Hereditary otovestibular dysfunction and Ménière's disease in a large Belgian family is caused by a missense mutation in the COCH gene

Interaural and sex differences in the natural evolution of hearing levels in pre-symptomatic and symptomatic carriers of the p.Pro51Ser variant in the COCH gene

Hearing impairment constitutes a significant health problem in developed countries. If hearing loss is slowly progressive, the first signs may not be noticed in time, or remain untreated until the moment the auditory dysfunction becomes more apparent. The present study will focus on DFNA9, an autosomal dominant disorder caused by pathogenic variants in the COCH gene. Although several cross-sectional studies on this topic have been conducted, a crucial need for longitudinal research has been reported by many authors. Longitudinal trajectories of individual hearing thresholds were established as function of age and superimposed lowess curves were generated for 101 female and male carriers of the p.Pro51Ser variant. The average number of times patients have been tested was 2.49 years with a minimum of 1 year and a maximum of 4 years. In addition, interaural and sex differences were studied, as they could modify the natural evolution of the hearing function. The current study demonstrates that, both in female carriers and male carriers, the first signs of hearing decline, i.e. hearing thresholds of 20 dB HL, become apparent as early as the 3rd decade in the highest frequencies. In addition, a rapid progression of SNHL occurs between 40 and 50 years of age. Differences between male and female carriers in the progression of hearing loss are most obvious between the age of 50 and 65 years. Furthermore, interaural discrepancies also manifest from the age of 50 years onwards. High-quality prospective data on the long-term natural evolution of hearing levels offer the opportunity to identify different disease stages in each cochlea and different types of evolution. This will provide more insights in the window of opportunity for future therapeutic intervention trials.

Radiologic Features in Cochlear Implant Candidates: A Prospective Study Comparing Candidates Carrying the p.Pro51Ser Mutation in Coagulation Factor C Homology With Noncarriers

BACKGROUND

DFNA9 is a form of autosomal progressive sensorineural hearing loss, caused by more than 30 variants in the COCH gene. p.Pro51Ser (p.P51S) variant is characterized by late-onset functional deterioration toward bilateral severe hearing loss and vestibulopathy. Focal sclerosis on computed tomography (CT) and T2-weighted magnetic resonance imaging (MRI) signal loss of semicircular canals are presumably radiologic biomarkers of advanced otovestibular deterioration.

OBJECTIVES

The aim of this study was to investigate whether these biomarkers are more frequent in cochlear implant candidates carrying the p.P51S mutation versus noncarriers. Second, the correlation between the hearing and vestibular function and carrier status was studied. Finally, the relationship between the presence of these radiologic features and the degree of hearing and vestibular deterioration was investigated.

METHODS

A prospective cohort study was performed on 38 candidates for cochlear implantation in a tertiary referral center. Patients underwent pure tone audiometry, videonystagmography, video head impulse tests and vestibular-evoked myogenic potentials. In addition, three dizziness questionnaires were used. All subjects were administered CT, MRI, and molecular genetic analysis.

RESULTS

Sixteen of 38 patients were carriers of the p.P51S COCH mutation. Radiologic lesions were almost exclusively observed in carriers. MRI was more sensitive in showing lesions than CT. Furthermore, p.P51S carriers showed significantly lower function on most vestibular tests, including questionnaires, than noncarriers. Patients with imaging abnormalities showed more pronounced vestibulopathy.

CONCLUSION

The present study supplements previous data that endorse the hypothesis that focal sclerosis of semicircular canals are biomarkers of advanced vestibular deterioration, especially in DFNA9.

Genotype-Phenotype Correlations of Pathogenic COCH Variants in DFNA9: A HuGE Systematic Review and Audiometric Meta-Analysis

Pathogenic missense variants in COCH are associated with DFNA9, an autosomal dominantly inherited type of progressive sensorineural hearing loss with or without vestibular dysfunction. This study is a comprehensive overview of genotype-phenotype correlations using the PRISMA and HuGENet guidelines. Study characteristics, risk of bias, genotyping and data on the self-reported age of onset, symptoms of vestibular dysfunction, normative test results for vestibular function, and results of audiovestibular examinations were extracted for each underlying pathogenic COCH variant. The literature search yielded 48 studies describing the audiovestibular phenotypes of 27 DFNA9-associated variants in COCH. Subsequently, meta-analysis of audiometric data was performed by constructing age-related typical audiograms and by performing non-linear regression analyses on the age of onset and progression of hearing loss. Significant differences were found between the calculated ages of onset and progression of the audiovestibular phenotypes of subjects with pathogenic variants affecting either the LCCL domain of cochlin or the vWFA2 and Ivd1 domains. We conclude that the audiovestibular phenotypes associated with DFNA9 are highly variable. Variants affecting the LCCL domain of cochlin generally lead to more progression of hearing loss when compared to variants affecting the other domains. This review serves as a reference for prospective natural history studies in anticipation of mutation-specific therapeutic interventions.

Genotype-phenotype Correlation Study in a Large Series of Patients Carrying the p.Pro51Ser (p.P51S) Variant in COCH (DFNA9): Part I-A Cross-sectional Study of Hearing Function in 111 Carriers

INTRODUCTION

DFNA9 is characterized by adult-onset progressive sensorineural hearing loss (SNHL) and vestibular impairment. More than 15 years ago, genotype-phenotype correlation studies estimated the initial age of hearing deterioration in the fourth to fifth decade (ranging from 32 to 43 years). However, these analyses were based on relatively limited numbers of mainly symptomatic carriers using markedly different methodologies. The starting point for the hearing deterioration is more correctly determined with larger numbers of carriers and with a more clearly defined starting point of the hearing deterioration.

