Self-reported tinnitus and ototoxic exposures among deployed Australian Defence Force personnel
From: Mil Med. 2011 Apr;176(4):461-7.
The association between military service and symptoms of hearing loss including tinnitus is well known, with a number of countries strengthening hearing conservation programs for their serving defense personnel. In many cases of occupation related hearing loss, the problem is attributed to noise exposure alone. Although noise is the most common preventable cause of irreversable sensorineural hearing loss in the general population, focusing solely on noise ignores a number of other potential causes of ototoxicity. A number of chemical compounds are known or suspected to have the ability induce ototoxic effects, including solvents, heavy metals, pesticides and asphyxiants such as carbon monoxide.
Although many occupational studies indicate a possible likely relationship between chemical exposures and hearing impairment, the exact nature of any effects in humans has proved difficult to establish. In particular, the impact of nonwork factors such as the ageing process and noisy recreation activities is difficult to assess. Tobacco smoking is a further confounding factor as cigarette smoke contains a number of known or suspected ototoxic chemicals, including hydrogen cyanide, carbon monoxide, cadmium and lead. A substantial body of research demonstrates that smoking behaviors impact negatively on hearing, particularly at high frequencies, although there is no clear relationship between tinnitus and smoking.
Similarities between severe tinnitus and chronic pain
From: J Am Acad Audiol. 2000 Mar;11(3):115-24
The symptoms and signs of severe tinnitus and chronic pain have many similarities and similar hypotheses have been presented regarding how the symptoms are generated. Pain and tinnitus have many different forms. The severity of the symptoms of both varies within wide limits, and it is not likely that all forms have the same pathology. Some individuals with severe tinnitus perceive sounds to be unpleasant or painful. This may be similar to what is known as allodynia, which is a painful sensation of normally innocuous stimulation of the skin. Many individuals with chronic pain experience a worsening of their pain from repeated stimulation (the “wind-up” phenomenon). This is similar to the increasingly unpleasant feeling from sounds that are repeated that many individuals with severe tinnitus experience. There are also similarities in the hypotheses about the generation of pain and tinnitus. Although less severe tinnitus may be generated in the ear, it is believed that severe tinnitus in many cases is caused by changes in the nervous system that occur as a result of neural plasticity. Acute pain caused by tissue injury is generated at the site of injury but chronic pain is often generated in the central nervous system, yet another similarity between chronic pain and severe tinnitus. The changes in the nervous system consist of altered synaptic efficacy including opening of dormant synapses. For pain, this is believed to occur in the wide dynamic range neurons of the spinal cord and brain stem. Less is known about the anatomic location of the changes that cause severe tinnitus but there are indications that it may be the inferior colliculus. It is also possible that other auditory systems than the classical ascending pathways may be involved in severe tinnitus.
Tinnitus and its risk factors in the Beaver Dam Offspring Study
From: Int J Audiol. 2011 Feb 10. [Epub ahead of print]
To assess the prevalence of tinnitus along with factors potentially associated with having tinnitus. Data were from the Beaver Dam Offspring Study, an epidemiological cohort study of aging. After a personal interview and audiometric examination, 3267 participants were classified as having tinnitus if in the past year they reported having tinnitus of at least moderate severity or that caused difficulty in falling asleep.
The prevalence of tinnitus was 10.6%. In a multivariable logistic regression model adjusting for age and sex, the following factors were associated with having tinnitus: hearing impairment, currently having a loud job, history of head injury, depressive symptoms, history of ear infection, history of target shooting, arthritis, and use of NSAID medications. For women, ever drinking alcohol in the past year was associated with a decreased risk of having tinnitus.
These results suggest that tinnitus is a common symptom in this cohort and may be associated with some modifiable risk factors.
The more the worse: the grade of noise-induced hearing loss associates with the severity of tinnitus
From: Int J Environ Res Public Health. 2010 Aug;7(8):3071-9. Epub 2010 Aug 4.
Tinnitus is a perception of sound without an external source. This perception can be induced by various dysfunctions on several levels of the peripheral or central auditory pathway. Regardless of the original cause, all patients complain of hearing a tinnitus tone on either one (unilateral) or both sides (bilateral) of the head or ears. Depending on the case, tinnitus tone may have low, medium or high frequency and be either relatively quiet (0–3 dB), going up to relatively loud (more than 16 dB). Tinnitus may take acute (up to 3 months), sub-acute (4–12 months) or a chronic turn (longer than a year). Regarding the level of disturbance, tinnitus can be classified as compensated (low-level distress) or decompensated (high-level distress). The major problem in patients with decompensated tinnitus is sleep interference, because the tinnitus tone keeps the patients awake. Other diseases that follow include depression, a variety of phobias, anxiety disorders, problems with concentration and in extreme cases—suicide. In other words, decompensated tinnitus seriously reduces the quality of life. Approximately 30 per 100 adults experience tinnitus, whereas about 1–5 persons per 100 suffer from tinnitus and seek medical help. In the Western world, tinnitus has a big economic impact.
