Dynamic Molecular Markers of Otosclerosis in the Human Cochlea

OBJECTIVE

To investigate the role and distribution of various molecular markers using immunohistochemistry and immunofluorescence to further elucidate and understand the pathogenesis of otosclerosis.

METHODS

Archival celloidin formalin-fixed 20-micron thick histologic sections from 7 patients diagnosed with otosclerosis were studied and compared to controls. Sections in the mid-modiolar region were immunoreacted with rabbit polyclonal antibodies against nidogen-1, β2-laminin, collagen-IX, BSP, and monoclonal antibodies against TGF β-1 and ubiquitin. Digital images were acquired using a high-resolution light and laser confocal microscope.

RESULTS

Nidogen-1, BSP, and collagen-IX were expressed in the otospongiotic regions, and to lesser extent, in the otosclerotic regions, the latter previously believed to be inactive. β2-laminin and ubiquitin were uniformly expressed in both otospongiotic and otosclerotic regions. There was a basal level of expression of all of these markers in the normal hearing and sensorineural hearing loss specimens utilized as control. TGF β -1, however, though present in the otosclerosis bones, was absent in the normal hearing and sensorineural hearing loss controls.

CONCLUSIONS

Our results propose that the activity and function of TGF-1 may play a key role in the development and pathogenesis of otosclerosis. Further studies utilizing a higher number of temporal bone specimens will be helpful for future analysis and to help decipher its role as a potential target in therapeutic interventions.

Genetic variants and altered expression of SERPINF1 confer disease susceptibility in patients with otosclerosis

Otosclerosis (OTSC) is a focal and diffuse bone disorder of the human middle ear characterized by abnormal bone growth and deposition at the stapes' footplate. This hinders the transmission of acoustic waves to the inner ear leading to subsequent conductive hearing loss. The plausible convections for the disease are genetic and environmental factors with yet an unraveled root cause. Recently, exome sequencing of European individuals with OTSC revealed rare pathogenic variants in the Serpin Peptidase Inhibitor, Clade F (SERPINF1) gene. Here, we sought to investigate the causal variants of SERPINF1 in the Indian population. The gene and protein expression was also evaluated in otosclerotic stapes to ameliorate our understanding of the potential effect of this gene in OTSC. A total of 230 OTSC patients and 230 healthy controls were genotyped by single-strand conformational polymorphism and Sanger sequencing methods. By comparing the case controls, we identified five rare variants (c.72 C > T, c.151 G > A, c.242 C > G, c.823 A > T, and c.826 T > A) only in patients. Four variants c.390 T > C (p = 0.048), c.440-39 C > T (p = 0.007), c.643 + 9 G > A (p = 0.035), and c.643 + 82 T > C (p = 0.005) were found to be significantly associated with the disease. Down-regulation of SERPINF1 transcript level in otosclerotic stapes was quantified by qRT-PCR, ddPCR and further validated by in situ hybridization. Similarly, reduced protein expression was observed by immunohistochemistry and immunofluorescence in otosclerotic stapes that corroborate with immunoblotting of patients' plasma samples. Our findings identified that SERPINF1 variants are associated with the disease. Furthermore, reduced expression of SERPINF1 in otosclerotic stapes might contribute to OTSC pathophysiology.

Otosclerosis under the magnifying glass

Otosclerosis is a bone condition affecting the stapes bone within the otic capsule, and its exact cause is still unknown. It is characterized by a lack of proper remodeling of newly formed vascular and woven bone, leading to the development of abnormal osteons and the formation of sclerotic bone. Bilateral otosclerosis is seen in 80% of patients and 60% of otosclerosis patients have a family history of the condition. The etiology of this disease is still unknown, there are lots of theories to explain it. The histopathological (HP) studies of otosclerosis showed that osteoblasts, osteoclasts, vascular proliferation, fibroblasts, and histiocytes were observed in the stapes footplate. The onset of the symptoms occurs by the early third decade of life, usually it doesn't start later. In otosclerosis, the energy exerted by sound at the level of the tympanic membrane is reduced in the inner ear due to the fixation and rigidity of the ossicular chain, leading to hearing loss, especially for low frequencies. The primary clinical symptom of otosclerosis is conductive hearing loss but it is important to note that sensorineural hearing loss and mixed hearing loss can also occur as secondary symptoms of the condition. Another symptom present in patients with otosclerosis is tinnitus. The paper carried out a retrospective study of 70 patients diagnosed with otosclerosis in the Department of Otorhinolaryngology of Emergency City Hospital, Timişoara, Romania, between January 2021 to December 2022. Tissue fragments were processed at Service of Pathology by standard Hematoxylin-Eosin staining. The HP diagnosis was completed using Masson's trichrome staining, Giemsa histochemical staining, and immunohistochemical (IHC) reactions with anti-cluster of differentiation (CD)20, anti-CD3, anti-CD4, anti-CD8, anti-CD34, and anti-CD31 antibodies. The microscopic examination showed a chronic diffuse inflammatory infiltrate that consisted predominantly of mature T-lymphocytes, immunohistochemically positive for CD3, CD4 and CD8. There were also present rare CD20-positive B-lymphocytes. Among the lymphocytes, relatively numerous mast cells were identified, highlighted histochemically by the Giemsa staining. They had numerous purple-violet intracytoplasmic granules. In the connective tissue support, a relatively rich vascular network was identified, consisting of hyperemic capillaries, highlighted immunohistochemically with anti-CD31 and anti-CD34 antibodies. Bone tissues trabeculae showed extensive areas of fibrosis. The collagen fibers were highlighted by Masson's trichrome staining, being stained in green, blue, or bluish green.

