Endolymphatic Sac Epithelium Research Articles

Immunohistochemical localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac.

This study aimed to determine the distribution and subcellular localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac. Ten samples of human endolymphatic sac were collected during acoustic neurinoma removal using the translabyrinthine approach. Immunohistochemistry and immunofluorescence were performed using aquaporin 2 and vasopressin type 2 receptor monoclonal antibodies. Confocal microscopy demonstrated that vasopressin type 2 receptor labelling was expressed in both the apical and basolateral plasma membranes, and in the cytoplasm of the endolymphatic sac epithelium, whereas aquaporin 2 was strongly expressed at the basolateral site of the endolymphatic sac epithelium, in both the intraosseous and extraosseous parts of the endolymphatic sac. Both aquaporin 2 and vasopressin type 2 receptor were detected in the epithelial cells of the human endolymphatic sac, suggesting that this channel may be involved in inner-ear fluid homeostasis. However, strong basolateral expression of aquaporin 2 in endolymphatic sac epithelium suggested that the function of aquaporin 2 may differ between the endolymphatic sac and kidney.

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

Epithelial ion transport pathologies of the endolymphatic sac (ES) are associated with large vestibular aqueduct syndrome (LVAS). 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. Histological and immunohistochemical analysis of the enlarged ES epithelium in postmortem temporal bones from two individuals with a clinical diagnosis of LVAS. 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. 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.

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.

Expression of renal cell markers and detection of 3p loss links endolymphatic sac tumor to renal cell carcinoma and warrants careful evaluation to avoid diagnostic pitfalls

Endolymphatic sac tumor (ELST) is a rare neoplasm arising in the temporal petrous region thought to originate from endolymphatic sac epithelium. It may arise sporadically or in association with Von-Hippel-Lindau syndrome (VHL). The ELST prevalence in VHL ranges from 3 to 16% and may be the initial presentation of the disease. Onset is usually in the 3rd to 5th decade with hearing loss and an indolent course. ELSTs present as locally destructive lesions with characteristic computed tomography imaging features. Histologically, they show papillary, cystic or glandular architectures. Immunohistochemically, they express keratin, EMA, and variably S100 and GFAP. Currently it is recommended that, given its rarity, ELST needs to be differentiated from other entities with similar morphologic patterns, particularly other VHL-associated neoplasms such as metastatic clear cell renal cell carcinoma (ccRCC). Nineteen ELST cases were studied. Immunohistochemistry (18/19) and single nucleotide polymorphism microarray testing was performed (12/19). Comparison with the immunophenotype and copy number profile in RCC is discussed. Patients presented with characteristic bone destructive lesions in the petrous temporal bones. Pathology of tumors showed characteristic ELST morphology with immunoexpression of CK7, GFAP, S100, PAX-8, PAX-2, CA-9 in the tumor cells. Immunostaines for RCC, CD10, CK20, chromogranin A, synaptophysin, TTF-1, thyroglobulin, and transthyretin were negative in the tumor cells. Molecular testing showed loss of 3p and 9q in 66% (8/12) and 58% (7/12) cases, respectively. Immunoreactivity for renal markers in ELST is an important diagnostic caveat and has not been previously reported. In fact, renal markers are currently recommended in order to rule out metastatic RCC although PAX gene complex and CA-9 have been implicated in the development of the inner ear. Importantly copy number assessment of ELST has not been previously reported. Loss of 3p (including the VHL locus) in ELST suggests similar mechanistic origins as ccRCC.

Tricellulin Expression and its Deletion Effects in the Endolymphatic Sac.

