Functional imaging of chronic tinnitus: the use of positron emission tomography

Artificial intelligence approaches for tinnitus diagnosis: leveraging high-frequency audiometry data for enhanced clinical predictions

This research investigates the application of machine learning to improve the diagnosis of tinnitus using high-frequency audiometry data. A Logistic Regression (LR) model was developed alongside an Artificial Neural Network (ANN) and various baseline classifiers to identify the most effective approach for classifying tinnitus presence. The methodology encompassed data preprocessing, feature extraction focused on point detection, and rigorous model evaluation through performance metrics including accuracy, Area Under the ROC Curve (AUC), precision, recall, and F1 scores. The main findings reveal that the LR model, supported by the ANN, significantly outperformed other machine learning models, achieving an accuracy of 94.06%, an AUC of 97.06%, and high precision and recall scores. These results demonstrate the efficacy of the LR model and ANN in accurately diagnosing tinnitus, surpassing traditional diagnostic methods that rely on subjective assessments. The implications of this research are substantial for clinical audiology, suggesting that machine learning, particularly advanced models like ANNs, can provide a more objective and quantifiable tool for tinnitus diagnosis, especially when utilizing high-frequency audiometry data not typically assessed in standard hearing tests. The study underscores the potential for machine learning to facilitate earlier and more accurate tinnitus detection, which could lead to improved patient outcomes. Future work should aim to expand the dataset diversity, explore a broader range of algorithms, and conduct clinical trials to validate the models' practical utility. The research highlights the transformative potential of machine learning, including the LR model and ANN, in audiology, paving the way for advancements in the diagnosis and treatment of tinnitus.

Focal tDCS of auditory cortex in chronic tinnitus: A randomized controlled mechanistic trial

OBJECTIVE

The goal of this pilot study was to understand how focal transcranial direct current stimulation (tDCS) targeting auditory cortex changes brain function in chronic tinnitus using magnetic resonance imaging (MRI).

METHODS

People with chronic tinnitus were randomized to active or sham tDCS on five consecutive days in this mechanistic trial (n = 10/group). Focal 4x1 tDCS (central anode, surround cathodes) targeted left auditory cortex, with single-blind 2 mA current during twenty-minute sessions. Arterial spin-labeled and blood oxygenation level dependent MRI occurred immediately before and after the first tDCS session, and tinnitus symptoms were measured starting one week before the first tDCS session and through four weeks after the final session.

RESULTS

Acute increases in cerebral blood flow and functional connectivity were noted in auditory cortex after the first active tDCS session. Reduced tinnitus loudness ratings after the final tDCS session correlated with acute change in functional connectivity between an auditory network and mediodorsal thalamus and prefrontal cortex. Reduced tinnitus intrusiveness also correlated with acute change in connectivity between precuneus and an auditory network.

CONCLUSIONS

Focal auditory-cortex tDCS can influence function in thalamus, auditory, and prefrontal cortex, which may associate with improved tinnitus.

SIGNIFICANCE

With future refinement, tDCS targeting auditory cortex could become a viable intervention for tinnitus.

[Functional neuroimaging options for tinnitus]

BACKGROUND

The pathophysiology behind tinnitus is still not well understood. Different imaging methods help in the understanding of the complex relationships that lead to the perception of tinnitus.

OBJECTIVE

Herein, different functional imaging methods that can be used in the study of tinnitus are presented.

MATERIALS AND METHODS

Considering the recent literature on the subject, the relevant imaging methods used in tinnitus research are discussed.

RESULTS AND CONCLUSION

Functional imaging can reveal correlates of tinnitus. Due to the still limited temporal and spatial resolution of current imaging modalities, a conclusive explanation of tinnitus remains elusive. With increasing use of functional imaging, additional important insights into the explanation of tinnitus will be gained in the future.

Focal transcranial direct current stimulation of auditory cortex in chronic tinnitus: A randomized controlled mechanistic trial

Objective

The goal of this pilot MRI study was to understand how focal transcranial direct current stimulation (tDCS) targeting auditory cortex changes brain function in chronic tinnitus.