The Stapes in Otosclerosis: Osteoarthritis of an Ear Ossicle

Otosclerosis is a pagetoid proliferation of bone remodeling, vascular proliferation, bone resorption and new bone formation in the tympanic region of the temporal bone. The resulting anklyosis of the stapes footplate as it articulates with the oval window is the most common cause of conductive hearing loss in young to middle aged, predominantly Caucasian individuals. The characteristic histologic features have been well documented by autopsy studies of the temporal bone. Although stapedectomy is the surgical treatment for otosclerosis, the stapes specimen may be submitted for gross examination only or not examined at all. A retrospective study of 73 stapedectomy specimens (2008-2019) not including the stapes footplate. Clinical features from the electronic medical record as well as standard histologic sections from surgical specimens were reviewed. Neither the stapedal head nor crura showed histologic features of otosclerosis. There was mild osteoarthritis affecting the head, possibly as a consequence of persistent ossicular vibration superimposed on the ankylosed rigidity. The most common changes were surface fissuring (65%), cartilaginous erosion (49%) and irregularity of the osteochondral interface (51%). An occasional osteophyte (8%) was observed. The ear ossicles, embryologically analogous to long bones of the extremities, develop via endochondral ossification and exhibit articular surfaces of hyaline cartilage. The present observations suggest that a consequence of otosclerotic ankylosis is osteoarthritis of the stapedal head. In this study, the histological features could not be correlated with the severity of hearing loss or duration of clinical disease.

Retrospective Review of Otic Capsule Contour and Thickness in Patients with Otosclerosis and Individuals with Normal Hearing on CT

BACKGROUND AND PURPOSE

Otosclerosis is commonly identified on CT as a focus of hypodensity in the otic capsule anterior to the oval window. However, otosclerosis can have a sclerotic phase approximating the density of normal bone, making diagnosis challenging. This study assesses differences in otic capsule contour and thickness anterolateral to the anterior margin of the oval window in patients with otosclerosis compared with individuals with normal hearing.

MATERIALS AND METHODS

Axial CT of 104 ears with clinically diagnosed otosclerosis and 108 consecutive ears of audiometrically normal individuals were retrospectively reviewed. Two radiologists independently evaluated the pattern of otosclerosis, otic capsule contour, and bone thickness on standardized axial images at the level of the oval window and cochleariform process. Measurements were made from the posterolateral margin of the cochlea to the apex of the otic capsule convex contour just anterolateral to the anterior margin of the oval window. In the absence of a convex contour, the sulcus between the oval window and the cochleariform process was identified, and measurement to the depth of the sulcus was used. Receiver operating characteristic analysis determined the best cutoff value of otic capsule thickness.

RESULTS

Mean otic capsule thickness (2 SDs) was 3.08 (0.93) mm and 1.82 (0.31) mm in patients with otosclerosis and individuals with normal hearing, respectively (P < .001), with excellent interobserver agreement. Otic capsule thickness of >2.3 mm had 96.2% sensitivity, 100% specificity, 100% positive predictive value, and 96.4% negative predictive value for otosclerosis. A bulging/convex contour of the otic capsule had 68.3% sensitivity, 98.1% specificity, 97.3% positive predictive value, and 76.3% negative predictive value.

CONCLUSIONS

Patients with otosclerosis have significantly thicker bone abutting the oval window than individuals with normal hearing.

Cavitary Plaques in Otospongiosis: CT Findings and Clinical Implications

BACKGROUND AND PURPOSE

Cavitary plaques have been reported as a manifestation of otospongiosis. They have been related to third window manifestations, complications during cochlear implantation, and sensorineural hearing loss. However, their etiology and clinical implications are not entirely understood. Our purpose was to determine the prevalence, imaging findings, and clinical implications of cavitary plaques in otospongiosis.

MATERIALS AND METHODS

We identified patients with otospongiosis at a tertiary care academic medical center from January 2012 to April 2017. Cross-sectional CT images and clinical records of 47 patients (89 temporal bones) were evaluated for the presence, location, and imaging features of cavitary and noncavitary otospongiotic plaques, as well as clinical symptoms and complications in those who underwent cochlear implantation.

RESULTS

Noncavitary otospongiotic plaques were present in 86 (97%) temporal bones and cavitary plaques in 30 (35%). Cavitary plaques predominated with increasing age (mean age, 59 years; P = .058), mostly involving the anteroinferior wall of the internal auditory canal (P = .003), and their presence was not associated with a higher grade of otospongiosis by imaging (P = .664) or with a specific type of hearing loss (P = .365). No patients with cavitary plaques had third window manifestations, and those with a history of cochlear implantation (n = 6) did not have complications during the procedure.

CONCLUSIONS

Cavitary plaques occurred in one-third of patients with otospongiosis. Typically, they occurred in the anteroinferior wall of the internal auditory canal. There was no correlation with the degree of otospongiosis, type of hearing loss, or surgical complications. Cavitary plaques tended to present in older patients.

Prevalence, size and distribution of microdamage in the human otic capsule

CONCLUSIONS

Age-dependent microdamage (MDx) accumulates excessively in human perilabyrinthine bone, where the bone turnover is almost absent. This may have pathological implications for bone-specific disorders such as otosclerosis. The role of MDx accumulation is discussed from an osteodynamic perspective.

OBJECTIVES

Bone remodelling is highly inhibited within the otic capsule compared with the rest of the skeleton. Consequently excessive accumulation of age-dependent capsular MDx is expected. This study describes the prevalence, size and topographical distribution of MDx in the human otic capsule.

METHODS

A total of 241 undecalcified human temporal bones were examined. Bulk staining and the cutting-grinding technique were used to separate in vivo MDx from microcrack artefacts induced post mortem by the milling procedure. Quantitative data were obtained by fluorescence microscopy by counting and measuring and by the use of stereology.

RESULTS

Microcracks accumulated continuously and extensively in the human otic capsule throughout life. Both the number and total length of MDx were higher close to the inner ear space as compared with the capsular periphery. The mean length of the MDx remained constant with age. There was no statistically significant sex difference.

The surgical concept for otosclerosis

The aggregate results of the stapedectomy operation for hearing improvement are highly satisfactory in the short and long term when carried out by an experienced and skilled surgeon, using a variety of techniques in carefully selected candidates. An initial bone-air gap of 10 dB or less is achieved in 80-90% of patients. The outcome of stapedectomy is dependent on the patient's level of sensorineural reserve which is age dependent, and on the limitations imposed by stapedial footplate pathology. The advantages of various types of piston prostheses for reconstruction have become increasingly clear. The infrequent complications of immediate and delayed sensorineural losses with impaired speech discrimination are certain to be reduced further in incidence by the increasing adoption of small fenestra techniques with piston prostheses and tissue seals. There is a definite need for fully informative statistical methods in reporting the results of surgery for hearing improvement if further advances are to be made.

