Prevalence of otosclerosis in an unselected series of temporal bones

BACKGROUND

Histologic otosclerosis is a disease process without clinical symptoms or manifestations that can be discovered only by sectioning of the temporal bone at autopsy. Clinical otosclerosis is otosclerosis at a site where it causes conductive hearing loss by interfering with the motion of the stapes or of the round window membrane. Various authors have studied the prevalence of histologic otosclerosis on laboratory collections of temporal bones. Some 12% to 15% of temporal bones with histologic otosclerosis have demonstrated stapedial fixation. Using these figures for calculating the prevalence of clinical otosclerosis gives an extrapolated clinical prevalence of 0.99% to 1.2%. This does not correlate well with the clinical data on otosclerotic families, from which a clinical prevalence of 0.3% has been estimated.

OBJECTIVE

To study the prevalence of histologic otosclerosis in an unselected series of temporal bones.

STUDY DESIGN

During a 1-year period, 118 consecutive pairs of temporal bones of deceased patients at a tertiary care center were collected to determine the prevalence of otosclerosis. Although histology remains the gold standard for evaluation of otosclerosis, the gross observation of temporal bone slices combined with microradiography was used to screen for otosclerotic lesions more rapidly and with a lower cost/benefit ratio. The temporal bones, which were suspected of having otosclerosis with these techniques, were further analyzed by conventional histology.

RESULTS

2.5% of the 236 temporal bones (or 3.4% of patients) studied demonstrated histologic otosclerosis.

CONCLUSIONS

Although the prevalence of 2.5% is much lower than previously published figures on histologic otosclerosis, the extrapolated data (extrapolated clinical prevalence = 0.30% to 0.38%) correlate well with clinical studies of otosclerotic families. The previous studies based on laboratory collections were likely biased by hearing loss or other otologic diseases.

Mitochondrial cytochrome oxidase immunolabeling in aged human temporal bones

Presbycusis, an age-related hearing loss, is accompanied by histopathological cochlear changes including variable amounts of degeneration of the auditory receptors, neurons and the stria vascularis. The causes of degeneration are unknown, although acoustic trauma and exposure to ototoxic agents are certainly contributors to the cellular degeneration. Acquired mitochondrial DNA defects are postulated as important determinants of aging in neuromuscular tissues. The cochlear neurons are highly metabolic and are, therefore, likely to be affected by mitochondrial DNA defects. Sequence analysis has demonstrated a significant number of acquired mutations in the cytochrome oxidase gene in the neurons from aged human cochleas. The current study used immunohistochemical labeling of cytochrome oxidase in the neuronal cell bodies in archival celloidin sections to evaluate relationships among label density, hearing loss, number of neurons and mitochondrial DNA changes within individual cochleas. Label density was less in many aged temporal bones, but not all. There was no relationship among any other variables. It is concluded that while there may be a decrease in the amount of cytochrome oxidase expression in aged spiral ganglion cell bodies, there are many other factors that contribute to hearing loss and cellular degeneration.

Histologic Studies of the Posterior Stapediovestibular Joint in Otosclerosis

OBJECTIVE

To determine the prevalence of ankylosis or otosclerosis at the posterior stapediovestibular joint (SVJ) in temporal bones with otosclerosis, with special reference to stapes surgery.

BACKGROUND

Long-term success of the laser stapedotomy minus prosthesis (STAMP) procedure, anterior crurotomy, and similar partial stapedectomy procedures depends on lack of ankylosis and lack of otosclerosis involving the posterior SVJ. Previous work has shown that the air-bone gap in otosclerosis correlates with narrowing and loss of the SVJ space. However, the prevalence and histologic features of otosclerotic involvement of the posterior SVJ space have not been well characterized.

METHODS

Histologic assessment of serial sections through the oval window niche in 140 temporal bones with otosclerosis that had been sectioned in the axial plane (age range 20-95 years, mean 68). Bones with stapes mobilization or stapedectomy were excluded.

RESULTS AND CONCLUSIONS

Two of 140 bones had otosclerosis exclusively at the posterior SVJ. Of the remaining 138 bones, all of which had otosclerosis at the anterior SVJ, 82 bones also had otosclerosis at the posterior joint. Of the 56 bones without otosclerosis of the posterior joint, there was bony ankylosis of the posterior joint in 3 bones. Thus, 53 bones (38%) had neither ankylosis nor otosclerosis involving the posterior joint, and they would be potentially suitable for a laser STAMP or a similar procedure. There was no correlation between otosclerosis at the posterior SVJ and age, sex, or duration of conductive hearing loss. Otosclerosis at the posterior joint in one ear was significantly associated with its presence at the posterior joint in the opposite ear (p = 0.01). The audiogram could not be used to reliably predict otosclerotic involvement of the posterior SVJ or the degree of footplate pathologic changes, such as ankylosis.

