Endolymphatic hydrops mimicking obstructive Eustachian tube dysfunction: preliminary experience and literature review.

PURPOSE: Aural fullness is a common symptom of middle ear diseases, most importantly Eustachian tube dysfunction (ETD). Yet, aural fullness may also be caused by inner ear disorders, such as hydropic ear diseases. Here, we report our experience with endolymphatic hydrops (EH) mimicking ETD. Furthermore, we review the literature related to (i) EH as a differential diagnosis of symptoms suggesting ETD and (ii) the pathophysiology and treatment of aural fullness due to inner ear disorders. METHODS: We retrospectively included adult patients with aural fullness as chief complaint and radiographically diagnosed EH. Hearing and Eustachian tube function were assessed using audiometry, tympanometry, and tubomanometry. Primarily suspected ETD was treated by balloon dilatation of the Eustachian tube (BDET). The endolymphatic space of the inner ear was imaged using gadolinium-enhanced MRI (Gd-MRI) including a 3D-real inversion-recovery sequence after intravenous gadolinium administration. RESULTS: We report three affected ears of two patients (two females, age 42 and age 51) with aural fullness as chief complaint. Audiometry of main speech frequencies was normal in all affected ears. In one ear, there was a type A tympanogram and in two ears, there was a type B tympanogram. In both patients, medical treatment for ETD and BDET were unsuccessful. Gd-MRI of the inner ears revealed cochlear EH in 3/3 ears affected by aural fullness, but not in the unaffected ear. CONCLUSION: EH may underlay cases with aural fullness and could in these cases explain unsuccessful treatment for ETD. As ETD is often treated by invasive procedures, distinguishing ETD from EH as the underlying cause of aural fullness is important. Our findings raise the question whether Gd-MRI to rule out EH is indicated in patients with unexplained aural fullness, in particular after unsuccessful interventional treatment for ETD.

Immunolocalization of calcium sensing and transport proteins in the murine endolymphatic sac indicates calciostatic functions within the inner ear.

An exceptionally low calcium (Ca2+) concentration in the inner ear endolymph ([Ca2+]endolymph) is crucial for proper auditory and vestibular function. The endolymphatic sac (ES) is believed to critically contribute to the maintenance of this low [Ca2+]endolymph. Here, we investigated the immunohistochemical localization of proteins that are presumably involved in the sensing and transport of extracellular Ca2+ in the murine ES epithelium. Light microscopic and fluorescence immunolabeling in paraffin-embedded murine ES tissue sections (male C57BL/6 mice, 6-8 weeks old) demonstrated the presence of the calcium-sensing receptor CaSR, transient receptor potential cation channel subtypes TRPV5 and TRPV6, sarco/endoplasmic reticulum Ca2+-ATPases SERCA1 and SERCA2, Na+/Ca2+ exchanger NCX2, and plasma membrane Ca2+ ATPases PMCA1 and PMCA4 in ES epithelial cells. These proteins exhibited (i) membranous (apical or basolateral) or cytoplasmic localization patterns, (ii) a proximal-to-distal labeling gradient within the ES, and (iii) different distribution patterns among ES epithelial cell types (mitochondria-rich cells (MRCs) and ribosome-rich cells (RRCs)). Notably, in the inner ear membranous labyrinth, CaSR was exclusively localized in MRCs, suggesting a unique role of the ES epithelium in CaSR-mediated sensing and control of [Ca2+]endolymph. Structural loss of the distal ES, which is consistently observed in Meniere's disease, may therefore critically disturb [Ca2+]endolymph and contribute to the pathogenesis of Meniere's disease.

Inner ear pathologies impair sodium-regulated ion transport in Meniere's disease.

Meniere's disease (MD), a syndromal inner ear disease, is commonly associated with a pathological accumulation of endolymphatic fluid in the inner ear, termed "idiopathic" endolymphatic hydrops (iEH). Although numerous precipitating/exacerbating factors have been proposed for MD, its etiology remains elusive. Here, using immunohistochemistry and in situ protein-protein interaction detection assays, we demonstrate mineralocorticoid-controlled sodium transport mechanisms in the epithelium of the extraosseous portion of the endolymphatic sac (eES) in the murine and human inner ears. Histological analysis of the eES in an extensive series of human temporal bones consistently revealed pathological changes in the eES in cases with iEH and a clinical history of MD, but no such changes were found in cases with "secondary" EH due to other otological diseases or in healthy controls. Notably, two etiologically different pathologies-degeneration and developmental hypoplasia-that selectively affect the eES in MD were distinguished. Clinical records from MD cases with degenerative and hypoplastic eES pathology revealed distinct intergroup differences in clinical disease presentation. Overall, we have identified for the first time two inner ear pathologies that are consistently present in MD and can be directly linked to the pathogenesis of EH, and which potentially affect the phenotypical presentation of MD.

