Central tinnitus

Consensus Statements on the Definition, Classification, and Diagnostic Tests for Tinnitus: A Delphi Study Conducted by the Korean Tinnitus Study Group

BACKGROUND

Tinnitus is a bothersome condition associated with various symptoms. However, the mechanisms of tinnitus are still uncertain, and a standardized assessment of the diagnostic criteria for tinnitus is required. We aimed to reach a consensus on diagnosing tinnitus with professional experts by conducting a Delphi study with systematic review of the literature.

METHODS

Twenty-six experts in managing tinnitus in Korea were recruited, and a two-round modified Delphi study was performed online. The experts evaluated the level of agreement of potential criteria for tinnitus using a scale of 1-9. After the survey, a consensus meeting was held to establish agreement on the results obtained from the Delphi process. Consensus was defined when over 70% of the participants scored 7-9 (agreement) and fewer than 15% scored 1-3 (disagreement). To analyze the responses of the Delphi survey, the content validity ratio and Kendall's coefficient of concordance were evaluated.

RESULTS

Consensus was reached for 22 of the 38 statements. For the definition of tinnitus, 10 out of 17 statements reached consensus, with three statements achieving complete agreement including; 1) Tinnitus is a conscious perception of an auditory sensation in the absence of a corresponding external stimulus, 2) Tinnitus can affect one's quality of life, and 3) Tinnitus can be associated with hearing disorders including sensorineural hearing loss, vestibular schwannoma, Meniere's disease, otosclerosis, and others. For the classification of tinnitus, 11 out of 18 statements reached consensus. The participants highly agreed with statements such as; 1) Vascular origin is expected in pulse-synchronous tinnitus, and 2) Tinnitus can be divided into acute or chronic tinnitus. Among three statements on the diagnostic tests for tinnitus only Statement 3, "There are no reliable biomarkers for sensory or emotional factors of tinnitus." reached consensus. All participants agreed to perform pure-tone audiometry and tinnitus questionnaires, including the Tinnitus Handicap Inventory and Tinnitus Questionnaire.

CONCLUSION

We used a modified Delphi method to establish a consensus-based definition, a classification, and diagnostic tests for tinnitus. The expert panel reached agreement for several statements, with a high level of consensus. This may provide practical information for clinicians in managing tinnitus.

Blast Overpressures as a Military and Occupational Health Concern

PURPOSE

This tutorial reviews effects of environmental stressors like blast overpressures and other well-known acoustic contaminants (continuous, intermittent, and impulsive noise) on hearing, tinnitus, vestibular, and balance-related functions. Based on the overall outcome of these effects, detailed consideration is given to the health and well-being of individuals.

METHOD

Because hearing loss and tinnitus are consequential in affecting quality of life, novel neuromodulation paradigms are reviewed for their positive abatement and treatment-related effects. Examples of clinical data, research strategies, and methodological approaches focus on repetitive transcranial magnetic stimulation (rTMS) and electrical stimulation of the vagus nerve paired with tones (VNSt) for their unique contributions to this area.

RESULTS

Acoustic toxicants transmitted through the atmosphere are noteworthy for their propensity to induce hearing loss and tinnitus. Mounting evidence also indicates that high-level rapid onset changes in atmospheric sound pressure can significantly impact vestibular and balance function. Indeed, the risk of falling secondary to loss of, or damage to, sensory receptor cells in otolith organs (utricle and saccule) is a primary reason for this concern. As part of the complexities involved in VNSt treatment strategies, vocal dysfunction may also manifest. In addition, evaluation of temporospatial gait parameters is worthy of consideration based on their ability to detect and monitor incipient neurological disease, cognitive decline, and mortality.

CONCLUSION

Highlighting these respective areas underscores the need to enhance information exchange among scientists, clinicians, and caregivers on the benefits and complications of these outcomes.

Predictive coding and stochastic resonance as fundamental principles of auditory phantom perception

Mechanistic insight is achieved only when experiments are employed to test formal or computational models. Furthermore, in analogy to lesion studies, phantom perception may serve as a vehicle to understand the fundamental processing principles underlying healthy auditory perception. With a special focus on tinnitus-as the prime example of auditory phantom perception-we review recent work at the intersection of artificial intelligence, psychology and neuroscience. In particular, we discuss why everyone with tinnitus suffers from (at least hidden) hearing loss, but not everyone with hearing loss suffers from tinnitus. We argue that intrinsic neural noise is generated and amplified along the auditory pathway as a compensatory mechanism to restore normal hearing based on adaptive stochastic resonance. The neural noise increase can then be misinterpreted as auditory input and perceived as tinnitus. This mechanism can be formalized in the Bayesian brain framework, where the percept (posterior) assimilates a prior prediction (brain's expectations) and likelihood (bottom-up neural signal). A higher mean and lower variance (i.e. enhanced precision) of the likelihood shifts the posterior, evincing a misinterpretation of sensory evidence, which may be further confounded by plastic changes in the brain that underwrite prior predictions. Hence, two fundamental processing principles provide the most explanatory power for the emergence of auditory phantom perceptions: predictive coding as a top-down and adaptive stochastic resonance as a complementary bottom-up mechanism. We conclude that both principles also play a crucial role in healthy auditory perception. Finally, in the context of neuroscience-inspired artificial intelligence, both processing principles may serve to improve contemporary machine learning techniques.

Eavesdropping on Tinnitus Using MEG: Lessons Learned and Future Perspectives

Tinnitus has been widely investigated in order to draw conclusions about the underlying causes and altered neural activity in various brain regions. Existing studies have based their work on different tinnitus frameworks, ranging from a more local perspective on the auditory cortex to the inclusion of broader networks and various approaches towards tinnitus perception and distress. Magnetoencephalography (MEG) provides a powerful tool for efficiently investigating tinnitus and aberrant neural activity both spatially and temporally. However, results are inconclusive, and studies are rarely mapped to theoretical frameworks. The purpose of this review was to firstly introduce MEG to interested researchers and secondly provide a synopsis of the current state. We divided recent tinnitus research in MEG into study designs using resting state measurements and studies implementing tone stimulation paradigms. The studies were categorized based on their theoretical foundation, and we outlined shortcomings as well as inconsistencies within the different approaches. Finally, we provided future perspectives on how to benefit more efficiently from the enormous potential of MEG. We suggested novel approaches from a theoretical, conceptual, and methodological point of view to allow future research to obtain a more comprehensive understanding of tinnitus and its underlying processes.

Estimation of Tinnitus-Related Socioeconomic Costs in Germany

Despite the high prevalence of tinnitus in Germany of nearly 12% of the general population, there have been no systematic studies on the socioeconomic costs for German society caused by tinnitus so far. Here we analyzed data from 258 chronic tinnitus patients-namely tinnitus severity and health utility index (HUI)-and correlated them with their tinnitus-related public health care costs, private expenses, and economic loss due to their tinnitus percept as assessed by questionnaires. We found correlations of the HUI with health care costs and calculated the mean socioeconomic costs per tinnitus patient in Germany. According to our most conservative estimate, these sum up to EUR 4798.91 per year. Of that EUR 2206.95 account for the public health care, EUR 290.45 are carried by the patient privately and the remaining EUR 2301.51 account for economical loss due to sick leave. With a prevalence of 5.5% with at least bothersome tinnitus, this sums up to 21.9 billion Euro per year and with 25.82 sick leave days; tinnitus patients miss work more than double the time of the average German employee (10.9 days). The findings fit within the cost ranges of studies from other European countries and the USA and show that the socioeconomic burden of this disease-like symptom is a global problem. In comparison with the costs of other major chronic diseases in Germany-such as chronic obstructive pulmonary diseases (ca. 16 billion Euro) or diabetes mellitus (ca. 42 billion Euro)-the relevance of the 'symptom' tinnitus for the German social economy becomes even more obvious.