[Otosclerosis and Van der Hoeven's syndrome: a contribution]

Morphological and microchemical changes that effect to the otosclerotic stape in the Van der Hoeve's syndrome were examined with a scanning electron microscope equipped with an energy dispersive X-ray fluorescence. Using the Ca/P ratio as criterion--measured by the characteristic x-ray fluorescence--it was shown that the Van der Hoeve stape had a higher Ca/P ratio (2.6:1) as compared to the normal stape (2:1). The Van der Hoeve's syndrome lesions as poorly mineralized, with low calcium salt and apparent increase of phosphates. This finding indicates a possible change from hydroxyapatite (or apatite) to brushite, which imply an acidification of bone.

Pathophysiology of otosclerosis

OBJECTIVE

To review current knowledge of the pathophysiology of otosclerosis and to review hypotheses for the amelioration of this disease.

DATA SOURCES

Review of the literature and experimental observations by the authors.

CONCLUSIONS

Otosclerosis is a localized disease of bone remodeling within the otic capsule of the human temporal bone. Unlike other similar bone diseases, it does not occur outside of the temporal bone. These lesions seem to begin by resorption of stable otic capsule bone in adults, followed by a reparative phase with bone deposition. There are clearly genetic factors that lead to this disease, but measles virus infection and autoimmunity also may play contributing roles. Surgical correction of the conductive hearing loss is highly effective, but nonsurgical intervention has not yet been shown to prevent or slow the disease. Of the factors that may inhibit this process, fluorides, cytokine inhibitors, and bisphosphonates, third-generation bisphosphonates appear to hold the most promise.

Histopathology of residual and recurrent conductive hearing loss after stapedectomy

HYPOTHESIS

Histopathologic examination of temporal bones from patients who had undergone stapedectomy may provide information concerning the causes of both residual and recurrent conductive hearing loss (CHL).

BACKGROUND

Although closure of the air-bone gap to within 10 dB occurs in approximately 90% of primary stapedectomies, a residual CHL occurs in approximately 10% and recurrent CHL may occur in up to 35% of cases. Putative causes of failure of surgery as determined during revision include erosion of the incus, bony regrowth at the oval window, and displacement of the prosthesis. Most reports on the histopathologic findings of temporal bones from such patients have focused on complications of surgery, with little attempt to correlate postoperative air-bone gap with the observed histopathology.

METHODS

A retrospective review of the author's collection of temporal bones ascertained 22 cases with postoperative CHL of 10 dB or greater (air-bone gap averaged at 500, 1,000, 2,000, 3,000, and 4,000 Hz, using postoperative air- and bone-conduction levels) after stapedectomy. These temporal bones were prepared by standard methodology for light microscopy.

RESULTS

Of the 22 cases with postoperative CHL equal to or greater than 10 dB, there were 19 with residual CHL, 2 with recurrent CHL, and 1 with both residual and recurrent CHL. The most common histopathologic correlates of residual and recurrent hearing loss included resorptive osteitis of the incus (64%); obliteration of the round window by otosclerosis (23%); the prosthesis lying on a residual footplate fragment (23%); the prosthesis abutting the bony margin of the oval window (18%); adhesions in the middle ear (14%); and new bone formation in the oval window (14%).

CONCLUSIONS

Histopathologic examination of temporal bones from patients who in life had undergone stapedectomy provides useful information concerning causes of both residual and recurrent CHL. These data provide a basis for improving both surgical technique and prosthesis design.

Predilection of otosclerotic foci related to the bone turnover in the otic capsule

Using multiple fluorochrome tagging of eight mongrel dogs and a newly established methodology of measuring bone turnover (BTO) in the otic capsule, it has previously been demonstrated that BTO in the canine otic capsule is highly reduced close to the perilymphatic spaces (PLS) compared to the normal level of BTO in the periphery. Reanalysis of these data shows that this inhibition of BTO is far more pronounced around the cochlea and vestibule than around the semicircular canals. Similar tendencies are seen for the numerical density and mean label area of the bone remodelling units. With increasing distance to the PLS, these patterns are weakened, but still recognizable. In otosclerosis, foci of abnormal bone deposition are particularly frequent around the oval and round windows and in the cochlear capsule, i.e. where inhibition of bone remodelling is most prominent. A surpassing (or failure) of this pronounced inhibition must precede the tumultuous but delimited osteogenesis of otosclerosis. Otosclerosis may be a deviation of the normal BTO process in an osteometabolically abnormal site, perhaps initiated as an osteogenetic response to abnormal stress exposure.

