Otic capsule bony lesions in the Palmerston North autoimmune mouse

Otosclerosis is an otic capsule disorder of unknown etiology. While autoimmunity has been proposed as part of the etiopathogenesis of otosclerosis, no spontaneous autoimmune disease animal model has been identified. In the Palmerston North mouse, a model for systemic lupus erythematosus, sclerotic lesions consistently develop within the modiolus that are correlated with systemic autoimmune disease symptoms. No lesions were seen in 2-month-old mice, which is before autoimmune disease onset at 4 months. Lesions were first seen in mice at 6 to 8 months of age and increased in size and frequency thereafter. By 20 months, all ears examined had the otic capsule lesions, which were primarily perivascular in location and composed of both noncellular and cellular elements. The noncellular material was globular to fibrillar in arrangement and stained positively for calcium. The associated cells appeared to be metabolically active fibroblasts. It is proposed that the Palmerston North mouse may serve as a model to further investigate the role of autoimmunity in otosclerosis and other forms of otic capsule osteogenesis.

The incisor absent rat: an animal model for the study of otosclerosis

The incisor absent (ia) rat is introduced as an animal model for the study of otosclerosis. Previous animal models have failed to accurately reflect the dynamic nature of this disease. Auditory brainstem response testing suggested a conductive hearing loss in the incisor absent rat as compared to age-matched normal controls. The hearing loss, which was manifested during puberty, was progressive in nature up to 18 weeks of age. Microscopic dissection of the middle ear revealed bony abnormalities of the ossicles and oval window in the incisor absent rat. Scanning electron microscopy of the ossicles demonstrated bony lesions at the incudostapedial joint and stapes footplate. Histologic examination demonstrated thickened spongiotic bone involving the otic capsule and ossicles. The incisor absent rat model possesses an inheritable defect of the otic capsule and ossicles that results in a progressive conductive hearing loss. The genetically transmitted lesion appears histologically similar to otospongiosis. The bony pathology in the incisor absent rat is caused by defective osteoclasts and transplantation of bone marrow cells from normal rats to the incisor absent rats corrects the cellular abnormality. The incisor absent rat may represent the best animal model to date for the study of otosclerosis, its cause, and clinical treatment.

Otosclerosis involving the vestibular aqueduct and Menière's disease

The coexistence of otosclerosis and endolymphatic hydrops in the temporal bone have been described; however, the mechanism for the development of endolymphatic hydrops in otosclerosis remains unknown. Among 128 temporal bones with otosclerosis, involvement of the vestibular aqueduct by otosclerosis was observed in four temporal bones from two patients. In all four, the vestibular aqueduct was filled with active otosclerotic foci; the lumen of the endolymphatic duct and sac was narrowed as a result of fibrosis, and endolymphatic hydrops, more severe in the pars inferior than the pars superior, was observed. Collapse of the ductus reuniens and dilated saccule was seen in three temporal bones. Our study indicates that otosclerotic obstruction of the vestibular aqueduct may create a disturbance of the outflow and/or absorption of endolymph, leading to the development of endolymphatic hydrops and Meniere's disease, thus supporting the theory of longitudinal flow of endolymph.

Ultrastructural characterization of otospongiotic lesions in re-embedded celloidin sections

A technique of using re-embedded celloidin sections for ultrastructural analysis was used for the study of otospongiosis in human temporal bones. Celloidin sections stored in 80% alcohol with active lesions of cochlear otospongiosis were processed and re-embedded in epoxy resin. Semithin and thin sections were cut and analysed for a characterization of the ultrastructural cellular histopathology. The predominant cell types were found to be osteoblasts/osteocytes and macrophages. Lymphocytes were also noted but were rare. Several osteoblasts showed signs of active collagen and bone matrix production, indicative of ongoing new bone formation and repair. Macrophages often interacted physically to form cell clusters. The macrophages were frequently observed to endocytose the non-mineralized bone matrix as well as to degrade mononuclear cells presumed to represent osteoblasts. The observations may support the notion that increased osteolysis in active ostospongiosis is partly caused by a recruited osteoclast activity and partly by an impaired bone repair mechanism due to a macrophage digestion of osteoblast-deposited non-mineralized bone matrix. These two conditions may act in concert with cellular degradation of bone-producing cells.

