Otosclerosis: a genetically heterogeneous disease involving at least three different genes

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.

Modified Significance Analysis of Microarrays in Heterogeneous Diseases

Significance analysis of microarrays (SAM) provides researchers with a non-parametric score for each gene based on repeated measurements. However, it may lose certain power in general statistical tests to correctly detect differentially expressed genes (DEGs) which violate homogeneity. Monte Carlo simulation shows that the “half SAM score” can maintain type I error rates of about 0.05 based on assumptions of normal and non-normal distributions. The author found 265 DEGs using the half SAM scoring, more than the 119 DEGs detected by SAM, with the false discovery rate controlled at 0.05. In conclusion, the author recommends the half SAM scoring method to detect DEGs in data that show heterogeneity.

Otosclerosis: Incidence of Positive Findings on High-Resolution Computed Tomography and Their Correlation to Audiological Test Data

Objectives:

Computed tomographic (CT) scanning with slices of 1 mm or more has not been sufficient to demonstrate otosclerotic foci in most cases to date.

Methods:

We investigated the validity of CT scans with a 0.5-mm cubical scan technique, with and without planar reconstruction, and correlated these findings with audiological data. Forty-four temporal bone CT scans from 30 patients with conductive or mixed hearing loss were evaluated.

Results:

Otosclerotic foci were visualized in 74% of the cases. With reconstruction at the workstation, the sensitivity increased to 85%. Whereas in fenestral otosclerosis a correlation was found between the size of the focus and the air-bone gap, no correlation was seen between the size of the focus and bone conduction thresholds with cochlear involvement. Otosclerotic foci in patients treated with sodium fluoride were smaller than those in patients without treatment. This finding may indicate a beneficial effect of sodium fluoride on otosclerotic growth.

Conclusions:

High-resolution CT scans are a valid tool that can be used to confirm, localize, and determine the size of clinically suspected otosclerotic foci.

Optimal Trend Tests for Genetic Association Studies of Heterogeneous Diseases

The Cochran-Armitage trend test is a standard procedure in genetic association studies. It is a directed test with high power to detect genetic effects that follow the gene-dosage model. In this paper, the author proposes optimal trend tests for genetic association studies of heterogeneous diseases. Monte-Carlo simulations show that the power gain of the optimal trend tests over the conventional Cochran-Armitage trend test is striking when the genetic effects are heterogeneous. The easy-to-use R 3.1.2 software (R Foundation for Statistical Computing, Vienna, Austria) code is provided. The optimal trend tests are recommended for routine use.

Identification of target proteins involved in cochlear otosclerosis

HYPOTHESIS

Investigation of differential protein expression will provide clues to pathophysiology in otosclerosis.

BACKGROUND

Otosclerosis is a bone remodeling disorder limited to the endochondral layer of the otic capsule within the temporal bone. Some authors have suggested an inflammatory etiology for otosclerosis resulting from persistent measles virus infection involving the otic capsule. Despite numerous genetic studies, implication of candidate genes in the otosclerotic process remains elusive. We employed liquid chromatography-mass spectrometry (LC-MS) analysis on formalin-fixed celloidin-embedded temporal bone tissues for postmortem investigation of otosclerosis.

METHODS

Proteomic analysis was performed using human temporal bones from a patient with severe otosclerosis and a control temporal bone. Sections were dissected under microscopy to remove otosclerotic lesions and normal otic capsule for proteomic analysis. Tandem 2D chromatography mass spectrometry was employed. Data analysis and peptide matching to FASTA human databases was done using SEQUEST and proteome discoverer software.

RESULTS

TGFβ1 was identified in otosclerosis but not in the normal control temporal bone specimen. Aside from TGFβ1, many proteins and predicted cDNA-encoded proteins were observed, with implications in cell death and/or proliferation pathways, suggesting a possible role in otosclerotic bone remodeling. Immunostaining using TGFβ1 monoclonal revealed marked staining of the spongiotic otosclerotic lesions.

CONCLUSIONS

Mechanisms involved in cochlear extension of otosclerosis are still unclear, but the implication of TGFβ1 is supported by the present proteomic data and immunostaining results. The established role of TGFβ1 in the chondrogenesis process supports the theory of a reaction targeting the globulae interossei within the otic capsule.

