Typewriter tinnitus: a carbamazepine-responsive syndrome related to auditory nerve vascular compression

Easing the Burden of Tinnitus: A Narrative Review for Exploring Effective Pharmacological Strategies

Many individuals seek medical attention for tinnitus, desiring relief from the distress caused by the condition; however, the treatment process is far from straightforward. The most effective treatments for chronic subjective tinnitus, such as tinnitus retraining therapy (TRT) and cognitive behavioral therapy (CBT), require considerable time and efforts. As a result, many of them express a desire for alleviation through medication. While it is true that medication is not generally recommended in treatment guidelines for chronic subjective tinnitus, in specific situations such as when accompanied by symptoms of depression or anxiety-drugs like antidepressants or anxiolytics may have a meaningful impact on symptom reduction. Additionally, medication can prove effective in certain specialized forms of tinnitus, such as typewriter tinnitus, as opposed to chronic subjective tinnitus. Although intratympanic dexamethasone injections for tinnitus have been reported to lack efficacy compared to a placebo, if patients perceive subjective satisfaction due to a placebo effect, it holds significance. From the perspective of patients suffering from tinnitus, even if the therapeutic mechanism is set aside, experiencing some degree of relief through certain medications can enhance compliance with evidence-based treatments like TRT and CBT.

The "Near"-Narrowed Internal Auditory Canal Syndrome in Adults: Clinical Aspects, Audio-Vestibular Findings, and Radiological Criteria for Diagnosis

INTRODUCTION

Vestibular Paroxysmia (VP) refers to short attacks of vertigo, spontaneous or triggered by head movements, and implies the presence of a compressive vascular loop in contact with the cochleovestibular nerve (CVN). Classically, a narrowed internal auditory canal (IAC) corresponds to a diameter of less than 2 mm on CT, usually associated with a hypoplastic CVN on MRI. The aim of this study was to discuss a distinct clinical entity mimicking VP in relation to a "near"-narrowed IAC (NNIAC) and to propose radiological criteria for its diagnosis.

METHODS

Radiological measurements of the IAC were compared between three groups: the study group (SG, subjects with a clinical presentation suggestive of VP, but whose MRI of the inner ear and pontocerebellar angle excluded a compressive vascular loop) and two control groups (adult and children) with normal vestibular evaluations and no history of vertigo.

RESULTS

59 subjects (18 M and 41 F) were included in the SG. The main symptoms of NNIAC were positional vertigo, exercise- or rapid head movements-induced vertigo, and dizziness. The statistical analysis in the study group showed that the threshold values for diagnosis were 3.3 mm (in tomodensitometry) and 2.9 mm (in MRI) in coronal sections of IAC. Although a significantly lower mean value for axial IAC diameter was found in SG compared with controls, the statistics did not reveal a threshold due to the large inter-individual variations in IAC measurements in normal subjects. There was no significant difference in IAC diameter between the adult and pediatric controls.

CONCLUSIONS

In the present study, we report a new anatomopathological condition that appears to be responsible for a clinical picture very similar-but not identical-to VP in association with the presence of an NNIAC. The diagnosis requires a careful analysis of the IAC's shape and diameters in both axial and coronal planes.

Typewriter Tinnitus: Value of ABR as a Diagnostic and Prognostic Indicator

INTRODUCTION

Typewriter tinnitus refers to a special kind of staccato tinnitus, which is mostly described by patients as Morse code, popcorn, or machine-gun. It has been accepted that the mechanism of typewriter tinnitus is caused by the neurovascular compression of the cochleovestibular nerve. Patients who suffered from typewriter tinnitus have exhibited a good response to carbamazepine or oxcarbazepine, but there is a risk of recurrence after treatment cessation. The present study aims to determine the value of auditory brainstem response (ABR) in diagnosing typewriter tinnitus and predicting relapse after drug withdrawal.

METHODS

Patients who presented with typewriter tinnitus from March 2019 to March 2022 were included for the present retrospective study. The auditory and vestibular test results and drug treatment effects were collected and analyzed. Patients with idiopathic unilateral subjective tinnitus, who were matched by age to patients with typewriter tinnitus at a ratio of 2:1, were consecutively recruited for the control group.

RESULTS

Eighteen patients with typewriter tinnitus and 38 controls were included. Ears with typewriter tinnitus had longer interpeak latency (IPL) I-III, and wave III and V latencies, and a higher ratio of IPL I-III ≥2.3 ms based on ABR, when compared to the unaffected side and controls ( p <0.05). Seventeen patients with typewriter tinnitus responded positively to medication. Among these patients, seven patients had a relapse after drug cessation, while 10 patients did not have a relapse. The relapse group had significantly longer IPL I-III and wave V latency, older age, and poorer hearing, when compared to the nonrelapse group ( p < 0.05). Furthermore, IPL I-III had the largest area under the receiver operating characteristic curve, and the optimal cutoff was 2.4 ms (sensitivity, 100.0%; specificity, 66.7%). There were no significant differences in other demography or other clinical test results between the relapse and nonrelapse groups ( p > 0.05). Ramsay Hunt syndrome and neuromyelitis optica spectrum disorders were identified in two cases.

CONCLUSION

Prolonged IPL I-III based on ABR can help in the diagnosis of typewriter tinnitus and its prognosis after treatment cessation. Patients with IPL I-III greater than 2.4 ms, older age and poorer hearing are more likely to relapse. In addition to the neurovascular conflict of the cochleovestibular nerve, the etiologies of neuroinflammation and demyelinating diseases are also possible for typewriter tinnitus.