Definition of Tinnitus

Tinnitus is generally defined as the perception of sound in the absence of vibration of an external elastic body. If this definition appears useful to differentiate tinnitus from somatosounds, it is not suitable for distinguishing it from psychiatric hallucinations. Nor does this solution define a temporal limit of duration of the perception, which is important for distinguishing pathological tinnitus from those occasional noises that we all perceive from time to time. A complete definition appears necessary not only to achieve homogeneity in epidemiological studies but also to set up correct and personalized therapeutic schemes. An analogy with neuropsychiatric studies and, in particular, the concept of auditory hallucinosis are proposed by the authors to define tinnitus. According to the authors, tinnitus is auditory hallucinosis, and similarly, vertigo is spatial hallucinosis.

Cerebral Blood Flow Difference Between Acute and Chronic Tinnitus Perception: A Perfusion Functional Magnetic Resonance Imaging Study

Purpose: The central nervous mechanism of acute tinnitus is different from that of chronic tinnitus, which may be related to the difference of cerebral blood flow (CBF) perfusion in certain regions. To verify this conjecture, we used arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) in this study to compare the CBF alterations of patients with acute and chronic tinnitus. Methods: The current study included patients with chronic tinnitus (n = 35), acute tinnitus (n = 30), and healthy controls (n = 40) who were age-, sex-, and education-matched. All participants underwent MRI scanning and then ASL images were obtained to measure CBF of the entire brain and analyze the differences between groups as well as the correlations with tinnitus characteristics. Results: The chronic tinnitus group showed increased z-CBF in the right superior temporal gyrus (STG) and superior frontal gyrus (SFG) when compared with the acute tinnitus patients. Further connectivity analysis found enhanced CBF connectivity between the right STG and fusiform gyrus (FG), the right SFG and left middle occipital gyrus (MOG), as well as the right parahippocampal gyrus (PHG). Moreover, in the chronic tinnitus group, the tinnitus handicap questionnaire (THQ) score was positively correlated with the normalized z-CBF of right STG (r = 0.440, p = 0.013). Conclusion: Our results confirmed that the CBF changes in some brain regions were different between acute and chronic tinnitus patients, which was correlated with certain tinnitus characteristics. This is of great value to further research on chronicity of tinnitus, and ASL has a promising application in the measurement of CBF.

Tinnitus development is associated with synaptopathy of inner hair cells in Mongolian gerbils

Human hearing loss (HL) is often accompanied by comorbidities like tinnitus, which is affecting up to 15% of the adult population. Rodent animal studies could show that tinnitus may not only be a result of apparent HL due to cochlear hair cell damage but can also be a consequence of synaptopathy at the inner hair cells (IHCs) already induced by moderate sound traumata. Here, we investigate synaptopathy previously shown in mice in our animal model, the Mongolian gerbil, and relate it to behavioral signs of tinnitus. Tinnitus was induced by a mild monaural acoustic trauma leading to monaural noise induced HL in the animals, quantified by auditory brainstem response (ABR) audiometry. Behavioral signs of tinnitus percepts were detected by measurement of prepulse inhibition of the acoustic startle response in a gap-noise paradigm. Fourteen days after trauma, the cochleae of both ears were isolated, and IHC synapses were counted within several spectral regions of the cochlea. Behavioral signs of tinnitus were only found in animals with IHC synaptopathy, independent of type of HL. On the other hand, animals with apparent HL but without behavioral signs of tinnitus showed a reduction in amplitudes of ABR waves I&II but no significant changes in the number of synapses at the IHC. We conclude-in line with the literature-that HL is caused by damage to the IHC or by other reasons but that the development of tinnitus, at least in our animal model, is closely linked to synaptopathy at the IHC.

Tinnitus and tinnitus disorder: Theoretical and operational definitions (an international multidisciplinary proposal)

As for hypertension, chronic pain, epilepsy and other disorders with particular symptoms, a commonly accepted and unambiguous definition provides a common ground for researchers and clinicians to study and treat the problem. The WHO's ICD11 definition only mentions tinnitus as a nonspecific symptom of a hearing disorder, but not as a clinical entity in its own right, and the American Psychiatric Association's DSM-V doesn't mention tinnitus at all. Here we propose that the tinnitus without and with associated suffering should be differentiated by distinct terms: "Tinnitus" for the former and "Tinnitus Disorder" for the latter. The proposed definition then becomes "Tinnitus is the conscious awareness of a tonal or composite noise for which there is no identifiable corresponding external acoustic source, which becomes Tinnitus Disorder "when associated with emotional distress, cognitive dysfunction, and/or autonomic arousal, leading to behavioural changes and functional disability.". In other words "Tinnitus" describes the auditory or sensory component, whereas "Tinnitus Disorder" reflects the auditory component and the associated suffering. Whereas acute tinnitus may be a symptom secondary to a trauma or disease, chronic tinnitus may be considered a primary disorder in its own right. If adopted, this will advance the recognition of tinnitus disorder as a primary health condition in its own right. The capacity to measure the incidence, prevalence, and impact will help in identification of human, financial, and educational needs required to address acute tinnitus as a symptom but chronic tinnitus as a disorder.

Acute and Long-Term Circuit-Level Effects in the Auditory Cortex After Sound Trauma

Harmful environmental sounds are a prevailing source of chronic hearing impairments, including noise induced hearing loss, hyperacusis, or tinnitus. How these symptoms are related to pathophysiological damage to the sensory receptor epithelia and its effects along the auditory pathway, have been documented in numerous studies. An open question concerns the temporal evolution of maladaptive changes after damage and their manifestation in the balance of thalamocortical and corticocortical input to the auditory cortex (ACx). To address these issues, we investigated the loci of plastic reorganizations across the tonotopic axis of the auditory cortex of male Mongolian gerbils (Meriones unguiculatus) acutely after a sound trauma and after several weeks. We used a residual current-source density analysis to dissociate adaptations of intracolumnar input and horizontally relayed corticocortical input to synaptic populations across cortical layers in ACx. A pure tone-based sound trauma caused acute changes of subcortical inputs and corticocortical inputs at all tonotopic regions, particularly showing a broad reduction of tone-evoked inputs at tonotopic regions around the trauma frequency. At other cortical sites, the overall columnar activity acutely decreased, while relative contributions of lateral corticocortical inputs increased. After 4-6 weeks, cortical activity in response to the altered sensory inputs showed a general increase of local thalamocortical input reaching levels higher than before the trauma. Hence, our results suggest a detailed mechanism for overcompensation of altered frequency input in the auditory cortex that relies on a changing balance of thalamocortical and intracortical input and along the frequency gradient of the cortical tonotopic map.

