Histologic variants in otosclerosis

Cartilage tympanoplasty in smokers

OBJECTIVES

We compared the outcomes of cartilage tympanoplasty in nonsmokers and smokers.

METHODS

We performed a retrospective chart review of patients who underwent cartilage tympanoplasty in a tertiary academic medical center from 1991 to 2010. There were 129 operations in 118 patients; 84 operations were performed in nonsmokers and 45 operations were performed in smokers. The primary outcome measure was the tympanic membrane graft take rate at the interval and most recent follow-up visits. Secondary measures included recurrence, the need for revision surgery, and hearing outcomes.

RESULTS

Nonsmokers and smokers had comparable long-term rates of intact eardrums (90.6% versus 92.9%; p = 0.99). There was a trend toward a higher rate of recurrent or persistent disease requiring further operation for smokers (13.3% versus 4.7%; p = 0.09). Both groups had improvement in pure tone averages (12.1 dB in nonsmokers and 12.8 dB in smokers) and air-bone gaps (9.6 dB in nonsmokers and 5.1 dB in smokers), although the rates were not statistically significantly different from each other. The rates of success of cartilage tympanoplasty in smokers appear superior to previously published rates of noncartilage tympanoplasty.

CONCLUSIONS

Cartilage tympanoplasty has success rates and postoperative audiological measures that are comparable between smokers and nonsmokers. In smokers, cartilage grafting is superior to noncartilage grafting and is recommended for any patient who smokes and is undergoing tympanoplasty.

Evolution of otosclerosis to cochlear implantation

INTRODUCTION

Otosclerosis is an osteodystrophy of the labyrinthine capsule producing conductive hearing loss. If the process invades the cochlea, a sensorineural hearing loss usually takes place. The cochlear implant is a good alternative in these patients.

OBJECTIVE

To ascertain the behaviour of cochlear implantation in otosclerosis.

MATERIAL AND METHODS

We reviewed a database of 250 patients that underwent cochlear implantation, performing a retrospective study of 13 patients with clinical, audiological and/or imaging findings of bilateral otosclerosis. The 26 ears were studied as to their natural history, previous surgeries, evolution to profound hearing loss, computed tomography images, complications and functional results.

RESULTS

Of the cases studied, 46% were female and 54% were men, with a mean age of 26 years at the onset of conductive hearing loss. Stapes surgery was performed in 19 ears (73%), with a mean patient age of 29 years, and 53% of them underwent cochlear implantation. Computed tomography results showed that there were signs of different degrees of radiological affectation in 54% of the ears. A total of 3 complications took place (23%): implant failure, overstimulation of the facial nerve and bilateral tinnitus were found. One year after implantation, the average percentages of correct 2-syllable words were 80% and 85% in open sentences.

CONCLUSIONS

Patients having profound bilateral sensorineural hearing loss secondary to otosclerosis obtain great benefit from cochlear implantation.

Randomized study comparing fascia and cartilage grafts in myringoplasty

OBJECTIVES

The study compares the medium-term outcomes of myringoplasty procedures using fascia and cartilage grafts.

METHODS

Patients with chronic otitis media with perforations larger than 50% of the size of the tympanic membrane were included in a randomized, controlled, prospective clinical trial. The perforations were repaired with either temporalis fascia (20 ears) or cartilage (18 ears) grafts selected randomly. A search of the literature was performed to look for other randomized studies comparing fascia and cartilage.

RESULTS

The graft take rates of fascia and cartilage grafts at 24 months were 84.2% and 80%, respectively. The postoperative air-bone gaps and hearing gains at 24 months were 16.97 dB and 13.63 dB, respectively, in the fascia group and 20.63 dB and 12.60 dB, respectively, in the cartilage group. There was no significant difference in the graft take rates or postoperative hearing between the two groups. The literature search identified one other randomized study comparing fascia and cartilage grafts in the repair of large perforations. The pooled data from the two studies did not show a difference in the graft take rates or hearing gains between cartilage and fascia.

CONCLUSIONS

There was no statistical difference in the outcomes of fascia and cartilage grafts in the repair of large perforations.