Prevalence of chronic otitis media in a randomly selected population from two communes in southern Vietnam

The prevalence of chronic otitis media was studied in an urban and a rural community in southern Vietnam in 1995. A total of 3,300 children, aged from 6 months to 10 years, were selected randomly by taking every third child on the vaccination list. In this cross-sectional study, 453 ears were found to have chronic otitis media or sequelae otitidis, giving an overall prevalence of 6.86%. A total of 140 ears had perforations. Various attic changes were found in 73 ears and other chronic tympanic membrane changes, such as atrophy, tympanosclerosis and adhesions, in 219 ears. Cholesteatoma was seen in two ears.

A second gene for otosclerosis, OTSC2, maps to chromosome 7q34-36

Otosclerosis due to abnormal bone homeostasis of the otic capsule is a frequent cause of hearing loss in adults. Usually, the hearing loss is conductive, resulting from fixation of the stapedial footplate, which prevents normal ossicular vibration in response to sound. An additional type of sensorineural hearing loss may be caused by otosclerotic damage to the cochlea. The etiology of the disease is unknown, and both environmental and genetic factors have been implicated. Autosomal dominant inheritance with reduced penetrance has been proposed, but large families are extremely rare. To elucidate the pathogenesis of the disease, identification of the responsible genes is essential. In this study, we completed linkage analysis in a Belgian family in which otosclerosis segregates as an autosomal dominant disease. After excluding linkage to a known locus on chromosome 15 (OTSC1), we found linkage on chromosome 7q, with a multipoint LOD score of 3.54. Analysis of key recombinant individuals maps this otosclerosis locus (OTSC2) to a 16-cM interval on chromosome 7q34-36 between markers D7S495 and D7S2426.

Scanning electron microscopy images and energy-dispersive X-ray microanalysis of the stapes in otosclerosis and Van der Hoeve syndrome

OBJECTIVE/HYPOTHESIS

The objective of this study was to evaluate the morphological and microchemical changes that affect sclerotic stapes in otospongiosis and van der Hoeve syndrome.

METHODS

A scanning electron microscope equipped with an energy-dispersive x-ray analyzer was used in the experiments.

RESULTS

In otosclerosis, focal lesions are poorly mineralized, with low calcium salt and reduced calcium-to-phosphorus (Ca/P) ratio (1.9:1). This finding correlates with a spongiotic type of lesion and indicates unstable mineralization with possible change from hydroxyapatite to calcium triphosphate. In van der Hoeve syndrome the presence of magnesium in stapes suggests osteoclastic function stimulation. The osteoclasts secrete many protons, causing an acidified microenvironment. Brushite is formed, and Ca/P ratio decreases in comparison with that of control patients (2.0:1 vs. 2.6:1).

No evidence of measles virus in stapes samples from patients with otosclerosis

Otosclerosis is a localized bone dystrophy of unknown etiology mainly involving the stapes. The hypothesis of a persistent infection by the measles virus was based on the inconstant detection of the virus by various methods, including reverse transcription-PCR (RT-PCR) of patients' stapes samples. The aim of this work was to investigate the presence of the measles virus in stapedial otosclerosis foci by different sensitive methods. Pathologic stapes samples were obtained from 35 patients suffering from otosclerosis. Measles virus detection was performed by (i) cocultures of Vero cells and primary cell cultures of bone samples (n = 7), (ii) immunofluorescence study of these cocultures (n = 3), and (iii) RT-PCR on RNA directly obtained from fresh frozen samples (n = 28) and on RNA extracted from the primary cell cultures (n = 2). Viral genomic regions coding for N (nucleoprotein) and M (matrix) proteins were separately amplified. PCR sensitivity was optimized on the measles virus Edmonston strain. Glyceraldehyde-3-phosphate dehydrogenase mRNA was used as a marker of total RNA recovery. PCR products were tested by Southern blot hybridization technique to improve sensitivity and specificity. PCRs amplifying the M and the N protein genes were able to detect the control measles virus RNA at titers as low as 0.1 and 0.01 50% tissue culture infective dose, respectively. With these highly sensitive methods, we could not evidence the presence of the measles virus in any of our bone samples or primary bone cell cultures. Our results do not confirm the hypothesis of persistent measles virus infection in otosclerosis.