Numerical study of Hough technique in surgery of otosclerosis, using the finite element method

PURPOSE

Otosclerosis is a metabolic bone disease of the otic capsule that can cause the stapes fixation, resulting in conductive hearing loss or, in a profound sensorineural deafness threshold. Surgery is one of the possible treatments for the otosclerosis. To repair small focus of otosclerosis in the anterior crus of the stapes, in 1960, Hough suggested the implementation of a technique in which part of the anterior crus is fractured and the stapes turned. As a result, the posterior crus of the stapes is the only connection with the inner ear. In this work, the outcome of Hough's surgical technique was simulated.

METHODS

Based on computerized images, a finite element model of middle ear ossicles and tympanic membrane was created, as well as a model where the stapes has changed. The discretization of the tridimensional solid model was made using the ABAQUS software. The mechanical properties used were taken from the literature and adequate boundary conditions were applied.

RESULTS

The results obtained with the Hough technique simulation were compared with a representative model of the normal ear, taking into account the displacements obtained on the central part of the stapes footplate and the maximum principal stress in the stapes crus.

CONCLUSIONS

The results obtained are closer to the normal ear model, therefore Hough technique stands out as a good option to correct small focus of otosclerosis.

Atypical mature bone in the otosclerotic otic capsule as the differentiated zone of an invasive osseous neoplasm

CONCLUSION

A large proportion of the mature otic capsule bone in cases of otosclerosis lies in plaques in direct contiguity with active otosclerosis and, because it shows significant structural defects, it should be regarded as part of the otosclerotic process. These appearances support our previously described suggestion that otosclerosis is an invasive osseous neoplasm, the mature atypical bone representing differentiation of earlier-formed invasive neoplastic osseous tissue.

OBJECTIVES

We sought structural features in differentiated bone within the otic capsules of cases of otosclerosis that might indicate a relation to the underlying disease process.

METHODS

Fifty temporal bones from 42 adult patients with otosclerosis were processed into stained histological sections and the appearance of the otic capsule was compared with that of the same tissue, processed in the same way, in 10 cases that did not show otosclerosis.

RESULTS

In the cochlear otic capsules of otosclerotic temporal bones, when traced back along the otosclerotic plaque from the invasive front, atypical shapes and arrangements of osteons were seen, often with otospongiosis (severe dilatation of multiple Volkmann's canals), culminating in larger differentiated osteons with irregularities in structure. In the medial region of the otosclerotic cochlear otic capsule, at a similar position to that where giant normal osteons are present in the normal temporal bone, differentiated, giant abnormal osteons were seen. In the otosclerotic vestibular otic capsule there were changes similar to those of the otosclerotic cochlea (apart from the giant osteons) and many osteons composed of clusters of atypical osteoblast-like cells around highly atypical Volkmann's canals.

Defective postnatal endochondral bone development by chondrocyte-specific targeted expression of parathyroid hormone type 2 receptor

The human parathyroid hormone type 2 receptor (PTH2R) is activated by PTH and by tuberoinfundibular peptide of 39 residues (TIP39), the latter likely acting as its natural ligand. Although the receptor is expressed at highest levels in the nervous system, we have observed that both PTH2R and TIP39 are expressed in the newborn mouse growth plate, with the receptor localizing in the resting zone and the ligand TIP39 localizing exclusively in prehypertrophic and hypertrophic chondrocytes. To address the role of PTH2R in postnatal skeletal growth and development, Col2a1-hPTH2R (PTH2R-Tg) transgenic mice were generated. The mice were viable and of nearly normal size at birth. Expression of the transgene in the growth plate was limited to chondrocytes. We found that chondrocyte proliferation was decreased, as determined by in vivo BrdU labeling of proliferating chondrocytes and CDK4 and p21 expression in the growth plate of Col2a1-hPTH2R transgenic mice. Similarly, the differentiation and maturation of chondrocytes was delayed, as characterized by decreased Sox9 expression and weaker immunostaining for the chondrocyte differentiation markers collagen type II and type X and proteoglycans. As well, there was altered expression of Gdf5, Wdr5, and β-catenin, factors implicated in chondrocyte maturation, proliferation, and differentiation.These effects impacted on the process of endochondral ossification, resulting in delayed formation of the secondary ossification center, and diminished trabecular bone volume. The findings substantiate a role for PTH2R signaling in postnatal growth plate development and subsequent bone mass acquisition.

On the biology of the bony otic capsule and the pathogenesis of otosclerosis

In human otosclerosis, focal pathological bone remodeling occurs in significant amounts inside the normally anti-resorptive perilabyrinthine domain of the bony otic capsule. Otosclerosis causes hearing loss in 0.2-0.5% of the population by ankylosis of the footplate. The disease cannot be predicted, avoided or medically reversed as the pathogenesis remains unknown. Previously genetic research has failed to identify a specific otosclerosis-gene and earlier theories of virus infections, autoimmunity or association to generalized bone diseases have been unable to explain why otosclerosis only occurs in the bony otic capsule while the rest of the skeleton remains completely normal. Studies from the otopathological laboratory (RH) have revealed how the bone turnover rates increase centrifugally from a sub-normal 0.1% adjacent to the inner ear space towards a normal 10% per year at the capsular periphery. This graded restriction of bone remodeling is most likely caused by the anti-resorptive action of the cytokine osteoprotegerin (OPG), which is expressed in high levels (1000 x normal bone levels) by inner ear structures to inhibit perilabyrinthine osteoclast formation and function. OPG knockout mice develop excessive, irregular bone remodeling, stapes fixation and progressive hearing loss. The lacuno-canalicular porosity is the candidate anatomical routes for the transmission of OPG-derived signals to the surrounding bone. This extracellular signaling pathway depends crucially on the viability of individual osteocytes. When bone remodeling is low, the average age of the bone matrix and osteocytes increases. We detected a high fetal density of labyrinthine osteocytes, which may secure a life-long anatomical route for inner ear OPG despite accumulation of non-viable osteocytes. Moreover, 3-D reconstructions and vector-based stereology revealed a co-existence between non-viable osteocytes and otosclerosis. We suggest that bone remodeling may commence when the effect of anti-resorptive OPG fails locally within regions of non-viable osteocytes. A sustained OPG signal from surrounding osteocyte survivors might distort the process and account for the otosclerotic morphology.

