Mechanisms of tinnitus generation

New-Onset Tinnitus After Dorsal Root Ganglion Stimulator Implantation: A Case Report

Dorsal column (dcSCS) and dorsal root ganglion stimulation (DRG-S) complications are similar, typically related to placement and device failure. We present the first case of tinnitus after DRG-S implantation. The patient presented with complex regional pain syndrome (CRPS) type 2. After previous failed treatments, she had a lumbosacral DRG-S trial, which provided relief; however, she briefly noted ringing in her ears. After permanent implantation, she reported persistent, intolerable left-sided tinnitus. Tinnitus can be modulated by secondary somatosensory inputs to the cochlear nucleus from the dcSCS. Therefore, lumbosacral DRG-S stimulating distal sensory neurons leading to tinnitus is a feasible complication.

Atypical functional hierarchy contributed to the tinnitus symptoms in patients with vestibular schwannoma

Objective

Tinnitus is frequently found in patients with vestibular schwannoma (VS), but its underlying mechanisms are currently unclear.

Methods

Both preoperative (VS _pre ) and postoperative (VS _post ) functional MR images were collected from 32 patients with unilateral VS and matched healthy controls (HCs). Connectome gradients were generated for the identification of altered regions and perturbed gradient distances. Tinnitus measurements were conducted for predictive analysis with neuroimaging-genetic integration analysis.

Results

There were 56.25% of preoperative patients and 65.63% of postoperative patients suffering from ipsilateral tinnitus, respectively. No relevant factors were identified including basic demographics info, hearing performances, tumor features, and surgical approaches. Functional gradient analysis confirmed atypical functional features of visual areas in VS _pre were rescued after tumor resection, while the gradient performance in the postcentral gyrus continues to maintain (VS _post vs. HC : P = 0.016). The gradient features of the postcentral gyrus were not only significantly decreased in patients with tinnitus (P _FDR = 0.022), but also significantly correlated with tinnitus handicap inventory (THI) score (r = -0.30, P = 0.013), THI level (r = -0.31, P = 0.010), and visual analog scale (VAS) rating (r = -0.31, P = 0.0093), which could be used to predict VAS rating in the linear model. Neuropathophysiological features linked to the tinnitus gradient framework were linked to Ribosome dysfunction and oxidative phosphorylation.

Conclusion

Altered functional plasticity in the central nervous system is involved in the maintenance of VS tinnitus.

Spectrally Matched Near-Threshold Noise for Subjective Tinnitus Loudness Attenuation Based on Stochastic Resonance

Recently, we proposed a model of tinnitus development based on a physiological mechanism of permanent optimization of information transfer from the auditory periphery to the central nervous system by means of neuronal stochastic resonance utilizing neuronal noise to be added to the cochlear input, thereby improving hearing thresholds. In this view, tinnitus is a byproduct of this added neuronal activity. Interestingly, in healthy subjects auditory thresholds can also be improved by adding external, near-threshold acoustic noise. Based on these two findings and a pilot study we hypostatized that tinnitus loudness (TL) might be reduced, if the internally generated neuronal noise is substituted by externally provided individually adapted acoustic noise. In the present study, we extended the data base of the first pilot and further optimized our approach using a more fine-grained adaptation of the presented noise to the patients' audiometric data. We presented different spectrally filtered near-threshold noises (-2 dB to +6 dB HL, 2 dB steps) for 40 s each to 24 patients with tonal tinnitus and a hearing deficit not exceeding 40 dB. After each presentation, the effect of the noise on the perceived TL was obtained by patient's response to a 5-scale question. In 21 out of 24 patients (13 women) TL was successfully subjectively attenuated during acoustic near-threshold stimulation using noise spectrally centered half an octave below the individual's tinnitus pitch (TP). Six patients reported complete subjective silencing of their tinnitus percept during stimulation. Acoustic noise is able to reduce TL, but the TP has to be taken into account. Based on our findings, we speculate about a possible future treatment of tinnitus by near-threshold bandpass filtered acoustic noise stimulation, which could be implemented in hearing aids with noise generators.

Strain Comparison in Rats Differentiates Strain-Specific from More General Correlates of Noise-Induced Hearing Loss and Tinnitus

Experiments in rodent animal models help to reveal the characteristics and underlying mechanisms of pathologies related to hearing loss such as tinnitus or hyperacusis. However, a reliable understanding is still lacking. Here, four different rat strains (Sprague Dawley, Wistar, Long Evans, and Lister Hooded) underwent comparative analysis of electrophysiological (auditory brainstem responses, ABRs) and behavioral measures after noise trauma induction to differentiate between strain-dependent trauma effects and more consistent changes across strains, such as frequency dependence or systematic temporal changes. Several hearing- and trauma-related characteristics were clearly strain-dependent. Lister Hooded rats had especially high hearing thresholds and were unable to detect a silent gap in continuous background noise but displayed the highest startle amplitudes. After noise exposure, ABR thresholds revealed a strain-dependent pattern of recovery. ABR waveforms varied in detail among rat strains, and the difference was most prominent at later peaks arising approximately 3.7 ms after stimulus onset. However, changes in ABR waveforms after trauma were small compared to consistent strain-dependent differences between individual waveform components. At the behavioral level, startle-based gap-prepulse inhibition (gap-PPI) was used to evaluate the occurrence and characteristics of tinnitus after noise exposure. A loss of gap-PPI was found in 33% of Wistar, 50% of Sprague Dawley, and 75% of Long Evans rats. Across strains, the most consistent characteristic was a frequency-specific pattern of the loss of gap-PPI, with the highest rates at approximately one octave above trauma. An additional range exhibiting loss of gap-PPI directly below trauma frequency was revealed in Sprague Dawley and Long Evans rats. Further research should focus on these frequency ranges when investigating the underlying mechanisms of tinnitus induction.