Aberrant Frequency Related Change-Detection Activity in Chronic Tinnitus

Tinnitus is the perception of sound without the occurrence of an acoustic event. The deficit in auditory sensory or echoic memory may be the cause of the perception of tinnitus. This study considered the mismatch negativity (MMN) to investigate the potential difference between and within groups of persons with normal hearing (NH) and tinnitus. Using an auditory multi-feature paradigm to elicit the MMN, this study considered the MMN peak amplitude at two central frequencies for two MMN subcomponents. These central frequencies were 1 and 5 kHz, which the latter was closer to the perceived tinnitus frequency in the group with tinnitus. The deviants were higher frequency, lower frequency, higher intensity, lower intensity, duration, location (left), location (right), and gap. The pure tone audiometry (PTA) test and distortion product otoacoustic emissions (DPOAE) test showed no meaningful difference between the two groups. For the frontal subcomponent, the mean amplitudes of the MMN peak for the two groups illustrated less negative meaningful MMN peak amplitudes in the group of persons with tinnitus. For the supratemporal component at 5 kHz central frequency, amplitudes were lower for the group of persons with tinnitus, whereas for the central frequency of 1 kHz, most deviants exhibited meaningful differences. Additionally, within-group comparisons indicated that mean amplitudes for both groups were more negative at the central frequency of 1 kHz for the frontal MMN subcomponent. In comparison, the supratemporal component illustrated a lower peak amplitude at 5 kHz central frequency in the group of persons with tinnitus and no difference in the NH group, which is a unique observation of this study. Results of the between-groups are in accordance with previous studies and within-group comparisons consider the probability of decreasing the change detection capability of the brain. The results of this study indicate that increasing the frequency of the stimuli close to the tinnitus perceived frequencies decreases the prediction error, including the prediction error of the silence. Such a decrease may cause the prediction error of the spontaneous neural activity in the auditory pathway to exceed the silence prediction error, and as a result, increases the probability of occurrence of tinnitus in higher frequencies according to the predictive coding model.

Vagus nerve stimulation paired with tones for tinnitus suppression: Effects on voice and hearing

OBJECTIVE

In individuals with chronic tinnitus, our interest was to determine whether daily low-level electrical stimulation of the vagus nerve paired with tones (paired-VNSt) for tinnitus suppression had any adverse effects on motor-speech production and physiological acoustics of sustained vowels. Similarly, we were also interested in evaluating for changes in pure-tone thresholds, word-recognition performance, and minimum-masking levels. Both voice and hearing functions were measured repeatedly over a period of 1 year.

STUDY DESIGN

Longitudinal with repeated-measures.

METHODS

Digitized samples of sustained frontal, midline, and back vowels (/e/, /o/, /ah/) were analyzed with computer software to quantify the degree of jitter, shimmer, and harmonic-to-noise ratio contained in these waveforms. Pure-tone thresholds, monosyllabic word-recognition performance, and MMLs were also evaluated for VNS alterations. Linear-regression analysis was the benchmark statistic used to document change over time in voice and hearing status from a baseline condition.

RESULTS

Most of the regression functions for the vocal samples and audiometric variables had slope values that were not significantly different from zero. Four of the nine vocal functions showed a significant improvement over time, whereas three of the pure tone regression functions at 2-4 kHz showed some degree of decline; all changes observed were for the left ear, all were at adjacent frequencies, and all were ipsilateral to the side of VNS. However, mean pure-tone threshold changes did not exceed 4.29 dB from baseline and therefore, would not be considered clinically significant. In some individuals, larger threshold shifts were observed. No significant regression/slope effects were observed for word-recognition or MMLs.

CONCLUSION

Quantitative voice analysis and assessment of audiometric variables showed minimal if any evidence of adverse effects using paired-VNSt over a treatment period of 1 year. Therefore, we conclude that paired-VNSt is a safe tool for tinnitus abatement in humans without significant side effects.

LEVEL OF EVIDENCE

Level IV.

Computer-Aided Tinnitus Detection based on Brain Network Analysis of EEG Functional Connectivity

Background

Tinnitus known as a central nervous system disorder is correlated with specific oscillatory activities within auditory and non-auditory brain areas. Several studies in the past few years have revealed that in the most tinnitus cases, the response pattern of neurons in auditory system is changed due to auditory deafferentation, which leads to variation and disruption of the brain networks.

Objective

In this paper, we introduce an approach to automatically distinguish tinnitus individuals from healthy controls based on whole-brain functional connectivity and network analysis.

Material and Methods

The functional connectivity analysis was applied to the resting state electroencephalographic (EEG) data of both groups using Weighted Phase Lag Index (WPLI) for various frequency bands in 2-44 Hz frequency range. In this case- control study, the classification was performed on graph theoretical measures using support vector machine (SVM) as a robust classification method.

Results

Experimental results showed promising classification performance with a high accuracy, sensitivity, and specificity in all frequency bands, specifically in the beta2 frequency band.

Conclusion

The current study provides substantial evidence that tinnitus network can be successfully detected by consistent measures of the brain networks based on EEG functional connectivity.

The efficacy and safety of multiple sessions of multisite transcranial random noise stimulation in treating chronic tinnitus

Introduction

Objective

Methods

Results

Conclusions

Chronic tinnitus and the limbic system: Reappraising brain structural effects of distress and affective symptoms

Chronic tinnitus has been associated with brain structural changes in both the auditory system as well as limbic system. While there is considerable inconsistency across brain structural findings, growing evidence suggests that distress and other non-auditory symptoms modulate effects. In this study we addressed this issue, testing the hypothesis that limbic changes in tinnitus relate to both disease-related distress as well as co-morbid psychopathology. We obtained high-resolution structural magnetic resonance imaging (MRI) scans from a total of 125 subjects: 59 patients with bilateral chronic tinnitus (29 with a co-morbid psychiatric condition, 30 without), 40 healthy controls and 26 psychiatric controls with depression/anxiety disorders (without tinnitus). Voxel-based morphometry with the CAT12 software package was used to analyse data. First, we analysed data based on a 2 × 2 factorial design (tinnitus; psychiatric co-morbidity), showing trend-level effects for tinnitus in ROI analyses of the anterior cingulate cortex and superior/transverse temporal gyri, and for voxel-based analysis in the left parahippocampal cortex. Multiple regression analyses showed that the parahippocampal finding was mostly predicted by tinnitus rather than (dimensional) psychopathology ratings. Comparing only low-distress tinnitus patients (independent of co-morbid conditions) with healthy controls also showed reduced left parahippocampal grey matter. Our findings demonstrate that depression and anxiety (not only subjective distress) are major modulators of brain structural effects in tinnitus, calling for a stronger consideration of psychopathology in future neurobiological and clinical studies of tinnitus.

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Chronic tinnitus is associated with high psychiatric co-morbidity and distress.

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Parahippocamal grey matter is associated with tinnitus rather than distress.

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Psychiatric co-morbidity modulates tinnitus-related structural patterns.

The potential role of auditory prediction error in decompensated tinnitus: An auditory mismatch negativity study

INTRODUCTION

Some tinnitus subjects habituate to their tinnitus but some others do not and complain of its annoyance tremendously. Normal sensory memory and change detection processes are needed for detecting the tinnitus signal as a prediction error and habituation to tinnitus. The purpose of this study was to compare auditory mismatch negativity as the index of sensory memory and change detection among the studied groups to search for the factors involving in the perception of tinnitus and preventing habituation in decompensated tinnitus subjects.