Methods

People with chronic tinnitus were randomized to active or sham tDCS on five consecutive days in this pilot mechanistic trial (n=10/group). Focal 4×1 tDCS (central anode, surround cathodes) targeted left auditory cortex, with single-blind 2mA current during twenty-minute sessions. Arterial spin-labeled and blood oxygenation level dependent MRI occurred immediately before and after the first tDCS session, and tinnitus symptoms were measured starting one week before the first tDCS session and through four weeks after the final session.

Results

Acute increases in cerebral blood flow and functional connectivity were noted in auditory cortex after the first active tDCS session. Reduced tinnitus loudness ratings after the final tDCS session correlated with acute change in functional connectivity between an auditory network and mediodorsal thalamus and prefrontal cortex. Reduced tinnitus intrusiveness also correlated with acute change in connectivity between precuneus and an auditory network.

Conclusions

Focal auditory-cortex tDCS can influence function in thalamus, auditory, and prefrontal cortex, which may associate with improved tinnitus.

Significance

With future refinement, noninvasive brain stimulation targeting auditory cortex could become a viable intervention for tinnitus.

Evaluating the efficacy of hearing aids for tinnitus therapy - A Positron emission tomography study

Brain imaging studies have revealed neural changes in chronic tinnitus patients that are not restricted to auditory brain areas; rather, the engagement of limbic system structures, attention and memory networks are has been noted. Hearing aids (HA) provide compensation for comorbid hearing loss and may decrease tinnitus-related perception and annoyance. Using resting state positron emission tomography our goal was to analyze metabolic and functional brain changes after six months of effective HA use by patients with chronic tinnitus and associated sensorineural hearing loss. 33 age and hearing loss matched participants with mild/moderate hearing loss were enrolled in this study: 19 with tinnitus, and 14 without tinnitus. Participants with tinnitus of more than 6 months with moderate/severe Tinnitus Handicap Inventory (THI) and Visual Analogue Scale (VAS) scores composed the tinnitus group. A full factorial 2X2 ANOVA was conducted for imaging analysis, with group (tinnitus and controls) and time point (pre-intervention and post-intervention) as factors. Six months after HA fitting, tinnitus scores reduced statistically and clinically. Analysis revealed increased glycolytic metabolism in the left orbitofrontal cortex, right temporal lobe and right hippocampus, and reduced glycolytic metabolism in the left cerebellum and inferior parietal lobe within the tinnitus group. The hearing loss control group showed no significant metabolic changes in the analysis. Parsing out the contribution of tinnitus independent of hearing loss, allowed us to identify areas implicated in declines in tinnitus handicap as a result of the intervention. Brain regions implicated in the present study may be part of chronic tinnitus-specific network.

Structural correlates of the audiological and emotional components of chronic tinnitus

The objective is to investigate white matter tracts, more specifically the arcuate fasciculus and acoustic radiation, in tinnitus and assess their relationship with distress, loudness and hearing loss. DTI images were acquired for 58 tinnitus patients and 65 control subjects. Deterministic tractography was first performed to visualize the arcuate fasciculus and acoustic radiation tracts bilaterally and to calculate tract density, fractional anisotropy, radial diffusivity, and axial diffusivity for tinnitus and control subjects. Tinnitus patients had a significantly reduced tract density compared to controls in both tracts of interest. They also exhibited increased axial diffusivity in the left acoustic radiation, as well as increased radial diffusivity in the left arcuate fasciculus, and both the left and right acoustic radiation. Furthermore, they exhibited decreased fractional anisotropy in the left arcuate fasciculus, as well as the left and right acoustic radiation tracts. Partial correlation analysis showed: (1) a negative correlation between arcuate fasciculus tract density and tinnitus distress, (2) a negative correlation between acoustic radiation tract density and hearing loss, (3) a negative correlation between acoustic radiation tract density and loudness, (4) a positive correlation between left arcuate fasciculus and tinnitus distress for radial diffusivity, (5) a negative correlation between left arcuate fasciculus and tinnitus distress for fractional anisotropy, (6) a positive correlation between left and right acoustic radiation and hearing loss for radial diffusivity, (7) No correlation between any of the white matter characteristics and tinnitus loudness. Structural alterations in the acoustic radiation and arcuate fasciculus correlate with hearing loss and distress in tinnitus but not tinnitus loudness showing that loudness is a more functional correlate of the disorder which does not manifest structurally.