An introduction of genetics in otosclerosis: a systematic review

OBJECTIVE

To present an easy to read systematic review concerning the genetic etiology of otosclerosis to help health care providers in counseling otosclerosis patients more accurately.

DATA SOURCES

PubMed, Embase, CINAHL, and the Cochrane Library.

REVIEW METHODS

Studies on the genetic etiology of otosclerosis were selected. Association studies and family-based studies were included for further review. After quality assessment (risk of bias), data were extracted from the included studies. When available, odds ratios were presented. In case of corresponding genetic anomalies between the studies, it was the aim to combine results.

RESULTS

The number of available studies with low risk of bias is limited to 2 association studies and 1 family-based study. These high-quality studies show that otosclerosis in Japanese patients is not linked to the NOG gene and that a polymorphism in the Sp1 binding site located on the COL1A1 gene is associated with otosclerosis as well as OTSC1. Association and family-based studies with moderate risk of bias show a statistically significant association with the ACE gene, AGT gene, OTSC2, RELN gene, TGFB1 gene, 11q13.1, OTSC2, OTSC5, OTSC8, and OTSC10. These results may be spurious associations due to their bias and low statistical power.

CONCLUSION

The present systematic review shows that there is scattered evidence of limited quality and a lack of replication studies. It is not possible to point out 1 or more responsible genes, which play a key role within the genetic pathophysiologic mechanism of otosclerosis.

Detection of otosclerosis-specific measles virus receptor (cd46) protein isoforms

Genetic predisposition of otosclerosis has long been suspected, but unclarified. Unique coexpression pattern of measles virus receptor (CD46) splicing isoforms in the human otic capsule is assumed, since otosclerosis is a measles virus-associated organ-specific disease. In order to identify CD46 involved in the pathogenesis of otosclerosis, we used representative groups of histologically diagnosed otosclerotic, nonotosclerotic, and normal stapes footplates (n = 109). Consecutive histopathological examinations and CD46-specific Western blot analysis were performed. Normal and nonotosclerotic stapes footplates showed consistent expression of the conventional c, d, e, f, and l CD46 isoforms. In contrast, four novel isoforms (os1–4) translated as intact proteins were additionally detected in each otosclerotic specimen. The study herein presented provides evidence for the otosclerosis-associated expression pattern of CD46. This finding might explain the organ-specific, virus-associated and autoimmune-inflammatory pathogenesis of otosclerosis. Regarding our current knowledge, this is the first report that confirms the presence of four new disease-specific protein variants of CD46.

No evidence for the expression of renin-angiotensin-aldosterone system in otosclerotic stapes footplates

INTRODUCTION

Recent studies have reported genetic associations between with single nucleotide polymorphism (SNP) of the several genes of the renin-angiotensin-aldosterone (RAA) system in otosclerosis without the confirmation of RAA system expression in human stapes footplates. There are conflicting results. These results are conflicting because RAA system expression has been attributed exclusively to neural, vascular, and renal tissues, exclusively.

MATERIALS AND METHODS

Ankylotic stapes footplates (n = 20), cortical bone fragments (n = 10), and human kidney tissue specimens (n = 10) were processed to hematoxylin-eosin (HE) staining and RAA system-specific immunofluorescent assay (IFA), respectively.

RESULTS

Histologic diagnosis of otosclerosis was established in all ankylotic stapes footplates. Histologically active- (n = 13) and inactive (n = 7) foci of otosclerosis were consequently characterized by negative immunoreactions for renin, angiotensin converting enzyme (ACE), angiotensin-II (AT-II), and angiotensin-II receptor (AT-IIR), consequently. In cortical bones, a considerable RAA system expression was observed confirmed in the perivascular bone marrow progenitor cells. Kidney specimens, applied as positive controls, showed intense RAA system-specific immunoreactions.

CONCLUSION

Concerning current observations, the 4 studied members of RAA system that did not display active expression were not expressed at protein level in otosclerotic stapes footplates. This phenomenon was independent from the histologic activity of otosclerosis. Between these conditions, the etiologic role of RAA system is questionable in the pathogenesis of otosclerosis.

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.

