Current clinical and pathological features of round window diseases

The round window niche and membrane can be involved in clinical problems including perilymphatic fistulas, sensorineural hearing loss in otitis media, and a variety of others. The background of these problems is documented by a review of the literature and recent experimental evidence on round window grafting and tracer studies. Clinical pathological correlates including recent clinical experience are discussed for perilymphatic fistulas (sudden deafness, chronic progressive fluctuating sensorineural hearing loss, and association with Meniere's disease), sensorineural hearing loss in acute and chronic otitis media, and findings in round window membrane including absent round window reflex in cases of exploratory tympanotomy and otosclerosis. In addition, a new syndrome termed perilymphatic hypertension is described as seen in a subset of patients with sudden sensorineural hearing loss.

The possible role of immunologic injury in the dysplastic bony lesion in LP/J mice

An immunohistologic study was performed on temporal bones from 30 LP/J mice and 17 CBA/J mice to assess the role of immunologic injury in the pathogenesis of dysplastic bony lesions in LP/J mice. Temporal bones were harvested from animals aged 2 to 31 months to evaluate the progression of the disease. As early as 2 months of age, before the onset of bony lesions, the tympanic cavities frequently contained small effusions coating the ossicles and otic capsules that were demonstrated to contain immunoglobulins and pockets of macrophages. Later in the course of the disease, bony lesions grossly and histologically similar to human otosclerosis developed, which stained for immunoglobulins. No similar bony lesions, effusions, cellular infiltrates, or staining for immunoglobulins was detected in the control animals, even in the presence of acute otitis media. This study suggests a role of immunologic injury in the pathogenesis of dysplastic bony lesions in LP/J mice.

Morphologic and immunohistochemical observation of otosclerotic stapes: a preliminary study

Stapes with otosclerotic lesions obtained during stapedectomies were examined with light microscopy, histochemistry, immunochemistry, and electron microscopy to elucidate the cellular mechanism(s) involved in this disease process. Three types of lesions were identified: cellular (spongiotic), fibrotic, and sclerotic. The cellular type is characterized by monocyte, macrophage, osteoblast, and osteoclast recruitment and their activation. Macrophage recruitment is an early event of otosclerosis. The fibrotic type is characterized by extensive fibrosis of the bone, and the sclerotic type is characterized by a paucity of bone cells. Cytochemical results showed a large accumulation of granular substances positive for periodic acid-Schiff stain along the edge of the marrow spaces coinciding with ultrastructural calcospherite deposits, suggesting that glycosaminoglycans are involved in the mineralization process. Acid phosphatase is largely localized in the osteoclasts, but a sporadic diffusion of this enzyme was observed in the demineralizing front of the preotosclerotic lesion. Immunoglobulin G and complement C3 were colocalized in pericapillary tissue, suggesting deposit of immune complex in the spongiotic lesion. This finding indicates a possibility that immune mechanisms are involved in otosclerosis.

Pathology of otosclerosis: a review

Otosclerosis is a bone disorder of unknown etiology confined to the otic capsule. Failure of remodeling of newly formed vascular, woven bone (otospongiosis) results in sclerotic bone (otosclerosis) with abnormal osteons. Involvement of the oval window causes conductive hearing loss. Electron microscopic, histochemical, and biochemical studies identify normal cellular and matrix components of otosclerotic bone without providing clues to the abnormal bone formation and resorption. Plastic-embedded, nondecalcified histologic sections with in vivo tetracycline labels permit the study of mineralization rates to separate this disorder from other bone dyscrasias that have similar histopathologic appearances. Characterization of the cells, matrix, and their mediators can yield an understanding of abnormalities that disorder bone.

Otosclerosis and sensorineural hearing loss: a histopathologic study

The precise role and mechanism whereby otosclerosis is associated with sensorineural hearing loss remains unclear. Previous histopathologic reports are inconsistent with regard to the location of the otosclerotic focus, invasion of the otic capsule, and the number of remaining peripheral sensorineural elements. From the combined temporal bone collections of the University of Chicago and the Mayo Clinic, we identified a group of 125 ears from 80 patients, all with confirmed otosclerosis. Six of these ears were associated clinically with sensorineural hearing loss without stapes fixation. The histopathology of the otosclerotic focus was reviewed in terms of its location and depth of invasion. The cochlea and spiral ganglion were reconstructed, and the state of the organ of Corti and the presence or absence of peripheral cochlear nerve fibers were noted. Correlations with ganglion cell counts were made. The present study showed that the pattern of degeneration of peripheral sensory and neural elements in the cases presented is very similar to that found in cases of age-related processes such as presbycusis.