Assessment of the Effectiveness of Transcranial Magnetic Stimulation in Subjective Tinnitus

Introduction  Increases in spontaneous activity in the neurons of the auditory cortex are presumed as the pathophysiology of tinnitus.

Objective  To investigate the effectiveness of transcranial magnetic stimulation (TMS) in the treatment of tinnitus.

Methods  A total of 62 patients between the ages of 22 and 74 with chronic subjective tinnitus were enrolled in the study. The inclusion criteria were normal findings on an otolaryngologic examination and normal ranges of complete blood count, routine biochemical parameter levels, thyroid function, air-bone gap on pure-tone audiometry, and middle-ear pressure and stapedial reflex on tympanometry. The patients were randomized into 2 groups: 40 patients were placed in the treatment for TMS (tTMS) group, and the rest (22 patients) were placed in the sham TMS group. The frequency and severity of the tinnitus, as well as the tinnitus handicap inventory (THI) score of each patient were measured before and one month after the treatment, and the values were statistically evaluated.

Results  We observed a statistically significant improvement in the tTMS group ( p  < 0.05 and p  < 0.05 respectively) regarding the THI and tinnitus severity scores. The sham TMS group showed no significant improvement in terms of the THI ( p  > 0.05). However, the tinnitus severity showed a significant increase in this group ( p  < 0.05). The comparison of differences in the changes in the THI and the tinnitus severity scores showed a significant statistical improvement in the tTMS group compared with the sham TMS group ( p  < 0.05 and p  < 0.05 respectively).

Conclusion  Transcranial magnetic stimulation was found to be effective in the treatment of tinnitus, and may be adopted as a treatment for tinnitus after further comprehensive studies.

Tinnitus Neuroimaging

This article reviews the use of human neuroimaging for chronic subjective tinnitus. Evidence-based guidance on the clinical use of imaging to identify relevant auditory lesions when evaluating tinnitus patients is given. After introducing the anatomy and imaging modalities most pertinent to the neuroscience of tinnitus, the article reviews tinnitus-associated alterations in key auditory and nonauditory networks in the central nervous system. Emphasis is placed on how these findings support proposed models of tinnitus and how this line of investigation is relevant to practicing clinicians.

Pairing sound with vagus nerve stimulation modulates cortical synchrony and phase coherence in tinnitus: An exploratory retrospective study

Recent research has shown that vagus nerve stimulation (VNS) paired with tones or with rehabilitative training can help patients to achieve reductions in tinnitus perception or to expedite motor rehabilitation after suffering an ischemic stroke. The rationale behind this treatment is that VNS paired with experience can drive neural plasticity in a controlled and therapeutic direction. Since previous studies observed that gamma activity in the auditory cortex is correlated with tinnitus loudness, we assessed resting-state source-localized EEG before and after one to three months of VNS-tone pairing in chronic tinnitus patients. VNS-tone pairing reduced gamma band activity in left auditory cortex. VNS-tone pairing also reduced the phase coherence between the auditory cortex and areas associated with tinnitus distress, including the cingulate cortex. These results support the hypothesis that VNS-tone pairing can direct therapeutic neural plasticity. Targeted plasticity therapy might also be adapted to treat other conditions characterized by hypersynchronous neural activity.

The added value of auditory cortex transcranial random noise stimulation (tRNS) after bifrontal transcranial direct current stimulation (tDCS) for tinnitus

Tinnitus is the perception of a sound in the absence of a corresponding external sound source. Research has suggested that functional abnormalities in tinnitus patients involve auditory as well as non-auditory brain areas. Transcranial electrical stimulation (tES), such as transcranial direct current stimulation (tDCS) to the dorsolateral prefrontal cortex and transcranial random noise stimulation (tRNS) to the auditory cortex, has demonstrated modulation of brain activity to transiently suppress tinnitus symptoms. Targeting two core regions of the tinnitus network by tES might establish a promising strategy to enhance treatment effects. This proof-of-concept study aims to investigate the effect of a multisite tES treatment protocol on tinnitus intensity and distress. A total of 40 tinnitus patients were enrolled in this study and received either bifrontal tDCS or the multisite treatment of bifrontal tDCS before bilateral auditory cortex tRNS. Both groups were treated on eight sessions (two times a week for 4 weeks). Our results show that a multisite treatment protocol resulted in more pronounced effects when compared with the bifrontal tDCS protocol or the waiting list group, suggesting an added value of auditory cortex tRNS to the bifrontal tDCS protocol for tinnitus patients. These findings support the involvement of the auditory as well as non-auditory brain areas in the pathophysiology of tinnitus and demonstrate the idea of the efficacy of network stimulation in the treatment of neurological disorders. This multisite tES treatment protocol proved to be save and feasible for clinical routine in tinnitus patients.