Detecting differentially expressed genes in heterogeneous diseases using control-only analysis of variance

PURPOSE

Microarray technology allows for simultaneously screening many genes and determining which gene(s) are differentially expressed in different disease statuses or different cell types. The analysis of variance (ANOVA) (for a K-sample situation with K>2) can be used in such occasions to gauge statistical significances. However, the test may be underpowered if the diseases under study are heterogeneous.

METHODS

The authors propose the "control-only ANOVA" for detecting differentially expressed genes in heterogeneous diseases. Monte-Carlo simulation shows that the test produces quite accurate type I error rates for both normal and non-normal data. The statistical power of the control-only ANOVA is higher than that of the conventional ANOVA when the diseases under study are heterogeneous.

RESULTS

Analysis of a real data set shows that after Bonferroni correction, the control-only ANOVA detects three differentially expressed genes, whereas the conventional ANOVA can detect only one.

CONCLUSIONS

The control-only ANOVA is recommended for use when the diseases under study are heterogeneous.

Genetics of otosclerosis

OBJECTIVES

Otosclerosis is a major cause of acquired hearing loss in adult life affecting exclusively the human temporal bone. Until recently, the etiopathogenesis of otosclerosis was still a matter of debate. Genetic research, however, has evolved enormously the last years and unveiled important clues regarding the cause of otosclerosis. The objective of this article is to review the genetics of otosclerosis with special attention for the links to the bone homeostasis of the otic capsule.

DATA SOURCES

A detailed literature study was performed focusing on the recent genetic findings in otosclerosis and the special bone turnover of the otic capsule. A PubMed search and own research data were used to bring the relevant information for this review together.

CONCLUSION

Unlike all other bones in the human skeleton, the otic capsule undergoes very little remodeling after development, possibly due to local inner ear factors. Otosclerosis is a process of pathologic increased bone turnover in the otic capsule, which in most cases leads to stapes fixation, resulting in a conductive hearing loss. Although environmental factors such as estrogens, fluoride, and viral infection have been implicated, it is clear that genetic factors play a significant role in the manifestation of otosclerosis. From a genetic viewpoint, otosclerosis is considered to be a complex disease with rare autosomal dominant forms caused by a single gene. Already, 7 monogenic loci have been published, but none of the genes involved have been identified. For the complex form of otosclerosis, caused by an interaction between genetic and environmental factors, the first susceptibility genes were identified by case-control association studies. All 3 replicated genes, TGFB1, BMP2, and BMP4, are a part of the transforming growth factor-beta1 pathway. Data from both genetic association studies and gene expression analysis of otosclerotic bone showed that the TGF-beta1 pathway is most likely an important factor in the pathogenesis of otosclerosis.

TNF-alpha receptor expression correlates with histologic activity of otosclerosis

HYPOTHESIS

Otosclerosis is an inflammatory bone remodeling disorder of the human otic capsule, which might be characterized by variable levels and unique expression pattern of TNF-alpha receptors.

BACKGROUND

Histologic characteristics of otosclerosis have been well described during the latest decades; however, the grading of different histopathologic and clinical stages has not been attributed precisely to the molecular biology of the pathologically increased metabolism of osteoclast-osteoblast axis.

METHODS

Forty otosclerotic- and 40 nonotosclerotic ankylotic stapes footplates (n = 80; men, 29; women, 51) were histologically analyzed: conventional hematoxylin-eosin staining and tumor necrosis factor-alpha receptor I and II (TNFRI/II)-specific immunofluorescent assay was performed.

RESULTS

Active otosclerosis (Grades I-II; n = 24) was featured by increased expression of TNFRII and moderate expression of TNFRI; inactive cases (Grades III-IV) were characterized by permanent expression of TNFRI; however, TNFRII-specific immunoreaction was absent. Nonotosclerotic stapes specimens showed a negligible TNFR expression. Tumor necrosis factor receptor expression pattern showed a strong correlation with the histologic activity of otosclerosis (chi2 test; p < 0.001).

CONCLUSION

Detection of elevated TNFR expression demonstrates activated osteoclast metabolism and inflammatory pathways in otosclerosis. Different etiopathogenesis of otosclerotic and nonotosclerotic stapes ankylosis should be distinguished. Administration of monoclonal anti-TNF-alpha antibody may be a reasonable option in the medical treatment of active stages of otosclerosis.

