The Mechanisms of Tinnitus: Research Progress and Treatment Implications

Therapies for tinnitus currently can be categorized as pharmacologic, behavioral, acoustic-physical, and combinations of the above.

Pharmaceuticals are a first-line therapy followed by instrumentation. Drugs used in tinnitus largely target the depression and anxiety that accompany the disorder. Agents used to varying extents include antidepressants, anticonvulsants, antihistamines, dexchlorpheniramine, antiarrhythmics, anesthetics, and the rheologic agent pentoxifylline. The tinnitus itself is usually not reduced or eliminated by the pharmacologic agents, but the effects seem to attenuate the patient’s annoyance. In a select cohort of patients with subjective idiopathic tinnitus (SIT) of central-type severe disabling tinnitus, gabapentin demonstrated safe and effective relief, but this is controversial. Although developing test drugs to reverse neuronal changes-those of neural activity, neural synchrony, and frequency map reorganization-is an obvious direction for exploration, the problem to date is that blocking activity in the auditory system is difficult to achieve without also blocking activity in other vital brain areas.

Psychological counseling is beneficial for a number of reasons. First, it may be used to reorient associations the individual has with the tinnitus signal such that a negative effect can be alleviated to a more neutral response, similar to the way patients are taught to manage chronic pain. Combining counseling, sound therapy (partial masking), and education can be highly effective in neutralizing a patient’s emotional reactions to tinnitus percepts.

Patients are sometimes counseled to avoid tinnitus-causing agents (such as salicylates). Some groups suggest that patients try a step-and dose-wise exploration of alternative therapies, including acupuncture, hypnotherapy, vitamins, and herbs such as gingko biloba extract.

Acoustic therapies (instrumentation) aim at masking or partially masking the tinnitus, or influencing the way the central nervous system works. Instrumentation has advanced for tinnitus patients who have near-normal hearing, mild high-frequency hearing losses, hyperacusis, and high-frequency tinnitus. Effective therapies include masking devices, hearing aids (for those with higher-level hearing loss), and acoustic (filtered music) therapy. If the aforementioned neural changes (increased activity, synchrony, and frequency-map reorganization) are triggered by damage to the inner ear or by hearing loss (regeneration from selectively damaged outer hair cells appears to be a root cause), stimulating the auditory system in a way that better restores activity to the damaged area may have the effect of reversing the plasticity. Instead of neurons remaining hyperactive, oversynchronized, or overselective to certain frequencies, directly stimulating the ear with frequencies that span the frequency range of the hearing loss might diminish those measures of change. In animal studies testing this hypothesis, data seemed to suggest that, in fact, that is what happens: In those with less than severe hearing loss, who have a high-pitched or high-frequency hearing loss similar to the tinnitus, and who still have residual function, stimulation of functional areas demonstrates that all three measures of change are diminished.