Acute high-intensity noise induces rapid Arc protein expression but fails to rapidly change GAD expression in amygdala and hippocampus of rats: Effects of treatment with D-cycloserine

Tinnitus is a devastating auditory disorder impacting a growing number of people each year. The aims of the current experiment were to assess neuronal mechanisms involved in the initial plasticity after traumatic noise exposure that could contribute to the emergence of tinnitus and to test a potential pharmacological treatment to alter this early neural plasticity. Specifically, this study addressed rapid effects of acute noise trauma on amygdalo-hippocampal circuitry, characterizing biomarkers of both excitation and inhibition in these limbic regions, and compared them to expression of these same markers in primary auditory cortex shortly after acute noise trauma. To assess excitatory plasticity, activity-regulated cytoskeleton-associated (Arc) protein expression was evaluated in male rats 45 min after bilateral exposure to acute high-intensity noise (16 kHz, 115 dB SPL, for 1 h), sufficient to cause acute cochlear trauma, a common cause of tinnitus in humans and previously shown sufficient to induce tinnitus in rat models of this auditory neuropathology. Western blot analyses confirmed that up-regulation of amygdalo-hippocampal Arc expression occurred rapidly post-noise trauma, corroborating several lines of evidence from our own and other laboratories indicating that limbic brain structures, i.e. outside of the classical auditory pathways, exhibit plasticity early in the initiation of tinnitus. Western blot analyses revealed no noise-induced changes in amygdalo-hippocampal expression of glutamate decarboxylase (GAD), the biosynthetic enzyme required for GABAergic inhibition. No changes in either Arc or GAD protein expression were observed in primary auditory cortex in this immediate post-noise exposure period, confirming other reports that auditory cortical plasticity may not occur until later in the development of tinnitus. As a further control, our experiments compared Arc protein expression between groups exposed to the quiet background of a sound-proof chamber to those exposed not only to the traumatic noise described above, but also to an intermediate, non-traumatic noise level (70 dB SPL) for the same duration in each of these three brain regions. We found that non-traumatic noise did not up-regulate Arc protein expression in these brain regions. To see if changes in Arc expression due to acute traumatic noise exposure were stress-related, we compared circulating serum corticosterone in controls and rats exposed to traumatic noise at the time when changes in Arc were observed, and found no significant differences in this stress hormone in our experimental conditions. Finally, the ability of D-cycloserine (DCS; an NMDA-receptor NR1 partial agonist) to reduce or prevent the noise trauma-related plastic changes in the biomarker, Arc, was tested. D-cycloserine prevented traumatic noise-induced up-regulation of Arc protein expression in amygdala but not in hippocampus, suggesting that DCS alone is not fully effective in eliminating regionally-specific early plastic changes after traumatic noise exposure.

Intrinsic network activity in tinnitus investigated using functional MRI

Tinnitus is an increasingly common disorder in which patients experience phantom auditory sensations, usually ringing or buzzing in the ear. Tinnitus pathophysiology has been repeatedly shown to involve both auditory and non-auditory brain structures, making network-level studies of tinnitus critical. In this magnetic resonance imaging (MRI) study, two resting-state functional connectivity (RSFC) approaches were used to better understand functional network disturbances in tinnitus. First, we demonstrated tinnitus-related reductions in RSFC between specific brain regions and resting-state networks (RSNs), defined by independent components analysis (ICA) and chosen for their overlap with structures known to be affected in tinnitus. Then, we restricted ICA to data from tinnitus patients, and identified one RSN not apparent in control data. This tinnitus RSN included auditory-sensory regions like inferior colliculus and medial Heschl's gyrus, as well as classically non-auditory regions like the mediodorsal nucleus of the thalamus, striatum, lateral prefrontal, and orbitofrontal cortex. Notably, patients' reported tinnitus loudness was positively correlated with RSFC between the mediodorsal nucleus and the tinnitus RSN, indicating that this network may underlie the auditory-sensory experience of tinnitus. These data support the idea that tinnitus involves network dysfunction, and further stress the importance of communication between auditory-sensory and fronto-striatal circuits in tinnitus pathophysiology. Hum Brain Mapp 37:2717-2735, 2016. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Deafferentation-based pathophysiological differences in phantom sound: Tinnitus with and without hearing loss