Association between Statin Use and Sensorineural Hearing Loss in Type 2 Diabetic Patients: A Hospital-Based Study

Statins have emerged as protective agents against sensorineural hearing loss (SNHL) associated with dyslipidemia, but the effects of statins on SNHL are not consistent. The purpose of this study was to investigate the association between statin use and the risk of SNHL using a hospital cohort. This nested case-control study included type 2 diabetic patients over the age of 18 years without a history of hearing loss. Of these, 1379 patients newly diagnosed with SNHL or tinnitus were classified as cases, and 5512 patients matched to the cases based on age, sex, and index year were classified as controls. Chi-squared tests were used to compare categorical variables between the two groups. Odds ratios (ORs) and adjusted odds ratios (AOR) were calculated from univariate and multivariable unconditional logistic regression analyses, respectively. There was a significant difference in the prevalence of statin use between the cases and controls (53.7% vs. 61.2%, respectively; p < 0.001). The use of statins in type 2 diabetic patients significantly reduced the risk of SNHL or tinnitus by 24.8% (95% CI 14.2–34.1%, p < 0.001) after controlling for confounders. Similar results were found for the association between statin use and SNHL (AOR = 0.706; 95% CI 0.616–0.811, p < 0.001). The protective effects of statins against SNHL were consistent regardless of age and sex. The use of statins for type 2 diabetic patients was significantly associated with a reduced risk of SNHL, regardless of age and sex. Further studies are needed, especially large cohort studies, to evaluate the long-term protective effects of statins.

A proof-of-concept study comparing tinnitus and neural connectivity changes following multisensory perceptual training with and without a low-dose of fluoxetine

Background. This proof-of-concept study investigated a method of multisensory perceptual training for tinnitus, and whether a short, low-dose administration of fluoxetine enhanced training effects and changed neural connectivity.Methods. A double-blind, randomized placebo controlled design with 20 participants (17 male, 3 female, mean age = 57.1 years) involved 30 min daily computer-based, multisensory training (matching visual, auditory and tactile stimuli to perception of tinnitus) for 20 days, and random allocation to take 20 mg fluoxetine or placebo daily. Behavioral measures of tinnitus and correlations between pairs of a priori regions of interest (ROIs), obtained using resting-state functional magnetic resonance imaging (rs-fMRI), were performed before and after the training.Results. Significant changes in ratings of tinnitus loudness, annoyance, and problem were observed with training. No statistically significant changes in Tinnitus Functional Index, Tinnitus Handicap Inventory or Depression Anxiety Stress Scales were found with training. Fluoxetine did not alter any of the behavioural outcomes of training compared to placebo. Significant changes in connectivity between ROIs were identified with training; sensory and attention neural network ROI changes correlated with significant tinnitus rating changes. Rs-fMRI results suggested that the direction of functional connectivity changes between auditory and non-auditory networks, with training and fluoxetine, were opposite to the direction of those changes with multisensory training and placebo.Conclusions. Improvements in tinnitus measures were correlated with changes in sensory and attention networks. The results provide preliminary evidence for changes in rs-fMRI accompanying a multisensory training method in persons with tinnitus.

Eye movement desensitization and reprocessing as a treatment for tinnitus

OBJECTIVES/HYPOTHESIS

To determine the effectiveness of eye movement desensitization and reprocessing (EMDR) as a treatment for tinnitus.

STUDY DESIGN

Single-site prospective interventional clinical trial at a university hospital in the United Kingdom.

METHODS

Participants were provided with tEMDR. This is a bespoke EMDR protocol that was developed specifically to treat individuals with tinnitus. Participants received a maximum of 10 sessions of tEMDR. Outcome measures including tinnitus questionnaires and mood questionnaires were recorded at baseline, discharge, and at 6 months postdischarge.

RESULTS

Tinnitus Handicap Inventory and Beck Depression Inventory scores demonstrated a statistically significant improvement at discharge after EMDR intervention (P = .0005 and P = .0098, respectively); this improvement was maintained at 6 months postdischarge. There was also a moderate but not significant (P = .0625) improvement in Beck Anxiety Inventory scores.

CONCLUSIONS

This study has demonstrated that the provision of tEMDR has resulted in a clinically and statistically significant improvement in tinnitus symptoms in the majority of those participants who took part. Furthermore, the treatment effect was maintained at 6 months after treatment ceased. This study is of particular interest, as the study protocol was designed to be purposefully inclusive of a diverse range of tinnitus patients. However, as a small uncontrolled study, these results do not consider the significant effects of placebo and therapist interaction. Larger high-quality studies are essential for the verification of these preliminary results.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:2384-2390, 2019.

A methodological assessment of studies that use voxel-based morphometry to study neural changes in tinnitus patients

BACKGROUND

The scientific understanding of tinnitus and its etiology has transitioned from thinking of tinnitus as solely a peripheral auditory problem to an increasing awareness that cortical networks may play a critical role in tinnitus percept or bother. With this change, studies that seek to use structural brain imaging techniques to better characterize tinnitus patients have become more common. These studies include using voxel-based morphometry (VBM) to determine if there are differences in regional gray matter volume in individuals who suffer from tinnitus and those who do not. However, studies using VBM in patients with tinnitus have produced inconsistent and sometimes contradictory results.

OBJECTIVE

This paper is a systematic review of all of the studies to date that have used VBM to study regional gray matter volume in people with tinnitus, and explores ways in which methodological differences in these studies may account for their heterogeneous results. We also aim to provide guidance on how to conduct future studies using VBM to produce more reproducible results to further our understanding of disease processes such as tinnitus.