Immunohistologic findings in otosclerosis

The cause of otosclerosis is still unclear. Between 1981 and 1988 we obtained 186 biopsy specimens of otosclerotic bone during the course of stapedectomies. Serial sections of the specimens were examined histologically (H & E) and immunohistologically (peroxidase-antiperoxidase technique) for immunoglobulin G, immunoglobulin M, and C1q and C3 complements. Active otosclerotic foci were found in 61 cases, 43 of which had IgG deposits. IgM antibodies were absent. In specimens with inactive otosclerosis, IgG and IgM were not evident, C1q and C3 complements were demonstrated together with IgG, but sometimes also in the mucosa independent of the phase of the otosclerosis. Our findings suggest that an immunologic process may be important in the pathogenesis of otosclerosis.

Cochlear otosclerosis: does bone formation affect cochlear implant surgery?

This study aimed to demonstrate that new bone formation in the scala tympani of patients deaf from otosclerosis does not preclude cochlear implant surgery. In seven temporal bones from patients with otosclerosis, we measured the extent of new bone from the round window to the distal part of the new growth. We compared results to surgical data on the extent of drilling and depth and ease of placement of the electrode in 20 patients deaf from otosclerosis. We also examined clinical performance and voltage requirements for long-term implant use in patients with and patients without ossification of the scala tympani. Findings in our limited sample of patients and bones show that obstruction of the basal turn, which occurs in some otosclerotic patients, does not preclude implant surgery. The dynamic range in the studied sample was relatively stable long-term and clinical performance did not differ between groups with and without an ossified scala tympani.

Menière's symptoms resulting from bilateral otosclerotic occlusion of the endolymphatic duct: an analysis of a causal relationship between otosclerosis and Menière's disease

An association between otosclerosis and Menière's disease has been proposed on both a clinical and temporal bone histopathologic basis for well over three-quarters of a century. Controversy persists over a causal relationship between these two entities, however, and the underlying pathophysiologic mechanisms relating capsular otosclerosis with Menière's disease remain speculative. The first case of total, bilateral endolymphatic duct occlusion resulting from extensive capsular otosclerosis is presented in a woman manifesting Menière's symptoms. The severe endolymphatic hydrops resulting from otosclerotic endolymphatic duct occlusion is given as histopathologic proof of a causal relationship between these two entities. Analysis of 18 of our own temporal bone cases of extensive capsular otosclerosis without endolymphatic hydrops and review of the literature indicates the uniqueness of such a firm causal relationship in the present case.

Pathology of the otic capsule

The otic capsule is unique in retaining calcified cartilage, known as globuli interossei, throughout life and shows changes consequently, which are peculiar to it. In Paget's disease of bone, the otic capsule appears resistant to involvement and this occurs with extensive disease at a late stage. In contrast, otosclerosis is a new bone formation of unknown cause that is limited to the otic capsule. In osteogenesis imperfecta, the poor formation of collagen leads to abnormally thin bony trabeculae with a poorly formed otic capsule. In osteopetrosis, the otic capsule is greatly expanded by increased globuli interossei, as a result of defective osteoclast function. When fractured the middle layer of the otic capsule does not form callus, but heals by fibrosis.

Immunohistochemistry of otosclerosis

Immunoglobulins G (IgG) and A (IgA) were found in plasma cells, osteocytes, chondrocytes and in connective tissue of active otosclerotic (= otospongiotic) lesions. The application of antibodies against paramyxovirus and rubella virus antigens reproducibly determined the expression of these antigens at different sites in the otosclerotic stapes, but also in the epithelial cells of the overlying middle ear mucosa. By using specific T-lymphocyte and B-lymphocyte markers, about 80% of the lymphocytes present in the otosclerotic footplate were revealed to be T-lymphocytes. There was neither deposition of immunoglobulins nor any expression of viral antigens in non-otosclerotic footplates which were investigated as controls.

Endolymphatic hydrops after fenestration: a temporal bone study with implications on the function of the utriculo-endolymphatic valve

A temporal bone specimen demonstrating endolymphatic hydrops 13 years after fenestration of the lateral semicircular canal is presented. Fibro-osseous tissue extending from the lateral semicircular canal and reaching the vestibule produced fixation of the membranous wall of the utricle to the bony wall. Fixation and retraction of the utricule appears to have resulted in a permanently open utriculo-endolymphatic valve leaflet. Similar findings of fibro-osseous changes arising from the area of the crus commune and an open valve were found in a Meniere's disease specimen. The implications of these findings on the function of the valve are discussed.

Temporal bone laboratory training for stapedectomy

Practice in the Temporal Bone laboratory is a fundamental part of Otological training. Performing a stapedectomy on a normal temporal bone is handicapped by the mobility of the footplate. We describe a simple method of producing stapes footplate fixation in a normal temporal bone so that the operative conditions found in otosclerosis are more closely simulated.

