Subspecialty Clinics: Otorhinolaryngology Tinnitus MITCHELL S. MARION, M.D.,* Section of Otolaryngology-Head and Neck Surgery; MICHAEL J. CEVETTE, Ph.D.,* Section ofAudiology
Tinnitus, a common complaint, reportedly affects more than 37 million Americans. Most often, it is associated with a sensorineural hearing loss in the high-frequency range. Tinnitus, however, is a symptom and not a disease. Complacency about this symptom complex may cause physicians to overlook a severe underlying pathologic process. Patients with unilateral tinnitus, pulsatile tinnitus, fluctuating tinnitus, or tinnitus associated with vertigo should undergo thorough assessment, including elicitation of a complete history, physical examination, and audiologic analysis. In many instances, treatment is effective. Masking of tinnitus, medical therapy, and biofeedback and counseling are some measures that have. been used in the management of tinnitus.
The word "tinnitus" is derived from the Latin word tinnire, which means "to ring." Tinnitus can be defined as an abnormal sound that is perceived in the ear or head area and is unrelated to an external source. 1-6 More than 37 million Americans have this common disorder. 7 Because most patients who complain of tinnitus have age-related sensorineural hearing loss, physicians may simply offer reassurance as the only treatment. Tinnitus, however, is a symptom rather than a disease, and it always reflects some underlying abnormality. Symptoms such as pulsatile tinnitus, tinnitus associated with vertigo, fluctuating tinnitus, and unilateral
tinnitus must be thoroughly reviewed. Herein we provide an overall scheme for assessment and management of patients with the complaint of tinnitus.
CLASSIFICATION Textbooks classify tinnitus as either subjective or objective. Subjective tinnitus, which is more common, can be heard only by the patient and is presumed to originate from some type of electrophysiologic derangement in the cochlea, cranial nerve VIII, or central nervous system. In contrast, objective tinnitus can be heard by a nearby observer or by an examiner using a stethoscope. It suggests a vascular, muscular, or neoplastic process. This classification system, however, is not diagnostic and is often imprecise. For ex*Mayo Clinic Scottsdale, Scottsdale, Arizona. ample, vascular tinnitus often can be heard only Address reprint requests to Dr. M. S. Marion, Section of subjectively, and recently, emissions thought to Otolaryngology-Head and Neck Surgery, Mayo Clinic Scottsdale, 13400 East Shea Boulevard, Scottsdale, AZ originate from the cochlear hair cells have been measured objectively." 85259. Mayo Clin Proc 66:614-620, 1991
614
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ETIOLOGIC THEORIES The precise cause of tinnitus is unknown and is most likely multifactorial. The auditory system is complicated and involves the organ of Corti, the peripheral fibers in the spiral lamina, multiple afferent and efferent pathways, and several central nuclei that are capable of complex integration involving higher centers of the central nervous system. Meller? proposed that spontaneous activity in several nerve fibers could fire in a phase-locked fashion and thereby result in the perception of sound. Another theory, the place theory, maintains that a defect in the cuticular membrane may cause depolarization of hair cells.!" Accordingly, the pitch of the tinnitus would correlate with the activity of a specific portion of the organ of Corti along the basilar membrane. A third theory, suggested by Tonndorf,'! postulates that a decoupling of hair cells from the tectorial membrane may be the basis of tinnitus in acute cochlear disorders. Furthermore, decoupling of hair cells may also cause cochlear nerve deafferentation and thereby trigger chronic tinnitus. HISTORY AND EVALUATION Tinnitus may be described as constant, intermittent, fluctuant, or pulsatile. Constant tinnitus associated with a high-frequency sensorineural hearing loss is often described as "chirping," similar to the sound produced by crickets. Lowtone tinnitus associated with low-frequency sensorineural hearing loss is often described as a whooshing or blowing, as if one were holding a seashell to the ear. Fluctuant tinnitus suggests a fluctuant hearing loss and is a common symptom of cochlear hydrops, such as that seen in Meniere's disease associated with recurrent vertigo. Serial audiograms may often document the fluctuant nature of the hearing loss. The physician must distinguish whether tinnitus is unilateral or bilateral. Unilateral tinnitus associated with a unilateral sensorineural hearing loss is the hallmark manifestation of a retrocochlear lesion, such as an acoustic neuroma (Fig. 1). Pulsatile tinnitus suggests a vascular origin. Pulsations may correspond to the patient's heart-
TINNITUS
615
beat and also may be positionally related. Recently, Levine and Snow'! reviewed the differential diagnosis of patients who had pulsatile tinnitus on initial examination. Pulsatile tinnitus may be the only symptom of a life-threatening and treatable disease such as a glomus jugulare tumor. The cause of pulsatile tinnitus may be found on otoscopic examination. In the presence of normal results on otoscopy, audiology, and enhanced computed tomography, however, pulsatile tinnitus is most likely attributable to turbulent blood flow through the great vessels, which pass close to the middle and inner ear. Most patients describe the onset oftinnitus as gradual. Some patients, however, report a precipitous onset oftinnitus, linked with some event such as an upper respiratory tract infection, a blow to the head, exposure to noise, or an emotional stress. Tinnitus can be a stressful experience and may be interpreted differently by individual patients. The related distress may range from mild irritation to suicidal desires. In patients with severe disabling tinnitus, anxiety and depression are often major factors. 13 All patients-but particularly those patients whose tinnitus and hearing loss are thought to be noise-related-should be aware of the hazards of exposure to excessive levels of noise. Counseling is important because further exposure to noise may not only exacerbate the tinnitus but also increase the risk of sustaining additional hearing loss. Adequate ear protectors, which are relatively inexpensive, may be obtained from most audiologists. In some cases, custom ear protectors are made for patients when maximal attenuation and comfort are priorities. After elicitation of the history, a complete head and neck examination should be performed, including cranial nerve testing, assessment of the optic fundi, and auscultation of the head, neck, and ears. A thorough otologic examination should attempt to identify any pathologic processes ofthe tympanic membrane or middle ear.