Otosclerosis: exclusion of linkage to the OTSC1 and OTSC2 loci in four Italian families: Otoesclerosis: exclusión de enlaces entre los loci OTSC1 y OTSC2 en cuatro familias italianas

Otosclerosis is the single most common cause of hearing impairment among adult caucasians. Little is known about its aetiology and its molecular aspects. Until now, genetic linkage in otosclerosis has been demonstrated in an Indian family and a Belgian family, showing the presence of two otosclerosis loci, OTSC1 and OTSC2, respectively. Linkage analysis has never been applied to Italian otosclerotic families. We have collected four multigenerational Italian otosclerotic families that show dominant transmission for the pathology. Here, we report a detailed audiological analysis of these families and a genetic linkage study on the OTSC1 and OTSC2 loci. Statistical analysis revealed the absence of linkage between the disease in our families and the OTSC1 and OTSC2 loci. These data strongly suggest the presence of one or more additional loci for otosclerosis, which still need to be defined.

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.

No evidence of linkage between 7q33-36 locus (OTSC2) and otosclerosis in seven British Caucasian pedigrees

BACKGROUND

The aetiology of otosclerosis is complex, and probably involves an interaction between genes and environmental factors. Previous studies have revealed genetic linkage with a number of chromosome regions, including position 7q33-36.

AIM

To confirm whether linkage exists between otosclerosis and chromosome region 7q33-36.

MATERIALS AND METHODS

Seven multiply affected families were ascertained. Deoxyribonucleic acid from members of these families was extracted, and six markers were genotyped to cover a 16 cM region at 7q33-36. Both parametric and non-parametric multipoint linkage analyses were performed.

RESULTS

Parametric multipoint linkage analysis excluded any linkage at 7q33-36 (logarithm of odds score <-4.0). Non-parametric linkage analysis also failed to confirm any linkage (non-parametric linkage < 1.66). When tested individually, pedigree four was the only one to show a significant non-parametric linkage score between D7s684 and D7s2513 (non-parametric linkage = 1.96).

CONCLUSION

No linkage was detected between otosclerosis and the 7q33-36 region. This could be explained by the study's lack of power, due to the limited number of families available.

A review on the genetics of otosclerosis

BACKGROUND

The aetiology of otosclerosis is not fully understood despite intensive research. It is, however, certain that a genetic component plays a significant role in the manifestation of otosclerosis, although the precise mode of inheritance is still uncertain.

OBJECTIVE OF REVIEW

To provide an up-to-date review for the genetics of otosclerosis. The mode of inheritance, chromosomal and linkage studies are presented. In addition, the possible genetic relationship between otosclerosis and osteogenesis imperfecta, and the association between otosclerosis and specific human leucocyte antigen types are described.

TYPE OF REVIEW

Systematic analysis of the literature was focused on any information related to the genetics of otosclerosis.

SEARCH STRATEGY

A MEDLINE search (1960-2007) was undertaken to perform a comprehensive review. Articles were also identified through searches of the files of authors.

RESULTS

The majority of epidemiological studies on families with otosclerosis suggest an autosomal dominant mode of inheritance with reduced penetrance of approximately 40%. Genetic linkage studies have demonstrated the presence of six loci (OTSC1, OTSC2, OTSC3, OTSC4, OTSC5 and OTSC7) located on chromosomes 15q, 7q, 6p, 16q, 3q and 6q respectively. Although these loci have been mapped, no causative genes have been identified, and we have little idea of the molecular process involved in this disease. While clinical similarities and some unreplicated genetic association studies suggest an aetiological relationship between otosclerosis and osteogenesis imperfecta-type I, there is no definite evidence of a common pathological process between the two diseases.

CONCLUSIONS

Otosclerosis may be considered as a complex disease with relatively common monogenic forms. Knowledge of these genes could lead to substantial improvements in our ability to diagnose and possibly even prevent or treat this type of hearing deterioration.

