Tinnitus in Normal-Hearing Participants after Exposure to Intense Low-Frequency Sound and in Ménière's Disease Patients

Rare Deletions or Large Duplications Contribute to Genetic Variation in Patients with Severe Tinnitus and Meniere Disease

Meniere disease (MD) is a debilitating disorder of the inner ear defined by sensorineural hearing loss (SNHL) associated with episodes of vertigo and tinnitus. Severe tinnitus, which occurs in around 1% of patients, is a multiallelic disorder associated with a burden of rare missense single nucleotide variants in synaptic genes. Rare structural variants (SVs) may also contribute to MD and severe tinnitus. In this study, we analyzed exome sequencing data from 310 MD Spanish patients and selected 75 patients with severe tinnitus based on a Tinnitus Handicap Inventory (THI) score > 68. Three rare deletions were identified in two unrelated individuals overlapping the ERBB3 gene in the positions: NC_000012.12:g.56100028_56100172del, NC_000012.12:g.56100243_56101058del, and NC_000012.12:g.56101359_56101526del. Moreover, an ultra-rare large duplication was found covering the AP4M1, COPS6, MCM7, TAF6, MIR106B, MIR25, and MIR93 genes in another two patients in the NC_000007.14:g.100089053_100112257dup region. All the coding genes exhibited expression in brain and inner ear tissues. These results confirm the contribution of large SVs to severe tinnitus in MD and pinpoint new candidate genes to get a better molecular understanding of the disease.

Burden of rare variants in synaptic genes in patients with severe tinnitus: An exome based extreme phenotype study

BACKGROUND

tinnitus is a heterogeneous condition associated with audiological and/or mental disorders. Chronic, severe tinnitus is reported in 1% of the population and it shows a relevant heritability, according to twins, adoptees and familial aggregation studies. The genetic contribution to severe tinnitus is unknown since large genomic studies include individuals with self-reported tinnitus and large heterogeneity in the phenotype. The aim of this study was to identify genes for severe tinnitus in patients with extreme phenotype.

METHODS

for this extreme phenotype study, we used three different cohorts with European ancestry (Spanish with Meniere disease (MD), Swedes tinnitus and European generalized epilepsy). In addition, four independent control datasets were also used for comparisons. Whole-exome sequencing was performed for the MD and epilepsy cohorts and whole-genome sequencing was carried out in Swedes with tinnitus.

FINDINGS

we found an enrichment of rare missense variants in 24 synaptic genes in a Spanish cohort, the most significant being PRUNE2, AKAP9, SORBS1, ITGAX, ANK2, KIF20B and TSC2 (p < 2E-04), when they were compared with reference datasets. This burden was replicated for ANK2 gene in a Swedish cohort with 97 tinnitus individuals, and in a subset of 34 Swedish patients with severe tinnitus for ANK2, AKAP9 and TSC2 genes (p < 2E-02). However, these associations were not significant in a third cohort of 701 generalized epilepsy individuals without tinnitus. Gene ontology (GO) and gene-set enrichment analyses revealed several pathways and biological processes involved in severe tinnitus, including membrane trafficking and cytoskeletal protein binding in neurons.

INTERPRETATION

a burden of rare variants in ANK2, AKAP9 and TSC2 is associated with severe tinnitus. ANK2, encodes a cytoskeleton scaffolding protein that coordinates the assembly of several proteins, drives axonal branching and influences connectivity in neurons.

Genetic Inheritance and Its Contribution to Tinnitus

Tinnitus is the abnormal perception of sound that affects more than 15% of adult population around the globe. Severe tinnitus is considered a complex disorder that arises as result of the interaction of genetic and environmental factors, and it is associated with several comorbidities such as hearing loss, anxiety, and insomnia. We begin this review with an introduction to human molecular genetics and the role of genetic variation on the inheritance. There are some genetic reports on tinnitus heritability including concordance studies in twins and adoptees or aggregation in families providing some evidence for familial aggregation in patients with severe tinnitus and high concordance in monozygotic twins with bilateral tinnitus. So, sex differences in familial aggregation and heritability of bilateral tinnitus suggest a potential sexual dimorphism in tinnitus inheritance.Molecular genetic studies have been demonstrated to be a useful tool to understand the role of genetic variation in rare diseases and complex disorders. The reported associations in common variants in neurotrophic factors such as GDNF, BDNF, or potassium channels genes were underpowered, and the lack of replication questions these findings. Although candidate gene approaches have failed in replicating these genetic associations, the development of high throughput sequencing technology and the selection of extreme phenotypes are strategies that will allow the clinicians and researchers to combine genetic information with clinical data to implement a personalized diagnosis and therapy in patients with tinnitus.