AUDIOLOGIC ASSESSMENT The audiologic assessment is the single most important step in the evaluation of tinnitus. It
616
TINNITUS
Fig. 1. Computed tomographic scan with axial TI-weighted image after injection of gadolinium-diethylenetriamine pentaacetic acid, showing I-cm brightly enhancing neuroma (n) that has expanded the right internal auditory canal and bulged into the cerebellopontine angle.
establishes a base from which to pursue more advanced diagnostic tests and also rehabilitative measures. Routine audiometric tests reveal the degree (mild to profound), the type (conductive, sensorineural, or mixed), and the symmetry of hearing impairment associated with the tinnitus. Immittance measures substantiate both middle ear function and acoustic reflex patterns that may be affected by middle ear disorders and abnormalities of the auditory neural and brain-stem pathways, respectively. Electrophysiologic measures of auditory evoked potentials are sensitive for detection of retrocochlear disorders that may interfere with the transmission of acoustic stimuli at the level of the auditory nerve and brain stem. Moreover, the advent of evoked otoacoustic emissions provides additional data that may prove helpful in delineating neural from cochlear disorders. 14 Thus, the initial audiologic battery, in combination with a complete case history, determines the course for further diagnostic and rehabilitative efforts.
MEASUREMENT AND MASKING OF TINNITUS For evaluation ofthe success of treatment, tinnitus must be quantified. Nevertheless, no clear
Mayo Clin Proc, June 1991, Vol 66
relationship exists between the effectiveness of a certain type of masking signal and its ability to render a specific type of tinnitus imperceptible. For example, a wide range of sounds will effectively mask tinnitus in a variety of patients. This outcome undoubtedly is related to the complexity of the underlying causes of tinnitus. The tinnitus-matching procedure, despite the noted weaknesses, has merit for numerous patients with tinnitus who request hearing aids, tinnitus maskers, or hearing instruments (a hearing aid plus a masker). For measurement oftinnitus, the patient must be able to assess how similar an externally generated sound is to their internal "ringing" or "buzzing." The successful outcome of reliable judgments in matching the tinnitus is contingent on many factors. First, the audiologist must effectively provide the patient, through the audiologic test equipment, the frequency-to-pitch and intensity-to-loudness characteristics of the tinnitus. Second, the psychophysical procedure should be conducive to simple and reliable judgments by the patient. Third, the tinnitus must be relatively unchanging. The accuracy of determining the tinnitus match often has implications for selecting the masking sounds. For those patients who describe their tinnitus as a pure tone, tinnitus matching is usually successful, whereas noiselike tinnitus is more difficult to replicate for evaluation by the patient. Because the greatest amount of sensorineural hearing loss occurs in the high frequencies, most patients match their tinnitus to signals in that range. In a report by Vernon and Meikle.!" patients matched tinnitus to sounds that exceeded 3,000 Hz in almost 83% of cases and to sounds that exceeded 9,000 Hz in more than 14%. They reported that 91% oftheir patients had their tinnitus masked completely with a tinnitus synthesizer and that an additional 5.9% had at least partial masking oftheir tinnitus. Hearing aids, tinnitus maskers, and hearing instruments have been shown to relieve tinnitus effectively in selected patients. Vernon and colleagues'" reviewed various characteristics of tinnitus (duration, loudness, minimal masking
Mayo Clin Proc, June 1991, Vol 66
level, and residual inhibition) to determine whether they were associated with efficacy of masking. In general, no individual characteristic was consistently correlated with effective treatment by masking. Thus, such factors should not, be used to determine whether a patient should be offered a trial period for use of a tinnitus masker, a hearing aid, or a hearing instrument. Sound presented in the frequency ofthe hearing impairment has proved to be effective in the reliefoftinnitus. Hearing aids are a logical first approach for the management of tinnitus because of the potential for not only the relief of tinnitus but also the enhancement of the ability to hear conversation. In one study.!? approximately half of the patients fitted with hearing aids found that the device was effective in reducing or eliminating tinnitus. If the patient is not a candidate for a hearing aid, a tinnitus masker can be considered. Tinnitus maskers resemble hearing aids but simply produce noise rather than providing amplification. They are designed to provide a variety of sound spectra. Masking sounds that are very low or high in frequency are less likely than other noises to interfere with the center of the speech spectra (Fig. 2). Because tinnitus can be bilateral or can be masked by noise in the contralateral ear, a trial with a tinnitus masker in each ear may be worthwhile. Currently, the greatest limitation of maskers is the inability to modify acoustic spectra specifically for each patient. This capability may be forthcoming with future developments in digital hearing aid technology. Vernon'" reported that hearing instruments relieve severe tinnitus in most cases (67%). Because most patients with tinnitus have a hearing loss and need amplification of normal sounds, the addition of both a hearing aid and a tinnitus masker (hearing instrument) increases the ability to relieve or eliminate tinnitus with a wearable device. Tyler and Bentler!" outlined the possible complications associated with successfully fitting a hearing instrument: (1) the speech amplified by the hearing aid may influence the masking effectiveness ofthe noise, and (2) the presence ofthe masking noise may dimin-
TINNITUS
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Frequency (kHz)
.125
..J :l:
co
"
.25
.5
1
2
4
8
0 10 20 30 40 50 60
70 80 90 100
Fig. 2. Long-term speech spectra superimposed on audiogram of patient with tinnitus. White area of speech spectra represents the portion that is unavailable because of severe high-frequency hearing loss above 2,000 Hz. HL = hearing level.