Prediction of stapes footplate thickness based on the level of hearing loss in otosclerosis

During surgical treatment of a patient with otosclerosis, the probability of success depends in large part on the extent of the surgeon's experience. Therefore, predicting the preoperative severity of disease may help determine the choice of surgeon based on how experienced the surgeon should be. We conducted a study to evaluate the relationship between hearing thresholds and footplate thickness in otosclerosis patients who underwent stapes surgery. We used a qualitative method for measuring footplate thickness that was based on the simplicity or difficulty of opening the footplate. Our study population was divided into two groups; group 1 was made up of 66 patients whose footplates were easily opened with low pressure or with repeated motions by hand, and group 2 was made up of 14 patients whose footplate was either opened by drilling or not opened because it had been obliterated. We found that the patients in group 2, who had more severe disease, had significantly higher air- and bone-conduction thresholds than did the patients in group 1. According to our findings, otosclerotic patients with high air- and bone-conduction thresholds generally have more severe disease and thus require a more experienced surgeon.

Expression of bone morphogenetic protein 2, 4, 5, and 7 correlates with histological activity of otosclerotic foci

CONCLUSION

This study is the first to establish that bone morphogenetic protein 5 (BMP5) plays a role in the pathogenesis of otosclerosis. These results confirm that elevated expression levels of BMPs, members of the transforming growth factor (TGF)-β superfamily, contribute to the pathologically increased bone turnover in early, active stages of otosclerosis.

OBJECTIVES

Otosclerosis is a complex bone remodeling disorder of the otic capsule, which might be characterized by increased expression of different types of BMPs. TGF-β and BMP are both members of the TGF-β superfamily and play a critical role in bone resorption and new bone formation. It has been suggested that BMP and its receptors may be involved in the pathologically increased bone turnover observed in otosclerosis.

METHODS

Fifty-one otosclerotic and 16 non-otosclerotic ankylotic stapes footplates were histologically analyzed: conventional hematoxylin-eosin staining and BMP2, 4, 5, and 7specific immunofluorescent assays were performed. Cortical bone fragments (n = 35) and incus specimens (n = 6) were used as negative controls.

RESULTS

Active otosclerosis (n = 39) was characterized by increased expression of BMP2, 4, 5, and 7. Inactive cases of otosclerosis (n = 12) were characterized by negative immunoreaction for BMPs. Non-otosclerotic stapes specimens (n = 16) and negative controls (n = 41) showed negligible BMP expression. The BMP expression pattern showed a strong correlation with the histological activity of otosclerosis.

Challenges in fitting a hearing aid to a severely collapsed ear canal and mixed hearing loss

BACKGROUND

Collapsed ear canals typically occur when an outside force, such as a headset for audiometric testing, is present. However, when a collapsed ear canal occurs without external pressure, this creates a challenge not only for performing audiometric testing but also for coupling a hearing aid to the ear canal.

PURPOSE

This case report highlights the challenges associated with fitting a hearing aid on a patient with a severe anterior-posterior collapsed ear canal with a mixed hearing loss.

RESEARCH DESIGN

A 67-yr-old female originally presented to Washington University in St. Louis School of Medicine in 1996 with a long-standing history of bilateral otosclerosis. She had chronic ear infections in the right ear and a severely collapsed ear canal in the left ear and was fit with a bone anchored hearing aid (BAHA®) on the right side in 2003. However, benefit from the BAHA started to decrease due to changes in hearing, and a different hearing solution was needed. It was proposed that a hearing aid be fit to her collapsed left ear canal; however, trying to couple a hearing aid to the collapsed ear canal required unique noncustom earmold solutions.

CONCLUSIONS

This case study highlights some of the obstacles and potential solutions for coupling a hearing aid to a severely collapsed ear canal.

[Otosclerosis- <<the mysterious sphinx>> or the loss of the natural variant of inertness (<<bradytrophicity>> of the labyrinth capsule)]

The author suggests an original hypothesis of otosclerosis based on the analyses of the literature publications for many years and his personal clinical observations. The normal labyrinth capsule is considered to be bradytrophic, i.e. inert and showing an extremely low level of metabolic processes. The disturbance of bradytrophicity under the action of individual factors and/or especially their combination make it involved in the maintenance of calcium homeostasis in the body. The validity of this conjecture is confirmed by the results of histological investigations, viz. the appearance of diquide or xplasma-like, bone in the labyrinth of the patients suffering otosclerosis. Such bone resorption is known to occur in other parts of the bony skeletontoo and should be regarded as a normal physiological process contributing to the replenishment of blood calcium deficiency.The subsequent reorganization (remodeling) of any part of the bony skeleton is physiologically neutral. In the labyrinth capsule,with its small size and delicate structure, such reorganization induces the otosclerotic process responsible for dysfunction of the membranaceous labyrinth. The surgical treatment of the patients presenting with otosclerosis should be supplemented by conservative treatment intended to slow down the otosclerotic reorganization and to restore bradytrophicity of the labyrinth capsule.

Origin and growth of otosclerosis

CONCLUSION

The external layer of the otic capsule arises from periosteal osteoblasts, which produce large numbers of Volkmann's canals as well as lamellar bone. The main plaque of otosclerosis is a histologic replica of the external layer and seems to arise from similar cells in the periosteum and to follow a defined invasive course into the footplate of the stapes, the basal coil of the cochlea and the saccule.

OBJECTIVES

To determine by histologic study of the developing otic capsule and temporal bones with otosclerosis the site, tissue of origin, and pathways of growth of the disease.

METHODS

Step sections of 60 celloidin-embedded temporal bones from fetuses and 24 from patients aged between 1 and 52 years were examined in the study of the development of the otic capsule. Step sections of 65 temporal bones each with 2 or more deposits of otosclerosis were surveyed to obtain data on the site, tissue of origin, and pathways of its growth.