Origin and growth of otosclerosis

CONCLUSION

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

OBJECTIVES

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

METHODS

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

RESULTS

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

Correlations between CT scan findings and hearing thresholds in otosclerosis

CONCLUSION

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

OBJECTIVES

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

METHODS

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

RESULTS

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

Mechanical properties of stapedial annular ligament

Stapedial annular ligament (SAL) provides a sealed but mobile boundary between the stapes footplate and oval window bony wall. Mechanical properties of the SAL affect the transmission of ossicular movement into the cochlea in sound conduction. However, the mechanical properties of this tissue have never been investigated due to its complexity. In this paper, we report measurement of the viscoelastic properties of SAL on human cadaver temporal bones using a micro-material testing system with digital image correlation analysis. The measured load-deformation relations of SAL samples were converted into shear stress-shear strain relationship, stress relaxation function, and ultimate shear stress and shear strain of the SAL. The hyperelastic Ogden model was used to describe constitutive behavior of the SAL and a 3D finite element model of the experimental setup with SAL was created for assessing the effects of loading variation and measurement errors on results. The study demonstrates that the human SAL is a typical viscoelastic material with hysteresis, nonlinear stress-strain relationship and stress relaxation function. The shear modulus changes from 3.6 to 220 kPa when the shear stress increases from 2 to 140 kPa. These results provide useful information on quasi-static behavior of the SAL.

Computed tomography and otosclerosis: a practical method to correlate the sites affected to hearing loss

OBJECTIVES

We present a practical method for correlating computed tomography (CT) scans with hearing loss in otosclerosis.

METHODS

We reviewed the CT scans of 18 patients (34 ears) with clinical otosclerosis who were seen between 2007 and 2008. The scans were reviewed by an otologist in a clinical office setting, followed by a blinded radiologist working at an imaging workstation. The 5 most commonly affected sites in otosclerosis were evaluated for evidence of otospongiosis and then correlated with the degree of air-bone gap and sensorineural hearing loss.

RESULTS

Positive CT findings were noted in 70.5% of ears, with a 94% concordance between readings. The sites affected included the ante fenestram (21 ears), round window niche (12), cochlear promontory (4), cochlear apex (3), and posterior fenestram (2). The average air-bone gap increased with each additional site of involvement within an otic capsule (p = 0.004). The bone conduction threshold also increased, on average, with each additional affected site (p = 0.047).

CONCLUSIONS

Most patients with clinical evidence of otosclerosis have evidence of otosclerosis on CT that is readily detected in the office setting. Ears with more affected sites have a significantly greater degree of air-bone gap and sensorineural hearing loss.

Relationship between high-resolution computed tomography densitometry and audiometry in otosclerosis

OBJECTIVE

The aim of this study is to evaluate the usefulness of high-resolution computed tomography (HRCT) densitometry in the diagnosis of otosclerosis and to investigate the relationship between CT densitometry and audiometry.

METHODS

HRCT findings and audiometry were compared among 34 patients (34 ears, the otosclerosis group) with surgically confirmed otosclerosis between January 2007 and December 2007 and 33 patients (33 opposite normal ears, the control group) with facial paralysis diagnosed at the same period of time. Seven regions of interest (ROI) were set manually around the otic capsule on the axial slice of 0.75-mm-thick CT image. The mean CT values of these seven regions were measured. In each ROI, the mean CT value of the otosclerosis group and that of the control group were compared. Based on the CT findings, the ears with otosclerosis were classified into two groups: Group A showed no pathological CT findings; Group B showed low density around the cochlea. In the otosclerosis group, the relationship between the findings of CT and the results of audiometry was analyzed.

RESULTS

The mean CT values in the area posterior to the oval window and anterior to the oval window were significantly lower for the otosclerosis group compared with the control group (the former t=-2.030, p=0.046; the latter Z=-4.979, p<0.01). Group A consisted of 30 patients, 7 of which (23.33%) exhibited conductive hearing loss, and 23 of which (76.67%) exhibited mixed hearing loss; Group B had 4 patients, all with mixed hearing loss. For the otosclerosis group, the mean CT value in the area posterior to the oval window was positively correlated with the mean air conduction threshold (r=0.4273, p=0.0117) and with the mean air-bone gap (r=0.3995, p=0.0192).

CONCLUSION

Quantitative evaluation of CT with slices less than 1mm in thickness may provide important information for the diagnosis and assessment of otosclerosis which are unattainable through other methods.

Cochlear otosclerosis adjacent to round window and oval window: a histopathological temporal bone study

HYPOTHESIS

The purpose of this histopathological study is to examine temporal bones of patients with cochlear otosclerosis adjacent to the round window or adjacent to the oval window as compared with healthy controls.

BACKGROUND

It is unclear if the extent and site of otosclerosis affects the extent of damage to cochlear structures and hearing loss.