Tricellulin is a tight junction (TJ)-forming protein that participates in the sealing function of tricellular TJs. Tricellulin-knockout (Tric-/-) mice show progressive hearing loss with degeneration of hair cells in the cochlea without physiological or physical disorders. In the present study, we investigated the tricellulin expression and its deletion effects in the endolymphatic sac (ES) using Tric-/- mice. The ES epithelia from wild-type (WT) mice were laser-microdissected, and RT-PCR was performed. The ES sections from Tric-/- and WT mice were immunostained with an anti-tricellulin antibody. Hematoxylin and eosin staining was performed for morphological examination. The inner ear of Tric-/- mice was perfused with biotinylation reagents, and the ES sections were observed for tracer permeability assay after applying streptavidin-Alexa Fluor 488 conjugate. The tricellulin expression was confirmed by RT-PCR and by immunohistochemistry in the WT ES. The ES in Tric-/- mice showed normal morphology and revealed no biotin leakage from the lumen. The ES in Tric-/- mice showed no changes in morphology or disruption in macromolecular barrier function. The effects of solute leakages in the ES of Tric-/- mice may be very limited and compensatable, or that the ES epithelia may have other sealing system covering the lack of tricellulin.

Claudin expression in the rat endolymphatic duct and sac - first insights into regulation of the paracellular barrier by vasopressin

Hearing and balance functions of the inner ear rely on the homeostasis of the endolymphatic fluid. When disturbed, pathologic endolymphatic hydrops evolves as observed in Menière’s disease. The molecular basis of inner ear fluid regulation across the endolymphatic epithelium is largely unknown. In this study we identified the specific expression of the tight junction (TJ) molecules Claudin 3, 4, 6, 7, 8, 10, and 16 in epithelial preparations of the rat inner ear endolymphatic duct (ED) and endolymphatic sac (ES) by high-throughput qPCR and immunofluorescence confocal microscopy. Further we showed that Claudin 4 in the ES is a target of arginine-vasopressin (AVP), a hormone elevated in Menière’s disease. Moreover, our transmission-electron microscopy (TEM) analysis revealed that the TJs of the ED were shallow and shorter compared to the TJ of the ES indicating facilitation of a paracellular fluid transport across the ED epithelium. The significant differences in the subcellular localization of the barrier-forming protein Claudin 3 between the ED and ES epithelium further support the TEM observations. Our results indicate a high relevance of Claudin 3 and Claudin 4 as important paracellular barrier molecules in the ED and ES epithelium with potential involvement in the pathophysiology of Menière’s disease.

\u03b21- and \u03b22-adrenergic stimulation-induced electrogenic transport by human endolymphatic sac epithelium and its clinical implications

The endolymphatic sac (ES) is a cystic structure of the inner ear connected to the cochlea and vestibule, which plays a role in regulating ion homeostasis in inner ear fluid. Disruption of ion homeostasis can cause inner ear disorders with hearing loss and dizziness, such as Meniere’s disease. Herein, we found, for the first time, functional evidence for the involvement of β1- and β2-adrenergic receptors in apical electrogenic ion transport by human ES epithelium by using electrophysiological/pharmacological and molecular biological methods, which were dependent on K+ and Cl− ion transport. The apical electrogenic transport was absent or very weak in ES epithelia of patients with Meniere’s disease. These results suggested that adrenergic stimulation via β1- and β2-adrenergic receptors in the human ES was involved in regulation of inner ear fluid ion homeostasis and impairment of this response could be a pathological mechanism of Meniere’s disease.

Innate immune defense in the inner ear - mucines are expressed by the human endolymphatic sac.