Tinnitus has been considered an auditory phantom percept. Recently a theoretical multiphase compensation mechanism at a cortical level has been hypothesized linking auditory deafferentation to tinnitus. This Bayesian brain model predicts that two very different kinds of tinnitus should exist, depending on the amount of hearing loss: an auditory cortex related form of tinnitus not associated with hearing loss, and a (para)hippocampal form associated with hearing loss, in which the auditory cortex might be of little relevance. In order to verify this model, resting state source analyzed EEG recordings were made in 129 tinnitus patients, and correlated to the mean hearing loss, the range of the hearing loss and the hearing loss at the tinnitus frequency. Results demonstrate that tinnitus can be linked to 2 very different mechanisms. In patients with little or no hearing loss, the tinnitus seems to be more related to auditory cortex activity, but not to (para)hippocampal memory related activity, whereas in tinnitus patients with more severe hearing loss, tinnitus seems to be related to (para)hippocampal mechanisms. Furthermore hearing loss seems to drive the communication between the auditory cortex and the parahippocampus, as measured by functional and effective connectivity.

Reduction of cortical excitability and increase of thalamic activity in a low-frequency rTMS treatment for chronic tinnitus

Low-frequency repetitive transcranial magnetic stimulation (rTMS) has received increasing attention for the treatment of tinnitus, but its therapeutic mechanisms are unclear. We performed low-frequency rTMS treatment for a patient with chronic tinnitus and examined changes of cortical excitability and cerebral blood flow using paired-pulse TMS and single-photon emission computed tomography. After the rTMS treatment, tinnitus loudness was decreased, cortical excitability was reduced, and blood flow in the thalamus was increased. Our results suggest that low-frequency rTMS treatment reduces tinnitus loudness by an inhibitory effect on the cortical excitability and a remote activation effect on the thalamus through the corticothalamic networks.

A brain centred view of psychiatric comorbidity in tinnitus: from otology to hodology

Introduction. Comorbid psychiatric disorders are frequent among patients affected by tinnitus. There are mutual clinical influences between tinnitus and psychiatric disorders, as well as neurobiological relations based on partially overlapping hodological and neuroplastic phenomena. The aim of the present paper is to review the evidence of alterations in brain networks underlying tinnitus physiopathology and to discuss them in light of the current knowledge of the neurobiology of psychiatric disorders. Methods. Relevant literature was identified through a search on Medline and PubMed; search terms included tinnitus, brain, plasticity, cortex, network, and pathways. Results. Tinnitus phenomenon results from systemic-neurootological triggers followed by neuronal remapping within several auditory and nonauditory pathways. Plastic reorganization and white matter alterations within limbic system, arcuate fasciculus, insula, salience network, dorsolateral prefrontal cortex, auditory pathways, ffrontocortical, and thalamocortical networks are discussed. Discussion. Several overlapping brain network alterations do exist between tinnitus and psychiatric disorders. Tinnitus, initially related to a clinicoanatomical approach based on a cortical localizationism, could be better explained by an holistic or associationist approach considering psychic functions and tinnitus as emergent properties of partially overlapping large-scale neural networks.

Antidepressants for patients with tinnitus

BACKGROUND

This is an update of a Cochrane review first published in The Cochrane Library in Issue 4, 2006 and previously updated in 2009.Tinnitus is described as the perception of sound or noise in the absence of real acoustic stimulation. It has been compared with chronic pain, and may be associated with depression or depressive symptoms which can affect quality of life and the ability to work. Antidepressant drugs have been used to treat tinnitus in patients with and without depressive symptoms.

OBJECTIVES

To assess the effectiveness of antidepressants in the treatment of tinnitus and to ascertain whether any benefit is due to a direct tinnitus effect or a secondary effect due to treatment of concomitant depressive states.

