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Tinnitus: Prevalence, Causes and Treatment Approaches
by Burke S. Richmond, M.D.
Geriatric Times July/August 2003 Vol. IV Issue 4
Tinnitus, an auditory perception associated with normal and abnormal health states, is an awareness of sound that does not originate from an external source. Occurring at all ages, tinnitus is more common in the elderly. Like pain, tinnitus is a symptom that requires a careful history and physical examination to classify its type, identify any associated disease, and organize diagnostic and therapeutic considerations. In most cases, no specific cause is found.
Background and Prevalence
Descriptions and treatment strategies of tinnitus date to ancient Babylonian, Greek and Chinese texts (Stephens, 2000). However, in modern times--with increased life expectancy, an aging population and high levels of noise exposure--it may be anticipated that increasing numbers of patients will have concerns about hearing abnormal sounds.
Tinnitus prevalence increases with advancing age, occurs in both sexes (though more so in older males) and, in the United States, is almost twice as common in whites as it is in African-Americans (Adams et al., 1999). Most people will experience a transient tinnitus (less than five minutes long) that may not compel them to seek medical evaluation. Fortunately, severe forms are less common. The American Tinnitus Association estimates 50 million Americans may experience prolonged tinnitus, while tinnitus interferes with daily activities for up to 12 million Americans (American Tinnitus Association, undated). European population studies estimate 7% to 14% of the population have talked with their physician about tinnitus, while potentially disabling tinnitus occurs in approximately 1% to 2.4% of people (Vesterager, 1997). Tinnitus may be associated with many medical conditions; however, in the elderly, it is most commonly associated with hearing loss (Davis and El Refaie, 2000).
Categorizing Tinnitus
Tinnitus is commonly divided into two categories: objective and subjective (Stouffer and Tyler, 1990). Objective tinnitus (4% of reported cases) represents "real" sounds, theoretically audible to a listener. It is primarily generated within the body from sound sources external to the auditory sensory pathways.
In contrast, subjective tinnitus is a cognitive phenomenon not audible to an external listener. It is "the false perception of sound in the absence of an acoustic stimulus" (Lockwood et al., 2002). Abnormal signaling generated within one or more sites within the auditory pathways and central nervous system is thought to be responsible.
Clinical Assessment
Although patients often have a difficult time describing tinnitus, its clinical evaluation and categorization depend on a thorough history and physical exam. A standardized form detailing the quality, frequency, location and associated symptoms (particularly otologic, neurologic and psychiatric symptoms) can help characterize the perceived sound. Determining the circumstances of onset, level of intrusiveness, sleep disruption and psychological impact of the sound, along with any comorbidities, provides additional clues and directs treatment and prevention strategies. Individuals with persistent tinnitus require a complete head and neck exam and basic audiologic testing (pure tone testing and tympanometry). Additional laboratory testing, specialized audiologic or vestibular testing, and magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA) is directed by clinical suspicion for contributing disease.
Objective tinnitus. Objective tinnitus typically reflects mechanical or somatic sounds. Sound-generating sources include turbulent blood flow, normal and abnormal muscular contractions, amplification of normal body sounds such as the voice, or debris in the middle ear space or external auditory canal. Objective tinnitus may be perceived as unilateral, bilateral or "in the head." Typically, the quality of objective tinnitus is described as pulsating, clicking, whooshing or fluttering (Levine, 2000).
Pulsating tinnitus that corresponds with the cardiac cycle suggests a vascular source. Eustachian tube dysfunction or middle ear conductive hearing changes (e.g., inflammation, effusion or otosclerosis) can cause amplification of normal vascular sounds. Elevated blood pressure may be associated with a "venous hum." Metabolic disorders with a hemodynamic impact, such as anemia and thyroid dysfunction, should be considered. Benign intracranial hypertension may be associated with pulsatile tinnitus, but this is more common in young, obese females (Sismanis, 1998). Potentially modifiable vascular causes of pulsatile tinnitus include atherosclerotic disease, vascular tumors and arteriovenous malformations. Persistent pulsatile tinnitus associated with the cardiac cycle may require duplex carotid ultrasound, MRI or MRA, or angiography (Sismanis, 1998).
