perceptual and psychological components and should as such be differentiated from auditory hallucinations, which are generally considered to be a symptom of psychiatric or neurological disorders.

The characteristics used to classify tinnitus depend on the purpose of the classification (box).1 Furthermore, distinctions should be made between acute and chronic tinnitus and between chronic tinnitus occurring after an acute tinnitus and chronic tinnitus of insidious onset.2 Tinnitus is considered to be chronic when is has been present for more than three months without signs of spontaneously resolving.

Prevalence

Most people experience tinnitus occasionally, and most experience it in silent soundproofed rooms. The British national study of hearing found that 10% of adults had prolonged spontaneous tinnitus—that is, tinnitus “usually lasting for longer than 5 minutes”; 1% experienced severe annoyance due to tinnitus, and in 0.5% of adults tinnitus severely reduced the ability to lead a normal life. The same study ascertained that 7% of the population in the United Kingdom present to their general practitioners with tinnitus and 2.4% are referred to hospitals.3 A largescale Swedish study4 reported somewhat higher figures: for 2.4% of adults “tinnitus plagues me all day,” and 14.2% suffered from tinnitus “often” or “always.”

Aetiology

Tinnitus is a symptom of many diseases and may be triggered anywhere along the auditory pathway, but the emergence of persistent annoying tinnitus is considered to have psychological components (see below). The symptom may be associated with any form of sensorineural hearing impairment; difficulty in hearing is the major determinant of tinnitus, followed by aging and exposure to noise.3 Conductive hearing impairment with tinnitus occurs after middle ear surgery and myringoplasty, and in chronic suppurative otitis media and is a common feature of otosclerosis. Temporary tinnitus may be due to wax in the ear canal, to otitis media or Eustachian tube catarrh, to drug ingestion or toxaemia, or to recent exposure to noise. Causes of objective tinnitus may be divided into vascular or muscular (for an overview see Jackson5) (box box). In rare cases the onset of persistent unilateral tinnitus may be the first sign of an acoustic neuroma.

It is not exceptional for tinnitus to occur in patients with normal hearing. In a Swedish population study, 19% of subjects with subjective normal hearing said they suffered from tinnitus “always,”4 and the British national study found that 7% of adults were annoyed by prolonged spontaneous tinnitus but did not have difficulty hearing.3 Such data emphasise the role of the brain as the primary site of the perception and experience of tinnitus.

The clinical course of tinnitus is either no change or increasing loudness and decreasing annoyance. Most people learn to tolerate tinnitus, but a few do not; several theories give different explanations for this.

A recent neurophysiological model offers one explanation of tinnitus with implications for both diagnosis and management.6 7 The theory focuses on tinnitus as a threat, which in some patients evokes strong emotions, such as fear of serious illness and anger, which are easily enhanced by adverse professional intervention. Based on the principles of neural plasticity, the theory says the brain has potential to relearn patterns that will de-emphasise the impact of tinnitus. Treatment is by retraining, with the goal of removing inexpedient emotional responses and eventually the perception of tinnitus itself.

In the theory of habituation, factors such as chronic stress, high levels of arousal, the significance of the sound, or sudden onset and unpredictability of the stimulus may interfere with the process of normal habituation.8 9 Another model proposes dishabituation (renewed focus on the sound) instead of lack of habituation as the difference between those who complain of tinnitus and those who do not,10 and a nationwide Swedish questionnaire study found that the most important predictors of discomfort from and adaptation to tinnitus were controllability and degree of maskability by external sounds.11

Investigation

In primary health care, investigation of tinnitus should include an ear, nose, and throat examination; an evaluation of current health state; a thorough history, covering previous ear disease, recent noise exposure, hearing status, and drug intake; and an impression of the psychosociological situation of the patient, with special attention to signs of depression. If tinnitus is persistent or annoying the patient should be referred to an ear, nose, and throat clinic, tinnitus clinic, or audiology department for further examination and counselling (box). Although loudness measures and reported severity of tinnitus are poorly correlated, these tests are normally included in tinnitus protocols. Measuring tinnitus is important both for diagnostic reasons and to reassure the patient that the symptom is being carefully assessed.

Annoyance due to tinnitus or its severity is measured or graded by questionnaires, which are available in many forms and lengths. They deal with both the perceptual aspects of the symptom and its individual psychosocial consequences—impact on concentration, hearing, memory, irritability, sleep, and overall psychological wellbeing.13

Management

Tailoring treatment to individual needs is a cornerstone of management: both undertreatment and overtreatment may lock the patient in a vicious circle and produce a “sufferer.” Preventing the patient being annoyed by tinnitus begins in primary practice with an explanation of the basic psychological mechanisms involved in the perception of tinnitus and, for most patients, reassurance as to the benign nature of their problem.