AIM

The aim of this study was to determine milestone ages (start and maximal hearing deterioration, potential eligibility for hearing aids and cochlear implants based on pure-tone average [PTA]) in a large series of p.Pro51Ser COCH variant carriers. The degree of individual interaural asymmetry and the degree of variability (interquartile range) with which the hearing deterioration progresses across ages were also studied, and age-related typical audiograms (ARTA) were constructed.

MATERIAL AND METHODS

One hundred eleven Belgian and Dutch p.P51S variant carriers were identified and recruited for audiological investigation. Their hearing thresholds were compared with p50th, p95th, and p97.5th percentile values of presbyacusis (ISO 7029 standards). The onset and degree of hearing deterioration were defined and assessed for each frequency and with three PTAs (PTA0.5-4 [0.5, 1, 2, and 4 kHz]; PTA4-8 [4 and 8 kHz]; and PTA6-8 [6 and 8 kHz]). The milestones ages were derived from nonlinear regression model of hearing thresholds against age, for male and female carriers separately, because of different age-referenced limits. Interaural right-left asymmetry was assessed, and variability of hearing thresholds were calculated using interquartile range. ARTAs were built with both observed data and a prediction model.

RESULTS

Hearing dysfunction in p.P51S carriers begins at about 38 years of age (ranging from 28 to 43 years) on average in female and 46 years (ranging from 42 to 49 years) in male carriers (third decade: female, fifth decade: male carriers), depending on the hearing frequency and with differences in deterioration sequence between both genders. These differences, however, were mainly due to more stringent age-referenced limits for men. In contrast, predictions (ARTA) did not show any difference of phenotypic expression between genders. At about 48 to 50 years of age on average, the majority of DFNA9 patients may need conventional hearing aids (PTA ≥ 40 dB HL), whereas this is about 56 to 59 years for cochlear implants (PTA ≥ 70 dB HL). There is a high degree of individual interaural asymmetry and interindividual variability throughout all ages.

CONCLUSION

This study demonstrates that the onset of sensorineural hearing deterioration starts in the third decade and probably even earlier. Regardless of differences in estimates, DFNA9 expresses similarly in male and female carriers, but male carriers are much more difficult to identify in early stages of the disease. Comprehensive assessment of the natural course of DFNA9 is of particular interest to predict the age of onset or critical period of most significant function deterioration in individual carriers of the pathogenic variant. This will help to design studies in the search for disease-modifying therapies.

Genotype-Phenotype Correlation Study in a Large Series of Patients Carrying the p.Pro51Ser (p.P51S) Variant in COCH (DFNA9) Part II: A Prospective Cross-Sectional Study of the Vestibular Phenotype in 111 Carriers

INTRODUCTION

DFNA9 is characterized by adult-onset hearing loss and evolution toward bilateral vestibulopathy (BVP). The genotype-phenotype correlation studies were conducted 15 years ago. However, their conclusions were mainly based on symptomatic carriers and the vestibular data exclusively derived from the horizontal (lateral) semicircular canal (SCC). The last decade was marked by the emergence of new clinical diagnostic tools, such as the video head impulse test (vHIT) and vestibular-evoked myogenic evoked potentials (VEMPs), expanding our evaluation to all six SCCs and the otolith organs (saccule and utricule).

AIM

The aim of this study was to comprehensively evaluate vestibular function in the largest series presymptomatic as well as symptomatic p.P51S variant carriers, to determine which labyrinthine part shows the first signs of deterioration and which SCC function declines at first and to determine the age at which p.P51S variant carriers develop caloric areflexia on VNG and vHIT vestibulo-ocular reflex (VOR)-gain dysfunction as defined by the Barany Society criteria for BVP.

MATERIAL AND METHODS

One hundred eleven p.P51S variant carriers were included. The following vestibular function tests were applied in two different centers: ENG/VNG, vHIT, and VEMPs. The following parameters were analyzed: age (years), hearing loss (pure-tone average of 0.5-4 kHz [PTA0.5-4, dB HL]), sum of maximal peak slow-phase eye velocity obtained with bi-thermal (30°C and 44°C, water irrigation; 25°C and 44°C, air irrigation) caloric test (°/s), vHIT VOR-gain on LSCC, superior SCC and posterior SCC, C-VEMP both numerical (threshold, dB nHL) and categorical (present or absent), and O-VEMP as categorical (present or absent). The age of onset of vestibular dysfunction was determined both with categorical (onset in decades using Box & Whisker plots) and numeric approach (onset in years using regression analysis). The same method was applied for determining the age at which vestibular function declined beyond the limits of BVP, as defined by the Barany Society.

RESULTS

With the categorical approach, otolith function was declining first (3rd decade), followed by caloric response (5th decade) and vHIT VOR-gains (5th-6th decade). Estimated age of onset showed that the deterioration began with C-VEMP activity (31 years), followed by caloric responses (water irrigation) (35 years) and ended with vHIT VOR-gains (48-57 years). Hearing deterioration started earlier than vestibular deterioration in female carriers, which is different from earlier reports. BVP was predicted at about 53 years of age on average with VNG caloric gain (water irrigation) and between 47 and 57 years of age for the three SCCs. Loss of C-VEMP response was estimated at about 46 years of age.