Ojective tinnitus also has nonvascular sources. Unilateral sounds may be associated with debris against the tympanic membrane. Crackling sounds following an upper respiratory infection may represent a resolving middle ear space effusion or eustachian tube dysfunction. Crunching sounds may reflect temporomandibular joint dysfunction. Rhythmic clicking can be associated with voluntary or involuntary muscular contractions of middle ear and eustachian tube structures and, rarely, palatal myoclonus. Reports of echoing sounds, distortion of one's own voice (autophonia) and recent weight loss suggest a patulous eustachian tube. Spontaneous oto-acoustic emissions, thought to be produced by vibrating cochlear hair cells, are considered a relatively rare type of objective tinnitus. Treatment of objective tinnitus depends upon identifying and modifying the underlying condition (Levine, 2000).
Subjective tinnitus. Subjective tinnitus is not a real sound. It is a complex auditory perception of variable intensity and duration. Considered a phantom sound, it may be induced by, and associated with, many factors. The fundamental pathophysiology is unknown, however, changes in one or more locations within the auditory pathways, the auditory cortex and the emotional limbic systems are proposed (Lockwood et al., 1998). Disabling tinnitus has been considered analogous to chronic pain (Moller, 1997). Imaging technology is beginning to clarify the neurophysiologic basis of subjective tinnitus; the ability to "see" subjective tinnitus holds significant promise for improved understanding and for evaluating treatment strategies (Levine and Melcher, undated).
Typically, the quality of subjective tinnitus is described as ringing, buzzing, cricket-like, hissing, whistling or humming. The perceived tone often corresponds with the frequency of clinically evident hearing loss (Meikle et al., 1984). High-pitched tones are most common and up to 40% of people report multiple tones (Stouffer and Tyler, 1990). The sounds may be "nonlocalized," bilateral or unilateral. Nonverbal auditory hallucinations, such as crashing sounds or "train-like" sounds, are considered a benign tinnitus variant; however, verbal hallucinations or associated neurological symptoms require further evaluation (Levine, 2000).
Conditions associated with unilateral subjective tinnitus include inflammation, infection, acoustic or physical trauma, and hereditary disease. Brief bursts of sound (typically less than five minutes in duration) without additional symptoms are considered a normal tinnitus variant. Unilateral tinnitus associated with external canal disorders (e.g., otitis externa, cerumen impaction) and middle ear space processes (e.g., otitis media and otosclerosis) often resolves, or is attenuated, after treatment of the underlying condition. Unilateral tinnitus with a sudden, fixed hearing loss raises concern for a viral or microvascular cochlear insult. Tinnitus (usually low-pitched or roaring) with vertigo, ear pressure and documented fluctuating hearing loss may represent Ménière's disease or syndrome; periodic monitoring is required given a potential for progressive hearing loss and vestibular dysfunction. Unilateral tinnitus, a progressive asymmetric hearing loss, dysequilibrium and focal neurological symptoms raise concern for auditory nerve pathology (e.g., an acoustic neuroma) or brain stem pathology (e.g., masses or infarction). Persistent, unexplained unilateral tinnitus is an indication for auditory brain stem response testing or MRI (Levine, 2000).
Bilateral subjective tinnitus, particularly in the elderly, is usually associated with a clinically significant hearing loss, although tinnitus and normal hearing is possible. Any cause of hearing loss may be associated with persistent subjective tinnitus. Common causes of hearing loss include age-related cochlear changes (presbycusis), chronic noise exposure and congenital hearing loss. Less common causes of hearing loss include metabolic disorders, autoimmune processes, infectious disease and exposure to ototoxic medications (particularly aminoglycoside antibiotics, high-dose loop diuretics, nonsteroidal anti-inflammatory drugs [NSAIDs] and chemotherapeutic agents) (Lockwood et al., 2002). External factors can also influence tinnitus perception. Widely fluctuating tinnitus suggests somatic factors, such as bruxism or head and neck muscle tension (Rubinstein et al., 1990). Mental illness, particularly anxiety and depression, is commonly associated with disabling tinnitus; suicidal thoughts may occur and, rarely, suicide results (Erlandsson, 2000). Additional modifiable factors influencing subjective tinnitus are discussed below. If no associated disease is identified, the tinnitus is considered idiopathic.