Integrating pharmacogenomics into clinical trials of hearing disorders

In 2019, the U.S. Food and Drug Administration issued guidance to increase the efficiency of drug development and support precision medicine, including tailoring treatments to those patients who will benefit based on genetic variation even in the absence of a documented mechanism of action. Although multiple advancements have been made in the field of pharmacogenetics (PGx) for other disease conditions, there are no approved PGx guidelines in the treatment of hearing disorders. In studies of noise-induced hearing loss (NIHL), some progress has been made in the last several years associating genomic loci with susceptibility to noise damage. However, the power of such studies is limited as the underlying physiological responses may vary considerably among the patient populations. Here, we have summarized previous animal studies to argue that NIHL subtyping is a promising strategy to increase the granularity of audiological assessments. By coupling this enhanced phenotyping capability with genetic association studies, we suggest that drug efficacy will be better predicted, increasing the likelihood of success in clinical trials when populations are stratified based on genetic variation or designed with multidrug combinations to reach a broader segment of individuals suffering or at risk from NIHL.

The Impact of Vascular Loops in the Cerebellopontine Angle on Audio-Vestibular Symptoms: A Systematic Review

It has been suggested that vascular loops in the cerebellopontine angle and internal auditory canal are involved in the etiology of audio-vestibular symptoms. Several studies have focused on the compression of the eighth cranial nerve by vascular loops but have yielded contradictory results regarding their clinical significance. The aim of this study was to investigate whether vascular loops in this region correlate with audio-vestibular symptoms and which loop features - if any - can potentially lead to symptom manifestation. This systematic review was conducted according to the PRISMA guidelines. We performed on PubMed a literature search from November 2005 to October 2020. The search strategy included the following keywords ("vascular loops" OR "AICA loops" OR "vascular compression syndrome") AND ("hearing loss" OR "tinnitus" OR "vertigo"). Fifteen studies were eligible and included in the analysis. Overall, the studies encompassed a total of 11,788 patients included in this review. The significantly larger group of patients (70%), in which no correlation of symptoms with vascular loops was found, suggests that vascular loops are probably anatomic variations in a substantial majority of cases with an uncommon subset causing some audio-vestibular symptoms. Even within the papers claiming a correlation, there is a multitude of symptoms that did not correlate with vascular loops. It has been suggested by most authors that magnetic resonance imaging should be performed to exclude the role of a vascular loop in the etiology of audio-vestibular symptoms only when vascular compression syndrome is suspected based on clinical indications and not routinely. Further studies would be useful in order to detail the relationship between the vascular structures and the nervous system.

Neuroprotective Effect of Valproic Acid on Salicylate-Induced Tinnitus

High-dose salicylate induces temporary moderate hearing loss and the perception of a high-pitched tinnitus in humans and animals. Previous studies demonstrated that high doses of salicylate increase N-methyl-d-aspartate (NMDA) receptor levels, resulting in a rise in Ca²⁺ influx and induction of excitotoxicity. Glutamate excitotoxicity is associated with failure in the maintenance of calcium homeostasis, mitochondrial dysfunction, and production of reactive oxygen species (ROS). Valproic acid (VPA) is widely used for the management of bipolar disorder, epilepsy, and migraine headaches, and is known to regulate NMDA receptor activity. In this study, we examined the beneficial effects of VPA in a salicylate-induced tinnitus model in vitro and in vivo. Cells were pretreated with VPA followed by salicylate treatment. The expression levels of NMDA receptor subunit NR2B, phosphorylated cAMP response element-binding protein—an apoptosis marker, and intracellular levels of ROS were measured using several biochemical techniques. We observed increased expression of NR2B and its related genes TNFα and ARC, increased intracellular ROS levels, and induced expression of cleaved caspase-3. These salicylate-induced changes were attenuated in the neuronal cell line SH-SY5Y and rat cortical neurons after VPA pretreatment. Together, these results provide evidence of the beneficial effects of VPA in a salicylate-induced temporary hearing loss and tinnitus model.

Tinnitus, Hyperacusis, Otalgia, and Hearing Loss

PURPOSE OF REVIEW

This article reviews the causes of tinnitus, hyperacusis, and otalgia, as well as hearing loss relevant for clinicians in the field of neurology.

RECENT FINDINGS

Important causes of unilateral and bilateral tinnitus are discussed, including those that are treatable or caused by serious structural or vascular causes. Concepts of hyperacusis and misophonia are covered, along with various types of neurologic disorders that can lead to pain in the ear. Hearing loss is common but not always purely otologic.

SUMMARY

Tinnitus and hearing loss are common symptoms that are sometimes related to a primary neurologic disorder. This review, tailored to neurologists who care for patients who may be referred to or encountered in neurology practice, provides information on hearing disorders, how to recognize when a neurologic process may be involved, and when to refer to otolaryngology or other specialists.

Microvascular compression of the vestibulocochlear nerve

PURPOSE

Vascular compression of cranial nerves has been widely accepted as a cause for trigeminal neuralgia and hemifacial spasm. In contrast, vascular compression of the vestibulocochlear nerve remains controversial.

METHOD

A comprehensive literature review including 175 articles between 1960 and 2020 was performed in an attempt to summarise the published hypotheses of the pathophysiological mechanisms of vascular compression of the vestibulocochlear nerve and their management strategies.

RESULTS

Vascular loops in the cerebellopontine angle (CPA) and internal auditory meatus (IAM) are very common and should be regarded primarily as a normal variant. Advances in anatomical understanding with the development of models for the tonotopy of the vestibulocochlear nerve help explain the complexity of symptoms created by possible neurovascular interaction.

CONCLUSION

Widely accepted, validated and sensitive diagnostic criteria and outcome measures need to be established in order to evaluate the role of surgery in vestibulocochlear nerve vascular compression.