CONCLUSION

Former hypothesis of vestibular decline preceding hearing deterioration by 9 years was confirmed by the numeric approach, but this was less obvious with the categorical approach. Wide confidence intervals of the regression models may explain deviation of the fits from true relationship. There is a typical vestibular deterioration hierarchy in p.P51S variant carriers. To further refine the present findings, a prospective longitudinal study of the auditory and vestibular phenotype may help to get even better insights in this matter.

The Price of Immune Responses and the Role of Vitamin D in the Inner Ear

OBJECTIVE

In this review the authors discuss evidence from the literature concerning vitamin D and temporal bone diseases (benign paroxysmal positional vertigo [BPPV], Menière's disease [MD], vestibular neuritis, idiopathic facial paralysis, idiopathic acute hearing loss). Common features shared by Menière's disease, glaucoma, and the possible influence by vitamin D are briefly discussed.

DATA SOURCES, STUDY SELECTION

Publications from 1970 until recent times have been reviewed according to a keyword search (see above) in PubMed.

CONCLUSIONS

MD, BPPV, vestibular neuritis, idiopathic facial paralysis, idiopathic acute hearing loss may all have several etiological factors, but a common feature of the current theories is that an initial viral infection and a subsequent autoimmune/autoinflammatory reaction might be involved. Additionally, in some of these entities varying degrees of demyelination have been documented. Given the immunomodulatory effect of vitamin D, we postulate that it may play a role in suppressing an eventual postviral autoimmune reaction. This beneficial effect may be enhanced by the antioxidative activity of vitamin D and its potential in stabilizing endothelial cells. The association of vitamin D deficiency with demyelination has already been established in other entities such as multiple sclerosis and experimental autoimmune encephalitis. Mice without vitamin D receptor show degenerative features in inner ear ganglia, hair cells, as well as otoconia. The authors suggest further studies concerning the role of vitamin D deficiency in diseases of the temporal bone. Additionally, the possible presence and degree of demyelination in these entities will have to be elucidated more systematically in the future.

Correlations Between Vestibular Function and Imaging of the Semicircular Canals in DFNA9 Patients

Background and Purpose: Radiologic abnormalities on computed tomography (CT), including narrowing or sclerosis of the semicircular canals (SCCs), and T2-weighted magnetic resonance imaging (MRI), including signal loss in the SCC, have been reported as potential biomarkers in patients with P51S mutations in the COCH gene (i.e., DFNA9). The aim of our study was to correlate caloric responses through electronystagmography (ENG) data with imaging results in DFNA9 patients.

Materials and Methods: A retrospective study was performed in 45 patients; therefore, 90 ears with P51S mutations in the COCH gene were tested. Caloric responses and CT and MRI data were analyzed from June 2003 until May 2014. More than half of patients (54%) were candidates for cochlear implantation.

Results: In our population, 91% of tested ears had sclerotic lesions and/or narrowing in one or more SCCs on CT scan. All tested ears had narrowing or signal loss in at least one SCC on T2-weighted MRI. The lateral SCC was affected in 87% on CT scan and 92% on MRI. However, in 83% of tested ears, all three SCCs were affected on MRI. Furthermore, in 77% of tested ears, caloric responses were reduced bilaterally, while 11.5% showed unilateral hypofunction and the other 11.5% had normal caloric responses. CT abnormalities correlated with hypofunction of caloric responses. This statistically significant difference was present if abnormalities were observed in at least one of the SCCs as well as in ipsilateral lateral SCC function loss. MRI abnormalities in at least one of the SCCs correlated with ENG hypofunction, but there was no direct correlation between lateral SCC abnormalities on MRI and caloric responses of the investigated lateral canal.

Conclusion: Our retrospective analysis confirms the presence of CT and MRI abnormalities in DFNA9 patients with the P51S mutation in the COCH gene. A correlation between these radiologic features and vestibular function (tested by means of caloric response) was found in this population.

The Polymorphic Analysis of the Human Potassium Channel KCNE Gene Family in Meniere's Disease-A Preliminary Study

OBJECTIVES

To investigate the correlation between KCNE gene family and Meniere's disease (MD) in the Chinese population.

MATERIALS AND METHODS

This study analyzed the single-nucleotide polymorphism (SNP) of KCNE1 and KCNE3 genes between the MD group and the control group and between the familial Meniere's disease (FMD) group and the sporadic Meniere's disease (SMD) group.

RESULTS

A total of 653 C/T SNPs of KCNE1 had a statistical difference between the FMD and SMD groups (p=0.0082<0.05); 492 A/C SNPs of KCNE3 were statistically different between the FMD group and the control group (genotype p=0.037<0.05 and allele p=0.006<0.05).

CONCLUSION

SNPs of KCNE1 and KCNE3 gene mutations were, respectively, different between the SMD and FMD groups. KCNE3 gene polymorphism was key to FMD disease, whereas KCNE1 was more important to the onset of SMD.

Genetic susceptibility to bilateral tinnitus in a Swedish twin cohort

PURPOSE

Genetic contributions to tinnitus have been difficult to determine due to the heterogeneity of the condition and its broad etiology. Here, we evaluated the genetic and nongenetic influences on self-reported tinnitus from the Swedish Twin Registry (STR).