The onset of tinnitus can have various basis such as neurologic, traumatic, infectious or drug-related, however, the major cause of tinnitus is a hearing loss. Hearing loss is usually caused by the aging process (presbycusis) or by the overexposure to noise (noise-induced hearing loss). Occupational noise, together with environmental noise pollution, are two major factors contributing to the noise-induced hearing loss. Newly emerging noise-induced hearing loss victims are adolescents who inappropriately use MP3 or MP3-like personal players (too long/too loud, using earphone-insert type headphones). Between 57% and 76% of tinnitus patients were shown to have noise-induced hearing loss. These, and a lot of other data, strongly indicate coexistence of both hearing dysfunctions. Based on the above data the authors put forward a hypothesis that the degree of hearing loss could negatively influence the severity of tinnitus. To test the hypothesis we used a retrospective study using data acquired from 531 tinnitus patients. This data were randomly collected on the admission of patients who reported to the day ward of Tinnitus Center at the Charité – Universitätsmedizin in Berlin between January 2008 and March 2010. The authors have analyzed general audiometric and tinnitus-oriented psychometric parameters.
Prevalence and Characteristics of Tinnitus among US Adults
From: Am J Med. 2010 Aug;123(8):711-8
Tinnitus, derived from the Latin word tinnire meaning “to ring,” is the perception of noise in the absence of an acoustic stimulus. It is a common condition that is usually subjective, perceived only by the patient, and therefore diagnosis and monitoring rely on self-report. Data from the 1996 National Health Interview Survey (NHIS) showed tinnitus was experienced by approximately 35-50 million adults in the US, with 12 million seeking medical care, and 2-3 million reporting symptoms that were severely debilitating. Cases and proposed etiologies of tinnitus are clinically heterogeneous and, although several treatment options have been tried, no single cure exists for the condition.
Patients who experience tinnitus often report significant associated morbidities. Lifestyle detriment, emotional difficulties, sleep deprivation, work hindrance, interference with social interaction, and decreased overall health have been attributed to tinnitus. Although causative relations are yet unknown, patients with tinnitus can have increased risk for depression, anxiety, and insomnia.
A limited number of risk factors for tinnitus have been suggested, the best described of which include increasing age, hearing loss, and loud noise exposure. These associations merit further exploration in a large cohort. Furthermore, the relations between tinnitus and other demographic and health factors are minimally characterized in the current literature. Therefore, the authors examined the relation between tinnitus and several potential risk factors using data from the National Health and Nutrition Examination Survey (NHANES), a large nationally representative survey.
Assessing audiological, pathophysiological and psychological variables in tinnitus patients with or without hearing loss.
From: Eur Arch Otorhinolaryngol. 2010 Jun 25. [Epub ahead of print]
The aim of this work is to study the characteristics of tinnitus both in normal hearing subjects and in patients with hearing loss. The study considered tinnitus sufferers, ranging from 21 to 83 years of age, who were referred to the Audiology Section of Palermo University in the years 2006-2008. The following parameters were considered: age, sex, hearing threshold, tinnitus laterality, tinnitus duration, tinnitus measurements and subjective disturbance caused by tinnitus. The sample was divided into Group1 (G1), 115 subjects with normal hearing, and Group2 (G2), 197 subjects with hearing loss. Especially for G2, there was a predominance of males compared to females; the highest percentage of tinnitus resulted in the decades 61-70 and >70 with a significant difference for G2 demonstrating that the hearing status and the elderly represent the principal tinnitus-related factors.
The hearing impairment resulted in most cases of sensorineural hearing loss type and was limited to the high frequencies; the 72.1% of the patients with sensorineural hearing loss had a high-pitched tinnitus, while the 88.4% of the patients with a high-frequency sensorineural hearing loss had a high-pitched tinnitus. As to the subjective discomfort, the catastrophic category was the most representative among G1 with a significant difference between the two groups; no correlation was found between the level of tinnitus intensity and the tinnitus annoyance confirming the possibility that tinnitus discomfort is elicited by a certain degree of psychological distress as anxiety, depression, irritability and phobias.
Polysomnographic and quantitative electroencephalographic correlates of subjective sleep complaints in chronic tinnitus.
From: J Sleep Res. 2010 Jun 16. [Epub ahead of print]
Chronic tinnitus, or the perception of hearing sounds without the presence of external stimulation, is estimated at about 10-15% of the population, with highest prevalence after 50 years of age. Sleep complaints are among the most prominent complaints accompanying tinnitus, but objective data are rare. In this study, we examined prospectively the subjective and objective sleep parameters of this patient population in order to determine differences in sleep disturbances associated with chronic tinnitus compared to matched controls. Forty-four subjects (22 with tinnitus and 22 controls without tinnitus), unselected with respect to sleep complaints, participated in this study. The analysis involved 1-week sleep diaries, subjective sleep questionnaires and 1 night of polysomnographic (PSG) assessment. Compared to matched controls, the tinnitus group showed lower subjective sleep quality as measured with the Pittsburgh Sleep Quality Index (PSQI) and sleep diaries, but no significant difference in objective polysomnograph sleep parameters (i.e. sleep latency, efficiency). However, quantitative non-rapid eye movement sleep analysis revealed lower spectral power in the delta frequency band in the tinnitus group compared to controls, and this decrease was correlated with subjective sleep complaints (the lower the delta spectral power, the greater the complaints). This is the first report of an electrophysiological correlate of sleep difficulties supportive of subjective sleep complaints in the tinnitus population.