ish the optimal characteristics of the hearing aid. The fact that tinnitus can be successfully masked clinically does not ensure that the patient will be satisfied with a wearable device to mask the tinnitus. Variables such as severity of the tinnitus, personality characteristics of the patient, type of hearing instrument, and effect of the device on communication are important factors. For example, Spitzer and associates-" found that normal-hearing listeners had difficulty understanding words in the presence of background noise while wearing a tinnitus masker. Tinnitus that is bothersome only when the patient tries to sleep often can be alleviated by increasing the ambient noise in the room-for example, a television or radio can be played, or an FM radio can be set between stations to produce a constant "white noise." Electronic stores sell pillow speakers that can be plugged into a sound source and placed under a pillow, to avoid interfering with the sleep of others in the room. Several companies make so-called sleep machines that duplicate sounds of nature, such as rainfall or waves at the seashore. These
618
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machines can be used at the bedside to reduce the distraction from tinnitus.
MEDICAL THERAPY For some time, investigators have known that local anesthetic agents, such as intravenously administered lidocaine, can relieve tinnitus for brief'periods.P! The exact mechanism whereby these anesthetics relieve tinnitus and their site of action are unknown. In a double-blind study by Martin and Colman'" in 1980, subjective tinnitus decreased in 65% of their patients after treatment with lidocaine. Lidocaine, however, is not ideal for management of tinnitus because it is administered intravenously and has a short half-life. An oral analogue of lidocaine-tocainide hydrochloride-was described by Emmett and Shea.P This drug can be administered orally and has few or no side effects and a longer half-life. Unfortunately, after initial promising results, double-blind studies demonstrated minimal effectiveness of this drug in relieving tinnitus. 24 Because stress-related depression and anxiety disorders exacerbate subjective tinnitus, tricyclic antidepressants may be effective in individual cases." In such cases, antidepressant therapy should be prescribed by mentalhealth professionals. ELECTRICAL STIMULATION The use of electrical stimulation for suppression of tinnitus dates back to the early 1800S. 26 In 1960, however, Hatton and colleagues'? noted that anodal pulses suppressed tinnitus in 45% of their patients. Interest in this therapeutic modality for tinnitus has been renewed, although the results are not promising. As part of a cochlear implant program in 1984, House" identified 64 patients who were profoundly deafand also had tinnitus. After cochlear implantation, 53% reported a decrease in tinnitus, 36% had no change, 8% thought their condition was worse, and no findings were reported for 3%. On the basis of these results, five patients underwent cochlear implantation exclusively for the relief of tinnitus. The mixed results included only one definite success.i"
Mayo Clin Proc, June 1991, Vol 66
Electrical stimulation applied transdermally by electrodes placed on the preauricular, postauricular, and mastoid regions was performed by Vernon and Fenwick." Ofthe 50 patients tested, only 14 obtained relief. Therefore, they concluded that transdermal electrical stimulation was not a practical therapeutic procedure for the relief of tinnitus. A new device that uses electrical stimulation-the Audimax Therabanddelivers an inaudible transdermal mastoid electrical stimulus. A single-blind crossover study was performed with use of this device in 30 patients;" only 2 of whom had appreciable improvement. Research studies continue in the hope that electrical stimulation may eventually be used in the management oftinnitus. To date, however, no guidelines are available for treatment with use of specific devices, and this approach should still be considered experimental.