Retrolabyrinthine Bone Thickness as a Radiologic Marker for the Hypoplastic Endotype in Menière Disease.

BACKGROUND AND PURPOSE: Menière disease (MD) manifests in 2 major endotypes: one with a hypoplastic, underdeveloped endolymphatic sac (MD-hp) and the other with a normally developed sac that degenerates over time (MD-dg). Determining the specific endotype in patients is important for predicting disease progression, tailoring patient counseling, and optimizing treatment strategies. Endotype diagnosis involves measuring an angular trajectory of the vestibular aqueduct (ATVA), with an ATVA ≥140° indicative of MD-hp and an ATVA ≤120° of MD-dg. However, assessing the ATVA can be challenging. This study aimed to explore the link between ATVA and the thickness of the retrolabyrinthine bone as an alternative diagnostic measure that could provide differentiation between MD endotypes using CT and MR imaging. MATERIALS AND METHODS: Retrospective review of CT temporal bone imaging from 32 adult patients with definite MD (60 ears) and 33 age-matched controls without MD or other inner ear symptoms (61 ears) was performed. The ATVA and retrolabyrinthine bone thickness were measured using uniform methodology on standardized axial CT images. Comparative analyses were performed to determine the correlation between ATVA and retrolabyrinthine bone thickness. Additionally, from a separate cohort of 11 patients (22 ears), CT and MR examinations of the temporal bone were retrospectively reviewed for retrolabyrinthine bone thickness measurements, to verify the correlation across the 2 modalities. RESULTS: The average retrolabyrinthine bone thickness was statistically significantly different between MD endotypes, being a mean of 0.8 (SD, 0.3) mm in patients with MD-hp (ATVA ≥140°) and 2.0 (SD, 0.9) mm in patients with MD-dg (ATVA ≤120°), with a consistent pattern of thin retrolabyrinthine bone in MD-hp and variable thickness in MD-dg. Receiver operating characteristic curve analysis within the MD cohort revealed that a retrolabyrinthine bone thickness ≥1.2 mm effectively rules out MD-hp. Excellent interrater reliability was noted for the retrolabyrinthine measurement, and there was near-perfect correlation between CT and MR measurements. CONCLUSIONS: Retrolabyrinthine bone thickness proved to be a useful and straightforward alternative marker for distinguishing MD endotypes, being particularly useful for excluding MD-hp. Including information on retrolabyrinthine bone thickness should be considered a routine part of reporting in the context of MD imaging.

Poly(Ethylene Glycols) to Facilitate Celloidin Removal for Immunohistochemical Studies on Archival Human Brain and Temporal Bone Sections.

Pathology repositories worldwide store millions of celloidin-processed human brain and temporal bone (TB) sections vital for studying central nervous system diseases and sensory organs. However, accessing these sections for modern molecular-pathological research, like immunohistochemistry, is hindered by the challenge of removing celloidin without damaging tissue. In this study, we explored the use of polyethylene glycols (PEGs), a class of non-hazardous, ethylene glycol oligomers, combined with an improved section mounting technique, to gently and effectively dissolve celloidin from sections archived for up to 40 years. Optimizing our protocol involved exploring celloidin dissolution kinetics in PEGs of varying molecular weights and terminations, as well as different temperatures. Low molecular weight PEGs, particularly PEG 200, were the most efficient celloidin solvent. Nuclear magnetic resonance (NMR) spectroscopy of celloidin-PEG 200 dissolution products revealed no chemical alterations, suggesting pure solvation without chemical modification. Because the solvation of celloidin in PEG was inhibited by proteins, we further developed a protein-free mounting protocol allowing complete celloidin removal in 30 to 60 minutes by immersing in PEG 200. In summary, our approach overcomes major methodological hurdles, rendering decades-old archival celloidin sections viable for immunohistochemical and other molecular biological techniques, while enhancing safety and workflow efficiency.

Radiological feature heterogeneity supports etiological diversity among patient groups in Meniere's disease.