METHODS

Studies about tinnitus and VBM were searched for using PubMed and Embase. These returned 15 and 25 results respectively. Of these, nine met the study criteria and were included for review. An additional 5 studies were identified in the literature as pertinent to the topic at hand and were added to the review, for a total of 13 studies.

RESULTS

There was significant heterogeneity among the studies in several areas, including inclusion and exclusion criteria, software programs, and statistical analysis. We were not able to find publicly shared data or code for any study.

DISCUSSION

The differences in study design, software analysis, and statistical methodology make direct comparisons between the different studies difficult. Especially problematic are the differences in the inclusion and exclusion criteria of the study, and the statistical design of the studies, both of which could radically alter findings. Thus, heterogeneity has complicated efforts to explore the etiology of tinnitus using structural MRI.

CONCLUSION

There is a pressing need to standardize the use of VBM when evaluating tinnitus patients. While some heterogeneity is expected given the rapid advances in the field, more can be done to ensure that there is internal validity between studies.

The Influence of Tinnitus on the Audiometric Threshold of Sufferers

Introduction Tinnitus is a worldwide problem.

Objective The objective of this study is to evaluate the audiometric hearing thresholds of adult patients with ongoing tinnitus as their only otological symptom.

Methods We evaluated the hearing thresholds of 43 adult patients with ongoing tinnitus and no history of hearing loss from the otolaryngology department of a tertiary health institution at speech and high frequencies. A total of 56 tinnitus ears were compared against 30 contralateral normal ears as well as with the 100 ears of 50 healthy volunteers.

Results The study group consisted of 11 (25.6%) males and 32 (74.4%) females with a mean age of 40.9 ± 11.7. The mean Pure Tone Average of the 56 tinnitus ears was 14.8 ± 9, while that of the 100 control ears was 11.2 ± 6 (U = 2078, p = 0.008). The mean pure tone average of the control was also significantly lower than that of the 30 contralateral normal ears of the tinnitus sufferers (U = 1136, p = 0.02). We observed mild to moderate hearing loss in 10 (23%) of the participants. We observed no hearing loss among the control group.

Conclusion A proportion of tinnitus sufferers with self-professed normal hearing are likely to have mildly elevated pure tone audiometric thresholds. In patients with unilateral tinnitus, such elevated pure tone hearing thresholds are likely to be in the tinnitus ear and the contralateral non-tinnitus ear.

Salicylate-Induced Hearing Loss Trigger Structural Synaptic Modifications in the Ventral Cochlear Nucleus of Rats via Medial Olivocochlear (MOC) Feedback Circuit

Lesion-induced cochlear damage can result in synaptic outgrowth in the ventral cochlear nucleus (VCN). Tinnitus may be associated with the synaptic outgrowth and hyperactivity in the VCN. However, it remains unclear how hearing loss triggers structural synaptic modifications in the VCN of rats subjected to salicylate-induced tinnitus. To address this issue, we evaluated tinnitus-like behavior in rats after salicylate treatment and compared the amplitude of the distortion product evoked otoacoustic emission (DPOAE) and auditory brainstem response (ABR) between control and treated rats. Moreover, we observed the changes in the synaptic ultrastructure and in the expression levels of growth-associated protein (GAP-43), brain-derived neurotrophic factor (BDNF), the microglial marker Iba-1 and glial fibrillary acidic protein (GFAP) in the VCN. After salicylate treatment (300 mg/kg/day for 4 and 8 days), analysis of the gap prepulse inhibition of the acoustic startle showed that the rats were experiencing tinnitus. The changes in the DPOAE and ABR amplitude indicated an improvement in cochlear sensitivity and a reduction in auditory input following salicylate treatment. The treated rats displayed more synaptic vesicles and longer postsynaptic density in the VCN than the control rats. We observed that the GAP-43 expression, predominantly from medial olivocochlear (MOC) neurons, was significantly up-regulated, and that BDNF- and Iba-1-immunoreactive cells were persistently decreased after salicylate administration. Furthermore, GFAP-immunoreactive astrocytes, which is associated with synaptic regrowth, was significantly increased in the treated groups. Our study revealed that reduced auditory nerve activity triggers synaptic outgrowth and hyperactivity in the VCN via a MOC neural feedback circuit. Structural synaptic modifications may be a reflexive process that compensates for the reduced auditory input after salicylate administration. However, massive increases in excitatory synapses in the VCN may represent a detrimental process that causes central hyperactivity, leading to tinnitus.

Middle Latency Auditory Evoked Potential (MLAEP) in Workers with and without Tinnitus who are Exposed to Occupational Noise

Background

Tinnitus is an important occupational health concern, but few studies have focused on the central auditory pathways of workers with a history of occupational noise exposure. Thus, we analyzed the central auditory pathways of workers with a history of occupational noise exposure who had normal hearing threshold, and compared middle latency auditory evoked potential in those with and without noise-induced tinnitus.

Material/Methods

Sixty individuals (30 with and 30 without tinnitus) underwent the following procedures: anamnesis, immittance measures, pure-tone air conduction thresholds at all frequencies between 0.25–8 kHz, and middle latency auditory evoked potentials.

Results

Quantitative analysis of latencies and amplitudes of middle latency auditory evoked potential showed no significant differences between the groups with and without tinnitus. In the qualitative analysis, we found that both groups showed increased middle latency auditory evoked potential latencies. The study group had more alterations of the “both” type regarding the Na-Pa amplitude, while the control group had more “electrode effect” alterations, but these alterations were not significantly different when compared to controls.