Otosclerosis: a local manifestation of a generalized connective tissue disorder?

The hypothesis that otosclerosis is a local manifestation of a clinically and genetically heterogeneous group of generalized connective tissue disorders was tested by quantitative biochemical techniques. In contrast to previous studies, no significant differences were found in individual glycosaminoglycans excreted in urine of control subjects and patients with otosclerosis. Moreover, no significant differences were detected in the rate of synthesis and secretion of glycosaminoglycans and collagen in skin fibroblast cultures of patients and controls. Preliminary results obtained with more sensitive and specific methods suggest a possible error in collagen metabolism. Polyacrylamide gel electrophoresis revealed slight differences in migration patterns of several collagenous proteins between patients and control subjects. In addition, collagenase was significantly increased in three of five patients.

Fine morphology of bony dysplasia of the murine ear: comparisons with otosclerosis

Dysplastic bony lesions that bear certain similarities to otosclerosis occur spontaneously in LP/J inbred mice. These lesions develop after the fifth week of life and progressively enlarge; they are present in 90% of animals by 90 weeks of age. In the present study, the fine morphology of these lesions was investigated. Dysplastic lesions in the middle ear of LP/J mice appeared to begin as subperiosteal accumulations of amorphous material. These accumulations occurred adjacent to the bone surface below the epithelium of the middle ear. This amorphous material was often associated with macrophages on the adjacent epithelial surface. The material appeared to be replaced with collagen fibers in a disorganized manner, forming a homogeneous base (osteoid) on which calcification occurred. The fine morphology and periodicity of the collagen appeared normal. The lesions then calcified by forming calcospherites that became confluent. During this period, transformed fibroblasts (osteoblasts) appeared in the calcifying matrix, resulting in a lesion made of bone. These lesions could sometimes be seen replacing normal bony contours but most often were exophytic. The lesions at all stages of development may be associated with macrophages and effusions in the middle ear. The lesions in the middle ear of LP/J mice appeared to develop by an active process of bone formation; in contrast, otosclerosis is an active process of bone resorption and formation.

Bone resorption in experimental otosclerosis in rats

Localized bone resorption in the otic capsules of experimental rats was induced by immunization with type II collagen. The otospongiosis-like lesion showed enlarged vascular spaces that contained many fibroblasts and macrophages as well as occasional osteoclasts. A high level of acid phosphatase activity in the sera of immunized rats suggested that this enzyme is one of the important factors causing decalcification of the bony otic capsule, the first step of bone resorption. Immunofluorescent assay showed that collagenase and cyclooxygenase (prostaglandin synthetase) appeared within macrophages, fibroblasts, and osteoclasts in the bone resorption areas. These findings suggest that the collagenase and prostaglandin synthetase being produced by macrophages, fibroblasts, and osteoclasts are also involved in the processes of bone resorption in otospongiosis. Immunolocalization assay showed deposition of immunoglobulin and fibronectin on the bone matrix and vascular wall within the otospongiotic lesions. Chemotaxis studies showed that both anti-type II collagen serum and fibronectin might play a role as chemoattractants to recruit macrophages and fibroblasts to the bone resorption sites. In vitro studies also showed anti-type II collagen serum stimulates the fusion of macrophages to become multinucleated osteoclast-like cells. The antiserum also activate these cells to produce collagenase and prostaglandin synthetase. It is concluded that the chemotactic processes of macrophages and fibroblasts, the multinucleation of macrophages, and the activation of these cells may be basic processes causing bone resorption in otosclerosis. When sodium fluoride, an inhibitor of hydrolytic and proteolytic enzymes, was given to rats immunized with type II collagen, no obvious inhibition of bone resorption was seen in histologic sections.

Histological and morphological observations of the paravestibular canaliculus

The paravestibular canaliculus was studied by light microscopy in serial sections of the temporal bones from otosclerotic patients who underwent fenestration or stapes surgery. In all examined 23 specimens (13 cases), the endolymphatic duct and sac were observed to be normally developed with no pathological findings. The paravestibular canaliculus was found in 14 of the specimens (60.9%). Its course was traced from the proximal to the distal area in 12 specimens, and it appeared to merge into the distal portion of the endolymphatic sac in 7 of them. Twelve of the paravestibular canaliculi contained one vein, and 3 contained several veins. No artery was found. The paravestibular canaliculus was observed to originate from small vascular channels around the vestibule in the otic capsule, lateral to and near the internal aperture of the vestibular aqueduct.