Low inter-rater consistency in semantic profiles of tinnitus-like sounds rated by tinnitus patients

Characterizations of the tinnitus sound percept are always based on a subjective description by the person affected. Since the experimenter cannot have access to the tinnitus percept, it is not possible to verify whether individuals use the adjectives describing the sound in the expected way, i.e., whether a label given to the tinnitus percept corresponds to the label that the experimenter or another individual would give to the same sound percept. However, if it is assumed that tinnitus patients can reliably describe their own tinnitus, then they should also be able to reliably describe tinnitus-like sounds, presented acoustically. In this study, 26 tinnitus patients used a tablet computer to rate 18 pre-defined adjectives on their level of descriptiveness for their own tinnitus percept as well as 17 tinnitus-like sounds presented via headphones. The main interest of the current study was to calculate intraclass correlation (ICC) and Krippendorff's alpha coefficients for the rating profiles of the acoustically-presented sounds, in order to quantify how well the individuals agreed on the ratings of known sounds, i.e., whether the adjectives would receive similar ratings from all participants for a specific tinnitus-like sound. The results show that the level of agreement was low for all adjectives and sounds, meaning that the different individuals did not use the adjectives in a consistent manner. The conclusion is that subjective tinnitus descriptions should be interpreted with great caution, and that the inherent variability involved in the characterization of sounds by naïve listeners can contribute to the observed heterogeneity in tinnitus symptoms and treatment outcomes.

Classification of Tinnitus: Multiple Causes with the Same Name

Tinnitus is spoken of as if it were a single thing, but there are many different causes, likely many different mechanisms, and many different subtypes. This article reviews a broad range of approaches to understand and demarcate different tinnitus subtypes, which will be critical for exploring and finding cures for different subtypes.

Current Validated Medical Treatments: Pharmacologic Interventions

The search for an effective medication that will eliminate tinnitus has a long history. Currently, no drugs exist that universally cure tinnitus. Pharmacologic interventions that have been investigated can be divided into those that attempt to eliminate the perception of tinnitus, and those that are designed to treat the negative comorbidities associated with tinnitus, thereby mitigating tinnitus' negative impact on quality of life. A third category of drugs can also be considered that addresses an identified pathologic condition that has tinnitus as an associated symptom (for example, Meniere's disease, otosclerosis, migraine-associated vertigo). This third category is not addressed.

Typewriter tinnitus: An investigative comparison with middle ear myoclonic tinnitus and its long-term therapeutic response to carbamazepine

OBJECTIVES

Due to its rarity and similar sound, typewriter tinnitus (TT) can be misdiagnosed as middle ear myoclonic tinnitus (MEMT). We aim to clarify the characteristics of TT compared to MEMT, and the long-term therapeutic response to carbamazepine.

METHODS

Fourteen patients with TT and 28 patients with MEMT were enrolled.

RESULTS

TT patients were older than MEMT patients, and their tinnitus symptoms were mostly unilateral. Tinnitus symptoms, which is associated with dizziness, facial spasm, and head motion, were more common in TT, whereas MEMT were more related to noise. Acoustic reflex decay perturbation and low loudness discomfort level were diagnostic signs in MEMT patients, while decreased level of wave II in ABR was the most reliable sign in TT patients. All TT patients exhibited partial or complete response to carbamazepine, but there was a relapse rate after withdrawal of the drug was 60%. Increase in age and longer duration of symptoms were the risk factors of relapse of TT.

CONCLUSION

The different characteristics observed in this study will be helpful to diagnose TT and MENT. Duration of tinnitus was the most important long-term prognostic factor of the carbamazepine trial, which indicates the importance of its earlier diagnosis.

Unilateral cochleovestibular nerve compression syndrome in a patient with bilateral IAC osteoma

INTRODUCTION

Osteomas of the internal auditory canal are rarely reported in the literature. Patients may complain of disabling symptoms of dizziness, hearing loss, and vestibular dysfunction. We report the case of a patient with bilateral osteomas of the internal auditory canal (IAC) associated with bilateral neurovascular compression mainly affecting the right cochleovestibular nerve (VIII) and right anterior inferior cerebellar artery (AICA).

OBSERVATION

This 75-year-old woman patient complained of disabling paroxysmal vertigo, typewriter tinnitus and hearing loss of the right ear. Temporal bone computed tomography showed bilateral osteoma arising from the posterior superior wall of the IAC. MRI sequences of the right VIII demonstrated compression by the right AICA against the inferior wall of the narrowed IAC. Treatment with oxcarbazepine allowed marked and lasting improvement of the patient's symptoms.

CONCLUSION

To our knowledge, this is the first description of an ipsilateral neurovascular compression syndrome of the VIII secondary to the presence of an osteoma narrowing the IAC.

Tinnitus

Objective and subjective tinnitus can often be differentiated based on comprehensive history, physical examination, and audiogram. Examples of objective tinnitus include vascular abnormalities, palatal myoclonus, patulous eustachian tube, and stapedial/tensor tympani muscle spasm. Subjective tinnitus is usually associated with hearing loss. Rarely, tinnitus is the result of an underlying condition. In these cases, imaging and additional testing may be indicated. Classification of the type, quality, and intensity of tinnitus is helpful in the work-up and treatment of tinnitus. Treatment modalities include cognitive behavioral therapy, tinnitus retraining therapy, sound therapy, hearing aids, cochlear implants, pharmacotherapy, and brain stimulation.