BIOFEEDBACK AND COUNSELING Like other clinicians, we have found that patients with severe tinnitus may have high scores on the depression scale of the Minnesota Multiphasic Personality Inventory (MMPI).13 In 1984, Carmen and Svihovec'" found a significant correlation between tinnitus and tension levels on self-rating scales. They reported that their biofeedback regimen reduced tension and generated a sense of well-being. Subsequently, patients described their tinnitus as more tolerable; of 41 patients who underwent biofeedback training for tinnitus, 33 reported improvement. The best results occurred in patients who were motivated and who had depression and anxiety-type syndromes. Biofeedback training is not a specific treatment for tinnitus but rather a method for managing stress. Like other chronic symptoms, such as pain or headache, tinnitus is intricately related to the overall psychologic health and makeup of the patient. In a subpopulation of patients who suffer from severe tinnitus, a high level of psychiatric morbidity has been found. Hypnosis has been used in a controlled trial to relieve tinnitus in a select group of patients." Only one patient experienced a considerable
Mayo Clin Proc, June 1991, Vol 66
reduction in tinnitus; 36% ofthe patients thought that the effects of relaxation were beneficial even though hypnotherapy did not diminish the loudness of their tinnitus. We believe that general relaxation procedures are of definite benefit in the management of patients with tinnitus.
CONCLUSION
Tinnitus is a common complaint and is most often associated with sensorineural hearing loss. Unilateral tinnitus, pulsatile tinnitus, fluctuating tinnitus, and tinnitus associated with vertigo must be carefully evaluated. In conjunction with a thorough history and physical examination, audiologic assessment is an important factor in the evaluation of tinnitus. It establishes a baseline for determining what more advanced diagnostic tests should be performed and what specific rehabilitative measures might be appropriate. Although many patients have mild tinnitus that needs no treatment, the possibility of an underlying pathologic process should not be overlooked. Several methods are available to help patients cope with tinnitus: increasing the ambient noise by turning on the television or radio, using a "sleep machine" for generating soothing sounds, or wearing a hearing aid, tinnitus masker, or hearing instrument. Stress and anxiety can aggravate tinnitus; thus, biofeedback and stress management therapy may be beneficial. No drug has been approved by the US Food and Drug Administration for the treatment of tinnitus; however, antidepressant therapy may help relieve tinnitus associated with anxiety-depression syndromes. A stressful lifestyle should be minimized, ample sleep should be scheduled, and stimulants such as nicotine and caffeine should be avoided. Many patients have found relief by becoming involved with a tinnitus support group or support organizations. One of the best known groups is the American Tinnitus Association (PO Box 5, Portland, OR 97207).
ACKNOWLEDGMENT
We thank Dr. Wayne O. Olsen (Section of Audiology, Mayo Clinic Rochester) for helpful review
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of our manuscript and Jean Heiman for secretarial assistance.
REFERENCES 1.
2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
12. 13. 14. 15.
16. 17. 18.
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21.
Coles RRA, Hallam RS: Tinnitus and its management. Br Med Bull 43:983-998, 1987 Stephens SDG: The treatment oftinnitus-a historical perspective. J Laryngol Otol 98:963-972, 1984 House JW: Tinnitus: evaluation and treatment. Am J Otol 5:472-475, 1984 Mattox DE, Richtsmeier WJ: Tinnitus-the initial evaluation. OtolaryngolHeadNeckSurg 96:172-174, 1987 Shulman A: Medical audiological evaluation of the tinnitus patient. Semin Hearing 8:7-14, 1987 Bentler RA, Tyler RS: Tinnitus management. ASHA 29:27-32, May 1987 Tinnitus. MayoClinHealthLett 8:1-2,October1990 WilsonJP: Otoacoustic emissions and tinnitus. Scand Audiol Suppl 25:109-119, 1986 Meller AR: Pathophysiology of tinnitus. Ann Otol Rhinol Laryngol 93:39-44, 1984 Feldmann H: Pathophysiology oftinnitus. In Tinnitus: Pathophysiology and Management. Edited by M Kitahara. Tokyo, Igaku-Shoin, 1988, pp 7-35 Tonndorf J: Acute cochlear disorders: the combination of hearing loss, recruitment, poor speech discrimination, and tinnitus. Ann Otol Rhinol Laryngol 89:353-358, -1980 Levine SB, Snow JB Jr: Pulsatile tinnitus. Laryngoscope 97:401-406, 1987 House PR, House JW: The tinnitus patient: personality and biofeedback treatment. Semin Hearing 8:15-19, 1987 Robinette MS, Facer GW: Evoked otoacoustic emissions in differential diagnosis. Otolaryngol Head Neck Surg (in press) Vernon JA, Meikle MB: Measurement of tinnitus: an update. In Tinnitus: Pathophysiology and Management. Edited by M Kitahara. Tokyo, Igaku-Shoin, 1988, pp 36-52 Vernon J, Griest S, Press L: Attributes oftinnitus and the acceptance of masking. Am J Otolaryngol 11:4450, 1990 Surr RK, Montgomery AA, Mueller HG: Effect of amplification on tinnitus among new hearing aid users. Ear Hear 6:71-75, 1985 Vernon JA: Current use of masking for the relief of tinnitus. In Tinnitus: Pathophysiology and Management. Edited by M Kitahara. Tokyo, Igaku-Shoin, 1988, pp 96-106 Tyler RS, Bentler RA: Tinnitus maskers and hearing aids for tinnitus. Semin Hearing 8:49-60, 1987 Spitzer JB, Goldstein BA, Salzbrenner LG, Mueller G: Effect oftinnitus masker noise on speech discrimination in quiet and two noise backgrounds. Scand Audiol 12:197-200, 1983 Melding PS, Goodey RJ, Thorne PR: The use of intravenous lignocaine in the diagnosis and treatment of tinnitus. J Laryngol Otol 92:115-121,1978
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22.