SEARCH METHODS

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; PsycINFO; CINAHL; Web of Science; BIOSIS; ICTRP and additional sources for published and unpublished trials. The date of the most recent search was 5 January 2012.

SELECTION CRITERIA

Randomised controlled clinical studies of antidepressant drugs versus placebo in patients with tinnitus.

DATA COLLECTION AND ANALYSIS

Two authors critically appraised the retrieved studies and extracted data independently. Where necessary we contacted study authors for further information.

MAIN RESULTS

Six trials involving 610 patients were included. Trial quality was generally low. Four of the trials looked at the effect of tricyclic antidepressants on tinnitus, investigating 405 patients. One trial investigated the effect of a selective serotonin reuptake inhibitor (SSRI) in a group of 120 patients. One study investigated trazodone, an atypical antidepressant, versus placebo. Only the trial using the SSRI drug reached the highest quality standard. None of the other included trials met the highest quality standard, due to use of inadequate outcome measures, large drop-out rates or failure to separate the effects on tinnitus from the effects on symptoms of anxiety and depression. All the trials assessing tricyclic antidepressants suggested that there was a slight improvement in tinnitus but these effects may have been attributable to methodological bias. The trial that investigated the SSRI drug found no overall improvement in any of the validated outcome measures that were used in the study although there was possible benefit for a subgroup that received higher doses of the drug. This observation merits further investigation. In the trial investigating trazodone, the results showed an improvement in tinnitus intensity and in quality of life after treatment, but in neither case reached statistical significance. Reports of side effects including sedation, sexual dysfunction and dry mouth were common.

AUTHORS' CONCLUSIONS

There is as yet insufficient evidence to say that antidepressant drug therapy improves tinnitus.

Noise-induced hyperactivity in the inferior colliculus: its relationship with hyperactivity in the dorsal cochlear nucleus

Intense noise exposure causes hyperactivity to develop in the mammalian dorsal cochlear nucleus (DCN) and inferior colliculus (IC). It has not yet been established whether the IC hyperactivity is driven by hyperactivity from extrinsic sources that include the DCN or instead is maintained independently of this input. We have investigated the extent to which IC hyperactivity is dependent on input from the contralateral DCN by comparing recordings of spontaneous activity in the IC of noise-exposed and control hamsters before and after ablation of the contralateral DCN. One group of animals was binaurally exposed to intense sound (10 kHz, 115 dB SPL, 4 h), whereas the control group was not. Both groups were studied electrophysiologically 2-3 wk later by first mapping spontaneous activity along the tonotopic axis of the IC to confirm induction of hyperactivity. Spontaneous activity was then recorded at a hyperactive IC locus over two 30-min periods, one with DCNs intact and the other after ablation of the contralateral DCN. In a subset of animals, activity was again mapped along the tonotopic axis after the time course of the activity was recorded before and after DCN ablation. Following recordings, the brains were fixed, and histological evaluations were performed to assess the extent of DCN ablation. Ablation of the DCN resulted in major reductions of IC hyperactivity. Levels of postablation activity in exposed animals were similar to the levels of activity in the IC of control animals, indicating an almost complete loss of hyperactivity in exposed animals. The results suggest that hyperactivity in the IC is dependent on support from extrinsic sources that include and may even begin with the DCN. This finding does not rule out longer term compensatory or homeostatic adjustments that might restore hyperactivity in the IC over time.

Neural correlates of tinnitus duration and distress: a positron emission tomography study