A Pilot Study of Peripheral Muscle Magnetic Stimulation as Add-on Treatment to Repetitive Transcranial Magnetic Stimulation in Chronic Tinnitus

While brain stimulation techniques have been examined as treatment options for chronic tinnitus for many years, they have recently been extended to multimodal treatment approaches. As chronic tinnitus is often accompanied by comorbid muscular tension in the neck and back, we performed a one-arm pilot study to explore the feasibility of a new multimodal treatment approach. In detail, repetitive peripheral magnetic stimulation (rPMS) of the back was performed before and after each session of repetitive transcranial magnetic stimulation (rTMS) of the brain. Data of 41 patients were analyzed, all of which were treated with ten sessions of rTMS of the left prefrontal and left temporoparietal cortex followed by rPMS of the neck and back muscles. Tinnitus severity was measured using the tinnitus questionnaire (TQ). Neck pain was assessed using the neck pain and disability scale (NPAD). The new treatment approach was feasible and well accepted by the majority of patients. However, the overall patient group did not improve significantly in either of the questionnaires. If patients were divided in different subgroups depending on whether they were suffering from neck pain or somatosensory tinnitus, explorative post-hoc tests suggested differential effects: patients with both neck pain and somatosensory tinnitus had better outcomes than patients without those conditions or with neck pain only. This was true for both the TQ and the NPAD. This effect was of transient nature though: the TQ score went back to its baseline level after a follow-up period of 12 weeks. Based on our results we recommend that in studies that investigate tinnitus treatments targeting somatosensory afferents patients should be stratified according to somatic co-morbidities and somatosensory influence on the tinnitus percept.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, NCT02306447.

Typewriter tinnitus revisited: The typical symptoms and the initial response to carbamazepine are the most reliable diagnostic clues

Although neurovascular compression of the cochlear nerve (NVC-C) presenting as typewriter tinnitus is a discrete disease category, verified diagnostic criteria are lacking. We sought to refine the diagnostic criteria for NVC-C by reference to a relatively large case series. The medical records of 22 NVC-C patients were retrospectively reviewed. Psychoacoustic characteristics, the results of diagnostic work-up (including audiovestibular neurophysiological tests and radiological evaluations), and the initial treatment response to carbamazepine were investigated. All subjects described their tinnitus as a typical “typewriter” or “staccato” sound. Of the 22 subjects, 11 (50%) had histories of vertiginous spells, but none had ipsilesional hearing loss. Vestibular function tests in 11 subjects tested revealed only 2 (18.2%) isolated cervical vestibular evoked myogenic potential abnormalities. Radiological comparisons of the symptomatic and asymptomatic sides, regarding the type of the vascular loop and neurovascular contact, revealed no significant differences. However, all 22 subjects exhibited immediate and marked responses to short-term carbamazepine treatment. Meticulous history-taking in terms of the psychoacoustic characteristics and the response to initial carbamazepine, are more reliable diagnostic clues than are radiological or neurophysiological data in NVC-C subjects. Therefore, the typical psychoacoustic characteristics and the response to initial carbamazepine should be included in the diagnostic criteria.

The Role of MRI in Diagnosing Neurovascular Compression of the Cochlear Nerve Resulting in Typewriter Tinnitus

BACKGROUND AND PURPOSE

Typewriter tinnitus, a symptom characterized by paroxysmal attacks of staccato sounds, has been thought to be caused by neurovascular compression of the cochlear nerve, but the correlation between radiologic evidence of neurovascular compression of the cochlear nerve and symptom presentation has not been thoroughly investigated. The purpose of this study was to examine whether radiologic evidence of neurovascular compression of the cochlear nerve is pathognomonic in typewriter tinnitus.

MATERIALS AND METHODS

Fifteen carbamazepine-responding patients with typewriter tinnitus and 8 control subjects were evaluated with a 3D T2-weighted volume isotropic turbo spin-echo acquisition sequence. Groups 1 (16 symptomatic sides), 2 (14 asymptomatic sides), and 3 (16 control sides) were compared with regard to the anatomic relation between the vascular loop and the internal auditory canal and the presence of neurovascular compression of the cochlear nerve with/without angulation/indentation.

RESULTS

The anatomic location of the vascular loop was not significantly different among the 3 groups (all, P > .05). Meanwhile, neurovascular compression of the cochlear nerve on MR imaging was significantly higher in group 1 than in group 3 (P = .032). However, considerable false-positive (no symptoms with neurovascular compression of the cochlear nerve on MR imaging) and false-negative (typewriter tinnitus without demonstrable neurovascular compression of the cochlear nerve) findings were also observed.

CONCLUSIONS

Neurovascular compression of the cochlear nerve was more frequently detected on the symptomatic side of patients with typewriter tinnitus compared with the asymptomatic side of these patients or on both sides of control subjects on MR imaging. However, considering false-positive and false-negative findings, meticulous history-taking and the response to the initial carbamazepine trial should be regarded as more reliable diagnostic clues than radiologic evidence of neurovascular compression of the cochlear nerve.

Microvascular decompression for tinnitus: systematic review

OBJECTIVE

The objective of this study was to examine operative outcomes in cases of microvascular decompression (MVD) of cranial nerve (CN) VIII for tinnitus through a critical review of the literature.

METHODS

Forty-three English-language articles were gathered from PubMed and analyzed. In this review, two different case types were distinguished: 1) tinnitus-only symptomatology, which was defined as a patient with tinnitus with or without sensorineural hearing loss; and 2) mixed symptomatology, which was defined as tinnitus with symptoms of other CN dysfunction. This review reports outcomes of those with tinnitus-only symptoms.

RESULTS

Forty-three tinnitus-only cases were found in the literature with a 60% positive outcome rate following MVD. Analysis revealed a 5-year cutoff of preoperative symptom duration before which a good outcome can be predicted with 78.6% sensitivity, and after which a poor outcome can be predicted with 80% specificity.