METHODS

Cross-sectional data from the STR was obtained. Casewise concordance rates (the risk of one twin being affected given that his/her twin partner has tinnitus) were compared for monozygotic (MZ) and dizygotic (DZ) twin pairs (N = 10,464 concordant and discordant twin pairs) and heritability coefficients (the proportion of the total variance attributable to genetic factors) were calculated using biometrical model fitting procedures.

RESULTS

Stratification of tinnitus cases into subtypes according to laterality (unilateral versus bilateral) revealed that heritability of bilateral tinnitus was 0.56; however, it was 0.27 for unilateral tinnitus. Heritability was greater in men (0.68) than in women (0.41). However, when female pairs younger than 40 years of age were selected, heritability of 0.62 was achieved with negligible effects of shared environment.

CONCLUSION

Unlike unilateral tinnitus, bilateral tinnitus is influenced by genetic factors and might constitute a genetic subtype. Overall, our study provides the initial evidence for a tinnitus phenotype with a genetic influence.Genet Med advance online publication 23 March 2017.

POU4F3 mutation screening in Japanese hearing loss patients: Massively parallel DNA sequencing-based analysis identified novel variants associated with autosomal dominant hearing loss

A variant in a transcription factor gene, POU4F3, is responsible for autosomal dominant nonsyndromic hereditary hearing loss, DFNA15. To date, 14 variants, including a whole deletion of POU4F3, have been reported to cause HL in various ethnic groups. In the present study, genetic screening for POU4F3 variants was carried out for a large series of Japanese hearing loss (HL) patients to clarify the prevalence and clinical characteristics of DFNA15 in the Japanese population. Massively parallel DNA sequencing of 68 target candidate genes was utilized in 2,549 unrelated Japanese HL patients (probands) to identify genomic variations responsible for HL. The detailed clinical features in patients with POU4F3 variants were collected from medical charts and analyzed. Novel 12 POU4F3 likely pathogenic variants (six missense variants, three frameshift variants, and three nonsense variants) were successfully identified in 15 probands (2.5%) among 602 families exhibiting autosomal dominant HL, whereas no variants were detected in the other 1,947 probands with autosomal recessive or inheritance pattern unknown HL. To obtain the audiovestibular configuration of the patients harboring POU4F3 variants, we collected audiograms and vestibular symptoms of the probands and their affected family members. Audiovestibular phenotypes in a total of 24 individuals from the 15 families possessing variants were characterized by progressive HL, with a large variation in the onset age and severity with or without vestibular symptoms observed. Pure-tone audiograms indicated the most prevalent configuration as mid-frequency HL type followed by high-frequency HL type, with asymmetry observed in approximately 20% of affected individuals. Analysis of the relationship between age and pure-tone average suggested that individuals with truncating variants showed earlier onset and slower progression of HL than did those with non-truncating variants. The present study showed that variants in POU4F3 were a common cause of autosomal dominant HL.

Distinct vestibular phenotypes in DFNA9 families with COCH variants

Mutations of COCH can cause hearing loss and less frequently vestibular symptoms. However, vestibular phenotypes, especially in terms of the location of specific variants are not well documented yet. In this study, a retrospective and prospective cohort survey was performed in two tertiary referral hospitals to demonstrate vestibular phenotypes of DFNA9 subjects with a focus on the relationship with the location of COCH mutations. Two DFNA9 subjects were recruited from the previously collected cohort, each segregating p.G38D and p.C162Y of the COCH gene. Another two DFNA9 families were newly detected by targeted resequencing of known 129 deafness genes (TRS-129). These two families segregated the p.G38D variant of the COCH gene as the causative mutation, making p.G38D the most frequent COCH mutation in our Korean cohorts. Regarding the detailed clinical phenotype of the four DFNA9 families with documented vestibular phenotypes, we were able to classify them into two groups: one (p.C162Y variant) with a Meniere's disease (MD)-like phenotype and the other three (p.G38D variant) with significant bilateral vestibular loss without any definite MD symptoms. Distinct vestibular phenotypes depending on the location of COCH mutations were demonstrated, and this study correlates a genotype of p.G38D in COCH to the phenotype of bilateral total vestibular loss, therefore expanding the vestibular phenotypic spectrum of DFNA9 to range from bilateral vestibular loss without episodic vertigo to MD-like features with devastating episodic vertigo. In addition, the p.G38D variant of the COCH gene is suggested to be a frequent cause of progressive audiovestibular dysfunction in Koreans eventually requiring cochlear implantation.

Bilateral Vestibular Deficiency: Quality of Life and Economic Implications

IMPORTANCE

Bilateral vestibular deficiency (BVD) causes chronic imbalance and unsteady vision and greatly increases the risk of falls; however, its effects on quality of life and economic impact are not well defined.

OBJECTIVE

To quantify disease-specific and health-related quality of life, health care utilization, and economic impact on individuals with BVD in comparison with those with unilateral vestibular deficiency (UVD).

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional survey study of patients with BVD or UVD and healthy controls at an academic medical center. Vestibular dysfunction was diagnosed by means of caloric nystagmography.

INTERVENTIONS

Survey questionnaire.

MAIN OUTCOMES AND MEASURES

Health status was measured using the Dizziness Handicap Index (DHI) and Health Utility Index Mark 3 (HUI3). Economic burden was estimated using participant responses to questions on disease-specific health care utilization and lost productivity.