Cerebral (18)F-deoxyglucose positron emission tomography (FDG-PET) has shown altered auditory pathway activity in tinnitus. However, the corresponding studies involved only small samples and analyses were restricted to the auditory cortex in most studies. Evidence is growing that also limbic, frontal, and parietal areas are involved in the pathophysiology of chronic tinnitus. These regions are considered to mediate perceptual, attentional, and emotional processes. Thus, the aim of the present study was the systematic evaluation of metabolic brain activity in a large sample of tinnitus patients. Ninety one patients with chronic tinnitus underwent FDG-PET. The effects of tinnitus severity (assessed by a tinnitus questionnaire score), duration and laterality were evaluated with statistical parametric mapping (SPM) in whole brain analyses. In addition, region of interest analyses were performed for primary auditory areas. Tinnitus duration correlated positively with brain metabolism in right inferior frontal, right ventro-medial prefrontal, and right posterior cingulate cortex. Tinnitus distress correlated positively with activation of left and right posterior inferior temporal gyrus as well as left and right posterior parahippocampal-hippocampal interface. Region of interest analysis demonstrated an overactivation of left in contrast to right Heschl's gyrus independently from tinnitus laterality and anatomical hemispheric differences. Tinnitus duration and distress were associated with areas involved in attentional and emotional processing. This is in line with recent findings indicating the relevance of higher order areas in the pathophysiology of tinnitus. Earlier results of asymmetric activation of the auditory cortices in tinnitus were confirmed, i.e., left-sided overactivation was found independently from tinnitus laterality.

Repetitive transcranial magnetic stimulation (rTMS) for treatment of chronic tinnitus

OBJECTIVE

There is compelling evidence that tinnitus is associated with functional alterations in the central nervous system. Repetitive transcranial magnetic stimulation (rTMS) is a potent tool for modifying neural activity at the stimulated area and at a distance along the functional anatomical connections. Depending on the stimulation parameters, cortical networks can be functionally disturbed or modulated in their activities. Low-frequency rTMS has been shown to result in a decrease in cortical excitability. The technique can alleviate tinnitus by modulating the excitability of neurons in the auditory cortex. We aimed to investigate the effects of low-frequency rTMS in patients and determine the factors that predict a beneficial outcome with rTMS treatment.

METHODS

Sixteen patients (male 10, female 6) with chronic tinnitus underwent low-frequency (1Hz) rTMS (intensity: 110% motor threshold; number of stimuli: 1200) to the left auditory cortex. The treatment outcome was assessed with a visual analog scale (VAS) of loudness, annoyance and duration, loudness balance test, and tinnitus handicap inventory (THI). Therapeutic success was studied according to the patients' clinical characteristics.

RESULTS

A significant reduction in the VAS (loudness and annoyance) occurred immediately after rTMS, with a gradual return to pretreatment levels after 7 days. The tinnitus patients with sudden deafness were significant resistant to rTMS treatment compared with those diagnosed with age-related hearing loss.

CONCLUSION

These results support the potential of rTMS as a new therapeutic tool for the treatment of chronic tinnitus. Because this study was performed with a small sample size and showed high interindividual variability in treatment effects, further development of the technique is needed before it can be recommended for clinical applications.

Tuning out the noise: limbic-auditory interactions in tinnitus

Tinnitus, the most common auditory disorder, affects about 40 million people in the United States alone, and its incidence is rising due to an aging population and increasing noise exposure. Although several approaches for the alleviation of tinnitus exist, there is as of yet no cure. The present article proposes a testable model for tinnitus that is grounded in recent findings from human imaging and focuses on brain areas in cortex, thalamus, and ventral striatum. Limbic and auditory brain areas are thought to interact at the thalamic level. While a tinnitus signal originates from lesion-induced plasticity of the auditory pathways, it can be tuned out by feedback connections from limbic regions, which block the tinnitus signal from reaching auditory cortex. If the limbic regions are compromised, this "noise-cancellation" mechanism breaks down, and chronic tinnitus results. Hopefully, this model will ultimately enable the development of effective treatment.

Temporo-insular enhancement of EEG low and high frequencies in patients with chronic tinnitus. QEEG study of chronic tinnitus patients

Background

The physiopathological mechanism underlying the tinnitus phenomenon is still the subject of an ongoing debate. Since oscillatory EEG activity is increasingly recognized as a fundamental hallmark of cortical integrative functions, this study investigates deviations from the norm of different resting EEG parameters in patients suffering from chronic tinnitus.

Results

Spectral parameters of resting EEG of male tinnitus patients (n = 8, mean age 54 years) were compared to those of age-matched healthy males (n = 15, mean age 58.8 years). On average, the patient group exhibited higher spectral power over the frequency range of 2-100 Hz. Using LORETA source analysis, the generators of delta, theta, alpha and beta power increases were localized dominantly to left auditory (Brodmann Areas (BA) 41,42, 22), temporo-parietal, insular posterior, cingulate anterior and parahippocampal cortical areas.