CONCLUSIONS

As the 60% success rate is more promising than several other therapeutic options open to the chronic tinnitus sufferer, future research into this field is warranted.

Microvascular decompression of the cochleovestibular nerve for treatment of tinnitus and vertigo: a systematic review and meta-analysis of individual patient data

OBJECTIVE Microvascular decompression (MVD) is regarded as a valid treatment modality in neurovascular conflicts (NVCs) causing, for example, trigeminal neuralgia and hemifacial spasms. An NVC of the cochleovestibular nerve might cause tinnitus and/or vertigo; however, general acceptance of MVD for this indication is lacking. The aim of this study was to investigate the effectiveness, safety, and prognostic factors for success of MVD of the cochleovestibular nerve. METHODS A systematic review and meta-analysis of individual patient data (IPD) were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Individual Patient Data (PRISMA-IPD) guidelines. By a comprehensive search (conducted in January 2016) in MEDLINE, EMBASE, and Google Scholar, eligible studies were identified. The collected outcome was a global measurement of improvement of 1) tinnitus, 2) vertigo, and 3) tinnitus combined with vertigo. For the meta-analysis, IPD were collected from the papers and/or from the authors. IPD were analyzed with logistic regression analysis while accounting for study clustering. RESULTS Thirty-five studies (572 patients) were included. The level of evidence provided by these studies was low. In 28% of patients with tinnitus and 32% of patients with vertigo, complete relief following MVD was reported. Patients with both tinnitus and vertigo had complete relief in 62% of cases. In 11% of patients, ≥ 1 complications were reported. Meta-analysis of IPD (165 patients) demonstrated that patients with both tinnitus and vertigo had a higher chance of success (OR 3.8, 95% CI 1.45-10.10) than patients with tinnitus alone. No other variables were significantly related to success. CONCLUSIONS Due to low success rates, MVD cannot be considered as a standard treatment method for tinnitus or vertigo. Moreover, a substantial complication rate was found. However, patients with combined symptoms had a higher chance of success. When combined symptoms occur, it is more likely that an NVC is the underlying pathology and MVD might be appropriate. Due to the low level of evidence in the included studies, this conclusion must be taken with caution. Further validation is necessary to evaluate whether patients with combined symptoms are indeed better candidates for MVD.

Treatment of tinnitus

PURPOSE OF REVIEW

Tinnitus, the perception of sound in the absence of a corresponding external acoustic stimulus, is a highly prevalent and frequently severely impairing disorder with worldwide impact. In this article after a short overview about epidemiology and pathophysiology the currently available treatment options will be discussed with specific consideration of the available evidence, their mechanisms of action and their limitations.

RECENT FINDINGS

During the last decades, advances in neuroimaging methods and the development of animal models have contributed to an increasing understanding of the neuronal correlates of tinnitus and have motivated the development of innovative brain-based treatment approaches for directly targeting the neuronal correlates of tinnitus. A further important development has been the insight that there exist different forms of tinnitus that differ in their pathophysiology and their response to specific treatments.

SUMMARY

Treatment of tinnitus should be based on a comprehensive diagnosis of etiologic and concomitant aspects of an individual's tinnitus. Already today a large variety of therapeutic interventions are available, which can efficiently reduce tinnitus severity. Several innovative treatment approaches are currently under development.

Tinnitus Holistic Simplified Classification (THoSC): A New Assessment for Subjective Tinnitus, With Diagnostic and Therapeutic Implications

OBJECTIVE

One of the most debated topics in tinnitus is its standard and practical classification. The most popular classification distinguishes subjective from objective tinnitus. Other classifications are based on different features. On the whole, they seem incomplete, and the diagnostic and therapeutic algorithms are often difficult for practical purposes. The aim of this work is to develop a new diagnostic and therapeutic algorithm.

METHODS

Our model is based on 10 years of experience. In particular, the starting point is the data retrieved from 212 consecutive patients in our Tinnitus Unit between May and December 2013: We found a clear auditory disorder in 74.5% of the population, muscolo-skeletal disorders and/or trigeminal disease in 57.1%, and psychiatric comorbidities in 43.8%. Different features coexisted in 59.9% of the population.

RESULTS

Following such data we propose the Tinnitus Holistic Simplified Classification, which takes into account the different tinnitogenic mechanisms and the interactions between them. It differentiates tinnitus that arises from: (1) auditory alterations (Auditory Tinnitus), (2) complex auditory-somatosensory interactions (Somatosensory Tinnitus), (3) psychopathological-auditory interactions (Psychopathology-related Tinnitus), and (4) 2 or all of the previous mechanisms (Combined Tinnitus).

CONCLUSIONS

In our opinion this classification provides an accurate and easy tailored path to manage tinnitus patients.

Microvascular decompression for typewriter tinnitus-case report

BACKGROUND

Microvascular decompression has been tested as a treatment for tinnitus.

METHODS

However, only a fraction of patients appear to benefit from surgery if the combination of findings such as paroxysmal vertigo, ABR changes and tinnitus is used to select patients for microvascular decompression.

RESULTS

Instead, a more specific syndrome of staccato or "typewriter" tinnitus, which is highly responsive to carbamazepine, was suggested to be caused by a neurovascular conflict.

CONCLUSION

We present the first case of typewriter tinnitus with complete long-term symptom relief following microvascular decompression of the vestibulocochlear nerve. We suggest that this specific syndrome is caused by a neurovascular conflict and treatable by microvascular decompression.