RESULTS

Fifteen patients with BVD, 22 with UVD, and 23 healthy controls participated. In comparison with patients with UVD and controls, patients with BVD had significantly worse DHI (P < .001) and HUI3 scores. Statistically significant between-group differences were observed for overall HUI3 score (P < .001) and for specific attributes including vision, hearing, ambulation, emotion, and pain (P < .001 for all). Generalized linear model analysis of clinical variables associated with HUI3 scores after adjustment for other variables (including sex, race, education, age, and frequency of dizziness-related outpatient clinic visits) showed that the presence of UVD (P < .001) or BVD (P < .001), increased dizziness-related emergency room visits (P = .002), and increased dizziness-related missed work days (P < .001) were independently associated with worse HUI3 scores. Patients with BVD and UVD incurred estimated mean (range) annual economic burdens of $13,019 ($0-$48,830) and $3531 ($0-$48,442) per patient, respectively.

CONCLUSIONS AND RELEVANCE

Bilateral vestibular deficiency significantly decreases quality of life and imposes substantial economic burdens on individuals and society. These results underscore the limits of adaptation and compensation in BVD. Furthermore, they quantify the potential benefits of prosthetic restoration of vestibular function both to these individuals and to society.

The genetics of Ménière's disease

Our understanding of the genetic basis of Ménière’s disease (MD) is still limited. Although the familial clustering and the geographical and racial differences in incidence strongly suggest a certain role for genetic factors in the development of MD, no convincing evidence for an association with any gene exists, at present. In this review, starting from rational bases for a genetic approach to MD, we explored the numerous reports published in literature and summarize the recent advances in understanding of the genetic fundaments of the disease.

Auditory and vestibular symptoms and chronic subjective dizziness in patients with Ménière's disease, vestibular migraine, and Ménière's disease with concomitant vestibular migraine

OBJECTIVE

To compare presentations of Ménière's disease (MD), vestibular migraine (VM), and Ménière's disease plus vestibular migraine (MDVM), with and without comorbid chronic subjective dizziness (CSD).

STUDY DESIGN

Retrospective review with diagnosis confirmed by consensus conference of investigators using published criteria for MD, VM, and CSD.

SETTING

Ambulatory, tertiary dizziness clinic.

PATIENTS

Approximately 147 consecutive patients with diagnoses of MD, VM, or MDVM, with/without comorbid CSD.

INTERVENTIONS

Diagnostic consultation.

MAIN OUTCOME MEASURES

Similarities and differences between diagnostic groups in demographics; symptoms; and results of neurotologic, audiometric, and vestibular laboratory assessments.

RESULTS

Seventy-six patients had MD, 55 MD alone. Ninety-two patients had VM, 71 VM alone. Twenty-one patients had MDVM, representing about one-quarter of those diagnosed with MD or VM. Clinical features thought to differentiate VM from MD were found in all groups. Twenty-seven patients with VM (38%) had ear complaints (subjective hearing loss, aural pressure, and tinnitus) during episodes of vestibular symptoms and headache, including 10 (37%) with unilateral symptoms. Conversely, 27 patients with MD alone (49%) had headaches with migraine features that did not meet full IHS diagnostic criteria, migrainous symptoms (photophobia, headache with vomiting), or first-degree relative with migraine. Including MDVM patients, 59% (45/76) of all patients with MD had migrainous features. Thirty-two patients had CSD; most (29; 91%) were in the VM group.

CONCLUSION

Comorbidity was common between MD and VM, and their symptoms overlapped. More specific diagnostic criteria are needed to differentiate these diseases and address their coexistence. CSD co-occurred with VM but was rarely seen with MD.

Does Ménière's Disease in the Elderly Present Some Peculiar Features?

Object. Aim of our study was to establish some peculiar features of Ménière's Disease (MD) in a group of elderly MD patients, in which the first vertigo spell happened when over 65 years old. Material and Methods. We analyzed a group of 73 younger than 65-years-old and a group of 30 elderly MD patients. All patients underwent a neurotological evaluation, an anamnestic evaluation including a lifetime history of migraine, and blood withdrawal for autoantibody screening. Results. Some differences were found between elderly and younger MD patients. Elderly MD patients presented a higher prevalence of Tumarkin attacks and a lower prevalence of lifetime history of migraine; moreover, they presented a faster develop of hearing loss and vertigo spells than a subgroup of 32 younger patients matched for the duration of illness. Conclusions. Some clinical features of MD in elderly have been pointed out. Particularly, the lower rate of migrainous history and positivity for autoantibodies often associated with MD, in our opinion, support the hypothesis of a vascular disorder acting as a predisposing factor for MD in elderly.

Contemporary perspectives on the pathophysiology of Meniere's disease: implications for treatment

PURPOSE OF REVIEW

Meniere's disease is characterized by episodic vertigo, fluctuating hearing loss, aural fullness and tinnitus. Endolymphatic hydrops, found on post-mortem examination, is the histologic hallmark. Recent research suggests that endolymphatic hydrops results from cytochemical perturbations of unknown etiology that lead to disturbance of the normal endolymphatic fluid homeostasis. This consequent hydropic state or the associated cytochemical perturbations appears to create a neurotoxic environment that ultimately leads to spiral ganglion cell death likely via the apoptotic mechanism. This review highlights some of the recent advances in the understanding of the pathophysiology of endolymphatic hydrops and progressive cochleovestibular deterioration, with emphasis placed on its potential therapeutic implications.

