The Phantom Sound Of Tinnitus




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Anyone who has ever been to a loud nightclub has probably experienced that ringing in the ears that comes home with you. The feeling is uncomfortable, but it eventually disappears. Less fortunate are the 10-15% of people in the world that experience this continuously and, most likely, will experience it forever (and I am one of them).

Tinnitus (a Latin word  meaning “ringing”) is a hearing disorder characterized by the conscious perception of a sound in the absence of a corresponding external acoustic stimulus. Tinnitus can be transient, but after having lasted longer than 12 months it is considered chronic. Although in rare cases a treatable source can be identified, in the majority of situations tinnitus is subjective and occurs as an idiopathic condition with unknown mechanisms.

Tinnitus usually manifests as a ringing, hissing or sizzling, although it is possible for more complex sounds to arise, such as voices or music. Unlike auditory hallucinations associated with mental illnesses, voices or music heard as a form of tinnitus are indistinct and suggest no meaning. Tinnitus can be unilateral, bilateral, or be localized centrally within the head, although some patients describe an external point of origin. The sound can be continuous or intermittent, sometimes being a rhythmical or pulsatile sound. Pulsatile tinnitus can be synchronous with the heartbeat, in which case a vascular origin is likely.

The onset of tinnitus can be abrupt, but it is insidious in most cases. The perceived volume can range from just above hearing threshold to high-intensity sounds. Tinnitus becomes highly distressing in the latter case, when it is too loud to ignore. High-intensity tinnitus is commonly accompanied by other symptoms such as frustration, irritability, anxiety, insomnia, inability to concentrate, and decreased sound tolerance (hyperacusis).

The causes for tinnitus are mostly unclear, but there are several risk factors known to be associated with its development. The main risk factor is hearing loss, despite many people with tinnitus having otherwise normal hearing, and many people with hearing loss having no tinnitus. People commonly exposed to loud noises are naturally more likely to develop tinnitus. Other risk factors include smoking, alcohol consumption, history of head injuries, and hypertension. Various common drugs can also trigger tinnitus, as well as emotional factors and stress.

Little is known about the pathological mechanisms. Tinnitus is most likely a disorder involving both peripheral and central pathways in the nervous system. Although it can be triggered by peripheral mechanisms such as cochlear alterations, it usually persists after auditory nerve section, indicating that the brain plays a crucial role in its pathophysiology. Evidence exists for a tinnitus-associated brain network that includes sensory auditory areas and cortical regions involved in such functions as emotions, memory or attention.

Treatments are mostly ineffective. No pharmacological treatment has shown efficacy in long term reduction of tinnitus. Cochlear implants and hearing aids are frequently used for tinnitus associated with hearing loss.

Most commonly, therapeutic approaches are directed towards achieving habituation to the phantom sound. These approaches include counseling, cognitive behavioral therapy, sound therapy, and brain stimulation. Tinnitus retraining therapy, for example, is a protocol that combines counseling and sound therapy, aimed at achieving habituation by psycho-education, allowing the neutralization and strength reduction of the tinnitus signal.

Another approach is cognitive-behavioral therapy, which uses psycho-education, relaxation training, and attention-control techniques, among others, to reduce the tinnitus-related distress by altering maladaptive cognitive, emotional, and behavioral responses. Sound generators can also be used; these devices produce a sound less disturbing than the tinnitus sound, thereby reducing the perception of tinnitus. Environmental sound generators play relaxing sounds such as sea waves, waterfalls, rain, or white noise. Custom sound generators produce a sound with an adjusted frequency and volume that allow the masking of the tinnitus sound. Alternatively, many individuals also resort to complementary and alternative medicine aimed at inducing relaxation and allowing them to cope with their distress.

References

Adjamian P, Hall DA, Palmer AR, Allan TW, & Langers DR (2014). Neuroanatomical abnormalities in chronic tinnitus in the human brain. Neuroscience and biobehavioral reviews, 45C, 119-133 PMID: 24892904

Baguley D, McFerran D, & Hall D (2013). Tinnitus. Lancet, 382 (9904), 1600-7 PMID: 23827090

Knipper M, Van Dijk P, Nunes I, Rüttiger L, & Zimmermann U (2013). Advances in the neurobiology of hearing disorders: recent developments regarding the basis of tinnitus and hyperacusis. Progress in neurobiology, 111, 17-33 PMID: 24012803

Langguth B, & Elgoyhen AB (2012). Current pharmacological treatments for tinnitus. Expert opinion on pharmacotherapy, 13 (17), 2495-509 PMID: 23121658

Langguth B, Kreuzer PM, Kleinjung T, & De Ridder D (2013). Tinnitus: causes and clinical management. The Lancet. Neurology, 12 (9), 920-30 PMID: 23948178

Image via Dora Zett / Shutterstock.

Sara Adaes, PhD

Sara Adaes, PhD, has been a researcher in neuroscience for over a decade. She studied biochemistry and did her first research studies in neuropharmacology. She has since been investigating the neurobiological mechanisms of pain at the Faculty of Medicine of the University of Porto, in Portugal. Follow her on Twitter @saradaes
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