Densitometry of the cochlear capsule and correlation between bone density loss and bone conduction hearing loss in otosclerosis

Radiodensity of the bony cochlear capsule was investigated by CT-scanning in 134 ears with otosclerosis and 35 normal control ears. A technique of densitometry of the cochlea was developed comprising the measurement of maximum and minimum density together with mapping of the cochlea and measurement of the density at six predefined points in the cochlear capsule. Bone density in the normal cochlea showed very little interindividual variation. In the otosclerosis patients, minimum density was decreased in 58% of the ears, indicating the presence of a focus. At visual examination, foci were only detectable when density loss exceeded 200 Hounsfield. A positive correlation was found between bone density loss and bone conduction hearing loss with a maximum at 2,000 Hz and the medioventral point of the cochlear wall. The method appears to be useful for the follow-up during fluoride treatment, as is demonstrated by a case report.

Stapedectomy and round window closure

Round window closure is an uncommon complication of advanced otosclerosis found in 1% of 30,000 stapedectomy cases. A review of 81 patients representing 110 operation cases was made to determine what factors may alert the otologic surgeon to the patient with round window closure and what factors may identify the patient who will achieve the greatest benefit from stapedectomy.

Experimental tympanosclerosis following infection with Streptococcus pyogenes and vitamin D3 intoxication

A rat animal model was used to study the ultrastructure of submucosal calcifications induced in the middle ear following inoculation with Streptococcus pyogenes and high doses of parenteral vitamin D3. The morphological changes present in affected animals resembled the classical picture of tympanosclerosis. While calcification occurred about bacterial remnants and myelin structures, the most important calcification centers were lysosomal and non-lysosomal matrix vesicles in the extracellular spaces. These formed band-like calcifications close to the basal membrane without affecting the epithelial layer. This animal model offers the possibility of studying the effect of various therapeutic regimens in the treatment of the dynamic tympanosclerotic process.

Type II collagen-induced otospongiosis-like lesions in rats

Otospongiosis-like lesions were induced in rats by immunizing them with type II collagen. After seven months' immunization, the rats were killed and processed for histologic study. We found otospongiotic lesions in the bony cochlea, vestibule, semicircular canal, and in the regions near the oval window and round window. The spongiotic lesions in the otic capsules were similar to human otospongiosis and were characterized by the following types of microscopic appearances. 1) The classic type showed enlarged vascular spaces with congestion, macrophages, fibroblasts, and sometimes osteoclasts. 2) The fibrotic type showed vascular spaces filled with fibrous tissues. 3) The osteoporotic type had a porous appearance and was devoid of content. 4) The sclerotic type showed bone spaces partially or entirely being replaced by new bone with blue mantles and a mosaic appearance. Some spongiotic lesions showed a mixture of the above types. The findings suggest that this animal model may provide important information to help understand the process of human otosclerosis.

Temporal bone showing polyarteritis nodosa, otosclerosis, and occult neuroma

The clinical and general histopathologic manifestations of systemic vasculitis of the polyarteritis nodosa type are well known. Although hearing loss associated with polyarteritis nodosa has been reported, only two temporal bone studies are available. The findings in a 60-year-old man with well-documented hearing loss who had rheumatoid arthritis, polyarteritis nodosa, and otosclerosis are presented. Polyarteritis nodosa extensively involved the subarcuate arteries and arteries of the facial canal. There were decreased nerve fibers to and sensory cells in the crista of the semicircular canals and macula of the utricle and saccule. Focal and diffuse atrophy of the stria vascularis and decreased cellularity in the spiral prominence and ligament were present. There was a loss of outer hair cells. Otosclerosis involved the left and right oval window niches (bilateral stapedectomy had been performed). There was a small Antoni type A neuroma of the superior division of the vestibular nerve on the left.

Dynamics of otosclerosis-like lesions in LP/J mice

The LP/J inbred mouse is the first known animal to spontaneously develop otosclerosis-like bone lesions in the middle and inner ear. These abnormal bone foci resemble human otosclerotic lesions, are inherited, and produce a progressive hearing loss. On the basis of histological evaluation alone, it was unclear whether these otosclerosis-like lesions in LP/J mice develop suddenly or gradually as in human otosclerosis. To study the dynamics of lesion formation, four different colored fluorochrome bone labels were given in sequence to postpubertal LP/J mice and CBA/J mice as normal controls. All of the otosclerosis-like lesions incorporated at least one fluorochrome, and half were labeled with two or more markers indicating continuous lesion growth over many weeks. It appears that otosclerosis-like lesions in LP/J mice develop during early adulthood and progress gradually as in human otosclerosis.

Filamentous structures morphologically similar to viral nucleocapsids in otosclerotic lesions in two patients

Two of four patients with active stapedial otospongiosis had abnormal filamentous structures in osteoblast-like cells. These structures were rare in these cells and did not occur in any other cells. The structures were 17 nm wide and clustered in a loose skein in dilated cisternae of the rough endoplasmic reticulum. They resembled the nucleocapsids of subacute sclerosing panenecephalitis, a variant of measles virus.