RECENT FINDINGS

Recent evidence supports that endolymphatic hydrops is possibly an epiphenomenon, and is preceded by perturbation of the normal ionic transport regulatory mechanisms. Furthermore, chronic cochleovestibular deterioration appears to be the result of an excitotoxic response to chronic hydrops. A recently described animal model, the Phex mouse, carrying a mutation in the Phex Hyp-Duk gene, provides a novel insight to genetically regulated postnatal endolymphatic hydrops and a useful tool to expand our understanding.

SUMMARY

Despite encouraging recent advances, there are considerable challenges that remain in the development of targeted therapeutic interventions that may offer new avenues of neuroprotection in known cases of Meniere's disease. These advances will hopefully provide pharmacotherapeutic interventions aimed at preventing progressive cochleovestibular dysfunction.

Familiar Meniere's disease restricted to 1.48 Mb on chromosome 12p12.3 by allelic and haplotype association

Meniere's disease (MD) is a disorder of the inner ear characterized by episodes of vertigo, tinnitus and fluctuating sensorineural hearing loss. Most MD cases are sporadic, but 5-15% of patients are familial following an autosomal dominant mode of inheritance with incomplete penetrance. We have previously identified a candidate gene region for MD on chromosome 12p12.3 using linkage analysis. We genotyped 15 Swedish families segregating familial MD (FMD) to further clarify the role of chromosome 12p in a larger cohort of families. Highly polymorphic marker loci were analyzed over the 16-Mb candidate region in affected and healthy family members as well as in control subjects. The results revealed allelic association between FMD and several individual polymorphic marker alleles and single-nucleotide polymorphisms. Moreover, a common three-marker haplotype spanning 1.48 Mb co-segregates with FMD in 60% of the families investigated, forming the core of a possible ancestral haplotype associated with FMD in Sweden.

Imprecision in patient reports of dizziness symptom quality: a cross-sectional study conducted in an acute care setting

OBJECTIVE

To quantify precision in patient reports of different attributes of dizziness.

PATIENTS AND METHODS

In a cross-sectional study, we interviewed consecutive adult patients with dizziness at 2 urban academic emergency departments (EDs) from July 2, 2005, to August 26, 2005. We excluded patients who were too sick for an interview or who posed a risk to the interviewer. We included those who were "dizzy, light-headed, or off-balance" for 7 days or less or previously "bothered" by the same conditions. We assessed descriptions of dizziness quality elicited by 4 questions in different formats (open-ended, multiresponse, single-choice, and directed). Clarity was assessed qualitatively (vague, circular) and quantitatively (overlap of types of dizziness). Consistency was measured by frequency of mismatched responses across question formats. Reliability was determined by test-retest.

RESULTS

Of 1,342 patients screened, 872 (65%) were dizzy, light-headed, or off-balance in the past 7 days (n=677) or previously bothered by dizziness (n=195). Among these 872 patients with dizziness, 44% considered dizziness "the main reason" or "part of the reason" for the ED visit. Open-ended descriptions were frequently vague or circular. A total of 62% selected more than 1 dizziness type on the multiresponse question. On the same question, 54% did not pick 1 or more types endorsed previously in open description. Of 218 patients not identifying vertigo, spinning, or motion on the first 3 questions, 70% confirmed "spinning or motion" on directed questioning. Asked to choose the single best descriptor, 52% picked a different response on retest approximately 6 minutes later. By comparison, reports of dizziness duration and triggers were clear, consistent, and reliable.

CONCLUSION

Descriptions of the quality of dizziness are unclear, inconsistent, and unreliable, casting doubt on the validity of the traditional approach to the patient with dizziness. Alternative approaches, emphasizing timing and triggers over type, should be investigated.

Vertical corneal striae in families with autosomal dominant hearing loss: DFNA9/COCH

PURPOSE

Investigation of a possible association between vertical corneal striae and mutations in the COCH gene, observed in four DFNA9 families with autosomal dominant hearing loss and vestibular dysfunction.

DESIGN

Prospective case series.

METHODS

Ophthalmologic examinations with photography of the cornea after instillation of fluorescein were performed in 98 family members with 61 mutation carriers of four DFNA9 families at the Radboud University Nijmegen Medical Centre. Families 1 and 2 harbor the Pro51Ser mutation, and families 3 and 4 harbor the Gly88Glu and the Gly87Trp mutation, respectively. Statistical analysis was performed to find an association between the vertical corneal striae and the COCH mutation for each family and to test whether the four families were different in this respect.

RESULTS

The vertical corneal striae were exclusively visible after instillation of fluorescein. They caused minor problems, as dry eye symptoms, and were not present in the general Dutch ophthalmologic population. The striae were present from an age of 47 years in 32 individuals, of whom 27 individuals had a COCH mutation. Statistical analysis on the striae and the COCH mutations showed a significant association in families 1, 2, and 3 (P = .0006), but not in family 4 (P = .63).

CONCLUSIONS

Data analysis demonstrated a significant association between vertical corneal striae and the Pro51Ser and Gly88Glu mutations in the COCH gene in DFNA9 families 1, 2, and 3 with cochleovestibular dysfunction. Our findings suggest that the vertical corneal striae and cochleovestibular dysfunction may be caused by the same COCH mutations.

Expression of full-length Cochlin p63s is inner ear specific

OBJECTIVE

The COCH gene mutated in DFNA9, murine an autosomal dominant hereditary hearing impairment, encodes Cochlin. Cochlin is also suggested to be the self-antigen of autoimmune sensorineural hearing loss. We previously reported that Cochlin constitutes 70% of the inner ear proteins and is classified into three types of isoform, p63s, p44s, and p40s. To study the specificity of expression of Cochlin isoforms in various organs, here we have investigated expression of the COCH gene at both the transcriptional and translational level.