Conclusions

Tinnitus patients show a deviation from the norm of different resting EEG parameters, characterized by an overproduction of resting state delta, theta and beta brain activities, providing further support for the microphysiological and magnetoencephalographic evidence pointing to a thalamocortical dysrhythmic process at the source of tinnitus. These results also provide further confirmation that reciprocal involvements of both auditory and associative/paralimbic areas are essential in the generation of tinnitus.

[Tinnitus treatment: neurosurgical management]

Tinnitus is a very frequent symptom affecting 10% of the general population. It corresponds to the perception of an internal noise that can severely impair the quality of life. Tinnitus management requires a multidisciplinary approach in which neuromodulation and neurosurgery tend to play major roles. Classification of tinnitus separates objective tinnitus (i.e., tinnitus that can be heard or recorded) from the more frequent subjective tinnitus (i.e., tinnitus only perceived by the patient). Objective tinnitus is either pulsatile synchronous with heartbeat or asynchronous. In the former, appropriate radiological testing should search for a vascular abnormality as well as other neurological diseases (intracranial hypertension, Arnold-Chiari malformation, vascular loops, etc.). Asynchronous objective tinnitus generally corresponds to muscular contractions that require specific management. The pathophysiology of subjective tinnitus is more complex, showing strong analogies with postamputation pain syndromes. After peripheral middle ear or inner ear damage, auditory deafferentation could result in hyperactivity and/or functional reorganization within central auditory and nonauditory structures. This could explain the persistence of tinnitus after total hearing amputation (e.g., translabyrinthine approach for vestibular schwannoma) and associated symptoms such as hyperacusis or anxiety and depression. This central model finds strong support in animal experiments and in functional neuroimagery (PET, fMRI, MEG). Since no etiologically based therapies are currently available, severe subjective tinnitus management only targets tinnitus tolerance with sound enrichment or cognitive behavior therapy. However, in the near future better knowledge of tinnitus pathophysiology and innovative therapeutic tools could emerge from neuromodulation techniques such as repeated transcranial magnetic or epidural electric stimulation.

Antidepressants for patients with tinnitus

BACKGROUND

Tinnitus is described as the perception of sound or noise in the absence of real acoustic stimulation. It has been compared with chronic pain, and may be associated with depression or depressive symptoms which can affect quality of life and the ability to work. Antidepressant drugs have been used to treat tinnitus in patients with and without depressive symptoms.

OBJECTIVES

To assess the effectiveness of antidepressants in the treatment of tinnitus and to ascertain whether any benefit was due to a direct tinnitus effect or a secondary effect due to treatment of concomitant depressive states.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) The Cochrane Library Issue 1, 2006); MEDLINE (January 1951 to 2006); EMBASE (1974 to 2006), CINAHL (to 2006), PSYCINFO (to 2006), LILACS (to 2006), and Cambridge Scientific Abstracts. The date of the most recent search was March 2006.

SELECTION CRITERIA

Randomised controlled clinical studies of antidepressant drugs versus placebo in patients with tinnitus.

DATA COLLECTION AND ANALYSIS

The studies retrieved were critically appraised and data extracted independently by two authors. Where necessary study authors were contacted for further information.

MAIN RESULTS

Five trials involving 525 patients were included. Four of these trials looked at the effect of tricyclic antidepressants on tinnitus, investigating 405 patients. One trial investigated the effect of a selective serotonin reuptake inhibitor (SSRI) in a group of 120 patients. No trials involving other antidepressant agents met the inclusion criteria. Only the trial using the SSRI drug met the highest quality standard. None of the other included trials met the highest quality standard, due to use of inadequate outcome measures, large drop out rates or failure to separate the effects on tinnitus from the effects on symptoms of anxiety and depression. All the trials assessing tricyclic antidepressants suggested that there was a slight improvement in tinnitus but these effects may have been attributable to methodological bias. The trial that investigated the SSRI drug found no overall improvement in any of the validated outcome measures that were used in the study although there was possible benefit for a subgroup that received higher doses of the drug. This observation merits further investigation. Reports of side effects including sedation, sexual dysfunction and dry mouth were common.

AUTHORS' CONCLUSIONS

There is insufficient evidence to say that antidepressant drug therapy improves tinnitus.