RESULTS

The otic capsule differs from other bones in that the formation of the ultimate lamellar bone tissue is accompanied by very numerous intercommunicating channels. In the middle (cartilage origin) layer these are chondro-osseous canals and Volkmann's canals (like Haversian canals, but multidirectional). In the external (periosteal origin) layer these are Volkmann's canals only. In all, 63 of the 65 temporal bones with otosclerosis that were studied showed a prominent posterior otic capsule plaque. Evidence that this is derived from the periosteum of the external canal is as follows. (a) The otosclerotic tissue of the plaque--like all otosclerotic tissue--is composed of Volkmann's canals and lamellar bone only, as does external layer tissue. (b) All posterior plaques have an edge at the periosteum bordering the processus cochleariformis and tensor tympani muscle. The presumed invasive edge of the plaque on the opposite (cochlear) side shows a variable level of its front. (c) The tissue on the cochlear side of the plaque has a darkly stained appearance with large numbers of osteoblasts and poorly differentiated Volkmann's canals, suggesting that this is an invasive front. The otosclerosis becomes progressively better differentiated away from the darkly stained zone, indicating increasing maturation, which is greatest in the suggested origin of the plaque at the processus/tensor tympani muscle region because this would be the oldest region of the plaque. The pathway of the growth indicated by this study suggests a possible time sequence in the symptomatology of otosclerosis as it moves first to stapes footplate and then through the spiral ligament of cochlea to the saccule. An anterior plaque was seen in 42 of the 65 temporal bones with multiple sites of otosclerosis examined. These showed features similar to those listed above for the posterior plaque, with a base on the periosteum bordering the canal for the internal carotid artery, dark zonation at the invasive front near the cochlea, and increasing differentiation towards the base.

Correlations between CT scan findings and hearing thresholds in otosclerosis

CONCLUSION

High-resolution computed tomography (CT) scan may reveal an isolated fenestral form of otosclerosis, and an extensive form, which involves multiple foci around the otic capsule. Pre- and postoperative hearing thresholds are poorer in patients with extensive otosclerosis and their chance of overclosure is reduced by 90%.

OBJECTIVES

To evaluate the relationship between CT scan extension of otosclerotic foci and hearing thresholds in the operated ear, before and after stapedotomy.

METHODS

A preoperative CT scan was performed in 200 patients suspected of having otosclerosis. CT scan findings were categorized as negative, isolated fenestral otosclerosis, and extensive otosclerosis. Preoperative and 2 months postoperative air-conduction (AC) and bone-conduction (BC) thresholds were collected.

RESULTS

In the operated ear, 150 CT scans (75%) revealed an isolated fenestral otosclerosis; 35 (17.5%) were classified as extensive otosclerosis. Mean preoperative BC was significantly poorer in extensive otosclerosis (30.3 dB) than in isolated fenestral otosclerosis (24.6 dB). Mean postoperative BC remained lower in extensive otosclerosis (30.3 dB) than in isolated fenestral otosclerosis (21.2 dB). An overclosure greater than 10 dB was found in 20% of isolated fenestral otoscleroses and in 2.85% of extensive otoscleroses (chi-square: 5.5; p = 0.02).

The spatial distribution of otosclerosis: a quantitative study using design-based stereology

CONCLUSION

This study documents that otosclerotic bone remodeling is distributed centripetally around the inner ear space whereas normal bone remodeling is distributed centrifugally. We suggest that this inverse relation reflects the unique osteo-dynamic setting of the otic capsule: since perilabyrinthine bone remodeling is extremely low, osteocyte deficiency and microcracks accumulate in excess toward the inner ear space with age. This may disrupt the osseus functional network, impede propagation of anti-resorptive signals, and precipitate otosclerotic bone remodeling with a spatial preference for older bone.

OBJECTIVE

To quantify the spatial distribution of otosclerotic bone around the inner ear space in order to explore a possible spatial relation with normal capsular bone remodeling.

METHODS

Otosclerotic lesions in 53 undecalcified human temporal bones were identified and volume data were measured with the CAST-grid system and processed by dedicated software for advanced design-based stereology.

RESULTS

The maximum volume fraction of otosclerotic bone was observed in the innermost perilabyrinthine zones of the otic capsule. The volume fraction of otosclerotic bone declined gradually but significantly from the inner ear space towards the capsular periphery with a general perilabyrinthine centripetal distribution.

Three-dimensional reconstruction of the otosclerotic focus

CONCLUSIONS

The location and three-dimensional (3D) shapes of the otosclerotic foci suggest a general centripetal distribution of otosclerotic bone remodeling around the inner ear space, whereas the normal bone remodeling is distributed centrifugally. The existence of an inverse spatial relation between normal and otosclerotic bone remodeling suggests that inner ear mechanisms in control of bone remodeling may have a pathogenetic role in otosclerosis.

OBJECTIVES

To explore the 3D shape of otosclerotic lesions around the inner ear space by introducing the use of 3D reconstructions and to discuss the results in a new context of temporal bone dynamics and perilabyrinthine signaling pathways.

METHODS

Thirty-four otosclerotic lesions from 20 decalcified human temporal bones were rendered and visualized with the public 3D 'Reconstruct' software.

RESULTS

The majority of otosclerotic lesions were found close to the labyrinthine space at the well-established topographical sites of predilection with a smooth demarcation against the surrounding bone. However, in addition the virtual 3D technique revealed a new perilabyrinthine anisotropy of individual otosclerotic lesions, displaying a bulky end facing the inner ear space and a volumetric decline towards the capsular periphery.

[Clinical analysis of 118 patients with tympanosclerosis]

OBJECTIVE

To study the incidence of tympanosclerosis (TS) and the major risk factors of hearing loss.

METHODS

A total of 118 TS patients (137 ears) were compared with 265 patients with chronic otitis media (COM) (311 ears) for gender, age and course of disease. The disease regions and hearing loss of the TS patients were analyzed.

RESULTS

TS showed higher prevalence in women of older ages. Sclerosis was seen most frequently in the tympanic membrane, followed by the malleus, incus, incudomalleolar joint, other regions, ariticulus incudostapedius and stapes. The patients with sclerosis or deterioration in the ossicular chain had worse hearing loss than the other patients. Carhart notch occurred in 45 ears (32.85%), an incidence similar to that of inverted "V"-shaped curve of air-conduction audiometry near 2 kHz (47 ears, 34.31%). The factors contributing to the hearing loss, listed in the order of their importance, included pathologies in the incus, malleus, incudomalleolar joint, ariticulus incudostapedius, stapes, other regions, tympanic membrane, and gender.

CONCLUSIONS

Female patients may had increased risk of TS. The presence of Carhart notch and inverted "V"-shaped curve in air-conduction audiograph may indicate myringosclerosis or ossicular chain sclerosis. Abnormal ossicular chain is the leading factor contributing to hearing loss.