[Otosclerosis: experience at the Hotel-Dieu in France. 71 surgical cases]

Otosclerosis is one of the common causes of hearing loss. The incidence varies between 0.1% and 2%. In Lebanon otosclerosis is a common entity that has not been well evaluated. To the best of our knowledge there is no epidemiologic analysis of the incidence or outcomes of otosclerosis in Lebanon. We collected the number of stapedectomies performed for otosclerosis in different hospitals between Jan. 1994 and Dec. 1995. We also retrospectively reviewed the charts of 71 cases who underwent stapedectomy at Hôtel-Dieu de France-St Joseph University Hospital Medical Center, Beirut, Lebanon. Between 1992 and 1996 the incidence of otosclerosis in Lebanon as revealed through stapedectomy is 5/100,000. We report also on the pathology, technique, complications and outcomes of stapedectomy surgery for otosclerosis in Hôtel-Dieu Hospital. Further epidemiologic studies and screening is required to reveal the exact incidence of this common entity that could be underdiagnosed or untreated in our country.

[Parameters of normality in multifrequency tympanometry]

Multifrequency tympanometry studies consist of tympanography using probe tone frequencies ranging from 200 to 2000 Hz, improving the study of acoustic transmission through the tympano-ossicular system because then two components of admittance, conductance and susceptance, can be separated. The resonance frequency is the frequency at which mass and spring elements of the middle ear cancel each other out, leaving only the friction component. This measurement has been found to be more sensitive to the presence of pathologies that affect the tympano-ossicular system, such as otosclerosis and rheumatoid arthritis. It is necessary to know normal pattents of tympanometric parameters to improve the study of these diseases. Multifrequency tympanometry performed on 136 patients, 91 women and 45 men, age range 11-78 years. The mean resonant frequency of the middle ear was 1132.33 Hz, mean static admittance 0.76 dapa, and mean tympanometric amplitude 94.31 mmhos ac. Age showed no systematic effect of age on any of these measures in this population, and no significant association was found between static admittance or tympanometric amplitude and resonance frequency.

Malleus ankylosis: a clinical, audiometric, histologic, and surgical study of 123 cases

OBJECTIVE

Malleus ankylosis is a cause of conductive hearing loss that can be difficult to assess, particularly in association with otosclerotic stapes fixation. The aim of this study is to seek the clinical and audiometrical features unique to this pathology.

STUDY DESIGN

The study design was a review of malleus ankylosis cases and an analysis of functional results after ossiculoplasty.

SETTING

The study was performed at Jean Causse Clinic in France.

PATIENTS

The authors reviewed a series of 123 ears in 112 patients who underwent surgery for incudo-mallear ankylosis from January 1991 to September 1997.

INTERVENTION

The surgical technique depends on the type of pathology encountered. In case of associated stapedial fixation, a stapedotomy with vein graft interposition and reconstruction with a total prosthesis will be performed during a same step.

MAIN OUTCOME MEASURES

Clinical evaluation, preoperative and postoperative audiometrical evaluation, operative findings, histologic examination, and postoperative functional results.

RESULTS

In our series, a postoperative air-bone gap smaller than 10 dB was obtained in 77% of cases. These results confirm the possibility of managing both pathologies in a single surgical step.

CONCLUSION

Incudo-mallear ankylosis remains an unusual pathology but should be systematically assessed during surgery and preferably after separation of the incudo-stapedial joint. A preoperative diagnosis is difficult to ascertain; some audiometrical features allow a suspicion. In this series, it is shown that otosclerosis can be responsible for ankylosis as seems to be confirmed by the two cases presented in this study.

Otosclerosis and cochlear otosclerosis: a post mortem study on temporal bones

We have chosen among many temporal bones of donors deceased individuals with concomitant otosclerosis, three particular cases, one with classic otosclerosis, another with cochlear otosclerosis with concomitant oval window ankylosis and another with cochlear otosclerosis without stapes fixation. The different histopathologic features are discussed and clinical and therapeutical guidelines are proposed.