Conclusions

Individuals with normal hearing with or without tinnitus who are exposed to occupational noise have altered middle latency auditory evoked potential, suggesting impairment of the auditory pathways in cortical and subcortical regions. Although differences did not reach significance, individuals with tinnitus seemed to have more abnormalities in components of the middle latency auditory evoked potential when compared to individuals without tinnitus, suggesting alterations in the generation and transmission of neuroelectrical impulses along the auditory pathway.

A novel treatment for tinnitus and tinnitus-related cognitive difficulties using computer-based cognitive training and D-cycloserine

IMPORTANCE

Tinnitus affects more than 40 million people in the Unites States, and cognitive difficulties are among the most commonly associated symptoms.

OBJECTIVE

To test the feasibility and preliminarily the effectiveness of using a putative neuroplasticity-enhancing drug, D-cycloserine, to facilitate a computer-assisted CT program for improving tinnitus bother and related cognitive difficulties.

DESIGN, SETTING, AND PARTICIPANTS

Double-blind, randomized clinical trial at an outpatient academic medical center of 34 participants aged 35 to 65 years with subjective, unilateral or bilateral, nonpulsatile tinnitus of at least 6 months' duration.

INTERVENTIONS

Five weeks of twice-weekly computer-based CT with either 250 mg D-cycloserine or placebo orally prior to computer CT sessions.

MAIN OUTCOMES AND MEASURES

Difference in the change in Tinnitus Functional Index (TFI) score between the 2 groups.

RESULTS

After excluding 1 participant lost to follow-up, 1 who withdrew, 1 who did not complete 90% of sessions, and 1 outlier, 30 participants were included in the analysis. The D-cycloserine plus CT group showed a significant improvement in median TFI score (-5.8 [95% CI, -9.4 to -1.1]) and self-reported cognitive deficits (-4.5 [95% CI, -11.5 to -1.0]), but the placebo group did not (-1.0 [95% CI, -11.7 to 4.9] and -2.0 [95% CI, -5.1 to 2.0], respectively). After controlling for age and duration of tinnitus, there was no significant difference in TFI score change between the 2 groups (P = .41). After confounders were controlled for, the D-cycloserine group demonstrated a significantly greater improvement in self-reported cognitive deficits as compared with the placebo group (P = .03). No serious adverse events were reported.

CONCLUSIONS AND RELEVANCE

Use of a computer-based CT program with a putative neuroplasticity-sensitizing drug, D-cycloserine, was feasible and well tolerated. With the limited sample size, the adjuvant use of D-cycloserine was no more effective than placebo at improving tinnitus bother. The finding that D-cycloserine use was more effective than placebo at improving self-reported cognitive difficulties could be important given the high rate of concern for cognitive deficits in patients with tinnitus. D-cycloserine and other putative neuroplasticity-facilitating agents could be investigated in the future as a strategy to enhance neuroplasticity-based tinnitus treatments.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01550796.

Diagnostic utility of magnetic resonance imaging and magnetic resonance angiography in the radiological evaluation of pulsatile tinnitus

AIM

Our aim was to assess the diagnostic utility of magnetic resonance imaging with complimentary magnetic resonance angiography (MRI/MRA) in the radiological evaluation of patients with pulsatile tinnitus (PT).

MATERIALS AND METHODS

The present study was retrospectively conducted on 27 patients with pulsatile tinnitus. All patients showed normal otoscopic findings and were evaluated with magnetic resonance imaging (MRI) with complimentary magnetic resonance angiography (MRA), 9/27 (33.3%) patients were investigated by CT, and 12/27 (44.4%) were evaluated by angiography. All patients' clinical investigation was reviewed to discard systemic causes of PT.

RESULTS

All hard copies of MRI/MRA studies were evaluated. MRI/MRA detected the underlying etiology of subjective pulsatile tinnitus (PT) in 11/27 patients (40.7%), and 16/27 patients (59.5%) showed normal MRI/MRA examination. The most common cause was dural arteriovenous malformation (AFM) in 4/27 (14.8%) patients, high jugular bulbus in 2/27 (7.4%), aneurysm of internal carotid artery in 1/27 (3.7%), aberrant internal carotid artery in 1/27 (3.7%), vertebral artery hypoplasia in 2/27 (7.4%), and glomus tumor in 1/27 (3.7%). The statistical results of the present study showed that MRI/MRA had the following: 80% sensitivity, 88% specificity, 86% accuracy, 85% PPV, 83% NPV, and 15% error percentage for diagnosis of PT.

CONCLUSION

MRI/MRA was an effective radiological imaging method in detecting the underlying pathology of pulsatile tinnitus. Magnetic resonance may be considered a first line diagnostic imaging modality in the assessment of subjective pulsatile tinnitus.

Is the Degree of Discomfort Caused by Tinnitus in Normal-Hearing Individuals Correlated with Psychiatric Disorders?

Objective

To evaluate the annoyance of tinnitus in normal-hearing patients and to correlate it with outer hair cell function and with anxiety and depression disorders.

Study design

Case-control study.

Setting

Tertiary care medical center.

Subjects and Methods

Sixty-eight patients with tinnitus (study group) and a control group consisting of 46 subjects without tinnitus were studied. The subjects ranged in age from 20 to 45 years and had a hearing threshold of up to 25 dB in the frequency range of 500 to 8000 Hz. The subjects were submitted to otoacoustic emission (OAE) tests. Tinnitus annoyance was evaluated using the Tinnitus Handicap Inventory, and anxiety and depression were measured using the Beck Anxiety and Depression Inventories.