Detection and identification of CD46 splicing isoforms by nested RT-PCR

CD46 (Membrane Cofactor Protein, MCP) is a transmembrane glycoprotein, which is expressed by all nucleated human cells whose purpose is to protect against autologous complement attack. In addition, CD46 can serve as a receptor for several viruses and bacteria and as a potent regulator of the inflammatory response by affecting T cell differentiation. Multiple isoforms of CD46 exist due to alternative splicing and are coexpressed in human cells in various patterns and expression levels. However, specific diseases have not been associated with isoform coexpression. We applied a nested RT-PCR method to investigate the coexpression pattern of CD46 splicing variants in otosclerotic and normal stapes footplate specimens. Using this method, we detected an altered isoform expression pattern and identified four novel CD46 splicing variants overexpressed in otosclerotic bone. This study is the first comprehensive report to provide evidence for disease associated alternative splicing of CD46.

The influence of postoperative tissue formation on sound transmission after stapes surgery

In the surgical treatment of otosclerosis, the coupling between the stapes prosthesis and the long process of the incus is critical. After surgery, connective tissue and mucosa may grow over the coupling area and thereby influence the sound transmission properties of the incus-prosthesis interface. It was the hypothesis of this study that tissue ongrowth in the incus-prosthesis interface has little influence on sound transmission following stapes surgery. The goals of the study were to: (1) investigate the extent of postoperative tissue ongrowth over the stapes prosthesis; (2) objectively evaluate intra- and postoperative sound transmission properties of revision stapes surgery and compare the findings to those from primary surgery; (3) quantify the influence of ongrown tissue on sound transmission after stapes surgery. A group of 10 patients undergoing revision stapes surgery was investigated with audiological evaluations and intraoperative laser Doppler interferometry, and with scanning electron microscopy of the explanted incus with its adherent prosthesis in 6 patients. Results were compared to a group of patients undergoing primary otosclerosis surgery and temporal bone experiments. Results indicated that tissue grows over the prosthesis, as identified in all specimens. Sound transmission properties were evaluated intraoperatively (i.e., incus mobility and prosthesis-fixation quality), and found to correlate well with the functional hearing results. Ongrowing mucosa in the incus-prosthesis interface had only a minimal effect on sound transmission properties and cannot compensate adequately for insufficient prosthesis fixation. Therefore, it is essential that the stapes prosthesis is properly fixed during primary otosclerosis surgery.

Otosclerosis: an organ-specific inflammatory disease with sensorineural hearing loss

Otosclerosis is an inflammatory disease associated with persistent measles virus (MV) infection of the otic capsule. The nature of sensorineural hearing loss (SNHL) related to otosclerosis can be due to the chronic TNF-alpha release from the foci. TNF-alpha enters the inner ear fluid spaces in histologically active stages of otosclerosis and may cause outer hair cell functional disorder and subsequent SNHL without morphological changes of the organ of Corti. On the contrary, non-otosclerotic stapes ankylosis being a non-inflammatory disease is not harmful for hair cells. Theoretically, SNHL should not associate to this type of stapes fixation. Stapes footplates (N = 248) were examined by hematoxylin-eosin staining and corresponding MV-, OPG- and TNF-alpha-specific RT-PCR. Anti-measles IgG levels of serum specimens were measured by ELISA. Preoperative audiological results were correlated with otosclerotic and non-otosclerotic histopathologies. Among patients with stapes fixation, we found 93 active and 67 inactive otosclerosis, and 88 non-otosclerotic stapes ankylosis. MV could only be detected in otosclerotic stapes footplates. Audiometry revealed bone conduction threshold elevation toward the high frequencies in otosclerotic patients, which was associated to the duration of hearing loss. OPG mRNA expression was significantly lower in the TNF-alpha positive specimens, which was independent from virus positivity. In about one-third of stapes fixations, the etiology is non-otosclerotic stapes ankylosis. Histologic otosclerosis exhibits a strong correlation with MV presence in the bone as a sign of persistent MV infection and related inflammation with TNF-alpha release. This causes SNHL in the function of time. Non-otosclerotic stapes fixations do not cause high-frequency SNHL.

Superior semicircular canal dehiscence: prevalence in a population with clinical suspected otosclerosis-type hearing loss

Superior semicircular canal dehiscence (SSCD) can present with a variety of symptoms that can be predominantly auditory, predominantly vestibular or both. It can mimic a wide range of otological disorders, in particular otosclerosis-like stapes fixation. Our study revealed that, in 5.3% of our patients with clinically suspected otosclerosis, SSCD was detected in high-resolution multi-detector computed tomography (HRMDCT) of the temporal bone. We therefore emphasise the value of HRMDCT with reconstructions in the plane of the superior semicircular canal and perpendicular to the superior semicircular canal in the diagnostic work-up of each patient with a tentative diagnosis of otosclerosis-type stapes fixation. Where there are doubts, VEMP testing should be performed. We believe that a number of unexplained complications after an uneventful stapedotomy procedure might be explained by a pre-operatively undetected dehiscent superior semicircular canal and therefore unwarranted surgery. The typical feature of the conductive hearing loss due to SSCD compared to otosclerosis is an air-bone gap which is much more prominent at low frequencies than at high frequencies.

Tinnitus and otosclerosis

OBJECTIVE

To establish the origin of tinnitus in patients with otosclerosis.

METHODOLOGY

We performed a literature review to identify the characteristics of tinnitus in the general population and among patients with otosclerosis.

RESULTS

Characteristics of tinnitus among patients with otosclerosis differ from those among the general population, suggesting mechanisms other than those implicated in presbycusis. Considerable improvements in the prevalence of tinnitus following corrective surgery demonstrate the limited contribution of diffuse labyrinth lesions. Middle ear and possibly secondary inner ear dysfunction produced by stapes blockage appear to be major etiopathogenic factors in the development of tinnitus in patients with otosclerosis.

CONCLUSION

The conductive hearing deprivation produced by otosclerosis is associated with limited and reversible modifications in the central auditory pathway that are linked to tinnitus.

Does exogenous nitric oxide influence tympanosclerosis? An experimental study

OBJECTIVE

We aimed to elucidate the effects of exogenous nitric oxide application via myrigotomized rat tympanic membranes on tympanosclerosis.

MATERIALS AND METHODS

Forty male rats were included in the study. After myringotomy, nitric oxide was given to the left tympanic cavities and saline was given to the right as the control group. The procedure was repeated 3 times with weekly intervals. Three months after the first procedure, otomicroscopic examination was made and the rats were sacrificed for histologic examination.