Electron microscopy of hyalin bodies in the human intraosseous endolymphatic sac

Hyalin bodies are amorphous, eosinophilic masses protruding from the subepithelial connective tissue into the lumen of the intraosseous endolymphatic sac (ES). We studied hyalin bodies at the electron microscopic level. Celloidin- embedded temporal bone sections known to have hyalin bodies were re-embedded into plastic and cut into thin sections appropriate for electron microscopy. The results revealed that the hyalin bodies are composed predominantly of thick bundles of collagenous fibers arranged in various directions. Fibroblasts and disintegrated macrophages were occasionally observed among the collagen fibers. Concentric calcific structures found within the hyalin bodies were composed of multiple smaller, concentric, lamellar calcifications. The results of this study support the hypothesis that the hyalin bodies are a repository of membranous cellular debris phagocytized by the macrophages.

Histologic and statistical studies on hyalin bodies in the human endolymphatic sac

Hyalin bodies are amorphous, eosinophilic masses that protrude from the subepithelial connective tissue into the lumen of the endolymphatic sac. In this study, hyalin bodies were analyzed in two groups of temporal bones: normal bones and bones with cochlear otosclerosis. The results revealed that bones with cochlear otosclerosis had significantly more and larger hyalin bodies that did normal bones. In addition, the hyalin bodies in cochlear otosclerosis were denser and associated with more edema and loose connective tissue in the surrounding areas. Foamy macrophages, concentric calcific structures, and bony ingrowth were frequent features of the hyalin bodies in the cochlear otosclerosis. Our current hypothesis is that these hyalin bodies are repository of membranous cellular debris phagocytized by the macrophages. If this is true, the hyalin bodies may further support the proposed resorptive and phagocytic functions of the endolymphatic sac and the enzymatic concept in cochlear otosclerosis.

Mastoid pneumatization in otosclerosis

The extent of mastoid pneumatization in 150 otosclerotic ears was compared with that of 150 healthy control ears. The size of mastoid pneumatization was measured by use of the Schüller lateral x-ray projection with the help of computed planimetry. The measurements showed the average pneumatized area in otosclerotic ears to be 17.4 +/- 5 cm2, in contrast to 12.9 +/- 4 cm2 for the healthy control ears. The difference between the two groups was highly significant (p less than .0001). While both groups showed a bell-shaped distribution of the measured pneumatized area, the curve of the otosclerotic ears was shifted significantly to the right. Our findings indicate a link between otosclerosis on the one hand and highly pneumatized mastoids on the other. This link between a hereditary disease and a specific type of pneumatization points to the likelihood that heredity also plays some role in determining the final type of pneumatization.

[Otosclerosis. A paramyxovirus-induced inflammatory reaction]

Despite intensive investigation the cause of otosclerosis remains unknown. Recent immunohistochemical and electron microscopic studies of otosclerotic stapes have revealed a possible viral aetiology. Therefore we investigated the histology, ultrastructure and immunohistochemistry of fragments of otosclerotic footplates. Immunoglobulins G (IgG) and A (IgA) were found in plasma cells, oseocytes, chondrocytes and connective tissue of the active lesions. Polyclonal and monoclonal antibodies against paramyxovirus and rubella virus antigens produced reproducible reactions with these antigens at different sites of otosclerotic stapes, especially in the epithelial cells of the overlying middle ear mucosa. Using specific T-lymphocyte and B-lymphocyte markers about 80% of the lymphocytes present in the otosclerotic footplate proved to be T-lymphocytes. There was neither deposition of immunoglobulins nor any expression of viral antigens in non-otosclerotic footplates which were investigated as controls. Our results indicate that otosclerosis is an inflammatory reaction of the otic capsule initiated or caused by paramyxovirus and/or rubella virus. The silent progress of the disease and its onset under certain conditions, e.g. endocrine upsets, show similarity to slow viral infections.

Cochlear hair cell stereocilia loss in LP/J mice with bone dysplasia of the middle ear

LP/J inbred mice spontaneously develop bony lesions of the middle ear and otic capsule that are similar to those of human otosclerosis and tympanosclerosis. These mice also have progressive loss of hearing due to cochlear hair cell loss. The purpose of this study was to describe quantitatively the deterioration and loss of cochlear hair cells to serve as a basis for future experiments attempting to alter the course of this disorder. Cochleas from 37 LP/J inbred mice were examined by scanning electron microscopy. The stereocilia loss in the cochlea was evident as early as 15 weeks of age and progressed from the basal turn to the apex. Outer hair cells were affected more than inner hair cells. As outer hair cells deteriorated we observed fusion, bending, and breakage of stereocilia. There were no apparent differences in the mode of deterioration among the three rows of outer hair cells. Stereocilia fusion of inner hair cells occurred at an older age, and giant, elongated stereocilia were found in some of the animals.