The human endolymphatic sac has been shown recently to have immunological capacities and has thus been proposed as the main entity protecting the inner ear from pathogen invasion, equivalent to mucosa-associated lymphoid tissue (MALT). Although the sac expresses molecules of the innate immune system, the potential expression of members of the important mucin family has not been detailed. Thus, this paper explores endolymphatic sac expression of a number of mucins and mucin precursors. Twelve fresh tissue samples from the human endolymphatic sac were obtained during translabyrinthine surgery. The expression of Mucin 1, 2, 5B/AC and 16, as well as the core structure elements (mucin precursors) T-antigen, Tn-antigen and Sialyl-Tn-antigen was investigated by immunohistochemistry. The endolymphatic sac epithelium expressed MUC1 (both apically towards the endolymphatic sac (ES) lumen and basally towards the capillary network), MUC 16 and Tn-antigen. There was no labeling after incubation with antibodies against T-antigen, sialyl-Tn-antigen, MUC2 and MUC5B/AC. We conclude that the human endolymphatic sac epithelium expresses a number of mucin molecules, which supports the hypothesis of the sac as the primary immunological tissue structure of the inner ear, equivalent to MALT in other organs. The mucins may also play a role in the formation and continuous homeostasis of the inner ear fluids, as well as the pathogenesis of Meniere's disease.

Electrogenic transport and K(+) ion channel expression by the human endolymphatic sac epithelium.

The endolymphatic sac (ES) is a cystic organ that is a part of the inner ear and is connected to the cochlea and vestibule. The ES is thought to be involved in inner ear ion homeostasis and fluid volume regulation for the maintenance of hearing and balance function. Many ion channels, transporters, and exchangers have been identified in the ES luminal epithelium, mainly in animal studies, but there has been no functional study investigating ion transport using human ES tissue. We designed the first functional experiments on electrogenic transport in human ES and investigated the contribution of K+ channels in the electrogenic transport, which has been rarely identified, even in animal studies, using electrophysiological/pharmacological and molecular biological methods. As a result, we identified functional and molecular evidence for the essential participation of K+ channels in the electrogenic transport of human ES epithelium. The identified K+ channels involved in the electrogenic transport were KCNN2, KCNJ14, KCNK2, and KCNK6, and the K+ transports via those channels are thought to play an important role in the maintenance of the unique ionic milieu of the inner ear fluid.

Expression of histamine receptors in the human endolymphatic sac: the molecular rationale for betahistine use in Menieres disease.

The human endolymphatic sac (ES) is situated in a duplicature of the dura in the posterior cranial fossa and constitutes a part of the inner ear. The sac possesses immunological capacities and is responsible for a major part of the trans-epithelial ion transport occurring within the inner ear, via molecular mechanisms similar to that of the kidney collecting duct epithelia. Dysfunction of the trans-epithelial ion transport has been hypothesized as the reason for the endolymphatic hydrops occurring in Menieres diseases. Thus, candidate drug selection for medical treatment of Menieres disease has been based on a potential capability of improving trans-epithelial ion transport. However, recent human studies seems to rule out diuretic therapy and The Committee for Medicinal Products for Human Use redrew the recommendation for trimetazidine (Vastarel) treatment in the management of Meniere disease in 2012. This leaves betahistine (Betaserc) as the only drug for potential prevention of the incapacitating attacks of dizziness, tinnitus and hearing loss. However, the histamine receptors targeted by betahistine have never been demonstrated in the human ES. Accordingly, this study aims to investigate the expression of histamine receptors of the human ES epithelium and sub-epithelial stroma. Following sampling of human endolymphatic sac tissue during translabyrinthine surgery, the expression of histamine receptor genes was determined by cDNA microarray analysis. Results were subsequently verified by immuno-histochemistry. The combined results of microarrays and immuno-histochemistry showed expression of the histamine receptor HRH1 in the epithelial lining of the ES, whereas HRH3 was expressed exclusively in the sub-epithelial capillary network. Receptors HRH2 and -4 were not expressed. The present data provide the first direct evidence of a molecular rationale for betahistine treatment in Menieres disease. A potential betahistine effect in Menieres disease may primarily be through the H3-receptor antagonism, leading to inhibition of vestibular neuro-transmission and central vaso-dilation. The H1-receptor localization in the ES epithelium suggests an immuno-regulatory effect.