Obliterative otosclerosis

From January 1990 to December 1996, 293 primary stapedectomies for otosclerosis were performed, among which 14 had obliterative otosclerosis (4.7 per cent). Probability of bilateral obliterative disease was 50 per cent. With this particular condition, a drill-out procedure was used to perform either a stapedectomy or a stapedotomy. In two patients with bilateral 'far-advanced otosclerosis', surgery was effective in enabling the patient to benefit from hearing-aids. In patients with a measurable hearing-loss, an air-bone gap closure to within 10 dB was achieved in 62.5 per cent of the cases and to within 10-20 dB in 37.5 per cent of the cases, with no deterioration of air-conduction thresholds at 8 kHz. A mild sensorineural hearing loss at 4 kHz was observed in 25 per cent of the cases. There was no statistical difference between stapedectomy and stapedotomy. According to these results, the drill-out technique is a safe and effective procedure in cases of obliterative otosclerosis.

Does otosclerosis occur only in the temporal bone?

HYPOTHESIS

Otosclerosis does not occur outside the temporal bone.

BACKGROUND

The widely accepted assumption that otosclerosis is confined to the temporal bone has never been tested. It is important to investigate this issue, particularly because of evidence that otosclerosis may be a systemic (genetic) disease that could affect other bones.

METHODS

Biopsies from 9 to 11 skeletal sites were obtained from 2 patients with clinical otosclerosis. Two hundred forty-one nontemporal bone sections were examined by light microscopy.

RESULTS

No nontemporal skeletal bone section showed histologic evidence of otosclerosis. The data indicate, with 95% confidence, that the true prevalence of otosclerosis in the extratemporal skeleton of the 2 patients examined was < 3%.

CONCLUSIONS

These findings suggest that otosclerosis is unlikely to occur outside the temporal bone. Factors unique to the otic capsule that may predispose it to otosclerosis are lack of bone remodeling and the presence of globuli interossei.

Myringosclerosis develops within 9h of myringotomy

The aim of the present experimental study was to elucidate the temporal development of myringosclerosis. Twenty-four Sprague-Dawley rats were myringotomized bilaterally. At 3, 6, 9, 12, 18, 24, 30, 36, 48, 60, 72 and 84 h after the myringotomy, 2 animals at each time were examined otomicroscopically and thereafter sacrificed. The pars flaccida and pars tensa were excised and prepared for light- and electron-microscopic studies. Otomicroscopically, myringosclerosis was visible in the pars tensa 24 h after myringotomy, whereas no sclerotic lesions were noted in the pars flaccida. Histologically, sclerotic lesions were present in the pars tensa and pars flaccida 9 and 12 h, respectively, after myringotomy. The pars flaccida responds promptly with an inflammatory reaction characterized by abundant macrophages. Myringosclerosis develops promptly after myringotomy and its establishment is related to an inflammatory reaction.

[Progressive sensorineural hearing loss in cochlear otosclerosis]

Otosclerosis is a bone dysplasia limited to the otic capsule causing abnormal resorption and redeposition of bone. The existence of the entity "pure labyrinthine otosclerosis" or "cochlear otosclerosis" is not accepted by all authors; however, there is clinical and histologic evidence to support the existence of a progressive sensorineural hearing loss due to otospongiotic-otosclerotic lesions of the labyrinthine capsule, although diagnosis of this condition may be difficult. The involvement of the inner ear is described as degenerative changes in the spiral ligament, stria vascularis, organ of Corti, and cochlear neurons. The most frequent audiometric configuration is a "bite-type" curve, but flat or rising shapes can also be observed; speech discrimination appears unusually good for a pure sensorineural hearing loss and recruitment is frequently absent. A cochlear otosclerosis should be suspected when there is a family history of otosclerosis, the onset of the hearing loss occurs from the third to fifth decade, and worsening of the hearing loss is observed during periods of intense hormonal and endocrine activity, a positive Schwartze sign is present and bilateral sensorineural loss is associated with signs of unilateral stapedial ankylosis. A definitive diagnosis of cochlear otosclerosis can be made only with computed tomography, which allows a quantitative assessment of the involvement of the labyrinthine capsule by spongiotic or sclerotic areas. The factors to be considered are: otosclerotic foci 1 mm or more in diameter and a density different from that of the normal otic capsule, partially or completely erased contour of the capsule, double ring effect, bony neoformation in the labyrinthine spaces, and increased thickness of the cochlear capsule. The medical management of cochlear otosclerosis is based on sodium fluoride, in association with calcium and vitamin D; some authors have also proposed diphosphonates as inhibitor agents of bone resorption. Surgery may be useful only in those patients presenting a hearing loss so severe that the bone threshold cannot be evaluated and a gap between air and bone conduction cannot be excluded; in these cases stapes operations can improve hearing to a level that may be useful in hearing aid application.