Results

In the study group, 67% of the transient-evoked OAE tests were altered, with the observation of significant differences for all frequencies tested. In addition, 65.2% of the distortion product–evoked OAE tests were altered at 3000, 6000, and 8000 Hz, and this difference was significant when compared with control. Anxiety (44.1%) and depression (33.3%) were significantly more frequent among patients with tinnitus. Tinnitus annoyance was not correlated with the OAE results or tinnitus duration but showed a correlation with the presence of anxiety and depression. In the study group, no difference in tinnitus annoyance, anxiety, or depression was observed between patients with normal and altered OAE tests.

Conclusion

This study showed altered OAE in patients with tinnitus and normal hearing. It also demonstrated a positive correlation between the annoyance of tinnitus and anxiety and depression in normal-hearing patients.

Tinnitus and insomnia: is hyperarousal the common denominator?

Tinnitus is an auditory sensation that is generated by aberrant activation within the auditory system. Sleep disturbances are a frequent problem in the tinnitus population. They are known to worsen the distress caused by the tinnitus which in turn worsens sleep quality. Beyond that, disturbed sleep is a risk factor for mental health problems and distressing tinnitus is often associated with enhanced depressivity, anxiety, and somatic symptom severity. Moreover there is evidence that therapies which alleviate tinnitus-related distress have a positive influence on sleep quality and help interrupt this vicious cycle. This suggests that distressing tinnitus and insomnia may both be promoted by similar physiological mechanisms. One candidate mechanism is hyperarousal caused by enhanced activation of the sympathetic nervous system. There is increasing evidence for hyperarousal in insomnia patients, and animal models of tinnitus and insomnia show conspicuous similarities in the activation pattern of limbic and autonomous brain regions. In this article we review the evidence for this hypothesis which may have implications for therapeutic intervention in tinnitus patients with comorbid insomnia.

Comparison and contrast of noise-induced hyperactivity in the dorsal cochlear nucleus and inferior colliculus

Induction of hyperactivity in the central auditory system is one of the major physiological hallmarks of animal models of noise-induced tinnitus. Although hyperactivity occurs at various levels of the auditory system, it is not clear to what extent hyperactivity originating in one nucleus contributes to hyperactivity at higher levels of the auditory system. In this study we compared the time courses and tonotopic distribution patterns of hyperactivity in the dorsal cochlear nucleus (DCN) and inferior colliculus (IC). A model of acquisition of hyperactivity in the IC by passive relay from the DCN would predict that the two nuclei show similar time courses and tonotopic profiles of hyperactivity. A model of acquisition of hyperactivity in the IC by compensatory plasticity mechanisms would predict that the IC and DCN would show differences in these features, since each adjusts to changes of spontaneous activity of opposite polarity. To test the role of these two mechanisms, animals were exposed to an intense hyperactivity-inducing tone (10 kHz, 115 dB SPL, 4 h) then studied electrophysiologically at three different post-exposure recovery times (from 1 to 6 weeks after exposure). For each time frame, multiunit spontaneous activity was mapped as a function of location along the tonotopic gradient in the DCN and IC. Comparison of activity profiles from the two nuclei showed a similar progression toward increased activity over time and culminated in the development of a central peak of hyperactivity at a similar tonotopic location. These similarities suggest that the shape of the activity profile is determined primarily by passive relay from the cochlear nucleus. However, the absolute levels of activity were generally much lower in the IC than in the DCN, suggesting that the magnitude of hyperactivity is greatly attenuated by inhibition.

Wavelet analysis demonstrates no abnormality in contralateral suppression of otoacoustic emissions in tinnitus patients

The efferent auditory system is thought to play a role in the origin of tinnitus. Part of this system can be tested in humans with contralateral suppression of otoacoustic emissions. Stimulation of the medial olivocochlear efferent system is responsible for this reduction of otoacoustic emissions after contralateral acoustic stimulation. Previous research on patients with tinnitus showed inconclusive results. With wavelet analysis both time and frequency information of the emission can be analysed and compared. Contralateral suppression of otoacoustic emissions was therefore measured in tinnitus patients (n = 26) and normal subjects (n = 37) and analysed using wavelets. No significant difference in suppression was found between the tinnitus patients and the control group.

Gabapentin for Tinnitus: A Systematic Review

Purpose

The main aim of this study was to assess the effect of gabapentin on tinnitus via a systematic review.

Method

An electronic search of literature as well as a hand search were conducted. Only double-blind randomized controlled trials (RCTs) that met all of the inclusion criteria were included in this review. The Cochrane Collaboration tool for risk of bias assessment was used to investigate the validity of the included studies. Meta-analysis was not appropriate due to inadequate details in reporting the data in the included studies. Hence, qualitative synthesis and interpretation of the data were carried out.

Results

Two studies that met the inclusion criteria were included in the review. Fourteen studies were excluded. There were substantive within-study clinical heterogeneities with regard to the baseline tinnitus handicap scores, duration of tinnitus, and severity of hearing loss in the included double-blind RCTs.

Conclusion

The authors of both studies reported that gabapentin was not superior to placebo in their primary outcomes. However, following the assessment of risk of bias and within-study clinical heterogeneities, this review concludes that there is insufficient evidence regarding the effect of gabapentin on tinnitus.