Prox1 expression in the endolymphatic sac revealed by whole-mount fluorescent imaging of Prox1-GFP transgenic mice

This study describes a technical breakthrough in endolymphatic sac research, made possible by the use of the recently generated Prox1-GFP transgenic mouse model. Whole-mount imaging techniques through the decalcified temporal bone and three-dimensional observations of Prox1-GFP mouse tissue revealed the positive labeling of the endolymphatic sac in adult stage, and allowed, for the first time, the GFP-based identification of endolymphatic sac epithelial cells. Prox1 expression was observed in all parts of the endolymphatic sac epithelia. In intermediate portion of the endolymphatic sac, mitochondria-rich cells did not express Prox1, although ribosome-rich cells showed strong GFP labeling. The anatomical relationship between the endolymphatic sac and the surrounding vasculature was directly observed. In the endolymphatic sac, expression of Prox1 may suggest progenitor cell-like pluripotency or developmental similarity to systemic lymphatic vessels in other organs. This whole-mount imaging technique of the endolymphatic sac can be combined with other conventional histological, sectioning, and labeling techniques and will be very useful for future endolymphatic sac research.

Cystic fibrosis transmembrane conductance regulator in the endolymphatic sac of the rat

Na(+) and Cl(-) are dominant ions in the endolymphatic fluid in the endolymphatic sac and are important for volume regulation in the endolymphatic sac. An epithelial sodium channel (ENaC) and other Na(+) transporters have been identified in the endolymphatic sac epithelia, and they are involved in the regulation of endolymph. Although the presence of Cl(-) channels in the endolymphatic sac epithelia has been speculated, no Cl(-) channels have been identified. In this study, we confirmed the expression of cystic fibrosis transmembrane conductance regulator (CFTR) in the endolymphatic sac by reverse transcriptase polymerase chain reaction (RT-PCR) and by immunohistochemical staining. Pure mRNA from endolymphatic sac epithelia was prepared using laser capture microdissection (LCM) and examined using RT-PCR. Localization of CFTR and ENaC in the endolymphatic sac was examined using immunohistochemistry. mRNA of the CFTR was expressed in the endolymphatic sac. Immunohistochemical analysis showed the expression of the CFTR on apical side of the endolymphatic sac epithelia and co-localization with the ENaC. RT-PCR and immunohistochemistry were used to identify the expression of CFTR in the endolymphatic sac epithelia, which gives us a clue for understanding Cl(-) transport in the endolymphatic sac. These results suggest a pathway for Cl(-), possibly through interaction with the ENaC, which may regulate the endolymph in the endolymphatic sac.

Presence of Adrenergic Receptors in Rat Endolymphatic Sac Epithelial Cells

Intravenous application of catecholamines produces a depression in the endolymphatic sac direct current potential (ESP) and increases endolymphatic pressure via the β-adrenergic receptor (AR) in guinea pigs, suggesting that catecholamines play a role in the endolymphatic system. However, the localization of ARs in the endolymphatic sac (ES) is still undetermined. The presence of ARs in the rat ES was investigated by reverse transcriptase-polymerase chain reaction using laser capture microdissection (LCM) and immunohistochemical analysis. Expression of α(1A)-, α(1B)-, α(2A)-, α(2B)-, β(1)-, β(2)- and β(3)-ARs was observed in LCM samples of ES epithelia. Immunohistochemical analysis using specific antibodies showed immunofluorescence of β(2)- and β(3)-ARs in epithelial cells of the ES intermediate portion, and no specific staining results were obtained for α(1)-, α(2A)-, α(2B)- and β(1)-ARs. The presence of β(2)-AR with no clear immunostaining of β(1)-AR in ES epithelial cells is in accordance with previous electrophysiological and pharmacological results, which suggests that β(2)-AR mediates the action of catecholamines on the ESP. The presence of β(3)-AR in the ES epithelial cells and its absence in the stria vascularis implies that β(3)-AR plays a specific role in the ES.