METHODS

Electroencephalography was recorded from scalp electrodes in compensated tinnitus, decompensated tinnitus, and no tinnitus control subjects. Mismatch negativity was obtained using the oddball paradigm with frequency, duration, and silent gap deviants. Amplitude, latency, and area under the curve of mismatch negativities were compared among the three studied groups.

RESULTS

The results showed lower mismatch negativity amplitude and area under the curve for the higher frequency deviant and for the silent gap deviant in decompensated tinnitus group compared to normal control and compensated tinnitus group.

CONCLUSIONS

This study revealed a deficit in sensory memory and change detection processing in decompensated tinnitus subjects. This causes persistent prediction errors; tinnitus signal is consistently detected as a new signal and activates the brain salience network and consequently prevents habituation to tinnitus. Mismatch negativity is proposed as an index for monitoring tinnitus rehabilitation.

MRI Verification of a 10-20 Targeting Protocol Used During Transcranial Magnetic Stimulation Sessions for Tinnitus

Langguth et al. (2006) described a method for targeting primary auditory cortex (PAC) during transcranial magnetic stimulation (TMS) using the 10–20 electroencephalography system. Study aims were to measure the degree of accuracy in placing the TMS coil on the scalp overlying PAC using the 10–20 method and determine the extent to which accuracy depends on the hemisphere of the coil placement. Twelve participants underwent anatomical magnetic resonance imaging (MRI) of their head in a 3T scanner. Before imaging, a fiducial marker was placed on their scalp corresponding to the TMS coil position. MRI scans were analyzed to determine the distance from the fiducial marker to PAC for each participant. On average, the 10–20 method resulted in distances in the medial–lateral, anterior-posterior, and inferior-superior dimensions that were within a few millimeters (~ 4 mm) of each other between the left and right hemispheres. The fiducial marker was, on average, 10.4 mm superior and 10.8 mm posterior to the optimal scalp location that minimized the distance to PAC. Individual asymmetries and other systematic differences found in this study raise important considerations to keep in mind that might necessitate using an MRI-guided method of coil-positioning when targeting PAC for TMS.

Randomized Controlled Trial of a Novel Device for Tinnitus Sound Therapy During Sleep

PURPOSE

The aim of this study was to determine if a customized stimulus from the Otoharmonics Levo System reduces tinnitus perceptions and reactions for people with bothersome tinnitus.

METHOD

Sixty participants were randomized to 1 of 3 groups that used sound therapy devices during sleep that differed in their acoustic stimulus: (a) tinnitus-matched (TM), (b) noise stimulus (NS), and (c) bedside sound generator (BSG). Outcome measures were the Tinnitus Functional Index (TFI), numeric rating scale of tinnitus loudness, and tinnitus loudness match. A Bayesian hierarchical model was fit to estimate the differences in treatment efficacy among groups.

RESULTS

Average tinnitus reactions and perceptions improved across treatment groups. We are at least 87% certain that treatment with TM or NS reduces mean TFI compared to treatment with BSG, with an estimated relative efficacy of 4.5-5 points greater reduction. We are at least 95% certain that treatment with TM results in greater reduction in mean numeric rating scale (NRS) of tinnitus loudness compared to the other groups, with an estimated relative efficacy of about 0.75 points greater reduction.

CONCLUSIONS

This study offers some support for greater average improvement in reactions to tinnitus with TM or NS devices compared to the BSG device. The TM group, compared to the BSG and NS groups, showed a greater reduction in ratings of tinnitus loudness on the NRS on average.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.5545759.

A New Statistical Approach for the Evaluation of Gap-prepulse Inhibition of the Acoustic Startle Reflex (GPIAS) for Tinnitus Assessment

Background: An increasingly used behavioral paradigm for the objective assessment of a possible tinnitus percept in animal models has been proposed by Turner and coworkers in 2006. It is based on gap-prepulse inhibition (PPI) of the acoustic startle reflex (ASR) and usually referred to as GPIAS. As it does not require conditioning it became the method of choice to study neuroplastic phenomena associated with the development of tinnitus. Objective: It is still controversial if GPIAS is really appropriate for tinnitus screening, as the hypothesis that a tinnitus percept impairs the gap detection ability ("filling-in interpretation" is still questioned. Furthermore, a wide range of criteria for positive tinnitus detection in GPIAS have been used across different laboratories and there still is no consensus on a best practice for statistical evaluation of GPIAS results. Current approaches are often based on simple averaging of measured PPI values and comparisons on a population level without the possibility to perform valid statistics on the level of the single animal. Methods: A total number of 32 animals were measured using the standard GPIAS paradigm with varying number of measurement repetitions. Based on this data further statistical considerations were performed. Results: We here present a new statistical approach to overcome the methodological limitations of GPIAS. In a first step we show that ASR amplitudes are not normally distributed. Next we estimate the distribution of the measured PPI values by exploiting the full combinatorial power of all measured ASR amplitudes. We demonstrate that the amplitude ratios (1-PPI) are approximately lognormally distributed, allowing for parametrical testing of the logarithmized values and present a new statistical approach allowing for a valid and reliable statistical assessment of PPI changes in GPIAS. Conclusion: Based on our statistical approach we recommend using a constant criterion, which does not systematically depend on the number of measurement repetitions, in order to divide animals into a tinnitus and a non-tinnitus group. In particular, we recommend using a constant threshold based on the effect size as criterion, as the effect size, in contrast to the p-value, does not systematically depend on the number of measurement repetitions.

Vagus Nerve Stimulation Paired with Tones for the Treatment of Tinnitus: A Prospective Randomized Double-blind Controlled Pilot Study in Humans

The aim of the pilot study was to evaluate the effect of Vagus Nerve Stimulation (VNS) paired with sounds in chronic tinnitus patients. All participants were implanted and randomized to a paired VNS (n = 16) or control (n = 14) group. After 6 weeks of home therapy, all participants received paired VNS. The device was used on 96% of days with good compliance. After 6 weeks, the paired VNS group improved on the Tinnitus Handicap Inventory (THI) (p = 0.0012) compared to controls (p = 0.1561). The between-group difference was 10.3% (p = 0.3393). Fifty percent of the participants in the paired VNS group showed clinically meaningful improvements compared to 28% in controls. At one year, 50% of participants had a clinically meaningful response. The therapy had greater benefits for participants with tonal and non-blast induced tinnitus at the end of 6 (24.3% vs. 2%, p = 0.05) and 12 weeks (34% vs. 2%, p = 0.004) compared to controls with 80% and 70% responding at 6 months and 1 year, respectively. Adverse effects were mild and well-tolerated and the therapy had a similar safety profile to VNS for epilepsy. VNS paired with tones may be effective for a subgroup of tinnitus patients and provides impetus for a larger pivotal study.

Tinnitus, Medial Olivocochlear System, and Music Exposure in Adolescents

INTRODUCTION

The most common cause of tinnitus is the exposure to noise; in the case of adolescents, music is the main sound source they are exposed to. Currently, one of the hypotheses about the genesis of tinnitus is related to the deterioration in the functioning of the medial olivocochlear system (MOCS).

AIM

The aim of this study was to determine the presence or absence of tinnitus in adolescents with normal hearing and to relate it to: (a) the functioning of the MOCS, by the contralateral suppression of the transient evoked otoacoustic emissions (TEOAEs) and (b) the musical general exposure (MGE).

MATERIALS AND METHODS

A cross-sectional descriptive correlational study was conducted. The sample was composed by adolescents with ages between 14 and 15. Two questionnaires were administered, one in relation to the subjective report of tinnitus and the other in relation to recreational activities to know the MGE.