Treatment Approaches
Reassurance. A common concern is that tinnitus represents a significant disorder, such as a brain tumor or the beginning of deafness. If no associated disease or modifiable factors are identified, provide explanation and reassurance; discuss environmental masking strategies and hearing protection; and review criteria for re-evaluation.
Identify modifiable factors. Many medications can exacerbate tinnitus. Although sensitivity varies widely, commonly associated medications include aspirin, NSAIDs and quinine. If medically tolerable, stopping a suspect medication is reasonable. In some individuals, alcohol, caffeine and nicotine/tobacco may increase tinnitus. Reduction or cessation advice should be provided for these behaviors. Poor sleep hygiene, elevated stress (psychological, social or physical) and comorbidities--particularly cerebrovascular risk factors, bruxism and muscle tension--should be identified and treated.
Environmental sound. Excessive noise can exacerbate tinnitus. Conversely, silence, or too little environmental sound, can increase the tinnitus perception. Environmental strategies to enrich the sound environment can reduce the tinnitus perception; fans, white noise machines, and specialized tapes or compact discs can provide relief.
Wearable masking technologies. If clinical hearing loss is present, hearing aids are associated with decreased tinnitus perception and relief. Tinnitus maskers without amplification are available if a hearing aid is inappropriate. Combined hearing aid and masking devices are also available. Results vary with masking technology, which only provides relief while worn; an audiologist trained to fit a masking device is recommended. Expense and the unwillingness of patients to wear the device are the main barriers to the use of this technology.
Behavioral and combined therapies. Hypnosis, cognitive therapy and biofeedback have shown benefit for some individuals, but definitive studies are lacking.
Tinnitus Retraining Therapy. A neurophysiological approach, Tinnitus Retraining Therapy (TRT) combines use of low-level sound (delivered with environmental or wearable devices to reduce tinnitus awareness) with cognitive therapy (to shape the emotional and intellectual response to tinnitus). Definitive outcome studies for TRT are lacking; however, specialized centers report up to 75% success in reducing severe tinnitus perception (Jastreboff and Jastreboff, 2000).
Pharmacological and other complementary therapies. A wide variety of pharmacologic and complementary strategies have been tried. These include antidepressants (nortriptyline [Pamelor, Aventyl]), neuromodulators (gabapentin [Neurontin]), dietary supplements (B vitamins and zinc), herbal medications (Ginkgo biloba), homeopathy, naturopathy, aromatherapy, craniosacral therapy, chiropractic manipulation, low-dose laser, Ultraquiet ultrasonic therapy and low-dose electrical stimulation. No therapy is predictably associated with a cure or sustained tinnitus relief, and no tinnitus therapy has been approved by the U.S. Food and Drug Administration. Typically, studies have had inadequate design, have not been replicated or show contradictory results (Lockwood et al., 2002; Murai et al., 1992). Placebo effects have been significant (Dobie et al., 1993). Surgery for subjective tinnitus is not recommended, though some cochlear implant recipients experience tinnitus relief (Vernon, 2000). For severe, disabling tinnitus, empiric medication trials are reasonable; choice should be directed by potential side effects and comorbidities.
Summary
Tinnitus, which varies greatly, may be a real or phantom sound. It may be transient or constant; tolerable or cognitively disabling. Tinnitus may reflect normal variants or be associated with potentially debilitating disease. Fortunately, the majority of individuals neither have significant underlying disease nor progress to a disabling form. Reassurance, education, masking strategies and limiting noise protection are adequate treatment for a majority of patients. Cerebrovascular risk factors, modifiable disease and behavioral factors should be addressed. Empiric trials of medication are appropriate for severe cases, but definitive therapies await a better understanding of the neurophysiology of tinnitus and further study of treatment strategies.
Dr. Richmond is board-certified in family medicine. He has a clinical practice in medical otolaryngology as a non-surgeon in the otolaryngology department of the University of Wisconsin.References
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