Presence of FXYD6 in the endolymphatic sac epithelia

A homeostasis of the electrochemical properties and volume of the endolymph in the inner ear is essential for hearing and equilibrium sensing and is maintained by ion-transport across an epithelial tissue, the endolymphatic sac. One of the key proteins in the maintenance is Na+, K+-ATPase. Although we previously found that the Na+, K+-ATPase in the sac plays a pivotal role in the control of the endolymphatic volume, the mechanism remains unclear. Therefore, in this study, we examined the expression of FXYD6, a functional modulator of the Na+, K+-ATPase, in the epithelial cells of the endolymphatic sac using various approaches. Laser capture microdissection RT-PCR was used to identify FXYD6 mRNA in the endolymphatic sac. Immunolabeling with the specific antibody showed that FXYD6 was predominantly expressed in the intermediate portion of the endolymphatic sac, and it was colocalized with the Na+, K+-ATPase. Because the Na+, K+-ATPase in this region is known to exhibit a high level of activity, an interaction of FXYD6 with this transporter may be critically involved in the regulation of the characteristics of the endolymph.

The mRNA of claudins is expressed in the endolymphatic sac epithelia

Claudins are a family of membrane proteins which localize to tight junctions (TJs). Recent studies have shown that claudins can form pores for ions in the TJs and regulate the permeability of epithelial paracellular ion transport. The endolymphatic sac (ES) is a part of the inner ear, absorbing the endolymphatic fluid. ES dysfunction may result in endolymphatic hydrops. In this study, we focused on the paracellular transport and examined claudin mRNA expression in the ES epithelia. Total RNA was isolated from whole ES epithelia of rats by laser capture microdissection. RT-PCR was used to evaluate the expression of claudins. The expression of each claudin mRNA in the epithelial cells of rat ES was confirmed by in situ hybridization. RT-PCR indicated the expression of cldn2, cldn4, cldn6, cldn7, cldn9, cldn11, cldn12, and cldn14. The expression of these claudin mRNAs in the epithelial cells of rat ES was confirmed by in situ hybridization. We demonstrated mRNA expression of multiple claudins in the rat ES epithelia. These results in the ES epithelia were consistent with a role of claudins in paracellular ion transport.

The expression of P2Y1, 2, 4, and 6 receptors in rat endolymphatic sac epithelia

Earlier studies have suggested that activation of the purinergic receptor causes Na absorption from the endolymph through nonselective cation channels in endolymphatic sac (ES) epithelia. In this study, the mRNA expression patterns of the P2Y(1, 2, 4, and 6) receptors in the rat ES were examined by conventional reverse-transcription PCR. Their cellular localization was investigated by high-specificity reverse-transcription PCR using laser capture microdissection and in-situ hybridization. Our experiments showed that the mRNA of these receptors is expressed in ES epithelia. These results indicate that extracellular nucleotides may regulate ion transport by several purinergic pathways that operate through these receptors in the ES and that some of these receptors may be responsible for regulating Na+ absorption through the activation of nonselective cation channels.

Expression of Aquaporin-2 in the Inner Ear of Water-Deprived Guinea Pigs

Background and ObjectivesZZAlthough the role of aquaporin-2 (AQP2) in the kidney has been well defined, its role in the inner ear remains to be determined. The present study was to investigate the effect of water deprivation on the expression of AQP2 in the inner ear. Materials and MethodZZHealthy male guinea pigs weighing 250 g were used. The experimental group underwent water restriction and the control underwent water loading with sucrose-containing water for 3 days. Concentrations of plasma arginine-vasopressin (AVP ) were determined and electrocochleography (ECoG) recordings were made. An RT-PCR, real-time PCR and Westernblotting analysis were used for quantitative analysis of AQP2 mRNA and AQP2 protein expression. Immunohistochemistry was also used to evaluate the distribution of AQP2 water channel proteins in the inner ear. ResultsZZAQP2 was mainly expressed in the epithelium of endolymphatic sac, spiral limbus, spiral ligament and stria vascularis of scala media. The concentrations of plasma AVP were 9.2± 0.8 pg/mL in the experimental group and 0.78±0.3 pg/mL in the control. The summation potential/ action potential (SP/AP) ratio in ECoG was markedly increased in the experimental group (0.55 in the experimental and 0.29 in the control). RT-PCR and real time PCR as well as Western blot analysis showed that the level of AQP2 mRNA and protein in the cochlea and endolymphactic sac of the water-deprived group was significantly higher than those in the control group. ConclusionZZThese data suggest that AQP2 is one of the important water channels in fluid homeostasis in the inner ear. Moreover, the volume of endolymphatic space can be increased via AVP-AQP2 system in response to water deprivation. Korean J Otorhinolaryngol-Head Neck Surg 2009;52:572-8 Key WordsZZAquaporin 2·Endolymphatic hydrops·Arginine vasopressin·Inner ear.