Correlations between pathologic changes in the stapes and conductive hearing loss in otosclerosis

The goal of this temporal bone study was to quantify the relationship between specific histologic changes at the stapes footplate and the magnitude of the air-bone gap in otosclerosis. The study material comprised 26 specimens with otosclerosis and 37 age-matched controls. Detailed anatomic measurements were made on each histologic section through the stapes footplate in each bone, resulting in 30 different measurement parameters for each bone. For frequencies 250 to 2,000 Hz, the conductive hearing loss correlated highly with (p < .01) and appeared to be caused primarily by narrowing and loss of the annular ligament, especially at the posterior stapediovestibular joint space. The size of the air-bone gap appeared to be determined by the extent and degree of this pathologic change. Schuknecht's hypothesis that bony ankylosis of the footplate would be associated with an air-bone gap of >30 dB was supported by our data. However, the degree and extent of bony footplate ankylosis could not be reliably predicted by the size of the air-bone gap.

[Isotopic studies on the regeneration of stapedial bone in otosclerosis]

The aim of the study was determining the bone rebuilding activity in stapes and otosclerotic focus and comparison the relation between bone rebuilding activity with some clinical features such as the patient's sex and age, duration of the disease and the degree of hearing impairment. The study covered 98 patients aged from 18 to 68 years (X = 37 years) in whom, due to otosclerosis, stapedectomy was performed at the Clinic of Otolaryngology--PAM in Szczecin. The rebuilding activity was estimated in bone fragments having been removed during the operation, i.e. in 98 specimens of canal wall bone, 97 specimens of stapedial crura, 88 fragments from posterior and 18 fragments from anterior parts of footplate as well as in 15 otosclerotic foci, using isotopic method implementing a complex of pyrophosphate labelled with technetium Tc-99m. The degree of bone rebuilding activity was defined by the amount of absorbed isotopic index. The "control group" was made up of 9 cases, in which stapedectomy was carried out for therapeutical purpose in consequence of other ailments, namely: in 3 cases of congenital stapedial ankylosis, 5 cases of stapedial tympanosclerosis, and 1 case of Menier's disease. It has been disclosed that otosclerosis is an active pathological process, involving the bone of the entire stapes with the strongest manifestation in the disease focus. An essential fact was linked with the very low bone rebuilding activity in the stapedial footplate and crura in the "control group". The bone rebuilding activity in otosclerotic foci and footplate of stapes was somewhat higher in males than in females. It was the highest in patients whose disease duration was the longest. In general the bone rebuilding activity didn't influence the degree of hearing impairment.

[Content of fluoride and calcium in stapedial bone in otosclerosis]

The study dealing with the content of fluoride and calcium in stapedial bone and canal wall bone in otosclerosis was performed in 69 subjects (48 females and 21 males) out of the patients, in whom bone rebuilding activity had earlier been studied isotopically. The control group comprised 20 normal stapedies taken during autopsies. Fluoride content was determined by means of fluoride ions meter, the content of calcium was assessed by resorting to atomic absorptiometer. The content of studied elements was compared with the bone rebuilding activity and some clinical features such as the patient's age and duration of the disease. High fluoride content in otosclerotic stapes was revealed, being several times greater than in the bone of normal stapes. Concurrently the stapedial bone in otosclerosis contained less calcium as compared with the bone of normal stapes. In principle, that referred to otosclerotic focus and next to stapedial crura. The bones of stapedial footplates and otosclerotic foci with rebuilding activity lover han the means value had statistically significant, higher content of fluoride and calcium than the bones with greater rebuilding activity. Fluoride content in stapedial bone during otosclerosis dramatically increased with the patient's age and the length of the disease duration period, however, the calcium content had the tendency to decrease.

Chondrosarcoma of the temporal bone and otosclerosis

Chondrosarcoma constitutes 6% of all primary bone tumors and 11% of malignant primary bone tumors. Nevertheless, in a review of the tumor registry of the University of Michigan covering a period of 50 years, there were only 3 cases involving the temporal bone. A case of a woman with a chondrosarcoma of the temporal bone that was partially resected by means of an infratemporal approach at the skull base is presented. This patient had previously undergone surgical treatment for otosclerosis of the other ear. Several considerations regarding survival factors in this type of tumor are dealt with in terms of the histological features, therapeutic options and anatomic location. The possibility that this lesion may originate from the persistence of the cartilaginous inclusions that some authors consider to be involved in the origin of otosclerosis is discussed.