Discrimination task reveals differences in neural bases of tinnitus and hearing impairment

We investigated auditory perception and cognitive processing in individuals with chronic tinnitus or hearing loss using functional magnetic resonance imaging (fMRI). Our participants belonged to one of three groups: bilateral hearing loss and tinnitus (TIN), bilateral hearing loss without tinnitus (HL), and normal hearing without tinnitus (NH). We employed pure tones and frequency-modulated sweeps as stimuli in two tasks: passive listening and active discrimination. All subjects had normal hearing through 2 kHz and all stimuli were low-pass filtered at 2 kHz so that all participants could hear them equally well. Performance was similar among all three groups for the discrimination task. In all participants, a distributed set of brain regions including the primary and non-primary auditory cortices showed greater response for both tasks compared to rest. Comparing the groups directly, we found decreased activation in the parietal and frontal lobes in the participants with tinnitus compared to the HL group and decreased response in the frontal lobes relative to the NH group. Additionally, the HL subjects exhibited increased response in the anterior cingulate relative to the NH group. Our results suggest that a differential engagement of a putative auditory attention and short-term memory network, comprising regions in the frontal, parietal and temporal cortices and the anterior cingulate, may represent a key difference in the neural bases of chronic tinnitus accompanied by hearing loss relative to hearing loss alone.

Contralateral suppression of otoacoustic emissions in tinnitus patients

OBJECTIVE

To compare the functioning of the medial olivocochlear efferent system between tinnitus patients and control subjects.

STUDY DESIGN

Prospective, nonrandomized controlled analysis of suppression of otoacoustic emissions with contralateral acoustic stimulation.

SETTING

Tertiary referral center.

PATIENTS

Initial analysis of 97 tinnitus patients and 44 control subjects with click-evoked otoacoustic emission measurement. If subjects had reproducible otoacoustic emissions at 80 dB SPL, suppression of otoacoustic emission with contralateral acoustic stimulation was measured with a 65-dB click stimulus. This resulted in inclusion of 44 ears of tinnitus patients and 57 ears of control subjects.

INTERVENTION

Suppression of the otoacoustic emissions generated by the 65-dB click stimulus was tested using contralateral broadband noise at 70 dB SPL. Suppression was calculated in half-octave frequency bands centered at 1.0, 1.4, 2.0, 2.8, and 4.0 kHz.

MAIN OUTCOME MEASURE

The amount of suppression of the OAE, calculated in half-octave frequency bands.

RESULTS

Otoacoustic emission amplitudes were equal in both groups. Contralateral suppression of the signal was found in both patients and controls. The amount of suppression was equal, except for the 2.0- and 2.8-kHz frequency bands in the right ear (p value of 0.03, 0.008, respectively), for which the patients had less suppression.

CONCLUSION

The suppression of otoacoustic emissions with CAS seems equally effective in tinnitus patients and healthy controls. The minor differences between both groups suggest subtle differences in the function of the medial olivocochlear efferent system.

The efficacy of auditory perceptual training for tinnitus: a systematic review

Auditory perceptual training affects neural plasticity and so represents a potential strategy for tinnitus management. We assessed the effects of auditory perceptual training on tinnitus perception and/or its intrusiveness via a systematic review of published literature. An electronic database search using the keywords ‘tinnitus and learning’ or ‘tinnitus and training’ was conducted, updated by a hand search. The ten studies identified were reviewed independently by two reviewers, data were extracted, study quality was assessed according to a number of specific criteria and the information was synthesised using a narrative approach. Nine out of the ten studies reported some significant change in either self-reported or psychoacoustic outcome measures after auditory training. However, all studies were quality rated as providing low or moderate levels of evidence for an effect. We identify a need for appropriately randomised and controlled studies that will generate high-quality unbiased and generalisable evidence to ascertain whether or not auditory perceptual training has a clinically relevant effect on tinnitus.

Sustained delivery of lidocaine into the cochlea using poly lactic/glycolic acid microparticles

OBJECTIVES/HYPOTHESIS

Lidocaine is a local anesthetic that is known to suppress tinnitus via systemic or local application; however, this effect has only limited duration. The current study aimed to establish a method for the sustained delivery of lidocaine into the cochlea using poly lactic/glycolic acid (PLGA) microparticles.

STUDY DESIGN

Experimental study.

METHODS

Lidocaine-loaded PLGA microparticles were produced and their in vitro-release profiles were examined. The lidocaine concentrations in the perilymph were measured at different time points following the application of the lidocaine-loaded PLGA microparticles to the round-window membranes of guinea pigs. The possible adverse effects of the local application of lidocaine-loaded PLGA microparticles were also examined.

RESULTS

The in vitro analyses revealed that the microparticles were capable of the sustained delivery of lidocaine. The in vivo experiments demonstrated the sustained delivery of lidocaine into the cochlear fluid, and the maintenance of high lidocaine concentrations in the perilymph for up to 3 days after application. Nystagmus and inflammation in the middle ear mucosa were not detected after the local application of lidocaine-loaded PLGA microparticles, although temporary hearing loss was observed.

CONCLUSIONS

Lidocaine-loaded PLGA microparticles were shown to be capable of the sustained delivery of lidocaine into the cochlea, suggesting that they could be used for the attenuation of peripheral tinnitus.

A compartment-based approach for the imaging evaluation of tinnitus

Tinnitus affects 10% of the US general population and is a common indication for imaging studies. We describe a sequential compartment-based diagnostic approach, which simplifies the interpretation of imaging studies in patients with tinnitus. The choice of the initial imaging technique depends on the type of tinnitus, associated symptoms, and examination findings. Familiarity with the pathophysiologic mechanisms of tinnitus and the imaging findings is a prerequisite for a tailored diagnostic approach by the radiologist.

[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.