RESULTS

The results showed that the amplitude of frequencies (1000, 1500, 2000, and 3000 Hz) and global amplitude of TEOAEs, with and without acoustic contralateral stimulation, were higher in the group without tinnitus, with a statistically significant difference (P < 0.05). The suppressive effect was higher in the group without tinnitus; however, there was no statistically significant difference. Contrastingly, a significant association (P < 0.05) between exposure to music and tinnitus was observed; 72.41% of the adolescents with high exposure to music had tinnitus.

DISCUSSION AND CONCLUSION

The results of the present investigation provide a contribution to the hypothesis of "the participation of the MOCS." Furthermore, a high MGE can be considered a risk factor for the onset of tinnitus.

Analysis of Audiometric Differences of Patients with and without Tinnitus in a Large Clinical Database

Human hearing loss (HL) and comorbidities like tinnitus pose serious problems for people's daily life, which in most severe cases may lead to social isolation, depression, and suicide. Here, we investigate the relationship between hearing deficits and tinnitus. To this end, we conducted a retrospective study on anonymized pure tone and speech audiometric data from patients of the ENT hospital Erlangen in which we compare audiometric data between patients with and without tinnitus. Overall data from 37,661 patients with sensorineural (SHL) or conductive HL (CHL) with (T, 9.5%) or without (NT, 90.5%) a tinnitus percept in different age groups and with different tinnitus pitches were included in this study. The results of the pure tone audiometry comparisons showed significant differences in T patients compared to NT patients. In young patients, we generally found lower hearing thresholds in T compared to NT patients. In adult patients, differences were more heterogeneous: hearing thresholds in T patients were lower in low frequency ranges, while they were higher at high frequencies. Furthermore, lower thresholds were more often found in CHL patients and could rarely be detected in SHL patients. In speech audiometry, only CHL patients with high-pitched tinnitus showed lower thresholds compared to NT patients' thresholds. The results of this study may point to a biologically plausible functional benefit on hearing thresholds in HL tinnitus patients. We hypothesize that the physiological mechanism of stochastic resonance counteracts HL by adding neuronal noise to the system. This neuronal noise may induce changes in the auditory pathway and finally-as a side effect of threshold improvement-lead to the development of a tinnitus percept. We propose a general model of changed hearing thresholds in T patients, being either decreased or increased compared to NT patients.

Characterization of tinnitus in different age groups: A retrospective review

Objectives:

The aim of this study was to characterize tinnitus in affected patients.

Methods:

A retrospective review of medical records from 470 consecutive patients who visited a tertiary care hospital for evaluation of chronic subjective tinnitus between January 2009 and June 2010 was performed. Patients were divided into three subgroups based on age. Clinical, audiological, and psychological characteristics of each subgroup were analyzed.

Results:

Of the 470 patients evaluated, 85 were less than 40, 217 between 40 and 60, and 168 above 60 years of age. Most patients were men and complained of unilateral, acute high-pitched tinnitus. Most patients above the age of 40 years complained of loud and annoying tinnitus and had worse stress and severity scores.

Conclusions:

Chronic tinnitus in older adults is subjectively louder, more annoying, and more distressing than that found in younger patients. We recommend considering age in the patient management plan.

Stochastic Resonance Controlled Upregulation of Internal Noise after Hearing Loss as a Putative Cause of Tinnitus-Related Neuronal Hyperactivity

Subjective tinnitus is generally assumed to be a consequence of hearing loss. In animal studies it has been demonstrated that acoustic trauma induced cochlear damage can lead to behavioral signs of tinnitus. In addition it was shown that noise trauma may lead to deafferentation of cochlear inner hair cells (IHC) even in the absence of elevated hearing thresholds, and it seems conceivable that such hidden hearing loss may be sufficient to cause tinnitus. Numerous studies have indicated that tinnitus is correlated with pathologically increased spontaneous firing rates and hyperactivity of neurons along the auditory pathway. It has been proposed that this hyperactivity is the consequence of a mechanism aiming to compensate for reduced input to the auditory system by increasing central neuronal gain, a mechanism referred to as homeostatic plasticity (HP), thereby maintaining mean firing rates over longer timescales for stabilization of neuronal processing. Here we propose an alternative, new interpretation of tinnitus-related development of neuronal hyperactivity in terms of information theory. In particular, we suggest that stochastic resonance (SR) plays a key role in both short- and long-term plasticity within the auditory system and that SR is the primary cause of neuronal hyperactivity and tinnitus. We argue that following hearing loss, SR serves to lift signals above the increased neuronal thresholds, thereby partly compensating for the hearing loss. In our model, the increased amount of internal noise-which is crucial for SR to work-corresponds to neuronal hyperactivity which subsequently causes neuronal plasticity along the auditory pathway and finally may lead to the development of a phantom percept, i.e., subjective tinnitus. We demonstrate the plausibility of our hypothesis using a computational model and provide exemplary findings in human patients that are consistent with that model. Finally we discuss the observed asymmetry in human tinnitus pitch distribution as a consequence of asymmetry of the distribution of auditory nerve type I fibers along the cochlea in the context of our model.

The impact of deep brain stimulation on tinnitus

Background:

Tinnitus is a disorder of the nervous system that cannot be adequately treated with current therapies. The effect of neuromodulation induced by deep brain stimulation (DBS) on tinnitus has not been studied well. This study investigated the effect of DBS on tinnitus by use of a multicenter questionnaire study.

Methods:

Tinnitus was retrospectively assessed prior to DBS and at the current situation (with DBS). From the 685 questionnaires, 443 were returned. A control group was one-to-one matched to DBS patients who had tinnitus before DBS (n = 61). Tinnitus was assessed by the tinnitus handicap inventory (THI) and visual analog scales (VAS) of loudness and burden.

Results:

The THI decreased significantly during DBS compared to the situation prior to surgery (from 18.9 to 15.1, P < .001), which was only significant for DBS in the subthalamic nucleus (STN). The THI in the control group (36.9 to 35.5, P = 0.50) and other DBS targets did not change. The VAS loudness increased in the control group (5.4 to 6.0 P < .01).

Conclusion:

DBS might have a modulatory effect on tinnitus. Our study suggests that DBS of the STN may have a beneficial effect on tinnitus, but most likely other nuclei linked to the tinnitus circuitry might be even more effective.

Deep brain stimulation of the inferior colliculus in the rodent suppresses tinnitus

In animal models of tinnitus pathological neuronal activity has been demonstrated. Deep brain stimulation disrupts pathological neuronal activity and might therefore be a potential treatment for patients who suffer severely from tinnitus. In this study, the effect of DBS in the inferior colliculi is investigated in an animal model of tinnitus. The external cortex of the inferior colliculus was targeted because of the key position of the inferior colliculus within the auditory network and the relation of the external cortex with the limbic system. In this study we show the effect of DBS in the inferior colliculus on tinnitus using a within-subject experimental design. After noise trauma, rats showed a significant increase in gap:no gap ratio of the gap-induced prepulse inhibition at 16 and 20kHz (p<0.05), indicating the presence of tinnitus in these frequency bands. During DBS the gap:no gap ratio returned back to baseline (p<0.05). Hearing thresholds before and during DBS did not differ, indicating that hearing function is probably not impaired by electrical stimulation. In summary, this study shows that DBS of the inferior colliculi is effective in reducing behavioral signs of tinnitus in an animal model. Impaired hearing function could not be objectified as a side effect of stimulation.