A new approach for selective rat endolymphatic sac epithelium collection to obtain pure specific RNA

The endolymphatic sac (ES) is an organ that is located in the temporal bone. Its anatomical location makes ES tissue collection without any contamination very difficult, and sometimes accurate molecular analyses of the ES are prevented due to this matter. In the present study, a new selective ES epithelial tissue collection method was attempted using laser capture microdissection to obtain pure ES RNA without any contamination. The validity of this method was demonstrated by RT-PCR with three specific primer pairs against osteocalcin, calponin H1, and NKCC2, which are specific proteins in bone, smooth muscle, and kidney/ES cells, respectively. From the RT-PCR results, the high specificity and sufficient sensitivity of the new method was indicated. It is considered that the new method is optimal for ES collection without contamination and it will be able to contribute to future analyses of the ES.

Profound hypokalemia and hypochloremic metabolic alkalosis during thiazide therapy in a child with Pendred syndrome

Pendred syndrome is a recessive autosomal disorder characterized by thyroid goiter and sensorineural hearing loss. The Pendred syndrome gene (SLC26A4) encodes a new anion exchanger named pendrin which mediates iodide transport by thyrocytes and regulates ion and fluid transport by the endolymphatic sac epithelium. Pendrin defects result in inner ear malformations, with enlargement of the endolymphatic sac and duct in association with a large vestibular aqueduct. Furthermore, patients may develop endolymphatic hydrops requiring diuretic therapy, mainly in the form of thiazides. Pendrin could also account for apical Cl(-)/ HCO3(-) exchange at level of intercalated cells of the cortical collecting duct in the kidneys, however, humans with Pendred syndrome have no symptoms attributable to renal pendrin abnormalities in basal conditions. We report the case of a child with Pendred syndrome and intercurrent endolymphatic hydrops, who developed profound hypokalemia and severe hypochloremic metabolic alkalosis (potassium 1.7, chloride 70, sodium 129, HCO3 43.8, base excess +17.8 mmol/l, pH 7.52) following thiazide therapy. In subjects with Pendred syndrome thiazide therapy seems to provoke more severe Cl(-) and extracellular volume depletion. A possible explanation could be the defective action of the disrupted pendrin, which exacerbates the effects of the inhibition of C1(-) reabsorption mediated by the thiazide-sensitive NaCl cotransporter (SLC12A3).

Magnetic resonance and computed tomography imaging of a grade IV papillary endolymphatic sac tumour

The endolymphatic sac tumour (ELST) is an adenomatous neoplasm of the papillary pattern originating from the endolymphatic sac's epithelium. We describe the computed tomography and magnetic resonance imaging features of a rare grade IV tumour with extensive skull base, cerebello-pontine and nasopharyngeal spread as well as involvement of the left temporomandibular joint. Papillary ELST may easily be misinterpreted on histopathological and even on immunohistochemical examination with other papillary lesions. Thus the radiological imaging features and localization in conjunction with histopathological features and clinical presentation play a paramount role in making the correct diagnosis.