Tinnitus

Tinnitus, the perception of sound in the absence of an external sound, usually results from a disorder of: (1) the auditory system (usually peripheral, rarely central); (2) the somatosensory system (head and neck); or (3) a combination of the two. Its cause can be determined through its characteristics. The history must include the tinnitus': (1) quality (including whether it can ever be pulsatile or have a clicking component); (2) location; (3) variability; (4) predominant pitch (low or high); and (5) whether the patient can do something to modulate the percept. In addition to the standard neuro-otologic examination, the exam should include inspection of the teeth for evidence of wear, listening around the ear and neck for sounds similar to the tinnitus, palpation of the craniocervical musculature for trigger points, and probing whether the tinnitus percept can be modulated with "somatic testing." All subjects should have a recent audiogram. Presently the most compelling tinnitus theory is the dorsal cochlear nucleus (DCN) hypothesis: both the auditory and somatosensory systems converge upon and interact within the DCN. If the activity of the DCN's somatosensory-interacting fusiform cells exceeds an individual's tinnitus threshold, then tinnitus results.

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

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

Tinnitus: therapeutic use of superficial brain stimulation

Tinnitus is a common disorder and traditional treatment approaches such as medication, active or passive sound enhancement, and cognitive behavioral therapy have limited efficacy. Thus, there is an urgent need for more effective treatment approaches. Functional imaging studies in patients with tinnitus have revealed alterations in neuronal activity of central auditory pathways, probably resulting as a consequence of sensory deafferentation. However, nonauditory brain areas are also involved. These nonauditory brain areas might represent both an "awareness" network involved in the conscious perception of the tinnitus signal as well as areas related to a nontinnitus-specific distress network consisting of the anterior cingulate cortex, anterior insula, and amygdala. Moreover, memory mechanisms involving the hippocampus and the parahippocampal region may play a role in the persistence of the awareness of the phantom percept, as well as in the reinforcement of the associated distress. All of these networks represent potential targets for treatment via pharmacological treatment or noninvasive and invasive brain stimulation. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive method of applying electromagnetic fields to the brain that can induce alterations of neuronal activity that outlast the stimulation period. Single sessions of rTMS over the temporal or temporoparietal cortex have been successful in transiently reducing tinnitus perception. Repeated sessions of rTMS have resulted in tinnitus relief in a subgroup of patients, lasting from several days to several months. However, effect sizes of rTMS in the treatment of tinnitus are only moderate, and interindividual variability is high. Larger and longer lasting effects have been observed with direct electrical stimulation of the auditory cortex via implanted epidural electrodes. Transcranial direct current stimulation (tDCS) has also shown potential for the treatment of tinnitus. Both auditory and frontal tDCS have shown tinnitus reduction in a subgroup of patients. In spite of the promising results of the different brain stimulation approaches, further research is needed before these techniques can be recommended for routine clinical use.

Pulsatile tinnitus: contemporary assessment and management

PURPOSE OF REVIEW

Pulsatile tinnitus is an uncommon otologic symptom, which often presents a diagnostic and management dilemma to the otolaryngologist. The majority of patients with pulsatile tinnitus have a treatable cause. Failure to establish correct diagnosis may have disastrous consequences, because a potentially life-threatening, underlying disorder may be present. The purpose of this review is to familiarize the otolaryngologist with the most common causes, evaluation, and management of pulsatile tinnitus.

RECENT FINDINGS

The pathophysiology, classification, various causes, evaluation, and management of the most common causes of pulsatile tinnitus are presented in this review.

SUMMARY

Pulsatile tinnitus deserves a thorough evaluation and, in the majority of cases, there is a treatable underlying cause. The possibility of a life-threatening cause needs to be ruled out in every patient with pulsatile tinnitus. The otolaryngologist should be familiar with the evaluation and management of this symptom.

Targeting inhibitory neurotransmission in tinnitus

Tinnitus perception depends on the presence of its neural correlates within the auditory neuraxis and associated structures. Targeting specific circuits and receptors within the central nervous system in an effort to relieve the perception of tinnitus and its impact on one's emotional and mental state has become a focus of tinnitus research. One approach is to upregulate endogenous inhibitory neurotransmitter levels (e.g., glycine and GABA) and selectively target inhibitory receptors in key circuits to normalize tinnitus pathophysiology. Thus, the basic functional and molecular properties of two major ligand-gated inhibitory receptor systems, the GABA(A) receptor (GABA(A)R) and glycine receptor (GlyR) are described. Also reviewed is the rationale for targeting inhibition, which stems from reported tinnitus-related homeostatic plasticity of inhibitory neurotransmitter systems and associated enhanced neuronal excitability throughout most central auditory structures. However, the putative role of the medial geniculate body (MGB) in tinnitus has not been previously addressed, specifically in terms of its inhibitory afferents from inferior colliculus and thalamic reticular nucleus and its GABA(A)R functional heterogeneity. This heterogeneous population of GABA(A)Rs, which may be altered in tinnitus pathology, and its key anatomical position in the auditory CNS make the MGB a compelling structure for tinnitus research. Finally, some selective compounds, which enhance tonic inhibition, have successfully ameliorated tinnitus in animal studies, suggesting that the MGB and, to a lesser degree, the auditory cortex may be their primary locus of action. These pharmacological interventions are examined in terms of their mechanism of action and why these agents may be effective in tinnitus treatment. This article is part of a Special Issue entitled: Tinnitus Neuroscience.

Ringing ears: the neuroscience of tinnitus

Tinnitus is a phantom sound (ringing of the ears) that affects quality of life for millions around the world and is associated in most cases with hearing impairment. This symposium will consider evidence that deafferentation of tonotopically organized central auditory structures leads to increased neuron spontaneous firing rates and neural synchrony in the hearing loss region. This region covers the frequency spectrum of tinnitus sounds, which are optimally suppressed following exposure to band-limited noise covering the same frequencies. Cross-modal compensations in subcortical structures may contribute to tinnitus and its modulation by jaw-clenching and eye movements. Yet many older individuals with impaired hearing do not have tinnitus, possibly because age-related changes in inhibitory circuits are better preserved. A brain network involving limbic and other nonauditory regions is active in tinnitus and may be driven when spectrotemporal information conveyed by the damaged ear does not match that predicted by central auditory processing.