A seventh locus for otosclerosis, OTSC7, maps to chromosome 6q13–16.1

Otosclerosis is a common form of hearing impairment among white adults with a prevalence of 0.3-0.4%. It is caused by abnormal bone homeostasis of the otic capsule that compromises free motion of the stapes in the oval window. Otosclerosis is in most patients a multifactorial disease, caused by both genetic and environmental factors. In some cases, the disease is inherited as a monogenic autosomal dominant trait, sometimes with reduced penetrance. However, families large enough for genetic linkage studies are extremely rare. To date, five loci (OTSC1-5) have been reported, but none of the responsible genes have been cloned yet. An additional locus, OTSC6, has been reported to the HUGO nomenclature committee but the relevant linkage study has not been published. In this study, a genome-wide linkage study was performed in a large Greek pedigree segregating autosomal dominant otosclerosis. A seventh locus, OTSC7, was localized on chromosome 6q13-16.1 with a multipoint LOD score of 7.5 in the 13.47 cM region defined by markers D6S1036 (centromeric) and D6S300 (telomeric). Linkage analysis of this new locus in 13 smaller Belgian and Dutch families has identified one family from The Netherlands in which allele segregation suggests linkage to this region. The overlap between the critical regions of these two families is a 1.06 Mb interval between the genetic markers D6S1036 (centromeric) and D6S406 (telomeric) on chromosome 6q13.

Bone conduction variation poststapedotomy

We evaluated the variation in bone conduction auditory thresholds in patients undergoing surgical intervention for otosclerosis as part of our report on the use of surgery in patients with a small air-bone gap. Of the 110 patients who underwent stapedotomy, 45 were treated by traditional surgery and 65 with carbon dioxide laser, with a follow-up of 3 years at 500-, 1000-, 2000-, and 3000-Hz frequencies. Both surgical techniques resulted in improvements in air conduction in more than 95% of cases; bone conduction improved more in patients treated with carbon dioxide laser (7.1 dB) compared to those treated with traditional surgery (4 dB) (P < .01). Furthermore, improvement in bone conduction was greater and more frequent in younger subjects (below 45 years) (P < .05). In conclusion, this study allows us to express a positive prognosis when considering otosclerotic patients with sensorineural hearing loss and small air-bone gap.

Histologic otosclerosis is associated with the presence of measles virus in the stapes footplate

HYPOTHESIS

Persistent measles virus infection of the otic capsule is presumed to be one of the etiologic factors in otosclerosis. The viral pathogenesis of otosclerosis could be established only by correlative analysis: histologic examination of the stapes footplates and reverse-transcriptase polymerase chain reaction amplification of the viral RNA. At present, histologic analysis of the removed stapes footplates is the only appropriate method of distinguishing otosclerotic and nonotosclerotic stapes fixations.

BACKGROUND

The presence of measles virus was shown in otosclerotic patients by reverse-transcriptase polymerase chain reaction amplification of the viral RNA and detecting the viral proteins by immunohistochemistry.

METHODS

Nucleic acids (mRNA, vRNA, and DNA) were extracted from ankylotic stapes footplates of stapes fixation patients (n = 44). Measles virus genomic nucleoprotein RNA was amplified by seminested reverse-transcriptase polymerase chain reaction. Amplification results were correlated to postoperative histologic findings.

RESULTS

Measles virus RNA was detectable only in histologically otosclerotic stapes footplates (n = 32). Histology for virus-negative footplates (n = 12) excluded otosclerosis. Virus-negative stapes footplates showed annular calcification (n = 8), bone resorption with increased numbers of hemosiderophages (n = 2), and mononuclear cell infiltration with osteolysis (n = 2).

CONCLUSION

Stapes ankylosis is a heterogenous disease causing conductive hearing loss with different causes. Nonotosclerotic stapes fixations may belong to degenerative disorders with variable histopathology. Otosclerosis is an inflammatory disease resulting from persisting measles virus infection of the otic capsule.

Does pregnancy affect otosclerosis?

OBJECTIVE

To evaluate the effect of pregnancy on the hearing of women with otosclerosis.

STUDY DESIGN

A retrospective study of women who had undergone stapedectomy. The women were equally divided into two groups: one group with children and a control group without children. Air and bone conduction, as well as discrimination, were measured before and after stapedectomy in both groups.

PATIENTS

Ninety-four women (47 with children and 47 without) were evaluated. Because many of the women had bilateral otosclerosis, the total number of ears studied was 128.