RESULTS

Neither otomicroscopic examination, nor histologic examination of middle ears and tympanic membranes revealed any significant difference between the right and left sides. Tympanic membrane thicknesses were also similar on both sides without showing any significant difference.

CONCLUSIONS

Data from this study indicate that exogenous nitric oxide application did not change the occurence of tympanosclerosis in the rat model. Other cytokine interactions are needed to start the reaction sequence leading to tympanosclerosis.

[Stapedotomy outcomes in the treatment of otosclerosis: our experience]

OBJECTIVE

The main objective of our study is to identify whether there is measurable audiometric deterioration in patients undergoing stapedotomy with a follow-up of more than eight years.

MATERIAL AND METHOD

We conducted a retrospective clinical study in which we reviewed a total of 150 case histories of patients with stapedotomy at our department between 1993 and 1997, with a successful initial audiological assessment using tone audiometry in the first three months after surgery and later audiometrical follow-up.

RESULTS

We obtained a significant mean post-operative hearing impairment of 1.02 dB per year, with a pre-operative mean PTA of 51.45 dB, going on to early post-operative mean PTA of 26.71 dB, and later post-operative mean PTA of 35.42 dB, with all these changes turning out to be statistically significant.

CONCLUSIONS

The auditory level obtained after surgery worsens as the years go by, but always without exceeding the hearing loss prior to surgery.

[Treatment of tympanosclerosis]

Tympanosclerosis is a scarring process with a remarkable variability in its localization within the middle ear. It can lead to conductive hearing loss in many cases. It is usually caused by recurrent chronic inflammation of the middle ear. It is generally accepted that functionally relevant tympanosclerotic findings of the middle ear structures should be treated by surgery. Depending on the extent of the surgical resection, the tympanic membrane and the ossicular chain must be reconstructed individually. In cases of isolated myringosclerosis with no hearing loss, no surgery is required. When the ossicular chain is affected by the sclerosis, sound conduction can often be restored only by interposition of grafts. Stapes footplate fixation can be treated by a stapesplasty. Tympanosclerosis of the oval window combined with other chronic inflammation usually requires two-stage surgery. Tympanosclerotic findings without any clinical symptoms should not be removed. The fitting of conventional or implantable hearing aids is the only treatment if chain reconstruction fails or is impossible.

Immunohistochemical evidence of BMP-2, -4 and -7 activity in otospongiosis

CONCLUSION

This study is the first to show that bone morphogenetic proteins (BMP)-2, -4 and -7 play a role in active phase otosclerotic bone remodelling (otospongiosis).

OBJECTIVES

The role of BMPs in various tissue growth and repair mechanisms is an ongoing topic in the literature. BMP-2, -4 and -7 are known to be of major importance in bone formation and repair. Their role in otosclerotic bone transformation has not been analysed previously. The main goal of this study was to perform an immunohistological analysis of BMP-2, -4 and -7 in otoclerosis.

MATERIALS AND METHODS

Parts of the stapedial footplates, collected during partial stapedectomies in 30 patients with clinical otosclerosis, were analysed for histological otosclerotic lesions after staining haematoxylin and eosin. Immunohistochemical analysis was performed using polyclonal IgG antibodies for BMP-2, -4 and -7, as well as biotinylated secondary antibodies, avidin-biotin-peroxidase complex reaction and alkaline phosphatase staining.

RESULTS

In all, 14 specimens contained otosclerosis; 3 of these were otospongiotic, 8 fibrotic, 2 sclerotic and 1 had both sclerotic and fibrotic lesions. Thus in total 14/30 specimens (47%) showed histological otosclerosis. Only the multiple osteoblasts and osteoclasts in those specimens exhibiting an otospongiotic phase showed distinct immunochemical staining for BMP-2, -4 and -7.

Contralateral ear in chronic otitis media: a histologic study

OBJECTIVE

The objective of this study is to determine the prevalence of the contralateral ear changes in human temporal bones of donors with chronic otitis media.

STUDY DESIGN

Transversal.

MATERIAL AND METHODS

The temporal bones were examined under light microscopy and then described. Chronic otitis media was defined by the presence of irreversible inflammatory alterations in the middle ear cleft. The contralateral ear was defined as the normal or the less affected ear. To compare the qualitative variables, the chi test was used. Spearman's nonparametric test was used for correlations. P values less than or equal to .05 were considered significant.

RESULTS

We studied 85 pairs of temporal bones. Cholesteatoma was observed in 22.4% of the more damaged ears. The prevalence of contralateral ears with alterations was 91.8%. The main alterations were granulation tissue (81%), effusion (58%), and tympanic membrane retractions (35%). There was a direct and moderately strong correlation between the extent of granulation tissue in the more damaged ear and the contralateral ear (r(s) = 0.345, P = .004). A strong correlation was observed between the extent of cholesteatoma in the more damaged ear and in the contralateral ear (rs = 0.617, P < .001).

CONCLUSION

We observed a high prevalence of changes in the contralateral ear. There was a direct correlation between the extent of both granulation tissue and cholesteatoma between the two ears, demonstrating that the more extensive the manifestation of these pathologies in the more damaged ear, the greater they will be in the contralateral ear.

Clinical and genetic analysis of two Tunisian otosclerosis families

Otosclerosis is caused by an abnormal bone homeostasis of the otic capsule resulting in a conductive hearing loss when the free motion of the stapes is compromised. An additional sensorineural hearing loss arises in some patients, most likely due to otosclerotic foci that invade the cochlear endosteum. Otosclerosis is a very common hearing impairment among Caucasians with a prevalence of about 0.3-0.4% among white adults. In the majority of cases, otosclerosis can be considered as a complex disease, caused by both genetic as environmental factors, but autosomal dominant forms of otosclerosis exist. However, families large enough for genetic analysis are very rare and often show reduced penetrance. To date five loci have been reported, but none of the genes have been cloned yet. In this study, we analyzed two new autosomal dominant otosclerosis families from Tunisia, and genotyped them with microsatellite markers for the known loci, the collagen genes COL1A1 and COL1A2, and NOG gene. In the family LK, linkage to all known loci was excluded. However, the family LS shows suggestive linkage to the OTSC3 region on chromosome 6p21.3-p22.3. This result points out that, besides the five reported loci, there must be at least one additional locus for autosomal dominant otosclerosis.