The Tinnitus Research Initiative (TRI) database: a new approach for delineation of tinnitus subtypes and generation of predictors for treatment outcome

Tinnitus, the phantom perception of sound, is a frequent disorder that causes significant morbidity and treatment is elusive. A large variety of different treatment options have been proposed and from most of them some patients benefit. However, a particular treatment that helps one patient may fail for others. This suggests that there are different forms of tinnitus which differ in their pathophysiology and their response to specific treatments. Therefore, it is a major challenge for tinnitus treatment to identify the most promising therapy for a specific patient.

However, most published clinical treatment studies have enrolled only relatively small patient samples, making it difficult to identify predictors of treatment response for specific approaches. Furthermore, inter-study comparability is limited because of varying methods of tinnitus assessment and different outcome parameters. Performing clinical trials according to standardized methodology and pooling the data in a database should facilitate both clinical subtypisation of different forms of tinnitus, and identification of promising treatments for different types of tinnitus. This would be an important step towards the goal of individualized treatment of tinnitus.

For these reasons, an international database of tinnitus patients, who undergo specific treatments, and are assessed during the course of this treatment with standardized instruments (e.g., psychoacoustic measures, questionnaires) has been established. The primary objectives of this database are (1) collecting a standardized set of data on patient characteristics, treatments, and outcomes from tinnitus patients consulting specialized tinnitus clinics all over the world (at present 13 centers in 8 countries), (2) delineating different subtypes of tinnitus based on data that has been systematically collected and (3) identifying predictors for individual treatment response based on the clinical profile. Starting in 2008, the database currently contains data from more than 400 patients. It is expected that more centers will join the project and that the patient numbers will rapidly grow, so that this international database will further facilitate future research and contribute to the development of evidence based on individualized treatment.

Tinnitus psychopharmacology: A comprehensive review of its pathomechanisms and management

BACKGROUND

Subjective tinnitus is a frequent, impairing condition, which may also cause neurotransmitter imbalance at the cochlea. Psychopharmacologic agents, although not being the first-line treatment for tinnitus, may modulate cochlear neurotransmission, thereby influencing the subjective tinnitus experience.

METHOD

A comprehensive review of MEDLINE literature (from January 1990-January 2010) was performed searching for: "tinnitus", major classes of psychopharmacological agents, and psychiatric disorders. The most relevant clinical evidence is reported briefly along with a concise description of the main neurotransmitters purported to be involved in tinnitus, in order to provide the reader with a rational evaluation of tinnitus therapy with psychopharmacological agents.

RESULTS

Although strong methodological issues limit the reliability of the current results, a broad number of psychopharmacological agents have already been considered for tinnitus, both as candidate triggers or potential therapies.

CONCLUSIONS

Selected psychopharmacological drugs may play a role in the clinical management of this disorder. While the rational use of these agents for the treatment of tinnitus should not be overlooked, research should be undertaken on their neuromodulating actions at the cochlea.

Is there a correlation between vascular loops in the cerebellopontine angle and unexplained unilateral hearing loss?

OBJECTIVE

This study was a retrospective analysis of patients who had received magnetic resonance imaging scans of the internal auditory canal (IAC) to evaluate unexplained asymmetric hearing loss. The study aimed to correlate structural features of vascular loops formed by the anterior inferior cerebellar artery (AICA) within the cerebellopontine angle and IAC with asymmetric hearing loss.

STUDY DESIGN

High-resolution thin-section T2 fast spin echo magnetic resonance imaging scans of 58 patients with asymmetric sensorineural hearing loss were obtained; the structure of the AICA was graded on both sides using 2 scoring systems. The grading senior head and neck radiologist was blinded to the clinical history. The first scoring system used was the Chavda classification, which is based on the anatomic location of the AICA loop. This system identified 92 loops within the cerebellopontine angle; 22 loops extending less than halfway into the IAC and 2 loops extending more than halfway into the IAC. A second classification system was used simultaneously to describe the extent of contact between the AICA loop and the vestibulocochlear nerve. The second system identified 24 loops that were not in contact with the nerve, 60 in which the loop was running adjacent to the nerve but not displacing it; 12 loops were identified that were displacing the vestibulocochlear nerve, and 24 loops were identified running between the facial and the vestibulocochlear nerve. Four loops were classified as both displacing the vestibulocochlear nerve and running between the facial and vestibulocochlear nerves. Tinnitus was present in addition to hearing loss. In 48 of the 58 patients, the statistical analysis was repeated for these patients.

RESULTS

No statistically significant association was found between loops classified by the Chavda system and hearing loss. No statistically significant association was present between loops that made no contact with the nerve, ran adjacent to the nerve, or displaced the nerve. A statistically significant association was found between loops that ran between the facial and vestibulocochlear nerve and hearing loss, with a p value of 0.0162. The subset who had tinnitus in addition to hearing loss had similar results, with the only significant association being found between loops running between the facial nerve and the vestibulocochlear nerve, and a p value of 0.0433 was obtained.

CONCLUSION

A correlation between vascular loops and hearing loss did not exist in the majority of the patients in this study. The subset of patients that had a vessel between the facial and vestibular cochlear nerves deserve further investigation.