We aimed to determine the prevalence of radiological temporal bone features that in previous studies showed only a weak or an inconsistent association with the clinical diagnosis of Meniere's disease (MD), in two groups of MD patients (n = 71) with previously established distinct endolymphatic sac pathologies; i.e. the group MD-dg (ES degeneration) and the group MD-hp (ES hypoplasia). Delayed gadolinium-enhanced MRI and high-resolution CT data were used to determine and compare between and within (affected vs. non-affected side) groups geometric temporal bone features (lengths, widths, contours), air cell tract volume, height of the jugular bulb, sigmoid sinus width, and MRI signal intensity alterations of the ES. Temporal bone features with significant intergroup differences were the retrolabyrinthine bone thickness (1.04 ± 0.69 mm, MD-hp; 3.1 ± 1.9 mm, MD-dg; p < 0.0001); posterior contour tortuosity (mean arch-to-chord ratio 1.019 ± 0.013, MD-hp; 1.096 ± 0.038, MD-dg; p < 0.0001); and the pneumatized volume (1.37 [0.86] cm3, MD-hp; 5.25 [3.45] cm3, MD-dg; p = 0.03). Features with differences between the affected and non-affected sides within the MD-dg group were the sigmoid sinus width (6.5 ± 1.7 mm, affected; 7.6 ± 2.1 mm, non-affected; p = 0.04) and the MRI signal intensity of the endolymphatic sac (median signal intensity, affected vs. unaffected side, 0.59 [IQR 0.31-0.89]). Radiological temporal bone features known to be only weakly or inconsistently associated with the clinical diagnosis MD, are highly prevalent in either of two MD patient groups. These results support the existence of diverse-developmental and degenerative-disease etiologies manifesting with distinct radiological temporal bone abnormalities.

A novel nonsense variant in the CENPP gene segregates in a Swiss family with autosomal dominant low-frequency sensorineural hearing loss.

Low-frequency sensorineural hearing loss (SNHL) is a rare hearing impairment affecting frequencies below 1000 Hz, previously associated with DIAPH1, WSF1, MYO7A, TNC, SLC26A4 or CCDC50 genes. By exome sequencing, we report a novel nonsense variant in CENPP gene, segregating low-frequency SNHL in five affected members in a Swiss family with autosomal dominant inheritance pattern. Audiological evaluation showed up-sloping audiometric configuration with mild-to-moderate losses below 1000 Hz, that progresses to high-frequencies over time. Protein modeling shows that the variant truncates five amino acids at the end, losing electrostatic interactions that alter protein stability. CENPP gene is expressed in the supporting cells of the organ of Corti and takes part as a subunit of the Constitutive Centromere Associated Network in the kinetochore, that fixes the centromere to the spindle microtubules. We report CENPP as a new candidate gene for low-frequency SNHL. Further functional characterization might enable us to elucidate its molecular role in SNHL.

Immunohistochemical Expression Pattern of Theragnostic Targets SSTR2 and PSMA in Endolymphatic Sac Tumors: A Single Institution Case Series.

BACKGROUND: Endolymphatic sac tumors are rare neoplasia characterized by slow growth. However, their clinical impact should not be underestimated, considering their potential for local aggressive behavior and strong association with von Hippel-Lindau syndrome. Therefore, early detection with emerging theragnostic examinations such as 68Ga-DOTATATE-PET/CT might improve patient management and reduce morbidity. METHODS: We report the clinicopathological features of seven endolymphatic sac tumors. In this cohort, we performed immunohistochemical analysis of somatostatin receptor 2A (SSTR2A) and prostate specific membrane antigen (PSMA) protein expression patterns; two targets providing rationale for novel imaging modalities such as PSMA- or SSTR-targeted PET. RESULTS: The tumor cells of all cases were negative for prostate specific membrane antigen and somatostatin receptor 2A, however immunolabeling was consistently detected in intratumoral endothelial cells of endolymphatic sac tumors for PSMA (7/7 cases, 100%), and for SSTR2A (5/7 cases, 71%). CONCLUSIONS: Our results show a high rate of PSMA and SSTR2A expression in the tumor vasculature of endolymphatic sac tumors. PSMA and SSTR2A can be targeted with appropriate radioligands for diagnostic and therapeutic purposes. This finding provides a rationale for prospective clinical studies to test this approach as a sensitive screening tool for patients with suspected endolymphatic sac tumors including an improved management of von Hippel-Lindau syndrome.

Radiological Configuration of the Vestibular Aqueduct Predicts Bilateral Progression in Meniere's Disease.