METHODS

COCH gene expression was studied by RT-PCR and Southern blot analysis. Cochlin isoforms were studied by Western blot analysis using an isoform specific antibody.

RESULTS

At the transcriptional level, COCH mRNA was detected only in the inner ear by RT-PCR. Southern blot analysis of RT-PCR products detected a high level of COCH mRNA in the inner ear, lower level in spleen, and very low levels in the cerebrum, cerebellum/brain stem, eye, liver and kidney. At the translational level, Western blot analysis showed that a set of isoform, p63s, p44s, and p40s was detected at high levels only in the inner ear. In contrast, multiple proteins were detected at much lower levels in other organs tested. Notably, full-length Cochlin p63s was detected only in the inner ear.

CONCLUSION

Our findings demonstrate that the COCH gene is expressed preferentially in the inner ear and that expression of full-length Cochlin p63s is specific to the inner ear. These results will be central to understanding the function of Cochlin and its role in the pathophysiology of DFNA9.

Vestibular deterioration precedes hearing deterioration in the P51S COCH mutation (DFNA9): an analysis in 74 mutation carriers

OBJECTIVES

To analyze cochleovestibular impairment features in P51S COCH mutation carriers (n = 22) in a new, large Dutch family and to compare the results to those obtained in previously identified similar mutation carriers (n = 52). To evaluate age-related features between progressive hearing and vestibular impairment of all mutation carriers (n = 74).

STUDY DESIGN

Family study.

METHODS

Regression analysis was performed in relation to age to outline the development of hearing thresholds, speech recognition scores, and vestibulo-ocular reflex time constant as the key vestibular response parameter.

RESULTS

Pure tone thresholds, phoneme recognition scores, and vestibular responses of the mutation carriers in the new family were essentially similar to those previously established in all other mutation carriers. Hearing started to deteriorate in all mutation carriers from 43 years of age onwards, whereas deterioration of vestibular function started from age 34.

CONCLUSION

Vestibular impairment starts earlier, progresses more rapidly, and, eventually, is more complete than hearing impairment in P51S COCH mutation carriers.

Cochlin immunostaining of inner ear pathologic deposits and proteomic analysis in DFNA9 deafness and vestibular dysfunction

Seven missense mutations and one in-frame deletion mutation have been reported in the coagulation factor C homology (COCH) gene, causing the adult-onset, progressive sensorineural hearing loss and vestibular disorder at the DFNA9 locus. Prevalence of COCH mutations worldwide is unknown, as there is no systematic screening effort for late-onset hearing disorders; however, to date, COCH mutations have been found on four continents and the possibility of COCH playing an important role in presbycusis and disorders of imbalance has been considered. Cochlin (encoded by COCH) has also been shown as a major target antigen for autoimmune sensorineural hearing loss. In this report, we present histopathology, immunohistochemistry and proteomic analyses of inner ear tissues from post-mortem DFNA9 temporal bone samples of an individual from a large Dutch kindred segregating the P51S mutation and adult human unaffected controls, and wild-type (+/+) and Coch null (-/-) knock-out mice. DFNA9 is an inner ear disorder with a unique histopathology showing loss of cellularity and aggregation of abundant homogeneous acellular eosinophilic deposits in the cochlear and vestibular labyrinths, similar to protein aggregation in well-known neurodegenerative disorders. By immunohistochemistry on the DFNA9 temporal bone sections, we have shown cochlin staining of the characteristic cochlear and vestibular deposits, indicating aggregation of cochlin in the same structures in which it is normally expressed. Proteomic analysis identified cochlin as the most abundant protein in mouse and human cochleae. The high-level expression and stability of cochlin in the inner ear, even in the absence and severe atrophy of the fibrocytes that normally express COCH, are shown through these studies and further elucidate the pathobiologic events occurring in DFNA9 leading to hearing loss and vestibular dysfunction.

Good Speech Recognition and Quality-of-Life Scores after Cochlear Implantation in Patients with DFNA9

OBJECTIVE

To compare audiometric and quality-of-life results in DFNA 9 patients who received a cochlear implant with cochlear implant patients with adult-onset progressive sensorineural hearing loss.

STUDY DESIGN

Prospective comparative design; results were collected cross-sectionally.

SETTING

Tertiary referral center.

PATIENTS

Eleven DFNA 9 patients were included in the study as well as a comparative group of 39 post-lingually deafened cochlear implant subjects with adult-onset progressive sensorineural hearing loss.

INTERVENTIONS

All patients received a cochlear implant. Subjects were implanted with either the Nucleus 24 M/RCS or Med-el Combi 40+ cochlear implant systems implementing the SPEAK, ACE, or CIS+ coding strategies.

MEAN OUTCOME MEASURES

Speech recognition was determined by means of phonetically balanced monosyllabic word lists. The Hearing Handicap Inventory for Adults, the Glasgow Benefit Inventory, and the Scale for the Prediction of Hearing Disability in Sensorineural Hearing Loss were used to quantify the quality of life.

RESULTS

The results show that the speech perception and the quality of life of the DFNA 9 patients do not differ significantly from the control group (p=0.179; p=0.56).