Martin FW, Colman BH: Tinnitus: a double-blind crossover controlled trial to evaluate the use of lignocaine. Clin Otolaryngol 5:3-11, 1980 Emmett JR, Shea JJ: Treatment of tinnitus with tocainide hydrochloride. Otolaryngol Head Neck Surg 88:442-446, 1980 Hulshof JH, Vermeij P: The effect of intra-venous lidocaine and several different doses oral tocainide HCl on tinnitus: a dose-finding study. Acta Otolaryngol (Stockh) 98:231-238, 1984 Mihail RC, Crowley JM, Walden BE, Fishburne J, ReinwallJE,ZajtchukJT: Thetricyclictrimipramine in the treatment of subjective tinnitus. Ann Otol Rhinol Laryngol 97:120-123, 1988 Shulman A: External electrical tinnitus suppression: a review. Am J 0001 8:479-484,1987 Hatton DS, Erulkar SD, Rosenberg PE: Some preliminary observations on the effect of galvanic cur-
23. 24.
25.
26. 27.
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28. 29. 30.
31. 32.
rent on tinnitus aurium. Laryngoscope 70:123-130, 1960 Thedinger B, House WF, Edgerton BJ: Cochlear implant for tinnitus: case reports. Ann Otol Rhinol Laryngol 94:10-13, 1985 VernonJA, FenwickJA: Attempts to suppress tinnitus with transcutaneous electrical stimulation. Otolaryngol Head Neck Surg 93:385-389,1985 Thedinger BS, Karlsen E, Schack SH: Treatment of tinnitus with electrical stimulation: an evaluation of the Audimax Theraband. Laryngoscope 97:33-37, 1987 Carmen R, Svihovec D: Relaxation-biofeedback in the treatment of tinnitus. Am J Otol 5:376-381, 1984 Marks NJ, Karl H, Onisiphorou C: A controlled trial of hypnotherapy in tinnitus. Clin Otolaryngol 10:4346, 1985
Tinnitus, a common complaint, reportedly affects more than 37 million Americans. Most often, it is associated with a sensorineural hearing loss in the high-frequency range. Tinnitus, however, is a symptom and not a disease. Complacency about this symptom complex may cause physicians to overlook a severe underlying pathologic process. Patients with unilateral tinnitus, pulsatile tinnitus, fluctuating tinnitus, or tinnitus associated with vertigo should undergo thorough assessment, including elicitation of a complete history, physical examination, and audiologic analysis. In many instances, treatment is effective. Masking of tinnitus, medical therapy, and biofeedback and counseling are some measures that have. been used in the management of tinnitus.
The word "tinnitus" is derived from the Latin word tinnire, which means "to ring." Tinnitus can be defined as an abnormal sound that is perceived in the ear or head area and is unrelated to an external source. 1-6 More than 37 million Americans have this common disorder. 7 Because most patients who complain of tinnitus have age-related sensorineural hearing loss, physicians may simply offer reassurance as the only treatment. Tinnitus, however, is a symptom rather than a disease, and it always reflects some underlying abnormality. Symptoms such as pulsatile tinnitus, tinnitus associated with vertigo, fluctuating tinnitus, and unilateral
tinnitus must be thoroughly reviewed. Herein we provide an overall scheme for assessment and management of patients with the complaint of tinnitus.