RESULTS

Mean pure tone air and bone conduction thresholds were not worse in women with children versus those women without children. In fact, mean pre- and postoperative pure tone air and bone conduction thresholds from 500 Hz through 4,000 Hz in women with children were slightly but significantly better than women without children. There was no difference in discrimination scores between groups. Within the group with children, no significant correlation was found between number of children and hearing loss. Also, no correlation was found between breastfeeding and the amount of hearing loss.

CONCLUSION

We found no adverse effect on hearing in otosclerotic women who had children compared with women without children. Even with increasing numbers of pregnancies, no deleterious impact was noted. Air conduction, bone conduction, and discrimination were not worse in women with children versus childless women. No significant correlation was found between the number of children and hearing loss, and neither did breastfeeding affect the amount of hearing loss.

Fixation of the Stapes Footplate in Children: A Clinical and Temporal Bone Histopathologic Study

OBJECTIVE

To clarify the anatomic characteristics, cause, and surgical outcomes relating to fixation of the stapes footplate in children.

STUDY DESIGN

Retrospective case review and four-center histopathologic study of temporal bones.

SETTING

Tertiary referral center.

PATIENTS

We reviewed charts and histologic specimens from 12 children, aged 7 to 13 years, who underwent surgery for footplate fixation. We also studied stapes footplates in 288 temporal bones from 181 children ranging from newborn (20-44 weeks of gestation) to 13 years of age.

MAIN OUTCOME MEASURE

Anomalies of the stapes footplate in children.

RESULTS

The average age of diagnosis of hearing loss was 6.6 years. Criteria for a diagnosis of otosclerosis were progression of a conductive hearing loss and an intraoperative finding of fixation of the anterior stapediovestibular joint in five patients. In contrast, a nonhomogeneous, thickened, fixed footplate and the absence of an annular ligament were indicators of congenital fixation in six children. In one child, there was neither new bone from the otic capsule nor any obvious otosclerotic foci. In the temporal bone study, 17 of 181 (9.4%) children had anomalies of the stapes footplates, with ankylosis in 4 (2.2%). In two subjects (1.1%), there was an otosclerotic focus not in contact with the stapes footplate.

CONCLUSION

Children younger than 6 years with various congenital anomalies are more likely to have congenital footplate fixation, which will present intraoperatively as a thickened footplate with a partial or absent annular ligament. Children older than 6 years with progressive conductive hearing loss are more likely to have otosclerosis, which presents as fixation of the anterior stapediovestibular joint. The difference in surgical outcomes is probably related to different degrees of footplate abnormality.

Quantification of Angiogenesis in Otosclerosis

OBJECTIVES/HYPOTHESIS

The determinants of clinical versus histologic otosclerosis are unknown, but angiogenesis is associated with active disease. We hypothesized that quantification of angiogenesis in otosclerotic human temporal bones could reveal significant differences between clinical and histologic cases.

STUDY DESIGN

We reviewed all otosclerosis specimens meeting criteria from the temporal bone collection of the Massachusetts Eye and Ear Infirmary and 10 normal controls.

METHODS

Digital images were taken at predilection sites, followed by computer-assisted analysis. Canalicular area (CA), the aggregate of vascular spaces within bone, microvessel density (MVD), area, and depth were the main measures. Evidence of a direct connection between local vessels and the vasculature of the otosclerotic focus was also recorded for each specimen.

RESULTS

The average area (mm) and depth (number of sections containing otosclerosis) of clinical lesions was significantly greater than histologic lesions. Total microvessel counts were significantly greater in clinical versus histologic lesions, and both clinical and histologic lesions contained significantly greater numbers of microvessels than the normal otic capsule. CA was also significantly higher in clinical lesions. MVD was slightly but not significantly higher in clinical lesions. Importantly, a direct connection between named vessels and the otosclerotic vasculature was significantly more frequent in clinical lesions.

CONCLUSIONS

Computer-assisted quantification revealed significantly greater measures of angiogenesis in clinical versus histologic otosclerosis. Direct connection to adjacent vessels may support angiogenesis in this disease. Sustained angiogenesis may be an important determinant of clinical otosclerosis.