Altered adenylate cyclase activity in human otosclerotic bone cell cultures

Adenylate cyclase (AC) activity was studied in whole homogenates of normal and otosclerotic bone cell cultures. When Mn2+ or Ca2+ was added to the medium there was a similar increase in AC activity in both cell types. F- provoked a greater rise in normal than in pathological cells, whereas 0.01 mM guanosine triphosphate (GTP) significantly raised cAMP synthesis in otosclerotic cells only. Mn2+ + calcitonin (Ct) increased AC activity in both cell preparations. With Ca2+ as cofactor there was no significant rise in either normal or pathological cells. However, while the combination Ca2+ + Ct + GTP had little effect on normal cells, it markedly increased cAMP synthesis in the pathological cells. 1 microgram/ml of the beta-blocker propranolol inhibited the effect Ct exerts on AC in normal cells, but enhanced it in otosclerotic cells. It would, therefore, seem that the pathogenesis of otosclerosis could be associated with an alteration in the AC system associated with Ct receptors.

Correlation of otosclerotic foci and degenerative changes in the organ of Corti and spiral ganglion

Statistical analyses of histopathologic findings in the cochlea and spiral ganglion of 37 temporal bones with otosclerosis, 12 controls of similar age, and seven controls with normal hearing were performed. In temporal bones with otosclerosis there was significant atrophy of the spiral ligament and stria vascularis in regions with endosteal involvement by otosclerosis, compared with regions without endosteal involvement (P less than .0001). There was more generalized atrophy of the stria vascularis in cochleae with two or more sites of endosteal involvement by otosclerosis than in cochleae with only one site of endosteal involvement (P less than .02), cochleae in temporal bones with otosclerosis but without endosteal involvement (P less than .05), or cochleae of controls of similar age (P less than .007). In addition, there was more atrophy of the spiral ligament in cochleae with two or more sites of endosteal involvement than in cochleae of similar age from the control group (P less than .03). In temporal bones with otosclerosis, there was no significant difference in counts of outer hair cells and density of spiral ganglion cells between regions demonstrating endosteal involvement by otosclerosis and regions without such involvement. However, total outer hair cell counts were lower in cochleae with two or more sites of endosteal involvement of otosclerosis than in cochleae with one site of endosteal involvement (P less than .04), cochleae in temporal bones with otosclerosis but without endosteal involvement (P less than .02), or cochleae from individuals of similar age but without otosclerosis (P = .05). Comparison of the mean bone conduction threshold, as measured in life, in temporal bones with otosclerosis compared with the air conduction threshold in aged-matched controls, demonstrated that only cochleae with two or more sites of endosteal involvement had a mild but statistically significant (P = .05) decrease in hearing. There was no evidence to support the concept that otosclerotic foci without stapedial fixation frequently cause significant degeneration of the cochlea or elevation of bone conduction thresholds.

Osteoclasts in chronic otitis media, cholesteatoma, and otosclerosis

Bone resorption and remodeling are characteristic of chronic otitis media with and without cholesteatoma and otosclerosis. The consequences of this remodeling process may be hearing loss, repeated infection, vestibular disturbance, or intracranial complications. Evidence of osteoclastic bone resorption was found in surgical specimens of 11 of 24 cases of cholesteatoma, two of three cases of chronic otitis media, and three of ten cases of otosclerotic stapes; all three spongiotic lesions had osteoclasts. With careful serial sectioning these cells are almost always multinucleate and have the typical appearance of osteoclasts with ruffled borders. Some specimens had evidence of bone erosion in the absence of osteoclasts; this finding represents an inactive phase of the remodeling process. Since the osteoclast plays an important role in the resorption and remodeling of bone in these middle ear diseases, the source, physiology, and local control of these cells are of prime importance in investigating the pathophysiology of these diseases. At the present time, the local control of activation and recruitment of osteoclasts, as well as their chemotactic responses, is poorly understood.

Otosclerosis--an inflammatory disease of the otic capsule of viral aetiology?