Transcutaneous electrical nerve stimulation (TENS) of upper cervical nerve (C2) for the treatment of somatic tinnitus
From: Exp Brain Res. 2010 May 28. [Epub ahead of print]
Somatic tinnitus has been defined as tinnitus temporally associated to a somatic disorder involving the head and neck. Several studies have demonstrated the interactions between the somatosensory and auditory system at the dorsal cochlear nucleus, inferior colliculus, and parietal association areas. The objective is to verify the effect of transcutaneous electrical nerve stimulation of the upper cervical nerve (C2) in the treatment of somatic tinnitus. As electrical stimulation of C2 increases activation of the dorsal cochlear nucleus through the somatosensory pathway and enlarges the inhibitory role of the dorsal cochlear nucleus on the central nervous system, C2 TENS can be considered for tinnitus modulation. A total of 240 patients in whom tinnitus is modulated by somatosensory events (e.g., tinnitus change with rotation, retro- and antiflexion of neck) or modulated by pressure on head or face were included in this study. Both a real and a sham TENS treatment were applied for 30 min (10 min of 6 Hz, followed by 10 min of 40 Hz and 10 min of sham). Significant tinnitus suppression was found. Only 17.9% (N = 43) of the patients with tinnitus responded to C2 TENS. They had an improvement of 42.92%, and six patients had a reduction of 100%.
Cochlear changes in presbycusis with tinnitus.
From: Am J Otolaryngol. 2010 Apr 29. [Epub ahead of print]
The pathophysiology of tinnitus is obscure and its treatment is therefore elusive. Significant progress in this field can only be achieved by determining the mechanisms of tinnitus generation, and thus, histopathologic findings of the cochlea in presbycusis with tinnitus become crucial. We revealed the histopathologic findings of the cochlea in subjects with presbycusis and tinnitus.
The subjects were divided into 2 groups, presbycusis with tinnitus (tinnitus) group and presbycusis without tinnitus (control) group, with each group comprising 8 temporal bones from 8 subjects. We quantitatively analyzed the number of spiral ganglion cells, loss of cochlear inner and outer hair cells, and areas of the stria vascularis and spiral ligament.
There was a significantly greater loss of outer hair cells in the tinnitus group compared with the control group in the basal and upper middle turns. The stria vascularis was more atrophic in the tinnitus group compared with the control group in the basal turn. Tinnitus is more common in patients with presbycusis who have more severe degeneration of outer hair cells and stria vascularis.
Note: We have changed the format of our Tinnitus Handicap Inventory to a form which generates scores and definitions online for immediate results.
Temporo-insular enhancement of EEG low and high frequencies in patients with chronic tinnitus.
From: BMC Neurosci. 2010 Mar 24;11(1):40. [Epub ahead of print]
Tinnitus is an auditory phantom perception, reported subjectively as a tone and/or a noise, in the absence of an external stimulus. Approximately 5-15 % of the general population experience tinnitus. In 1-3% of the general population the tinnitus affects the quality of life, involving sleep disturbance, work impairment and psychological distress. The underlying physiological mechanisms that lead to phantom sensation are still being explored. In most cases, tinnitus is accompanied by an audiometrically measurable hearing loss, and even in a majority of those cases with normal audiograms abnormal outer or inner hair-cell function has been reported correlating with the presence of tinnitus.
Contemporary views of tinnitus emphasize the role of the central auditory system. Studies in anaesthetized animals suggest enhanced firing rate and /or synchronized firing to be a necessary neurophysiological mechanism underlying tinnitus. A reduction of tinnitus intensity in patients has been correlated to reduction of delta band power.
Alterations in spontaneous central neuronal activity patterns after peripheral deafferentations have recently been proposed to be essential in the genesis of tinnitus. A relevance for peripheral deafferentation has also been proposed in the field of neurogenic pain, which prompted some authors to envisage that a similar mechanism might be at the source of tinnitus and neurogenic pain. Peripheral deafferentation leads to thalamic deactivation, which in turn disrupts normal thalamocortical interaction, thus leading to the appearance of tinnitus. The effects of an abnormal thalamocortical interaction can be analysed at the cortical level using magnetoencephalogram or electroencephalogram. This sequential view integrates both the induction in the periphery and the generation at the thalamocortical level of tinnitus. In the following, the authors refer to a mechanism that focuses on thalamocortical interplay. First evidence for this mechanism in tinnitus was the finding of low-threshold calcium spike bursts in the medial thalamus. 50% of neuronal activity in the medial thalamus (central lateral nucleus, central lateral nucleus) was characterized as low-threshold calcium spike bursts. Low-threshold calcium spike bursts displayed a delta/theta rhythmicity, with a mean interburst discharge rate of 4 Hz. low-threshold calcium spikes have been described intracellularly in in vitro and in vivo experiments and have been related to a state of membrane hyperpolarization. In tinnitus this would be a consequence of auditory deprivation caused by peripheral damage.