An Investigation of Feasibility and Safety of Bi-Modal Stimulation for the Treatment of Tinnitus: An Open-Label Pilot Study

Objectives

Tinnitus is the perception of sound in the absence of an external auditory stimulus. It is widely believed that tinnitus, in patients with associated hearing loss, is a neurological phenomenon primarily affecting the central auditory structures. However, there is growing evidence for the involvement of the somatosensory system in this form of tinnitus. For this reason it has been suggested that the condition may be amenable to bi‐modal stimulation of the auditory and somatosensory systems. We conducted a pilot study to investigate the feasibility and safety of a device that delivers simultaneous auditory and somatosensory stimulation to treat the symptoms of chronic tinnitus.

Methods

A cohort of 54 patients used the stimulation device for 10 weeks. Auditory stimulation was delivered via headphones and somatosensory stimulation was delivered via electrical stimulation of the tongue. Patient usage, logged by the device, was used to classify patients as compliant or noncompliant. Safety was assessed by reported adverse events and changes in tinnitus outcome measures. Response to treatment was assessed using tinnitus outcome measures: Minimum Masking Level (MML), Tinnitus Loudness Matching (TLM), and Tinnitus Handicap Inventory (THI).

Results

The device was well tolerated by patients and no adverse events or serious difficulties using the device were reported. Overall, 68% of patients met the defined compliance threshold. Compliant patients (N = 30) demonstrated statistically significant improvements in mean outcome measures after 10 weeks of treatment: THI (−11.7 pts, p < 0.001), TLM (−7.5dB, p < 0.001), and MML (−9.7dB, p < 0.001). The noncompliant group (N = 14) demonstrated no statistical improvements.

Conclusion

This study demonstrates the feasibility and safety of a new bi‐modal stimulation device and supports the potential efficacy of this new treatment for tinnitus.

Slow Cortical Potential Neurofeedback in Chronic Tinnitus Therapy: A Case Report

This study is the first to demonstrate outcomes of slow cortical potential (SCP) Neurofeedback training in chronic tinnitus. A 50-year old male patient with tinnitus participated in three SCP training blocks, separated with 1-month breaks. After the training the patient reported decreased tinnitus loudness and pitch, as well as improved quality of daily life. A quantitative electroencephalography analysis revealed close to normal changes of resting state bioelectrical activity in cortical areas considered to be involved in tinnitus generation. The present case study indicates that SCP Neurofeedback training can be considered a promising method for tinnitus treatment.

Auditory localization by subjects with unilateral tinnitus

Tinnitus is associated with changes in neural activity. How such alterations impact the localization ability of subjects with tinnitus remains largely unexplored. In this study, subjects with self-reported unilateral tinnitus were compared to subjects with matching hearing loss at high frequencies and to normal-hearing subjects in horizontal and vertical plane localization tasks. Subjects were asked to localize a pink noise source either alone or over background noise. Results showed some degree of difference between subjects with tinnitus and subjects with normal hearing in horizontal plane localization, which was exacerbated by background noise. However, this difference could be explained by different hearing sensitivities between groups. In vertical plane localization there was no difference between groups in the binaural listening condition, but in monaural listening the tinnitus group localized significantly worse with the tinnitus ear. This effect remained when accounting for differences in hearing sensitivity. It is concluded that tinnitus may degrade auditory localization ability, but this effect is for the most part due to the associated levels of hearing loss. More detailed studies are needed to fully disentangle the effects of hearing loss and tinnitus.

Cerebral Processing of Emotionally Loaded Acoustic Signals by Tinnitus Patients

This exploratory study determined the activation pattern in nonauditory brain areas in response to acoustic, emotionally positive, negative or neutral stimuli presented to tinnitus patients and control subjects. Ten patients with chronic tinnitus and without measurable hearing loss and 13 matched control subjects were included in the study and subjected to fMRI with a 1.5-tesla scanner. During the scanning procedure, acoustic stimuli of different emotional value were presented to the subjects. Statistical analyses were performed using statistical parametric mapping (SPM 99). The activation pattern induced by emotionally loaded acoustic stimuli differed significantly within and between both groups tested, depending on the kind of stimuli used. Within-group differences included the limbic system, prefrontal regions, temporal association cortices and striatal regions. Tinnitus patients had a pronounced involvement of limbic regions involved in the processing of chimes (positive stimulus) and neutral words (neutral stimulus), strongly suggesting improperly functioning inhibitory mechanisms that were functioning well in the control subjects. This study supports the hypothesis about the existence of a tinnitus-specific brain network. Such a network could respond to any acoustic stimuli by activating limbic areas involved in stress reactivity and emotional processing and by reducing activation of areas responsible for attention and acoustic filtering (thalamus, frontal regions), possibly reinforcing negative effects of tinnitus.

Flufenamic acid prevents behavioral manifestations of salicylate-induced tinnitus in the rat

INTRODUCTION

Tinnitus is defined as a phantom auditory sensation, the perception of sound in the absence of external acoustic stimulation. Given that flufenamic acid (FFA) blocks TRPM2 cation channels, resulting in reduced neuronal excitability, we aimed to investigate whether FFA suppresses the behavioral manifestation of sodium salicylate (SSA)-induced tinnitus in rats.

MATERIAL AND METHODS

Tinnitus was evaluated using a conditioned lick suppression model of behavioral testing. Thirty-one Wistar rats, randomly divided into four treatment groups, were trained and tested in the behavioral experiment: (1) control group: DMSO + saline (n = 6), (2) SSA group: DMSO + SSA (n = 6), (3) FFA group: FFA (66 mg/kg bw) + saline (n = 9), (4) FFA + SSA group: FFA (66 mg/kg bw) + SSA (400 mg/kg bw) (n = 10). Localization of TRPM2 to the plasma membrane of cochlear nucleus neurons was demonstrated by confocal microscopy.

RESULTS

Pavlovian training resulted in strong suppression of licking, having a mean value of 0.05 ±0.03 on extinction day 1, which is below the suppression training criterion level of 0.20 in control tinnitus animals. The suppression rate for rats having both FFA (66 mg/kg bw) and SSA (400 mg/kg bw) injections was significantly lower than that for the rats having SSA injections (p < 0.01).

CONCLUSIONS

We suggest that SSA-induced tinnitus could possibly be prevented by administration of a TRPM2 ion channel antagonist, FFA at 66 mg/kg bw.

Effects of unilateral acoustic trauma on tinnitus-related spontaneous activity in the inferior colliculus

This study describes the long-term effects of sound-induced cochlear trauma on spontaneous discharge rates in the central nucleus of the inferior colliculus (ICC). As in previous studies, single-unit recordings in Sprague-Dawley rats revealed pervasive increases in spontaneous discharge rates. Based on differences in their sources of input, it was hypothesized that physiologically defined neural populations of the auditory midbrain would reveal the brainstem sources that dictate ICC hyperactivity. Abnormal spontaneous activity was restricted to target neurons of the ventral cochlear nucleus. Nearly identical patterns of hyperactivity were observed in the contralateral and ipsilateral ICC. The elevation in spontaneous activity extended to frequencies well below and above the region of maximum threshold shift. This lack of frequency organization suggests that ICC hyperactivity may be influenced by regions of the brainstem that are not tonotopically organized. Sound-induced hyperactivity is often observed in animals with behavioral signs of tinnitus. Prior to electrophysiological recording, rats were screened for tinnitus by measuring gap pre-pulse inhibition of the acoustic startle reflex (GPIASR). Rats with positive phenotypes did not exhibit unique patterns of ICC hyperactivity. This ambiguity raises concerns regarding animal behavioral models of tinnitus. If our screening procedures were valid, ICC hyperactivity is observed in animals without behavioral indications of the disorder. Alternatively, if the perception of tinnitus is strictly linked to ongoing ICC hyperactivity, our current behavioral approach failed to provide a reliable assessment of tinnitus state.