Emerging pharmacotherapy of tinnitus

Tinnitus, the perception of sound in the absence of an auditory stimulus, is perceived by about 1 in 10 adults, and for at least 1 in 100, tinnitus severely affects their quality of life. Because tinnitus is frequently associated with irritability, agitation, stress, insomnia, anxiety and depression, the social and economic burdens of tinnitus can be enormous. No curative treatments are available. However, tinnitus symptoms can be alleviated to some extent. The most widespread management therapies consist of auditory stimulation and cognitive behavioral treatment, aiming at improving habituation and coping strategies. Available clinical trials vary in methodological rigor and have been performed for a considerable number of different drugs. None of the investigated drugs have demonstrated providing replicable long-term reduction of tinnitus impact in the majority of patients in excess of placebo effects. Accordingly, there are no FDA or European Medicines Agency approved drugs for the treatment of tinnitus. However, in spite of the lack of evidence, a large variety of different compounds are prescribed off-label. Therefore, more effective pharmacotherapies for this huge and still growing market are desperately needed and even a drug that produces only a small but significant effect would have an enormous therapeutic impact. This review describes current and emerging pharmacotherapies with current difficulties and limitations. In addition, it provides an estimate of the tinnitus market. Finally, it describes recent advances in the tinnitus field which may help overcome obstacles faced in the pharmacological treatment of tinnitus. These include incomplete knowledge of tinnitus pathophysiology, lack of well-established animal models, heterogeneity of different forms of tinnitus, difficulties in tinnitus assessment and outcome measurement and variability in clinical trial methodology.

Gabapentin responsive audiovestibular paroxysmia

Trigeminal neuralgia and hemifacial spasm are well-documented vascular compression syndromes involving the 5th and 7th cranial nerves. Drugs that stabilize the irritated nerves and vascular decompression surgery are accepted treatments. By contrast, the diagnosis and treatment of a comparable syndrome involving the 8th cranial nerve is controversial. We describe two patients with brief, spontaneous, recurrent attacks of tinnitus and vertigo that responded to low dose gabapentin and we argue that this clinical presentation represents the prototypical 8th nerve vascular compression syndrome.

PHARMACOLOGICAL TREATMENTS FOR TINNITUS: NEW AND OLD

Subjective tinnitus, the phantom ringing or buzzing sensation that occurs in the absence of sound, affects 12-14% of adults; in some cases the tinnitus is so severe or disabling that patients seek medical treatment. However, although the economic and emotional impact of tinnitus is large, there are currently no FDA-approved drugs to treat this condition. Clinical trials are now underway to evaluate the efficacy of N-methyl-d-aspartate (NMDA) and dopamine D(2) antagonists, selective serotonin reuptake inhibitors (SSRIs), γ-aminobutyric acid (GABA) agonists and zinc dietary supplements. Previous off-label clinical studies, while not definitive, suggest that patients with severe depression may experience improvement in their tinnitus after treatment with antidepressants such as nortriptyline or sertraline. A small subpopulation of patients with what has been described as "typewriter tinnitus" have been shown to gain significant relief from the anticonvulsant carbamazepine. Preliminary studies with misoprostol, a synthetic prostaglandin E1 analogue, and sulpiride, a dopamine D(2) antagonist, have shown promise. Animal behavioral studies suggest that GABA transaminase inhibitors and potassium channel modulators can suppress tinnitus. Additionally, improvements in tinnitus have also been noted in patients taking melatonin for significant sleep disturbances. Like other complex neurological disorders, one drug is unlikely to resolve tinnitus in all patients; therapies targeting specific subgroups are likely to yield the greatest success.

Microvascular decompression operations

Moving a blood vessel off the intracranial portion of the auditory nerve can successfully cure some individuals with specific forms of subjective tinnitus. This operation, known as microvascular decompression (MVD) is in general use to treat other hyperactive disorders such as hemifacial spasm (HFS) and trigeminal neuralgia (TGN) where the operation has a success rate of approximately 85%. MVD for tinnitus has lower success rate. MVD operations have also been used to treat some forms of vestibular disorders, disabling positional vertigo (DPV). In a study of treatment of a selected group of 72 patients with severe tinnitus and signs of change in the conduction properties of the auditory nerve 13 (18.2%) had total relief from tinnitus after MVD, 16 (22.2%) had marked improvement, 8 slight improvement and 33 (45.8%) no improvement. Two patients became worse (2.8%). There were 40 men and 32 women in the study group and there was considerable difference in the success rate for men and women. Fifty-five percent of the women and 29% of men showed relief or improvement. The success of the operation depended on the length of time the participants in the study had had their tinnitus and it was best for those who had had tinnitus for less than 3 years. The success rate for bilateral tinnitus was much lower than for unilateral tinnitus.

Imaging the cranial nerves: part II: primary and secondary neoplastic conditions and neurovascular conflicts

There have been unprecedented improvements in cross-sectional imaging in the last decades. The emergence of volumetric CT, higher field MR scanners and higher resolution MR sequences is largely responsible for the increasing diagnostic yield of imaging in patients presenting with cranial nerve deficits. The introduction of parallel MR imaging in combination with small surface coils allows the depiction of submillimetric nerves and nerve branches, and volumetric CT and MR imaging is able to provide high quality multiplanar and curved reconstructions that can follow the often complex course of cranial nerves. Seeking the cause of a cranial nerve deficit is a common indication for imaging, and it is not uncommon that radiologists are the first specialists to see a patient with a cranial neuropathy. To increase the diagnostic yield of imaging, high-resolution studies with smaller fields of view are required. To keep imaging studies within a reasonable time frame, it is mandatory to tailor the study according to neuro-topographic testing. This review article focuses on the contribution of current imaging techniques in the depiction of primary and secondary neoplastic conditions affecting the cranial nerves as well as on neurovascular conflicts, an increasingly recognized cause of cranial neuralgias.