Phenotype description of a Dutch otosclerosis family with suggestive linkage toOTSC7

This study reports on a clinical investigation of a Dutch family that shows suggestive linkage to OTSC7. Cross-sectional as well as longitudinal analyses of audiometric data were performed. Also, high-resolution computed tomography (CT) images of the temporal bones from genetically affected family members were obtained to study the incidence and extent of otospongiotic foci. Audiometric data showed a considerable degree of phenotypic variability. Cross-sectional regression analysis did not show age-dependent progression of bone conduction (BC), air conduction (AC), and air-bone gap (ABG) levels. Longitudinal analysis of audiometric follow-up data of one family member showed age-dependent progression of AC, BC, and ABG levels. High-resolution CT images revealed an otospongiotic focus in six of six (100%) clinically affected individuals that carried the disease haplotype. In none of the clinically unaffected family members that showed linkage to OTSC7, an otospongiotic focus was detected by CT. In conclusion, hearing impairment in the present otosclerosis family seems to be variable in terms of onset age and level of progression. Long-term audiometric data of one patient proved to be valuable in understanding progression of hearing impairment in this individual. The detection rate of otospongiotic foci in our study group is similar compared to previous reports on CT data in consecutive otosclerosis patients who had stapes replacing surgery.

Measles virus prevalence in otosclerotic foci

The etiology of otosclerosis is still unknown. Persistent measles virus infection of the otic capsule is supposed to be one of the etiologic factors in otosclerosis. The presence of measles virus was shown in otosclerotic patients by RT-PCR amplification of the viral RNA, detecting the viral proteins by immunohistochemistry and antimeasles immunoglobulin G in the perilymph samples. Nucleic acid (mRNA, vRNA, DNA) was extracted from pulverized, frozen stapes footplate samples of otosclerotic patients. Measles virus RNA was amplified by RT-PCR: reverse transcription and the first-round PCR amplification were performed by heat-stable recombinant Thermus thermophilus polymerase, while in the nested round PCR Taq polymerase was employed. Oligonucleotide primers specific to measles virus nucleoprotein and matrix protein RNA were used in these reactions. Edmonston- and Schwartze-type measles viruses served as positive controls and cortical bone fragments, stapes superstructures, cadaver stapes, incus and malleolar samples served as negative controls. Among 102 otosclerotic patients, 62 stapes footplate samples contained measles virus RNA. Measles virus RNA was not detected in other bone specimens of the patients. The etiologic role of measles virus in the pathogenesis of otosclerosis should be considered. The 40 negative samples may be genetically determined otosclerotic cases or stapes fixations due to other causes.

Too much bone: the middle ear in sclerosing bone dysplasias

The middle ear changes in Sclerosteosis and Van Buchem disease are described. Reduced bone resorption occurs due to faulty activity of the sclerostin molecule, a product of the recently discovered SOST gene in chromosome 17. Syndactyly draws attention to scleroteosis, and a conductive hearing loss develops before age six in both conditions. Acute, repeated attacks of facial palsy, similar to Bell's palsy, are usually the first symptoms in both conditions. Total facial nerve decompression can stop the attacks of facial paralysis. The hearing loss is a problem because new bone formation continues up to age 21. Life saving craniectomy becomes necessary when increased intracranial pressure develops, and this may have to repeated. The sclerostin molecule is now of major interest to the researchers who want to develop a treatment for osteoporosis.

Stapes pathology in otosclerosis: scanning electron microscopic examination

The human stapes is still a subject of considerable interest both to the clinician and to the research investigator. This is due to the stapes position between the middle and inner ear, and because of its involvement in the otosclerotic process. The purpose of this study was to determine scanning electron microscopic and histopathological features of normal and otosclerotic stapes. The specimens were obtained from adult human temporal bones and during operation of patients with otosclerosis. Our results show that the surface of the normal stapes had various degrees of structural features. The otosclerotic stapes is characterized by a typical irregular pattern. Histological examination of the stapedial footplate or its fragments showed three types of otosclerotic lesions: fibrotic, sclerotic, and spongiotic. Our observations could support the hypothesis that otosclerosis is not a static disease.

Dynamic bone studies of the labyrinthine capsule in relation to otosclerosis

The pathological perilabyrinthine bone remodelling of otosclerosis is associated with a genetic predisposition and triggered by mechanisms so far unknown. A proposed viral aetiology of otosclerosis originates from a similar concept of Paget's disease. However, at present, it is not clear why a virus should cause otosclerosis, confined to the bony otic capsule with no effects on the general skeleton in some patients, and systemic Paget's disease with only occasional involvement of the bony otic capsule in others. Moreover, the extent and distribution of pathological bone remodelling is different in Paget's disease of the temporal bone and in otosclerosis. Bone resorption and consequently bone remodelling which turns over the general skeleton at a rate of 10% per year is normally highly restricted in perilabyrinthine bone to a minimum of 0.13% per year except in otosclerosis, and systemic remodelling rates are normal even in otosclerotic patients. This suggests the existence of a local inner ear mechanism in control of capsular remodelling activity, which is either overruled, bypassed or most likely defective in otosclerosis, no matter what may have triggered the disease process. We present experimental data related to this mechanism, which may offer a truly local pathogenetic factor in otosclerosis.

Some remarks on the histopathology of otosclerosis

The histopathology of otosclerosis is described in detail in classical textbooks like Schuknecht's Histopathology of the Ear or Friedmann and Arnold's Pathology of the Ear. In this article, some of the important and new facts will be summarized which might affect the understanding of the pathomechanism of this unique measles-virus-associated inflammatory disease of the temporal bone.

Otosclerosis and associated otopathologic conditions

Otosclerosis occurring with other pathologies has received little attention in the literature although these concomitant occurrences can be clinically relevant. We studied the clinical and histopathological characteristics of 182 cases of otosclerosis from our human temporal bone collection, and found 81 (44%) to have associated pathologies. Clinical pathological findings included vestibular symptoms and findings (e.g. Ménière's syndrome), otitis media in various forms, and to a lesser extent labyrinthine anomalies, tumors and other associated pathologies. Whether these coexisting pathologies are coincidental (usually) or causative as in the case of Ménière's syndrome with extensive otosclerosis, appropriate diagnosis and treatment of the patient with otosclerosis requires recognition of these potential clinical pathological relationships.