CLASSIFICATION Textbooks classify tinnitus as either subjective or objective. Subjective tinnitus, which is more common, can be heard only by the patient and is presumed to originate from some type of electrophysiologic derangement in the cochlea, cranial nerve VIII, or central nervous system. In contrast, objective tinnitus can be heard by a nearby observer or by an examiner using a stethoscope. It suggests a vascular, muscular, or neoplastic process. This classification system, however, is not diagnostic and is often imprecise. For ex*Mayo Clinic Scottsdale, Scottsdale, Arizona. ample, vascular tinnitus often can be heard only Address reprint requests to Dr. M. S. Marion, Section of subjectively, and recently, emissions thought to Otolaryngology-Head and Neck Surgery, Mayo Clinic Scottsdale, 13400 East Shea Boulevard, Scottsdale, AZ originate from the cochlear hair cells have been measured objectively." 85259. Mayo Clin Proc 66:614-620, 1991
614
Mayo Clin Proc, June 1991, Vol 66
ETIOLOGIC THEORIES The precise cause of tinnitus is unknown and is most likely multifactorial. The auditory system is complicated and involves the organ of Corti, the peripheral fibers in the spiral lamina, multiple afferent and efferent pathways, and several central nuclei that are capable of complex integration involving higher centers of the central nervous system. Meller? proposed that spontaneous activity in several nerve fibers could fire in a phase-locked fashion and thereby result in the perception of sound. Another theory, the place theory, maintains that a defect in the cuticular membrane may cause depolarization of hair cells.!" Accordingly, the pitch of the tinnitus would correlate with the activity of a specific portion of the organ of Corti along the basilar membrane. A third theory, suggested by Tonndorf,'! postulates that a decoupling of hair cells from the tectorial membrane may be the basis of tinnitus in acute cochlear disorders. Furthermore, decoupling of hair cells may also cause cochlear nerve deafferentation and thereby trigger chronic tinnitus. HISTORY AND EVALUATION Tinnitus may be described as constant, intermittent, fluctuant, or pulsatile. Constant tinnitus associated with a high-frequency sensorineural hearing loss is often described as "chirping," similar to the sound produced by crickets. Lowtone tinnitus associated with low-frequency sensorineural hearing loss is often described as a whooshing or blowing, as if one were holding a seashell to the ear. Fluctuant tinnitus suggests a fluctuant hearing loss and is a common symptom of cochlear hydrops, such as that seen in Meniere's disease associated with recurrent vertigo. Serial audiograms may often document the fluctuant nature of the hearing loss. The physician must distinguish whether tinnitus is unilateral or bilateral. Unilateral tinnitus associated with a unilateral sensorineural hearing loss is the hallmark manifestation of a retrocochlear lesion, such as an acoustic neuroma (Fig. 1). Pulsatile tinnitus suggests a vascular origin. Pulsations may correspond to the patient's heart-
TINNITUS
615
beat and also may be positionally related. Recently, Levine and Snow'! reviewed the differential diagnosis of patients who had pulsatile tinnitus on initial examination. Pulsatile tinnitus may be the only symptom of a life-threatening and treatable disease such as a glomus jugulare tumor. The cause of pulsatile tinnitus may be found on otoscopic examination. In the presence of normal results on otoscopy, audiology, and enhanced computed tomography, however, pulsatile tinnitus is most likely attributable to turbulent blood flow through the great vessels, which pass close to the middle and inner ear. Most patients describe the onset oftinnitus as gradual. Some patients, however, report a precipitous onset oftinnitus, linked with some event such as an upper respiratory tract infection, a blow to the head, exposure to noise, or an emotional stress. Tinnitus can be a stressful experience and may be interpreted differently by individual patients. The related distress may range from mild irritation to suicidal desires. In patients with severe disabling tinnitus, anxiety and depression are often major factors. 13 All patients-but particularly those patients whose tinnitus and hearing loss are thought to be noise-related-should be aware of the hazards of exposure to excessive levels of noise. Counseling is important because further exposure to noise may not only exacerbate the tinnitus but also increase the risk of sustaining additional hearing loss. Adequate ear protectors, which are relatively inexpensive, may be obtained from most audiologists. In some cases, custom ear protectors are made for patients when maximal attenuation and comfort are priorities. After elicitation of the history, a complete head and neck examination should be performed, including cranial nerve testing, assessment of the optic fundi, and auscultation of the head, neck, and ears. A thorough otologic examination should attempt to identify any pathologic processes ofthe tympanic membrane or middle ear.
AUDIOLOGIC ASSESSMENT The audiologic assessment is the single most important step in the evaluation of tinnitus. It
616
TINNITUS
Fig. 1. Computed tomographic scan with axial TI-weighted image after injection of gadolinium-diethylenetriamine pentaacetic acid, showing I-cm brightly enhancing neuroma (n) that has expanded the right internal auditory canal and bulged into the cerebellopontine angle.
establishes a base from which to pursue more advanced diagnostic tests and also rehabilitative measures. Routine audiometric tests reveal the degree (mild to profound), the type (conductive, sensorineural, or mixed), and the symmetry of hearing impairment associated with the tinnitus. Immittance measures substantiate both middle ear function and acoustic reflex patterns that may be affected by middle ear disorders and abnormalities of the auditory neural and brain-stem pathways, respectively. Electrophysiologic measures of auditory evoked potentials are sensitive for detection of retrocochlear disorders that may interfere with the transmission of acoustic stimuli at the level of the auditory nerve and brain stem. Moreover, the advent of evoked otoacoustic emissions provides additional data that may prove helpful in delineating neural from cochlear disorders. 14 Thus, the initial audiologic battery, in combination with a complete case history, determines the course for further diagnostic and rehabilitative efforts.
