Applied Evidence

Tinnitus: Questions to reveal the cause, answers to provide relief

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References

Practice recommendations
  • If no treatable cause of tinnitus is found, assess the severity of tinnitus, secondary problems (such as depression, anxiety, and insomnia), and implement tinnitus management strategies (SOR:B).
  • Acoustic therapy is effective for tinnitus management (SOR:B).
  • All patients should wear hearing protection when they are exposed to loud sounds such as a gas lawnmower, leaf blower, power tools, or gunfire (SOR:A).
  • Successful management of insomnia, anxiety or depression will decrease the severity of tinnitus for most patients (SOR:B).

Tinnitus—the perception of sound that does not have an external source—can be constant or intermittent and perceived as ringing, buzzing, hissing, sizzling, roaring, chirping, or other sounds.

Acute tinnitus, which can last days or weeks, may be caused by ear infection, medications, head or neck injury, excessive sound exposure, earwax, and changes in blood pressure or metabolism. With appropriate evaluation, such underlying conditions usually can be identified and treated, often with resultant resolution of tinnitus.

Chronic tinnitus (persistence for 6 months or more) can also result from these conditions and is more likely to occur in people who have hearing loss.1 (See Prevalence of tinnitus.) Even though a true “cure” for most cases of chronic tinnitus is not available, patients can obtain relief from the symptom with assistance from clinicians who are familiar with tinnitus management strategies.

Prevalence of tinnitus

Seidman and Jacobson2 estimated that 40 million people in the United States experience chronic tinnitus. The prevalence of tinnitus increases with age: 27% of males and 15% of females aged 45 years or older experience the symptom.3

Tinnitus is rare in children who have normal hearing.4 However, the prevalence of tinnitus in children with severe or profound hearing loss has been reported as 33%5 or 64%.6 More males than females experience tinnitus because men traditionally have had a greater amount of noise exposure in military service, in the workplace, and during recreational activities. Consequently, hearing loss and tinnitus are both more prevalent among men aged 45 years or older compared with women in the same age group.3

Damage depends on intensity, length of exposure

Tinnitus is most commonly caused by exposure to excessively loud sounds such as gunfire, power tools, machinery, or music. Ringing in the ears occurs because of damage to stereocilia, microscopic appendages attached to the apical ends of hair cells in the cochlea.

Moderate sounds (80 decibels sound pressure level [dB SPL] or lower) normally cause stereocilia to make tiny movements, triggering the releaseof neurotransmitter molecules from the basal ends of hair cells that activate auditory neurons in the eighth cranial nerve.

Excessive sound exposure (85 dB SPL or louder) causes stereocilia to bend more than they should. People then perceive high-pitched ringing tinnitus because hair cells that respond to higher-frequency sounds are located at the base of the cochlea and are the first to be damaged by loud noise.

If the damage is modest and infrequent, stereocilia can recover, returning to their normal function in a few minutes or hours. The patient’s hearing will be restored and the tinnitus will stop. However, repeated exposure to hazardous sounds eventually causes irreparable damage to stereocilia and hair cells, resulting in permanent sensorineural hearing loss and possibly chronic tinnitus.

In addition to noise exposure, any condition that causes hearing loss or damages the auditory system can contribute to the generation of tinnitus (Table). Imaging studies using functional magnetic resonance imaging7 or positron-emission tomography8-9 demonstrated that the perception of chronic tinnitus usually occurs as a result of hyperactivity within central auditory areas of the human brain, especially the auditory cortex. As portions of the auditory system degenerate during the aging process or acquire damage from noise exposure, disease, and accidents, the natural balance of central auditory excitation vs inhibition is disrupted. In patients who hear tinnitus, excitatory pathways within the auditory system are active when they shouldn’t be: in quiet environments. This gives patients the perception of tinnitus sounds.

TABLE
Causes of subjective tinnitus

Presbycusis: hearing loss due to aging
Prolonged noise exposure: Noise-induced hearing loss
Acoustic trauma: one-time exposure to high intensity sound
Otosclerosis: abnormal accumulation of calcium on middle ear ossicles or cochlea
Infections: bacterial, viral, fungal
Autoimmune hearing loss
Meniere’s disease or endolymphatic hydrops: abnormally high inner ear pressure
Neoplasms: for example, acoustic neuroma or cholesteatoma
Genetic predisposition
Ototoxicity
  • – Medications: aminoglycoside antibiotics (such as gentamicin); valproate; quinine; cisplatin; loop diuretics (such as furosemide)
  • – Heavy metals such as lead
Vascular
  • – Hypertension; arteriosclerosis; cerebral aneurysm; cerebrovascular accident
Metabolic
  • – Anemia; hypothyroidism; hyperthyroidism; diabetes mellitus
Head or neck injury

Objective tinnitus

Objective tinnitus—which can be heard also by people in proximity to the patient’s ear—can be caused by vascular abnormalities (congenital arteriovenous fistula, acquired arteriovenous shunt, glomus jugulare, high-riding carotid artery, carotid stenosis, persistent stapedial artery, dehiscent jugular bulb or a vascular loop such as anterior inferior communicating artery [AICA] or posterior inferior communicating artery [PICA] compressing the auditory nerve) or mechanical disorders (abnormally patent Eustachian tube, palatal myoclonus, temporo-mandibular joint disorder, or stapedial muscle spasticity).10 However, objective tinnitus is rare, accounting for <1% of all cases. The vast majority of tinnitus cases are subjective—sounds are perceived only by the patient.

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