Objective: Meniere's disease (MD) progresses from unilateral to bilateral disease in up to 50% of patients, often chronically and severely impairing balance and hearing functions. According to previous studies, 91% of bilateral MD patients demonstrate bilateral hypoplasia of the endolymphatic sac (ES) upon histological and radiological examination of their inner ears. Here, we seek to validate a radiological marker for ES hypoplasia that predicts the risk for future progression to bilateral MD in individual patients. Methods: Patients with unilateral MD and radiological evidence for ES hypoplasia in either the clinically affected inner ear (cohort MDuni-hpuni) or both inner ears (cohort MDuni-hpbi) were included. Given our hypothesis that ES hypoplasia critically predisposes the inner ear to MD, we expected progression to bilateral MD only in the MDuni-hpbi cohort. To investigate eventual progression to bilateral MD, clinical, audiometric, and imaging data were retrospectively collected over follow-up periods of up to 31 years. Results: A total of 44 patients were included in the MD-hpuni (n = 15) and MDuni-hpbi (n = 29) cohorts. In line with our radiology-based predictions, none (0/15) of the MD-hpuni patients exhibited progression to bilateral MD, whereas 20/29 (69%) MD-hpbi patients have already progressed to bilateral MD. Using the Kaplan-Meier estimator, bilateral disease progression would be observed in 100% of MD-hpbi patients 31 years after the initial diagnosis with an estimated median time to bilateral progression of 12 years. The nine MD-hpbi patients who, so far, remained with unilateral disease demonstrated a median time since initial (unilateral) MD diagnosis of only 6 years and are thus still expected to progress to bilateral disease. Conclusion: Progression to bilateral MD adheres to predictions based on the radiological presence or absence of ES hypoplasia. This prognostic tool, if validated by prospective long-term studies, will provide clinically relevant information about a patient's future disease burden and will help to select more personalized treatment regimens.

Absence of Endolymphatic Sac Ion Transport Proteins in Large Vestibular Aqueduct Syndrome-A Human Temporal Bone Study.

HYPOTHESIS: Epithelial ion transport pathologies of the endolymphatic sac (ES) are associated with large vestibular aqueduct syndrome (LVAS). BACKGROUND: LVAS is defined by the pathognomonic features of a widened bony vestibular aqueduct (VA) and an enlarged ES. The underlying cause of its associated cochleovestibular symptoms remains elusive. Disturbances in epithelial ion transport in the enlarged ES, affecting inner ear fluid regulation, were proposed as a possible pathophysiology. However, although respective epithelial ion transport pathologies have been demonstrated in the enlarged ES from transgenic LVAS mouse models, these pathologies have not been investigated in human LVAS cases. METHODS: Histological and immunohistochemical analysis of the enlarged ES epithelium in postmortem temporal bones from two individuals with a clinical diagnosis of LVAS. RESULTS: The enlarged ES epithelium demonstrated an overall atypical epithelial differentiation and a lack of the immunolocalization of signature ion transport proteins. Notably, in both cases, a rudimentary branch of the ES with a typically differentiated ES epithelium was present. CONCLUSIONS: The described cellular and molecular pathologies of the enlarged ES in humans provide evidence of epithelial transport pathology as one potential cause of cochleovestibular symptoms in LVAS. The present findings also emphasize the clinical relevance of already established LVAS mouse models.

Mechanical Compression of Coverslipped Tissue Sections During Heat-induced Antigen Retrieval Prevents Section Detachment and Preserves Tissue Morphology.

Heat-induced antigen retrieval (HIAR) is routinely employed on aldehyde-fixed tissue sections to enhance the reactivity of antibodies that exhibit weak or no specific interactions with tissue antigens when applied in conventional immunohistochemical protocols. A major drawback of HIAR protocols is, however, the heat-induced detachment of sections from the microscope slide with resultant impaired tissue morphology or loss of the section. We developed a method in which tissue sections mounted on glass slides are temporally coverslipped, and a clamp is used to compress the sections on the microscope slide during HIAR treatment. This "pressurized coverslipping" during HIAR was tested on various formalin-fixed tissues (murine kidneys and temporal bones, human tonsils and temporal bones) that were embedded in paraffin or celloidin. The method reliably kept the sections adherent to the slide, preserved the tissue morphology, and effectively retrieved tissue antigens for improved results in immunohistochemical labeling, even for exceptionally delicate, large, and poorly adhering sections, that is, decalcified human temporal bone sections. In summary, we present a simple method for improved slide adherence and morphological preservation of tissue sections during HIAR treatment that can be combined with all HIAR protocols and that requires only basic lab equipment.

Clinical Imaging Findings of Vestibular Aqueduct Trauma in a Patient With Posttraumatic Meniere's Syndrome.