MEASUREMENT AND MASKING OF TINNITUS For evaluation ofthe success of treatment, tinnitus must be quantified. Nevertheless, no clear
Mayo Clin Proc, June 1991, Vol 66
relationship exists between the effectiveness of a certain type of masking signal and its ability to render a specific type of tinnitus imperceptible. For example, a wide range of sounds will effectively mask tinnitus in a variety of patients. This outcome undoubtedly is related to the complexity of the underlying causes of tinnitus. The tinnitus-matching procedure, despite the noted weaknesses, has merit for numerous patients with tinnitus who request hearing aids, tinnitus maskers, or hearing instruments (a hearing aid plus a masker). For measurement oftinnitus, the patient must be able to assess how similar an externally generated sound is to their internal "ringing" or "buzzing." The successful outcome of reliable judgments in matching the tinnitus is contingent on many factors. First, the audiologist must effectively provide the patient, through the audiologic test equipment, the frequency-to-pitch and intensity-to-loudness characteristics of the tinnitus. Second, the psychophysical procedure should be conducive to simple and reliable judgments by the patient. Third, the tinnitus must be relatively unchanging. The accuracy of determining the tinnitus match often has implications for selecting the masking sounds. For those patients who describe their tinnitus as a pure tone, tinnitus matching is usually successful, whereas noiselike tinnitus is more difficult to replicate for evaluation by the patient. Because the greatest amount of sensorineural hearing loss occurs in the high frequencies, most patients match their tinnitus to signals in that range. In a report by Vernon and Meikle.!" patients matched tinnitus to sounds that exceeded 3,000 Hz in almost 83% of cases and to sounds that exceeded 9,000 Hz in more than 14%. They reported that 91% oftheir patients had their tinnitus masked completely with a tinnitus synthesizer and that an additional 5.9% had at least partial masking oftheir tinnitus. Hearing aids, tinnitus maskers, and hearing instruments have been shown to relieve tinnitus effectively in selected patients. Vernon and colleagues'" reviewed various characteristics of tinnitus (duration, loudness, minimal masking
Mayo Clin Proc, June 1991, Vol 66
level, and residual inhibition) to determine whether they were associated with efficacy of masking. In general, no individual characteristic was consistently correlated with effective treatment by masking. Thus, such factors should not, be used to determine whether a patient should be offered a trial period for use of a tinnitus masker, a hearing aid, or a hearing instrument. Sound presented in the frequency ofthe hearing impairment has proved to be effective in the reliefoftinnitus. Hearing aids are a logical first approach for the management of tinnitus because of the potential for not only the relief of tinnitus but also the enhancement of the ability to hear conversation. In one study.!? approximately half of the patients fitted with hearing aids found that the device was effective in reducing or eliminating tinnitus. If the patient is not a candidate for a hearing aid, a tinnitus masker can be considered. Tinnitus maskers resemble hearing aids but simply produce noise rather than providing amplification. They are designed to provide a variety of sound spectra. Masking sounds that are very low or high in frequency are less likely than other noises to interfere with the center of the speech spectra (Fig. 2). Because tinnitus can be bilateral or can be masked by noise in the contralateral ear, a trial with a tinnitus masker in each ear may be worthwhile. Currently, the greatest limitation of maskers is the inability to modify acoustic spectra specifically for each patient. This capability may be forthcoming with future developments in digital hearing aid technology. Vernon'" reported that hearing instruments relieve severe tinnitus in most cases (67%). Because most patients with tinnitus have a hearing loss and need amplification of normal sounds, the addition of both a hearing aid and a tinnitus masker (hearing instrument) increases the ability to relieve or eliminate tinnitus with a wearable device. Tyler and Bentler!" outlined the possible complications associated with successfully fitting a hearing instrument: (1) the speech amplified by the hearing aid may influence the masking effectiveness ofthe noise, and (2) the presence ofthe masking noise may dimin-
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Frequency (kHz)
.125
..J :l:
co
"
.25
.5
1
2
4
8
0 10 20 30 40 50 60
70 80 90 100
Fig. 2. Long-term speech spectra superimposed on audiogram of patient with tinnitus. White area of speech spectra represents the portion that is unavailable because of severe high-frequency hearing loss above 2,000 Hz. HL = hearing level.
ish the optimal characteristics of the hearing aid. The fact that tinnitus can be successfully masked clinically does not ensure that the patient will be satisfied with a wearable device to mask the tinnitus. Variables such as severity of the tinnitus, personality characteristics of the patient, type of hearing instrument, and effect of the device on communication are important factors. For example, Spitzer and associates-" found that normal-hearing listeners had difficulty understanding words in the presence of background noise while wearing a tinnitus masker. Tinnitus that is bothersome only when the patient tries to sleep often can be alleviated by increasing the ambient noise in the room-for example, a television or radio can be played, or an FM radio can be set between stations to produce a constant "white noise." Electronic stores sell pillow speakers that can be plugged into a sound source and placed under a pillow, to avoid interfering with the sleep of others in the room. Several companies make so-called sleep machines that duplicate sounds of nature, such as rainfall or waves at the seashore. These
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machines can be used at the bedside to reduce the distraction from tinnitus.