Patients seen in clinical settings tend to be those who do not habituate to tinnitus. It is estimated that around 80% of patients referred to tinnitus clinics can be helped simply by relevant examination and reassurance.5 For those needing more treatment the approach varies among professionals and countries but is usually multidisciplinary. There is no cure for tinnitus in the common sense of the word—no drug has been proved effective in attenuating not to say abolishing tinnitus for an appreciable proportion of patients. Antidepressants or nocturnal sedatives may deal with the effects of tinnitus for highly emotional patients for a short period while the underlying psychological disturbance is being treated.

With a few exceptions, surgery specifically aimed at eliminating tinnitus is obsolete. A detailed overview of pharmacological and surgical approaches is available elsewhere.2 14

Fig 1

Maskers can be worn behind or in the ear

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Fig 1

Maskers can be worn behind or in the ear

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Prosthetic treatment

Since the late 1970s prosthetic treatment involving hearing aids, tinnitus maskers, or combination instruments has been widespread in tinnitus management.

Maskers look similar to hearing aids and produce a broad band of noise. The instruments generate an external, constant sound that can be controlled by the patient, allowing the patient to concentrate rather than be distracted by sounds from televisions, etc; they divert attention and thereby make tinnitus less troublesome. After therapeutic masking about 10% of patients experience a period of total absence of tinnitus,15 but because this residual inhibition is unpredictable it should not be overemphasised in counselling.

The neurophysiological approach focusing on behavioural retraining of the associations induced by perception of tinnitus uses devices similar to maskers but calls them tinnitus retraining instruments. According to this theory traditional masking is counterproductive, since for retraining to occur the stimulus has to be perceived during training.7 In 149 patients given retraining, 96% showed improvement, and in 19.6% tinnitus totally disappeared for an average of 10.5 days.16

When a hearing impairment is present, hearing aids should be fitted, as they distract attention away from tinnitus through amplification of ambient sounds and often provide a masking effect. The stress mechanisms involved in the experience of tinnitus cause some patients to attribute hearing problems to tinnitus; for them, improving hearing by means of amplification results in improvement of tinnitus. A thorough interview will reveal whether a hearing problem or tinnitus is the major complaint, and counselling in the use of the hearing aid should be delivered accordingly. Experienced hearing aid users whose hearing aid gives no relief from tinnitus may be provided with combination instruments or with hearing aids and maskers separately.

The percentage of patients who can be helped through instrumentation varies across studies and designs. Thus a multicentre study of 472 patients reported benefit from maskers or combination instruments in 89% of patients and for hearing aids in 69%,17 while two Swedish controlled studies concluded that masker treatment is not unequivocally superior to placebo and that hearing aids fitted exclusively for hearing purposes did not reduce tinnitus.18 19 Placebo effect or not, instruments are part of multidisciplinary management. As the basic mechanism of tinnitus becomes understood, patients will be more carefully selected for prosthetic treatment.

Psychological effects

The effects of tinnitus are primarily psychological, which is not to say that all patients with tinnitus need psychological therapy. Given the nature and the localisation of the symptom anxiety and distress are fully intelligible reactions that are initially best handled by proper medical examination, explanation, and reassurance. A person experiencing tinnitus will need a plausible explanation to counteract adverse and obstructive thoughts. Someone with a positive, non-threatening knowledge about tinnitus is likely to be better prepared than someone who has none.20 As patients often want to review information or share it with family or friends, some sort of written information is advisable. Several booklets are available and have been analysed in a recent study.20 box box shows the ten questions patients most often ask.

Patients with tinnitus often report insomnia, concentration difficulties, and emotional problems such as depression, frustration, and irritability. If further intervention is required, a thorough history taking is highly relevant for deciding whether tinnitus is the primary problem or if specific traits of personality or environmental factors, or both, preceded the symptom. Patients may have a long history of depressed moods, sleeping problems, or inexpedient ways of coping in stressed situations; in these cases tinnitus is not the single cause of all problems and should not be treated as such.

The literature contains descriptions of a variety of psychological methods, including cognitive approaches aimed at affecting attitudes, thoughts, and beliefs. In combination with behavioural strategies such as relaxation training and biofeedback these methods form the basis of self control or coping techniques.21 22 23 Methodological limitations such as lack of proper controls or small samples often preclude firm conclusions as to whether any treatment effect is due to specific factors, but the therapeutic effect in itself is great in any treatment of tinnitus—patients often express relief when they see a professional who has more than 10 minutes for listening and reassurance.

Conclusion

Empirical results justify a positive prospect if not for the “cure” of tinnitus then for the possibilities of alleviating the consequences of the symptom. Although patients should not just be told they will have to live with their tinnitus, this is still basically true, and indeed most people with tinnitus do habituate. Patients presenting with tinnitus need a thorough examination of current health state, an otoaudiological examination, and an evaluation of psychological wellbeing, as well as solid counselling based on current knowledge, preferably including some sort of written information. Patients who are depressed or have psychosocial problems should be identified as such and treated accordingly. When these services are not provided by the general practitioner, patients should be referred to a tinnitus clinic or audiology department.