920 www.thelancet.com/neurology Vol 12 September 2013 Review Tinnitus: causes and clinical management Berthold Langguth, Peter M Kreuzer, Tobias Kleinjung, Dirk De Ridder Tinnitus is the perception of sound in the absence of a corresponding external acoustic stimulus. With prevalence ranging from 10% to 15%, tinnitus is a common disorder. Many people habituate to the phantom sound, but tinnitus severely impairs quality of life of about 1–2% of all people. Tinnitus has traditionally been regarded as an otological disorder, but advances in neuroimaging methods and development of animal models have increasingly shifted the perspective towards its neuronal correlates. Increased neuronal firing rate, enhanced neuronal synchrony, and changes in the tonotopic organisation are recorded in central auditory pathways in reaction to deprived auditory input and represent—together with changes in non-auditory brain areas—the neuronal correlate of tinnitus. Assessment of patients includes a detailed case history, measurement of hearing function, quantification of tinnitus severity, and identification of causal factors, associated symptoms, and comorbidities. Most widely used treatments for tinnitus involve counselling, and best evidence is available for cognitive behavioural therapy. New pathophysiological insights have prompted the development of innovative brain-based treatment approaches to directly target the neuronal correlates of tinnitus. Introduction Tinnitus is the perceived sensation of sound in the absence of a corresponding external acoustic stimulus. Unlike auditory hallucinations, which are phantom phenomena that occur mainly in people with mental disorders and manifest as the perception of voices and musical hallucinations, in which instrumental music or sound is perceived, tinnitus sensations are usually of an unformed acoustic nature such as a buzzing, hissing, or ringing. Tinnitus can be unilateral or bilateral, but can also be described to emerge within the head. The perceived sensation can be intermittent or have a pulsatile character. The matched loudness of the phantom sound ranges from a subtle noise slightly above the hearing threshold to high-intensity sounds. Tinnitus is classified as objective tinnitus or somatosound if a sound is generated in the body and is also audible by the examiner (eg, myoclonic contractions of the tensor tympani muscle or altered blood flow in vessels near the ear), or as subjective tinnitus, which is much more common, if it does not have a specific inner-body sound source. In a large survey in Norway, 21∙3% of men and 16∙2% of women reported perception of tinnitus, with 4∙4% of men and 2∙1% of women reporting high tinnitus intensity. 1 Results of epidemiological studies show similar prevalence not only in other European countries, 2,3 the USA, 4,5 and Japan, 6 but also in low-income and middle-income countries in Africa 7,8 and Asia, 9 which indicates that the perception of phantom sounds is a global burden. Hearing impairment, increasing age, and male sex have been identified as the most relevant risk factors for tinnitus. 5 Because of demographic developments and an increase in professional and leisure noise exposure, tinnitus prevalence is expected to continue to increase. 10 Moreover, tinnitus is among the most frequent sequelae of modern warfare. 11 Tinnitus is clinically heterogeneous in its cause, perceptual characteristics, and accompanying symptoms. Many patients with tinnitus report symptoms such as frustration, annoyance, irritability, anxiety, depression, hearing difficulties, hyperacousis, insomnia, and concentration difficulties; these symptoms are highly relevant to determine tinnitus severity. 12 Thus, tinnitus is a highly prevalent and potentially distressing condition with a wide range of symptoms that can place a huge burden on patients and substantially impair quality of life. Its socioeconomic relevance is shown by the greatly increased risk of receiving a disability pension among patients with tinnitus. 13 Tinnitus was traditionally thought to be an otological disorder, but treatment approaches targeting the cochlea have had discouraging results. 14 With little evidence for successful therapies from randomised clinical trials, standardisation in the care of patients with tinnitus has been low, 15 with most patients left untreated. However, during the past decades advances in neuroimaging methods and the development of animal models 16 have shifted the perspective towards the neuronal correlates underlying different forms of tinnitus. 10,17 On the basis of this increased pathophysiological understanding, innovative therapeutic approaches to reduce the tinnitus signal are being developed and have had promising results. At the same time, clinical research methodology has substantially improved, providing convincing evidence for the efficacy of cognitive behaviour-based therapies to reduce tinnitus-related distress 18,19 and enabling evidence-based tinnitus treatment. 20 Causes and pathophysiology Tinnitus can arise from pathological changes along the entire auditory pathway. In most cases tinnitus develops as a consequence of initial cochlear lesions such as sudden hearing loss, noise trauma, presbyacusis, or administration of ototoxic drugs. These lesions can result in abnormal neuronal activity in central auditory pathways that can then be finally perceived as tinnitus. Abnormal changes to the auditory nerve (eg, microvascular compression or vestibular schwannoma) can also lead to perception of tinnitus. However, the association between hearing loss and tinnitus is not Lancet Neurol 2013; 12: 920–30 Department of Psychiatry and Psychotherapy (B Langguth MD, P M Kreuzer MD) and Interdisciplinary Tinnitus Center (B Langguth, P M Kreuzer, T Kleinjung MD), University of Regensburg, Regensburg, Germany; Department of Otolaryngology, University of Zurich, Zurich, Switzerland (T Kleinjung); Unit of Neurosurgery, Department of Surgical Sciences, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand (Prof D De Ridder MD); and BRAI²N, Sint Augustinus Hospital, Antwerp, Belgium (Prof D De Ridder) Correspondence to: Dr Berthold Langguth, Department of Psychiatry and Psychotherapy, University of Regensburg, Universitaetsstrassee 84, 93053 Regensburg, Germany berthold.langguth@medbo.de