Abnormal cross-frequency coupling in the tinnitus network

Neuroimaging studies have identified networks of brain areas and oscillations associated with tinnitus perception. However, how these regions relate to perceptual characteristics of tinnitus, and how oscillations in various frequency bands are associated with communications within the tinnitus network is still incompletely understood. Recent evidence suggests that apart from changes of the tinnitus severity the changes of tinnitus dominant pitch also have modulating effect on the underlying neuronal activity in a number of brain areas within the tinnitus network. Therefore, in a re-analysis of an existing dataset, we sought to determine how the oscillations in the tinnitus network in the various frequency bands interact. We also investigate how changes of tinnitus loudness, annoyance and pitch affect cross-frequency interaction both within and between nodes of the tinnitus network. Results of this study provide, to our knowledge, the first evidence that in tinnitus patients, aside from the previously described changes of oscillatory activity, there are also changes of cross-frequency coupling (CFC); phase-amplitude CFC was increased in tinnitus patients within the auditory cortex and the dorsolateral prefrontal regions between the phase of delta-theta and the amplitude of gamma oscillations (Modulation Index [MI] 0.17 in tinnitus patients vs. 0.08 in tinnitus free controls). Moreover, theta phase in the anterior cingulate region modulated gamma in the auditory (MI 0.1) and dorsolateral prefrontal regions (MI 0.19). Reduction of tinnitus severity after acoustic coordinated reset therapy led to a partial normalization of abnormal CFC. Also treatment induced changes in tinnitus pitch significantly modulated changes in CFC. Thus, tinnitus perception is associated with a more pronounced CFC within and between nodes of the tinnitus network. CFC can coordinate tinnitus-relevant activity in the tinnitus network providing a mechanism for effective communication between nodes of this network.

Protective effects of Ginkgo biloba extract EGb 761 against noise trauma-induced hearing loss and tinnitus development

Noise-induced hearing loss (NIHL) and resulting comorbidities like subjective tinnitus are common diseases in modern societies. A substance shown to be effective against NIHL in an animal model is the Ginkgo biloba extract EGb 761. Further effects of the extract on the cellular and systemic levels of the nervous system make it a promising candidate not only for protection against NIHL but also for its secondary comorbidities like tinnitus. Following an earlier study we here tested the potential effectiveness of prophylactic EGb 761 treatment against NIHL and tinnitus development in the Mongolian gerbil. We monitored the effects of EGb 761 and noise trauma-induced changes on signal processing within the auditory system by means of behavioral and electrophysiological approaches. We found significantly reduced NIHL and tinnitus development upon EGb 761 application, compared to vehicle treated animals. These protective effects of EGb 761 were correlated with changes in auditory processing, both at peripheral and central levels. We propose a model with two main effects of EGb 761 on auditory processing, first, an increase of auditory brainstem activity leading to an increased thalamic input to the primary auditory cortex (AI) and second, an asymmetric effect on lateral inhibition in AI.

Prescription of hearing-aid output for tinnitus relief

OBJECTIVE

Tinnitus is a perceived sound that cannot be attributed to an external source. This study attempts to identify a prescription of amplification that is optimized as a first-fit setting for tinnitus relief.

DESIGN

Participants compared the effect of high frequency amplification on their tinnitus. Stimuli were 13 speech files with different amounts of high frequency amplification (three cut-off frequencies and four gain settings) to simulate the effects of a change in DSL(I/O) v5.0 prescription in the high frequencies.

STUDY SAMPLE

Twenty-five participants with chronic tinnitus participated in the study.

RESULTS

A 6-dB reduction to prescribed gain at 2 kHz emerged as the most preferred output (26.47% participants) to interfere with participants' tinnitus. Overall, 70.58% of the participants' preferred a 3 to 6 dB reduction in output while 29.42% preferred a similar increase across all cut-off frequencies. A trend was observed in which the higher the tinnitus pitch the more similar the preferred output to DSL(I/O) v5.0.

CONCLUSION

DSL(I/O) v5.0 appears to be a good starting point for prescription of hearing-aid output for tinnitus management. Long-term benefits of different prescriptions for tinnitus still need to be ascertained.

Effect of tinnitus on distortion product otoacoustic emissions varies with hearing loss

PURPOSE

The aim of this study was to measure the effect of tinnitus, while accounting for the effect of hearing loss and aging, on distortion product otoacoustic emissions (DPOAEs).

METHOD

DPOAEs were measured twice in both ears in 5 groups of participants: young adults with normal hearing, middle-age adults with normal hearing, adults with high-frequency sensorineural hearing loss, age-matched adults with similar hearing loss and tinnitus, and adults with normal hearing and chronic tinnitus.

RESULTS

Multivariate analysis revealed a main effect of hearing loss and age, but no effect of tinnitus, across all 5 groups. Separate tests revealed significant effects of age and tinnitus in the normal-hearing groups and hearing loss in adults with or without tinnitus, but no effect of tinnitus in those with hearing loss.

CONCLUSION

DPOAE levels in the group of adults with hearing loss and tinnitus were diminished, but those in the group with normal hearing and tinnitus were enhanced, relative to DPOAE levels in the controls. Outer hair cell function, as indexed by DPOAEs, exhibits a complex association with tinnitus, and this has implications in the use of DPOAEs as a tool both for testing for tinnitus presence and for creating a model of neural mechanisms underlying tinnitus.

Neuromodulation: selected approaches and challenges

The brain operates through complex interactions in the flow of information and signal processing within neural networks. The 'wiring' of such networks, being neuronal or glial, can physically and/or functionally go rogue in various pathological states. Neuromodulation, as a multidisciplinary venture, attempts to correct such faulty nets. In this review, selected approaches and challenges in neuromodulation are discussed. The use of water-dispersible carbon nanotubes has been proven effective in the modulation of neurite outgrowth in culture and in aiding regeneration after spinal cord injury in vivo. Studying neural circuits using computational biology and analytical engineering approaches brings to light geometrical mapping of dynamics within neural networks, much needed information for stimulation interventions in medical practice. Indeed, sophisticated desynchronization approaches used for brain stimulation have been successful in coaxing 'misfiring' neuronal circuits to resume productive firing patterns in various human disorders. Devices have been developed for the real-time measurement of various neurotransmitters as well as electrical activity in the human brain during electrical deep brain stimulation. Such devices can establish the dynamics of electrochemical changes in the brain during stimulation. With increasing application of nanomaterials in devices for electrical and chemical recording and stimulating in the brain, the era of cellular, and even intracellular, precision neuromodulation will soon be upon us.

Characterization of tinnitus in Nigeria

OBJECTIVE

This study aimed to characterize tinnitus in middle aged and elderly out-patients attending a specialized clinic in a developing country.