Measles Virus Prevalence in Otosclerotic Stapes Footplate Samples

HYPOTHESIS

The cause of otosclerosis is still unknown. Persistent measles virus infection of the otic capsule is supposed to be one of the etiologic factors in otosclerosis. Chronic viral antigen expression on the surface of infected cells can induce a secondary autoimmune reaction against the otic capsule.

BACKGROUND

In the past 15 years, some reports proposed the possible etiologic role of measles virus in otosclerosis. The presence of measles virus was shown in otosclerotic patients by reverse-transcriptase polymerase chain reaction amplification of the viral RNA, detecting the viral proteins by immunohistochemistry and detecting antimeasles immunoglobulin G in the perilymph samples. Many concerns were elicited by these results.

METHODS

Nucleic acid was extracted from pulverized, frozen stapes footplate samples of otosclerotic patients. Measles virus RNA was amplified by reverse-transcriptase polymerase chain reaction: reverse transcription and the first round polymerase chain reaction amplification was performed by heat stable recombinant Thermus thermophilus polymerase, whereas in the nested round, polymerase chain reaction Taq-polymerase was used. Measles virus nucleoprotein RNA-specific oligonucleotide primers were used in these reactions. An Edmonston-type measles virus served as a positive control and cortical bone fragments or stapes superstructures served as negative controls.

RESULTS

Among 34 otosclerotic patients, 20 stapes footplate samples contained measles virus RNA. Measles virus RNA was not detected in other bone specimens of the patients.

CONCLUSION

The etiologic role of measles virus in the pathogenesis of otosclerosis should be considered. The 14 negative samples may be genetically determined otosclerotic cases.

Stapes surgery in osteogenesis imperfecta: results of a new series

OBJECTIVE

To evaluate the results of stapes surgery in osteogenesis imperfecta.

STUDY DESIGN

Audiological and clinical analysis of the results of stapes surgery in a consecutive series of 15 ears in 13 patients with osteogenesis imperfecta.

SETTING

Tertiary referral center.

RESULTS

Stapedotomy was successful in 11 of 12 ears in 11 patients with osteogenesis imperfecta type I. Air-bone gaps were within 10 dB in four ears and within 20 dB in the seven remaining ears. In one ear, revision surgery with malleovestibulopexy was needed to achieve this result. In another ear, the initial good result within 20-dB air-bone gap decreased to 28 dB; therefore, it is not considered as a success. In one other patient, revision surgery resulted in only marginal improvement in the hearing level. In one case of, probably, osteogenesis imperfecta type III, surgery resulted in a dead ear.

CONCLUSION

Stapedotomy successfully improved the hearing of patients with osteogenesis type I. These results are in accordance with those reported in a few previous series. It is questionable whether stapes surgery will be as successful in osteogenesis imperfecta types other than type I.

Do the genes that cause otosclerosis reduce susceptibility to otitis media?

HYPOTHESIS

The genetic factors that cause otosclerosis reduce susceptibility to otitis media.

BACKGROUND

Susceptibility to some infectious diseases is modulated by host genetic factors. Genes that reduce the morbidity and mortality of infectious diseases may confer a selective advantage and achieve high-frequency in at-risk populations. Acute otitis media in the pre-antibiotic era frequently led to complications with high morbidity and mortality. The long-term sequela of acute otitis media is chronic otitis media. Chronic otitis media has a prevalence of 0.5 to 2 percent in the Caucasian population. Clinical otosclerosis occurs in 1 percent of Caucasians. Histologic otosclerosis occurs in 10 percent of Caucasians.

MATERIALS AND METHODS

Retrospective analysis of 2,362 subjects with surgically confirmed otosclerosis. Subjects' medical records were reviewed for evidence of chronic otitis media. The incidence of chronic otitis media in the general population was compared with the subject population.

RESULTS

Of the 2,362 subjects with surgically confirmed otosclerosis, one subject with evidence of chronic otitis media was identified. The incidence of chronic otitis media in the subject population is 0.04 percent (p < 0.0001).

CONCLUSIONS

The incidence of chronic otitis media in subjects with a surgically confirmed diagnosis of otosclerosis is significantly lower than expected. The genes that cause otosclerosis may confer resistance to the pathogens that cause chronic otitis media and/or acute otitis media. The mechanism of resistance is unknown.