MEDICAL THERAPY For some time, investigators have known that local anesthetic agents, such as intravenously administered lidocaine, can relieve tinnitus for brief'periods.P! The exact mechanism whereby these anesthetics relieve tinnitus and their site of action are unknown. In a double-blind study by Martin and Colman'" in 1980, subjective tinnitus decreased in 65% of their patients after treatment with lidocaine. Lidocaine, however, is not ideal for management of tinnitus because it is administered intravenously and has a short half-life. An oral analogue of lidocaine-tocainide hydrochloride-was described by Emmett and Shea.P This drug can be administered orally and has few or no side effects and a longer half-life. Unfortunately, after initial promising results, double-blind studies demonstrated minimal effectiveness of this drug in relieving tinnitus. 24 Because stress-related depression and anxiety disorders exacerbate subjective tinnitus, tricyclic antidepressants may be effective in individual cases." In such cases, antidepressant therapy should be prescribed by mentalhealth professionals. ELECTRICAL STIMULATION The use of electrical stimulation for suppression of tinnitus dates back to the early 1800S. 26 In 1960, however, Hatton and colleagues'? noted that anodal pulses suppressed tinnitus in 45% of their patients. Interest in this therapeutic modality for tinnitus has been renewed, although the results are not promising. As part of a cochlear implant program in 1984, House" identified 64 patients who were profoundly deafand also had tinnitus. After cochlear implantation, 53% reported a decrease in tinnitus, 36% had no change, 8% thought their condition was worse, and no findings were reported for 3%. On the basis of these results, five patients underwent cochlear implantation exclusively for the relief of tinnitus. The mixed results included only one definite success.i"
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Electrical stimulation applied transdermally by electrodes placed on the preauricular, postauricular, and mastoid regions was performed by Vernon and Fenwick." Ofthe 50 patients tested, only 14 obtained relief. Therefore, they concluded that transdermal electrical stimulation was not a practical therapeutic procedure for the relief of tinnitus. A new device that uses electrical stimulation-the Audimax Therabanddelivers an inaudible transdermal mastoid electrical stimulus. A single-blind crossover study was performed with use of this device in 30 patients;" only 2 of whom had appreciable improvement. Research studies continue in the hope that electrical stimulation may eventually be used in the management oftinnitus. To date, however, no guidelines are available for treatment with use of specific devices, and this approach should still be considered experimental.
BIOFEEDBACK AND COUNSELING Like other clinicians, we have found that patients with severe tinnitus may have high scores on the depression scale of the Minnesota Multiphasic Personality Inventory (MMPI).13 In 1984, Carmen and Svihovec'" found a significant correlation between tinnitus and tension levels on self-rating scales. They reported that their biofeedback regimen reduced tension and generated a sense of well-being. Subsequently, patients described their tinnitus as more tolerable; of 41 patients who underwent biofeedback training for tinnitus, 33 reported improvement. The best results occurred in patients who were motivated and who had depression and anxiety-type syndromes. Biofeedback training is not a specific treatment for tinnitus but rather a method for managing stress. Like other chronic symptoms, such as pain or headache, tinnitus is intricately related to the overall psychologic health and makeup of the patient. In a subpopulation of patients who suffer from severe tinnitus, a high level of psychiatric morbidity has been found. Hypnosis has been used in a controlled trial to relieve tinnitus in a select group of patients." Only one patient experienced a considerable
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reduction in tinnitus; 36% ofthe patients thought that the effects of relaxation were beneficial even though hypnotherapy did not diminish the loudness of their tinnitus. We believe that general relaxation procedures are of definite benefit in the management of patients with tinnitus.
CONCLUSION
Tinnitus is a common complaint and is most often associated with sensorineural hearing loss. Unilateral tinnitus, pulsatile tinnitus, fluctuating tinnitus, and tinnitus associated with vertigo must be carefully evaluated. In conjunction with a thorough history and physical examination, audiologic assessment is an important factor in the evaluation of tinnitus. It establishes a baseline for determining what more advanced diagnostic tests should be performed and what specific rehabilitative measures might be appropriate. Although many patients have mild tinnitus that needs no treatment, the possibility of an underlying pathologic process should not be overlooked. Several methods are available to help patients cope with tinnitus: increasing the ambient noise by turning on the television or radio, using a "sleep machine" for generating soothing sounds, or wearing a hearing aid, tinnitus masker, or hearing instrument. Stress and anxiety can aggravate tinnitus; thus, biofeedback and stress management therapy may be beneficial. No drug has been approved by the US Food and Drug Administration for the treatment of tinnitus; however, antidepressant therapy may help relieve tinnitus associated with anxiety-depression syndromes. A stressful lifestyle should be minimized, ample sleep should be scheduled, and stimulants such as nicotine and caffeine should be avoided. Many patients have found relief by becoming involved with a tinnitus support group or support organizations. One of the best known groups is the American Tinnitus Association (PO Box 5, Portland, OR 97207).
ACKNOWLEDGMENT
We thank Dr. Wayne O. Olsen (Section of Audiology, Mayo Clinic Rochester) for helpful review
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of our manuscript and Jean Heiman for secretarial assistance.
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