Expression and localization of K channels KCNQ2 and KCNQ3 in the mammalian cochlea

KCNQ1 and KCNQ4 voltage-gated potassium channel subunits play key roles in hearing. Other members of the KCNQ family also encode slow, low voltage-activated K(+) M currents. We have previously reported the presence of M-like K(+) currents in sensory hair cells, and expression of Kcnq family genes in the cochlea. Here, we describe Kcnq2/3 gene expression and distribution of M channel subunits KCNQ2 and 3 in the cochlea. By using RT-PCR, we found expression of Kcnq2 in the modiolus and organ of Corti, while Kcnq3 expression was also detected in the cochlear lateral wall. Five alternative splice variants of the Kcnq2 gene, one of which has not been reported previously, were identified in the rat cochlea. KCNQ2 and KCNQ3 immunoreactivities were observed in spiral ganglion auditory neurons. In addition, the unmyelinated parts of the nerve fibers innervating hair cells and synaptic regions under hair cells showed KCNQ2 immunoreactivity. KCNQ3 immunoreactivity was also prominent in spiral ganglion satellite cells. These findings suggest that cochlear M channels play important roles in regulation of cellular excitability and maintenance of cochlear K(+) homeostasis in the auditory system.

[Therapy of tinnitus in children]

Tinnitus in childhood is quite common when children are directly asked about this syndrom. Children rarely spontaneously complain of tinnitus. Material consists of 67 children (6-18 year old) with tinnitus, treated in the Pediatric Otolaryngology Clinic and Outpatient. Between children there were 2 groups: I tinnitus connected with hearing loss--35 children, II tinnitus without hearing loss--32 children. Methods. Anamnesis, otolaryngologic, neurologic, psychologic examinations, panel of audiologic tests before and after treatment of betahistine. In 12 patients there were recognized conductive hearing loss and they were excluded from therapy of betahistine. 55 children were treated with betahistine (Betaserc). Results indicates that betahistine is a good drug in therapy of tinnitus in children.

Relation of distortion product otoacoustic emission with tinnitus

OBJECTIVE

To investigate cochlear outer hair cell function based on distortion product otoacoustic emission (DPOAE) in patients with tinnitus.

STUDY DESIGN

This is a case control study.

SUBJECTS AND METHODS

The subjects are patients who attended the Otorhinolaryngology Clinic in Hospital Universiti Kebangsaan Malaysia over a period of 19 months from April 2005 until October 2006. All patients underwent a full ENT assessment and had tympanometry, pure tone audiometry, and DPOAE tests. The UKM Research and Ethics Committee reviewed and approved the study proposal prior to commencement of this study.

RESULTS

The study population included 49 patients. They consisted of 16 patients (32 ears) with tinnitus and reduced hearing, 13 patients (26 ears) with tinnitus and normal hearing, 7 patients (13 ears) without tinnitus with reduced hearing, and 13 patients (26 ears) without tinnitus with normal hearing. Statistical analysis showed significant differences (P = .00) of mean DPOAE levels between the four groups of patients.

CONCLUSION

Our results suggest that reduced outer hair cell activity, as detected by reduced DPOAE levels, may manifest as tinnitus even before there is a shift on hearing threshold. We also postulate that further reduction of cochlear outer hair cell activity, as shown by further reduced DPOAE levels, may actually terminate the source of tinnitus.

The role of central nervous system plasticity in tinnitus

Tinnitus is a vexing disorder of hearing characterized by sound sensations originating in the head without any external stimulation. The specific etiology of these sensations is uncertain but frequently associated with hearing loss. The "neurophysiogical" model of tinnitus has enhanced appreciation of central nervous system (CNS) contributions. The model assumes that plastic changes in the primary and non-primary auditory pathways contribute to tinnitus with the former perhaps sustaining them, and the latter contributing to perceived severity and emotionality. These plastic changes are triggered by peripheral injury, which results in new patterns of brain activity due to anatomic alterations in the connectivity of CNS neurons. These alterations may change the balance between excitatory and inhibitory brain processes, perhaps producing cascades of new neural activity flowing between brainstem and cortex in a self-sustaining manner that produces persistent perceptions of tinnitus. The bases of this model are explored with an attempt to distinguish phenomenological from mechanistic explanations.

LEARNING OUTCOMES

(1) Readers will learn that the variables associated with the behavioral experience of tinnitus are as complex as the biological variables. (2) Readers will understand what the concept of neuroplastic brain change means, and how it is associated with tinnitus. (3) Readers will learn that there may be no one brain location associated with tinnitus, and it may result from interactions between multiple brain areas. (4) Readers will learn how disinhibition, spontaneous activity, neural synchronization, and tonotopic reorganization may contribute to tinnitus.

A Clinical Study of the Efferent Auditory System in Patients With Normal Hearing Who Have Acute Tinnitus

OBJECTIVE

Etiological diagnosis and treatment of tinnitus still remain challenging in clinical practice. The aim of this study was to determine the potential contribution of a defective cochlear efferent innervation to the onset of tinnitus in patients with normal hearing.

STUDY DESIGN

Prospective randomized controlled study.

SETTING

Otorhinolaryngology department of a general hospital.

PATIENTS

The patient group consisted of 18 normal-hearing adults (7 men, 11 women) with acute tinnitus (bilateral in 3 patients).

INTERVENTIONS

Tympanogram, stapedial muscle reflex, pure tone audiometry, tinnitus pitch matching, spontaneous otoacoustic emissions, and distortion product otoacoustic emissions (DPOAEs) in the absence and presence of contralateral suppression by white noise.

MAIN OUTCOME MEASURE

DPOAEs suppression amplitudes recorded from tinnitus and nontinnitus ears of the patients' group were compared with each other and with a control group.

RESULTS

The contralateral application of white noise induced the enhancement of DPOAE amplitudes in some patients. The suppression of DPOAE amplitudes by contralateral white noise did not reach statistically significant levels in either ear (with or without tinnitus). On the contrary, under the same conditions, our control group demonstrated statistically significant reduction of DPOAE amplitudes at all frequencies.