METHODS

A cross sectional study of patients attending the ear, nose and throat (ENT) clinic of Olabisi Onabanjo University Teaching Hospital, OOUTH Sagamu, Nigeria. Data was collected with the use of a structured questionnaire. Data collected included socio demographics, medical history including experience of tinnitus, PTAs, BMI and BP. Data was analyzed using SPSS version 17.0.

RESULTS

79 patients had complaints of tinnitus thus making a crude prevalence of 14.5%, the prevalence increased steadily along the age groups. 51.9% of patients experienced tinnitus for a short period. 53.2% of the patients had symptoms referable to only one ear, while 54.4% had discrete as opposed to multiple types of tinnitus. Occurrence of intermittent symptoms was experienced by 75.9% of the patients and 70.9% were non-pulsatile in nature. Tinnitus was significantly associated with abnormal audiographic pattern, global increased hearing thresholds, high tone hearing loss, vertigo, hypertension and obesity.

CONCLUSION

Tinnitus character was majorly short term, unilateral, discrete, intermittent, and non-pulsatile in nature, and it is associated with otological, audiological, anthropometric and cardiovascular anomalies. The characteristics of tinnitus in Nigerian patients were similar to those described in developed countries, but the major risk factors for tinnitus except hearing impairment, may be different from the latter.

The evaluation of ozone and betahistine in the treatment of tinnitus

The aim of the study is to evaluate the effectiveness of ozone and betahistine treatments in the treatment of tinnitus. Sixty-eight patients were enrolled in this randomized, prospective controlled study. The ozone group consisted of 27, betahistine group consisted of 26 and control group consisted of 15 patients. The patients in ozone group received 10 sessions of ozone treatment via major autohemotherapy. Betahistine group received 48 mg/day betahistine tablets per oral for 3 months duration. The control group was followed up without any treatment given. The evaluation of tinnitus was made by tinnitus loudness and tinnitus handicap inventory (THI). The changes in findings from baseline to 3rd and 6th months were assessed, and the group results were compared. Comparison of the initial mean tinnitus loudness and 3 and 6 months after treatment in each of the three groups did not reveal a significant difference. The comparison between the groups in terms of the improvement of tinnitus loudness was not significant (p = 0.821). Comparison of the initial mean THI and 3 and 6 months after treatment revealed a significant difference in ozone and betahistine groups but not in the control group. When the delta (Δ) THI (the change of mean THI between the initial and 6th month) was compared between the groups, there was no significant difference. This randomized controlled study investigating the effects of ozone in tinnitus tries to shed light to a new method of treatment in tinnitus. The findings of the study does not provide enough evidence to support ozone and betahistine as a treatment for tinnitus and further research on the subject is necessary.

Predisposition for and prevention of subjective tinnitus development

Dysfunction of the inner ear as caused by presbyacusis, injuries or noise traumata may result in subjective tinnitus, but not everyone suffering from one of these diseases develops a tinnitus percept and vice versa. The reasons for these individual differences are still unclear and may explain why different treatments of the disease are beneficial for some patients but not for others. Here we for the first time compare behavioral and neurophysiological data from hearing impaired Mongolian gerbils with (T) and without (NT) a tinnitus percept that may elucidate why some specimen do develop subjective tinnitus after noise trauma while others do not. Although noise trauma induced a similar permanent hearing loss in all animals, tinnitus did develop only in about three quarters of these animals. NT animals showed higher overall cortical and auditory brainstem activity before noise trauma compared to T animals; that is, animals with low overall neuronal activity in the auditory system seem to be prone to develop tinnitus after noise trauma. Furthermore, T animals showed increased activity of cortical neurons representing the tinnitus frequencies after acoustic trauma, whereas NT animals exhibited an activity decrease at moderate sound intensities by that time. Spontaneous activity was generally increased in T but decreased in NT animals. Plastic changes of tonotopic organization were transient, only seen in T animals and vanished by the time the tinnitus percept became chronic. We propose a model for tinnitus prevention that points to a global inhibitory mechanism in auditory cortex that may prevent tinnitus genesis in animals with high overall activity in the auditory system, whereas this mechanism seems not potent enough for tinnitus prevention in animals with low overall activity.

Ondansetron in patients with tinnitus: randomized double-blind placebo-controlled study

The aim of this study was to assess the effect of ondansetron on symptoms of patients with subjective tinnitus accompanied by sensorineural hearing loss or normal hearing. Sixty patients with a chief complaint of tinnitus (with duration of more than 3 months) were equally randomized to ondansetron or placebo for 4 weeks. The dose of ondansetron was gradually increased from 4 mg/day (one tablet) to 16 mg/day (4 tablets) during 12 days and then continued up to 4 weeks. The exact number of tablets was prescribed in the placebo group. Patients underwent audiologic examinations and filled questionnaires at baseline and after 4 weeks of treatment. Our primary outcomes were changes in Tinnitus Handicap Inventory questionnaire (THI), Tinnitus Severity Index (TSI) and visual analog scale (VAS) scores. Our secondary outcomes were the changes in depression and anxiety based on Hospital Anxiety and Depression (HADS) questionnaire, side effects, tinnitus loudness matching, tinnitus pitch matching, pure tone audiometry and speech recognition threshold (SRT). In the ondansetron and placebo groups, 27 and 26 patients completed the study, respectively. The changes in VAS (P = 0.934), THI (P = 0.776), anxiety (P = 0.313) and depression (P = 0.163) scores were not different between the groups. TSI score decreased significantly in the ondansetron compared with the placebo group (P = 0.004). Changes in tinnitus loudness matching (P = 0.75) and pitch matching (P = 0.56) did not differ between the two groups. Ondansetron, but not placebo, decreased the SRT threshold (right, P < 0.001; left, P = 0.043) and mean PTA (right, P = 0.006; left, P < 0.001). In conclusion, ondansetron reduces the severity of tinnitus hypothetically through cochlear amplification.

Effectiveness of Repetitive Transcranial Magnetic Stimulation for Chronic Tinnitus

Objective

This systematic review aimed to assess the effectiveness of repetitive transcranial magnetic stimulation (rTMS) treatment for chronic tinnitus.

Data Sources

Relevant electronic databases and a reference list of articles published up to January 2012 were searched. Randomized controlled clinical trials of all types of rTMS treatment for patients with chronic tinnitus were included.

Review Methods

A literature search was conducted with structured criteria to select studies evaluated for systematic review.

Results

Five trials (160 participants) were included in this review. Repetitive transcranial magnetic stimulation treatment showed benefits in the short term, but the long-term effects are questionable. The Tinnitus Handicap Inventory (THI) and the visual analog scale (VAS) were the major assessment methods used. After active TMS stimulation, the reduction in the THI total score and VAS was significant compared with baseline at the first time point assessed and in the short term (2 weeks and 4 weeks). The longest follow-up time was 26 weeks after treatment, and the shortest follow-up time was 2 weeks. No severe side effects were reported from the use of rTMS. Differences in age, hearing level, duration of tinnitus of the included patients, and the condition of sham treatment may influence the effect.

Conclusion

Repetitive transcranial magnetic stimulation could be a new therapeutic tool for the treatment of chronic tinnitus, and thus far we have not been able to demonstrate any substantial risk from rTMS treatment. However, the long-term effects of rTMS treatment for tinnitus are not clear and will require further study.