Posttraumatic Meniere's syndrome is a rare clinical entity. The pathomechanism by which temporal bone trauma leads to fluctuating audiovestibular symptoms, in some cases with a delay of onset many years after trauma, remains elusive. Here, a clinical case and the respective temporal bone imaging data were reviewed to investigate the underlying inner ear pathology. A 44-year-old patient presented with left-sided Meniere's syndrome 34 years after he suffered an ipsilateral temporal bone fracture caused by a car accident. Clinical imaging showed left cochleovestibular hydrops (gadolinium-enhanced MRI) and bony obliteration of the left VA (CT imaging), resulting in discontinuity of the ES. Our findings suggest that a temporal bone fracture with a "retrolabyrinthine" course, traversing the VA, caused intraaqueductal callus bone formation and progressive blockage of the VA. As a result, the extraosseous (distal) endolymphatic sac (eES) became separated from the cochleovestibular labyrinth, an event that presumably underlies endolymphatic hydrops formation and that precipitates the onset of clinical Meniere's symptoms in this case.

Endotype-Phenotype Patterns in Meniere's Disease Based on Gadolinium-Enhanced MRI of the Vestibular Aqueduct.

Two histopathological subtypes of Meniere's disease (MD) were recently described in a human post-mortem pathology study. The first subtype demonstrated a degenerating distal endolymphatic sac (ES) in the affected inner ear (subtype MD-dg); the second subtype (MD-hp) demonstrated an ES that was developmentally hypoplastic. The two subtypes were associated with different clinical disease features (phenotypes), suggesting that distinct endotype-phenotype patterns exist among MD patients. Therefore, clinical endotyping based on ES pathology may reveal clinically meaningful MD patient subgroups. Here, we retrospectively determined the ES pathologies of clinical MD patients (n = 72) who underwent intravenous delayed gadolinium-enhanced inner ear magnetic resonance imaging using previously established indirect radiographic markers for both ES pathologies. Phenotypic subgroup differences were evidenced; for example, the MD-dg group presented a higher average of vertigo attacks (ratio of vertigo patterns daily/weekly/other vs. monthly, MD-dg: 6.87: 1; MD-hp: 1.43: 1; p = 0.048) and more severely reduced vestibular function upon caloric testing (average caloric asymmetry ratio, MD-dg: 30.2% ± 30.4%; MD-hp: 13.5% ± 15.2%; p = 0.009), while the MD-hp group presented a predominantly male sex ratio (MD-hp: 0.06:1 [f/m]; MD-dg: 1.2:1 [f/m]; p = 0.0004), higher frequencies of bilateral clinical affection (MD-hp: 29.4%; MD-dg: 5.5%; p = 0.015), a positive family history for hearing loss/vertigo/MD (MD-hp: 41.2%; MD-dg: 15.7%; p = 0.028), and radiographic signs of concomitant temporal bone abnormalities, i.e., semicircular canal dehiscence (MD-hp: 29.4%; MD-dg: 3.6%; p = 0.007). In conclusion, this new endotyping approach may potentially improve the diagnosis, prognosis and clinical decision-making for individual MD patients.

Vestibular Aqueduct Morphology Correlates With Endolymphatic Sac Pathologies in Menière's Disease-A Correlative Histology and Computed Tomography Study.

HYPOTHESIS: The vestibular aqueduct (VA) in Menière's disease (MD) exhibits different angular trajectories depending on the presenting endolymphatic sac (ES) pathology, i.e., 1) ES hypoplasia or 2) ES degeneration. BACKGROUND: Hypoplasia or degeneration of the ES was consistently found in inner ears affected by MD. The two etiologically distinct ES pathologies presumably represent two disease "endotypes," which may be associated with different clinical traits ("phenotypes") of MD. Recognizing these endotypes in the clinical setting requires a diagnostic tool. METHODS: 1) Defining the angular trajectory of the VA (ATVA) in the axial plane. 2) Measuring age-dependent normative data for the ATVA in postmortem temporal bone histology material from normal adults and fetuses. 3) Validating ATVA measurements from normative CT imaging data. 4) Correlating the ATVA with different ES pathologies in histological materials and CT imaging data from MD patients. RESULTS: 1) The ATVA differed significantly between normal adults and MD cases with ES degeneration, as well as between fetuses and MD cases with ES hypoplasia; 2) a strong correlation between ATVA measurements in histological sections and CT imaging data was found; 3) a correlation between the ATVA, in particular its axial trajectory in the opercular region (angle αexit), with degenerative (αexit < 120°) and hypoplastic ES pathology (αexit > 140°) was demonstrated. CONCLUSION: We established the ATVA as a radiographic surrogate marker for ES pathologies. CT-imaging-based determination of the ATVA enables endotyping of MD patients according to ES pathology. Future studies will apply this method to investigate whether ES endotypes distinguish clinically meaningful subgroups of MD patients.