Histologic variants in otosclerosis

A study of 164 temporal bones with otosclerosis revealed stapes fixation in 123. Large lesions (4 mm or larger) were characterized by involvement of the cochlear endosteum, increased cellular activity, and bone resorption. Anatomical sites of predilection were: 1. anterior to the oval window, 2. margins of the round window, and 3. apical-medial wall of the cochlea. Two of the five ears with cochlear otosclerosis were from a patient with severe bilateral hearing loss. The size, cellular activity, and location of otosclerotic lesions showed no correlation with the magnitude of sensorineural hearing loss. Subjects over 69 years of age had greater bone-conduction losses than age-matched controls. Nine ears showed occlusion of the round window niche.

Ossicular and otic capsular lesions in LP/J mice

Otosclerosis is an inherited disease in which abnormal bone growth results in ossicular fixation and hearing loss. Although the disease affects up to 10% of humans, it has not been observed in other animals. The LP/J inbred mouse has been found to develop abnormal bony lesions of the middle ear which resemble human otosclerosis. In this study of 113 temporal bones from LP/J mice, we found that the lesions develop after puberty and involve only the ossicles and the otic capsule. The most frequent site of involvement was the incus (46.9%), followed by the anterior crus of the stapes (31.3%), the malleus (14.2%), the otic capsule (14.2%), and the stapes footplate (8%). Cochlear hair cell loss was progressive throughout the lifespan of these animals. Although this disease is not identical in histologic appearance to human otosclerosis, understanding its disease process may shed light upon the pathophysiology of the human disease.

Vitamin D deficiency and otosclerosis

A prospective study of 47 patients with otosclerosis was undertaken to investigate the possible etiologic role of vitamin D undernutrition. The population comprised 27 women and 20 men, with a mean age of 46.4 years (range 21 to 79). The disease was bilateral in 43 patients, and cochlear involvement was present in 84.4%. The mean duration of symptoms was 17.1 years. Vitamin D status was evaluated by measuring the plasma 25-hydroxy vitamin D3 (25-OHD), which is the main storage metabolite. Abnormally low 25-OHD levels were found in 10 patients (21.7%) and borderline low levels in another two. Raised serum alkaline phosphatase levels were present in 32.6%, calcium in 6.5%, and inorganic phosphate in 4.3%. Calcium and vitamin D replacement therapy resulted in significant hearing improvement in 3 of 16 patients; these data support a causal correlation. Vitamin D deficiency is probably a factor in the etiology of some cases of otosclerosis and is important, since the deafness resulting from cochlear involvement may be reversible.

Histopathology of the stapes in osteogenesis imperfecta

Conventional histological studies of stapes footplates from patients with osteogenesis imperfecta revealed, in nine out of 15 stapes examined, an otospongiotic-like lesion. Although the morphology of the stapedial lesion was comparable to the early otosclerotic focus, a greater structural disorganization and larger resorption spaces in osteogenesis imperfecta distinguished the two conditions. The histopathology of the stapes was related to the morphology of cortical and trabecular bone from the iliac crest. Various degrees of immature, osteogenic bony tissue were found in the iliac crest, showing no resemblance to the otospongiotic-like focus in the footplate. Even though the histologic appearance of the stapes footplates differed from the findings in peripheral bone, the present study indicates that the stapedial lesion in osteogenesis imperfecta is most likely a manifestation of the generalized bone and connective tissue disorder. The study further supports the view that osteogenesis imperfecta and otosclerosis are of different aetiology.

The investigation and management of petrous apex erosion

Disease of the apex of the petrous temporal bone, while rarely encountered, can present a unique challenge to the otologist. Lesions tend to be advanced at presentation, as massive bony erosion can remain asymptomatic. When symptoms occur, they reflect involvement of the neurovascular contents of the temporal bone. The earliest clinical features, such as headache, facial numbness and middle-ear effusion, do not immediately suggest the site or gravity of the underlying pathology. Anterior extension of disease may produce ophthalmoplegia and diplopia whilst posterior spread involves the lower cranial nerves, within the internal auditory canal, jugular foramen and hypoglossal canal. Evaluation of apical disease relies on radiological evidence of bony erosion and should include polytomography, CT scanning and angiography. The clinical features and radiological findings in a series of patients with various apical lesions are presented. The surgical approaches reviewed aim to reconcile the need for adequate access to this remote site, with the desire to preserve residual facial nerve and cochlear function and to protect the brain-stem.