CONCLUSION

Patients with normal hearing acuity who have acute tinnitus seem to have a less effective functioning of the cochlear efferent system because the application of contralateral noise enhanced the DPOAEs or suppressed them less intensely than it did in a control group. Further studies may establish the clinical applications for the diagnosis of changes in efferent function, in the subjective evaluation, patient etiological grouping, treatment, or prognosis of tinnitus.

The radiologic evaluation of tinnitus

Tinnitus ("ringing in the ears") is a prevalent symptom in the general population, and often brings patients to medical attention. Many causes of tinnitus are evident radiographically. The most frequently-encountered causes of tinnitus are discussed, and imaging recommendations are provided.

Differential Lidocaine Sensitivity of Human Voltage-gated Potassium Channels Relevant to the Auditory System

HYPOTHESIS

Lidocaine may lead to an alteration in the processing of hearing as observed during tinnitus by inhibiting voltage-gated potassium channels at clinically relevant concentrations.

BACKGROUND

Recent molecular evidence suggests that the voltage-gated potassium channels Kv 3.1 and Kv 1.1 play an important functional role in the auditory system. Lidocaine is known to influence the auditory system and may thus exert pharmacological effects on these human potassium channels.

METHODS

Patch-clamp recordings were performed on the pharmacologic action of lidocaine on Kv 3.1 channels natively expressed in SH-SY5Y cells and Kv 1.1 channels expressed in HEK 293 cells.

RESULTS

Lidocaine reversibly inhibited Kv 3.1 and Kv 1.1 channels in a concentration-dependent manner. The half-maximal inhibitory concentration for conductance block was 607 micromol/L for Kv 3.1 (n=47) and 4,550 micromol/L for Kv 1.1 channels (n=56), respectively. The Hill coefficients were 0.9 and 0.8. Conductance block was voltage dependent for Kv 3.1 but not for Kv 1.1 channels. The midpoint of current activation of both channels was shifted to hyperpolarized potentials. At free plasma concentrations determined during suppression (0.5-1 mg/L; 1.75-3.5 micromol/L) or induction (>1-2 mg/L; >3.5-7 micromol/L) of tinnitus Kv 3.1 and K v1.1 channels would be suppressed by at most 1.5 to 2%.

CONCLUSION

Human Kv 3.1 and Kv 1.1 channels exhibited different sensitivities to the inhibitory action of lidocaine. The small effect at clinically relevant concentrations suggests that the physiologic roles of Kv 3.1 and Kv 1.1 channels in auditory neurons seem not to be impaired during the therapeutic or diagnostic application of lidocaine in the auditory system.

Terapia de reentrenamiento (TRT) en el acúfeno de la enfermedad de Ménière

OBJECTIVE

To evaluate the response of tinnitus in Meniere's disease patients (MD) using the Tinnitus Retraining Therapy (TRT). This management includes a wide cognitive medical counselling and natural or prosthetic sound therapies (hearing aid or noise generator).

DESIGN

Descriptive prospective study (EBM level 3).

PATIENTS

Twenty-five patients diagnosed as definitive MD (AAO-HNS 95 criteria) were enrolled in our tinnitus protocol.

MAIN OUTCOME MEASURES

Tinnitus changes were reported according to patient's self-evaluation, a visual analogue scale on tinnitus intensity (EVA) and the Tinnitus Handicap Inventory (THI).

RESULTS

Seventy-three percent of the patients improved their tinnitus after 6 months of treatment (p < 0.05). THI scores were reduced from the initial 47% to 24% (p < 0.05) and EVA from 6.6 to 5.2 (p < 0.05). After 12 months, the response was slightly worse: 68% improved according to their self-evaluation (p < 0.05), THI score reached 20% (p < 0.05) but EVA did not improve significantly (6.4). Patients that refused prosthesis adaptation (hearing aid or noise generator) did not improved and the THI score (48%) and EVA score (6.6) did not change.

CONCLUSIONS

TRT has proved to be an effective method for tinnitus treatment in MD that improves patient's self-evaluation, tinnitus loudness and handicap scores. Individualized medical counselling and an exhaustive prosthesis adaptation are crucial to guarantee satisfactory results.

Neuromagnetic indicators of auditory cortical reorganization of tinnitus

Animal studies show that following damage to inner-ear receptors, central representations of intact lesion-edge (LE) frequencies become enlarged (map reorganization). One theory of tinnitus holds that this process could be related to the tinnitus sensation. To test this hypothesis, neuromagnetic evoked fields of tinnitus participants with high-frequency hearing loss and normal hearing controls were measured, while subjects listened to monaurally presented LE or control (CO; an octave below LE) tones. The predictions made based on the map reorganization hypothesis of tinnitus were that neuronal responses to LE frequencies would be enhanced, and that source localizations for LE would be distorted. N1m equivalent dipole moments for LE were not supranormal in the tinnitus group, whereas responses to CO of tinnitus patients compared to controls were enlarged in the right hemisphere. This effect was positively associated with tinnitus-related distress. Abnormal source locations were found for generators activated by LE tones in the right hemisphere of the tinnitus group. This right-hemispheric map distortion was not associated with subjective variables of tinnitus. A positive correlation with tinnitus distress was found for the left hemisphere with more anterior sources being associated with enhanced distress. However, this result was independent of the frequency of the stimulus. Overall, the present study suggests that mechanisms of map reorganization, although present in the data, cannot satisfactorily explain the emergence of tinnitus and that differential hemispheric involvement must be considered.