Exploring tinnitus heterogeneity

INTRODUCTION

Tinnitus experiences differ widely. A greater understanding of the core processes underlying these variations is needed. Moreover, meaningful definitions for different subgroups are required to better manage this heterogeneous population. The objective of the present research was to contribute toward the understanding of tinnitus heterogeneity by identifying factors that can predict tinnitus severity and to ascertain if distinct subgroups of tinnitus presentation can be identified.

METHODS

This cross-sectional study consisted of 326 adults subdivided into subgroups of those with mild tinnitus (n=32; 10%), significant tinnitus (n=99; 30%) and severe tinnitus (n=195; 60%) according to their scores from the Tinnitus Functional Index. Multiple regression was used to identify factors associated with tinnitus severity. These factors included personal traits, tinnitus-related traits, treatment modalities and clinical comorbidities.

RESULTS

Insomnia, hearing distress, and anxiety were the best predictors of tinnitus severity (explaining 53% of the variability). These comorbidities were stronger predictors than any demographical factors (that explained 11% of the variability). Distinct subgroups based on tinnitus severity (mild, significant, and severe) and anxiety levels were evident. Those with severe tinnitus had significantly more severe comorbidities compared with the mild and significant groups.

CONCLUSIONS

This study highlights that people with tinnitus could initially be grouped according to tinnitus severity to direct further management. Those with higher tinnitus severity should receive more immediate and intensive care. Due to the strong associations between tinnitus severity and tinnitus-related comorbidities (e.g., insomnia, hearing disability, and anxiety), tinnitus assessment and interventions should focus on these comorbidities.

Approach to Ménière disease management

OBJECTIVE

To provide family physicians with an updated approach to the diagnosis and management of Ménière disease (MD), detailing the natural course of MD and describing how to initiate medical therapy while awaiting consultation with otolaryngology-head and neck surgery.

SOURCES OF INFORMATION

The approach is based on the authors' clinical practices and review articles from 1989 to 2018. Most of the cited studies provided level II or III evidence.

MAIN MESSAGE

Ménière disease is an uncommon disorder of the inner ear causing vertigo attacks with associated unilateral hearing loss, tinnitus, and aural fullness. It has a degenerative course that often results in permanent sensorineural hearing loss. On average, MD stabilizes with no further vestibular attacks by about 8 years after the onset of symptoms; however, this is highly variable. Vertigo symptoms can be controlled through a combination of dietary salt restriction, stress reduction, and medical therapy (betahistine, diuretics, or both). These can be initiated by family physicians before consultation with otolaryngology-head and neck surgery. Symptoms refractory to such strategies can be treated using nonablative, and occasionally ablative, therapies.

CONCLUSION

A thorough history is key to the approach to and management of MD and permits differentiating MD from other vestibular and nonvestibular conditions.

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Objectif

Fournir aux médecins de famille une approche actualisée pour le diagnostic et la prise en charge de la maladie de Ménière, décrivant en détail l’évolution naturelle de la maladie de Ménière et la façon d’instaurer un traitement médical en attendant une consultation en otorhinolaryngologie–chirurgie cervico-faciale.

Sources de l’information

L’approche se base sur les pratiques cliniques des auteurs et sur des articles de synthèse publiés entre 1989 et 2018. La plupart des études citées ont fourni des données probantes de niveau II ou III.

Message principal

La maladie de Ménière est une affection peu fréquente de l’oreille interne, qui cause des crises de vertige et qui est associée à une perte auditive unilatérale, un acouphène et une sensation de plénitude auditive. La maladie est dégénérative et entraîne souvent une perte auditive neurosensorielle permanente. En moyenne, la maladie de Ménière se stabilise sans autre crise vestibulaire environ 8 ans après l’apparition des symptômes; cela est cependant très variable. Les symptômes de vertige peuvent être maîtrisés en combinant une alimentation hyposodée, une réduction du stress et un traitement médical (bétahistine, diurétiques ou les 2). Ces interventions peuvent être instaurées par le médecin de famille avant la consultation en otorhinolaryngologie–chirurgie cervico-faciale. Les symptômes réfractaires à ces interventions sont traités par l’entremise de traitements non ablatifs et, occasionnellement, ablatifs.

Conclusion

Une anamnèse détaillée est la clé de l’approche à adopter pour la prise en charge de la maladie de Ménière et permet de différencier la maladie de Ménière des autres affections vestibulaires et non vestibulaires.