Fragments of otospongiotic and otosclerotic footplates were investigated by immunohistochemical methods. Antibodies IgG, IgA, IgM were found to be bound to the vascular connective tissue of the resorption lacunae, IgG also to osteocytes. The application of antibodies against mumps, measles and rubella antigens showed the expression of the relevant viral antigens in the large cells of the resorption lacunae, in the vascular connective tissue, and in osteocytes, osteoclasts and chondrocytes, present in or around the otospongiotic areas. In the sclerotic stage only the perivascular connective tissue and chondrocytes have expressed viral antigens whereas IgG was restricted to the osteocytes of the sclerotic focus and to the residual perivascular tissue. Two footplates with postinflammatory sclerosis serving as controls revealed only IgG in some chondrocytes. Healthy footplates showed neither a deposition of antibodies nor any expression of viral antigens. These results favour a viral aetiology of otosclerosis as an inflammatory vascular reaction of the otic capsule initiated or caused by the viruses of measles, rubella and mumps.

Surgically confirmed clinical otosclerosis among the Chinese

We report herein on 163 cases of surgically confirmed otosclerosis among Chinese. Our results suggest significant racial differences between Chinese and whites in respect to the incidence of this disease, and the likelihood of a family history. Surgical and histopathological findings, while confirming otosclerosis identical to that experienced in whites, suggest that generally the disease is milder among Chinese. The sex ratio, age range, and bilateral involvement, on the other hand, were discovered to be basically similar between the two races. A detailed description is given of the postauricular surgical technique used, and it is argued that it may be more suitable in cases where there is a small ear canal, since the results achieved (80% success rate) are comparable with other reports.

Study on normal and otosclerotic bone cell cultures: an advance in understanding the pathogenesis of otosclerosis

The authors first reviewed the main theories concerning the pathogenesis of otosclerosis and studied the morphologic and functional characteristics of cell cultures derived from normal and otosclerotic bones. Light transmission and scanning electron microscopy did not permit definite identification of the cultured cells as predominantly osteoblasts, nor did these techniques show significant differences between cultured cells derived from normal and pathologic bone. Functional tests of the cell cultures proved more interesting. First, the bony nature of the cultured cells was demonstrated by studying the intracellular 45Ca++ uptake after stimulation with calcitonin and dybutryl-cAMP. Second, cell cultures derived from otosclerotic bone behaved differently from those derived from normal bone. Their peak uptake of calcium appeared later, and post-stimulatory values were higher, suggesting that cells derived from otosclerotic bone store a greater quantity of 45Ca++. Furthermore, after stimulation with calcitonin and propranolol, we observed an inhibition of the calcium uptake and decreased intracellular cAMP levels in normal bone cell cultures. In contrast, the cell cultures derived from otosclerotic bone exhibited an initial inhibition of calcium absorption followed by massive calcium penetration. The response of adenylate cyclase to the action of Mg++, Ca++, and F- ions was evaluated in cultures derived from normal bone, otosclerotic bone, and normal skin fibroblasts. The resulting data show that activation due to Mg++ is much lower in cultured cells derived from otosclerotic bone than in those from either normal bone or skin fibroblasts. No significant differences were found after Ca++ inhibition in any of the cell cultures. Moreover, in cell cultures derived from normal bone, F- ions induced a strong activation that was lower than the levels observed in cultures of otosclerotic bone or in normal fibroblasts. We hypothesize that an alteration at the calcitonin receptor site is responsible for the difference in calcium uptake and cAMP levels observed in the cells derived from otosclerotic bone as compared to those cultured from normal cells.

Multiple otopathologic disorders

Temporal bones (1,383) from 713 patients were studied systematically for multiple pathologic lesions. Eleven percent (152 temporal bones) were found to have more than one pathologic finding. Males (60.5%) had multiple diseases more commonly than did females (37.7%). The most frequently occurring findings were otitis media (71.1%), otosclerosis (43.4%), endolymphatic hydrops (38.8%), labyrinthitis (25.0%), and cancer (24.3%). We conclude that multiple coexisting pathologic conditions can have coincidental or causative relationships. The otolaryngologist should consider multiple pathologic conditions when diagnosing and treating diseases of the ear.

Persistent stapedial artery associated with otosclerosis

A 43-year-old female had bilateral otosclerosis with a persistent stapedial artery in the left ear which measured approximately 0.4 mm in diameter, lying on the floor of the tympanic cavity, running between the crura of the stapes and entering the facial canal. Stapedectomy was performed following section of this vessel and controlling the hemorrhage. Satisfactory hearing gain was obtained in both ears after stapedectomy.