CONCLUSION

In spite of the fact that DFNA 9 is a disease that is known to involve cochlear dendrites, cochlear implantation is a good option for treatment of deafness in DFNA 9.

Targeted disruption of mouse Coch provides functional evidence that DFNA9 hearing loss is not a COCH haploinsufficiency disorder

Dominant progressive hearing loss and vestibular dysfunction DFNA9 is caused by mutations of the human COCH gene. COCH encodes cochlin, a highly abundant secreted protein of unknown function in the inner ear. Cochlin has an N-terminal LCCL domain followed by two vWA domains, and all known DFNA9 mutations are either missense substitutions or an amino acid deletion in the LCCL domain. Here, we have characterized the auditory phenotype associated with a genomic deletion of mouse Coch downstream of the LCCL domain. Homozygous Coch (-/-) mice express no detectable cochlin in the inner ear. Auditory brainstem responses to click and pure-tone stimuli (8, 16, 32 kHz) were indistinguishable among wild type and homozygous Coch (-/-) mice. A Coch-LacZDeltaneo reporter allele detected Coch mRNA expression in nonsensory epithelial and stromal regions of the cochlea and vestibular labyrinth. These data provide functional evidence that DFNA9 is probably not caused by COCH haploinsufficiency, but via a dominant negative or gain-of-function effect, in nonsensory regions of the inner ear.

Identification of a novel Cochlin isoform in the perilymph: insights to Cochlin function and the pathogenesis of DFNA9

The COCH gene mutated in DFNA9, an autosomal dominant hereditary sensorineural hearing loss and vestibular disorder, encodes Cochlin. Previously, we reported three bovine Cochlin isoforms, p63s, p44s, and p40s, which exhibit significant molecular heterogeneity in vivo. Here we have characterized Cochlin isoforms by generating four isoform-specific anti-Cochlin antibodies. The same three Cochlin isoforms, p63s, p44s, and p40s, were detected in human and cow inner ear tissue; however, p44s and p40s were not detected in perilymph. We identified a novel short 16kDa isoform in human perilymph and a 18-23kDa isoform in cow perilymph, named Cochlin-tomoprotein (CTP), corresponding to the N-terminus of full-length Cochlin (p63s) and the LCCL domain. Notably, CTP contains all of the known mutation sites associated with DFNA9. The pathogenesis of DFNA9 is not fully clarified as yet, and this novel perilymph-associated CTP isoform might provide mechanistic clues to how mutations in the COCH gene damage the inner ear function.

Mutations in COCH that result in non-syndromic autosomal dominant deafness (DFNA9) affect matrix deposition of cochlin

The COCH gene mutated in autosomal dominant sensorineural deafness (DFNA9) encodes cochlin, a major constituent of the inner ear extracellular matrix. Sequence analysis of cochlin from DFNA9 patients identified five distinct single-amino-acid mutations within a conserved region (the LCCL domain) of cochlin. To define the molecular basis of DFNA9, we have generated myc-tagged wild-type and mutant cochlins and explored their behavior in transient transfection systems. Western blotting of cell lysates and culture media indicates that wild-type and mutant cochlins are synthesized and secreted in similar amounts. Immunofluorescent staining confirms that all are detected within the endoplasmic reticulum and the Golgi complex of transfected cells. Our findings suggest that COCH mutations are unlikely to cause abnormalities in secretion and suggest that extracellular events might cause DFNA9 pathology. In agreement, we show that wild-type cochlin accumulates in extracellular deposits that closely parallel the matrix component fibronectin, whereas mutant cochlins vary in the amount and pattern of extracellular material. Whereas some mutants exhibit an almost normal deposition pattern, some show complete lack of deposition. Our results suggest that DFNA9 results from gene products that fail to integrate correctly into the extracellular matrix. The partial or complete penetrance of integration defects suggests that DFNA9 pathology may be caused by multiple molecular mechanisms, including compromised ability of cochlin to self-assemble or to form appropriate complexes with other matrix components.

Mutations in the COCH gene are a frequent cause of autosomal dominant progressive cochleo-vestibular dysfunction, but not of Meniere's disease

The COCH gene is the only gene identified in man that causes autosomal dominantly inherited hearing loss associated with vestibular dysfunction. The condition is rare and only five mutations have been reported worldwide. All affected families showed a similar progressive hearing loss and vestibular dysfunction. Since Meniere's disease-like symptoms have also been described in some families, it was suggested that COCH mutations might be present in some patients diagnosed with Meniere's disease. In this study, using a Japanese population, we performed a COCH mutation analysis in 23 patients from independent families with autosomal dominant hearing impairment, four of whom reported vestibular symptoms, and also in 20 Meniere's patients. While a new point mutation, A119 T, was found in a patient with autosomal dominant hearing loss and vestibular symptoms, no mutations were found in the Meniere's patients. Like all other previously identified COCH mutations, the mutation identified here is a missense mutation located in the FCH domain of the protein. The current mutation is located in close spatial proximity to W117, in which a mutation (W117R) had previously been associated with autosomal dominant hearing loss. Model building suggests that, like the W117R mutation, the A119 T mutation does not affect the structural integrity of the FCH domain, but may interfere with the interaction with a yet unknown binding partner. We conclude that mutations in the COCH gene are responsible for a significant fraction of patients with autosomal dominantly inherited hearing loss accompanied by vestibular symptoms, but not for dominant hearing loss without vestibular dysfunction, or sporadic Meniere's disease.