METHODS

Twelve temporal bones from 10 patients with cochlear otosclerosis adjacent to the round window, 11 temporal bones from 8 patients with cochlear otosclerosis adjacent to the oval window, and 12 bones of healthy age-matched controls were selected for study. We calculated the number of spiral ganglion cells, changes in cochlear structures, the extent and site of cochlear otosclerosis, and audiometric data.

RESULTS

The loss of spiral ganglion cells and the absence of outer hair cells in patients with cochlear otosclerosis adjacent to the round window were significantly higher than those in patients with cochlear otosclerosis adjacent to the oval window and healthy controls. The area of the spiral ligament in patients with cochlear otosclerosis adjacent to the oval window was significantly smaller than that in healthy controls. However, no significant difference was found in the spiral ligament of patients with cochlear otosclerosis adjacent to the round window and healthy controls. There was no significant difference between patients with cochlear otosclerosis and age-matched controls in audiometric data.

CONCLUSION

Cochlear otosclerosis adjacent to the round window caused significantly more damage to spiral ganglion cells and outer hair cells than cochlear otosclerosis adjacent to the oval window without loss of spiral ligament.

Factors associated with incomplete insertion of electrodes in cochlear implant surgery: a histopathologic study

OBJECTIVES

Atraumatic and complete insertion of the electrode array is a stated objective of cochlear implant surgery. However, it is known that obstructions within the cochlea such as new bone formation, cochlear otosclerosis, temporal bone fracture, and cochlear anomalies may limit the depth of insertion of the electrode array. In addition, even among patients without obvious clinical or radiographic indicators of obstruction, incomplete insertion may occur. The current study is a histopathologic evaluation of possible sources of resistance to insertion of the electrode array using the temporal bone collection of the Massachusetts Eye and Ear Infirmary.

METHODS

Forty temporal bones from patients who in life had undergone cochlear implantation were evaluated. Temporal bones were removed at autopsy and fixed and prepared for histologic study by standard techniques. Specimens were then serially sectioned and reconstructed by 2-dimensional methods. Two electrode metrics were determined for each bone: the inserted length (IL: the distance measured from the cochleostomy site to the apical tip of the electrode) and the active electrode length (AEL: the distance between the most basal and most apical electrodes on the electrode array). The ratio of these two metrics (IL/AEL) was used to split the temporal bones into two groups: those with incomplete insertion (n = 27, IL/AEL <1.0) and those with complete insertion (n = 13, IL/AEL ≥ 1.0). Seven possible histopathologic indicators of resistance to insertion of the electrode due to contact with the basilar membrane, osseous spiral lamina and/or spiral ligament were evaluated by analysis of serial sections from the temporal bones along the course of the electrode tracks.

RESULTS

Obvious obstruction by abnormal intracochlear bone or soft tissue accounted for only 6 (22%) of the 27 partial insertions. Of the remaining 21 bones with incomplete insertions and 13 bones with complete insertions, dissection of the spiral ligament to the lateral cochlear wall was the only histopathologic indicator of insertion resistance identified with significantly higher frequency in the partial-insertion bones than in the complete-insertion bones (p = 0.003). An observed trend for the percentage of complete insertions to decrease with the number of times the electrode penetrated the basilar membrane did not reach significance. In the bones without an obvious obstruction, the most frequently observed indicator of insertion resistance was dissection of the spiral ligament (with no contact of the lateral cochlear wall) identified in 67% (14/21) of partial-insertion bones and in 92% (12/13) of complete-insertion bones.

CONCLUSION

These results are consistent with the view that (1) electrode contact with cochlear structures resulting in observable trauma to the basilar membrane, osseous spiral lamina and/or spiral ligament does not necessarily impact the likelihood of complete insertion of the electrode array and (2) once contact trauma to the spiral ligament reaches the point of dissection to the cochlear wall, the likelihood of incomplete insertion increases dramatically.

Three-dimensional reconstruction of the otosclerotic focus

CONCLUSIONS

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

OBJECTIVES

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

METHODS

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

RESULTS

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

Reliability of high-resolution CT scan in diagnosis of otosclerosis

OBJECTIVE

To assess the reliability of high-resolution computed tomographic scan (HRCT scan) for the diagnosis of otosclerosis and to determine its usefulness to predict hearing deterioration and surgical difficulties.

STUDY DESIGN

Prospective study.

SETTING

Tertiary reference center.

PATIENTS

Two hundred nine ears (200 patients) presenting progressive conductive hearing loss with normal tympanic membrane, abnormal stapedial reflex, and scheduled for stapes surgery. The mean age was 47.3 years.

INTERVENTION

All patients underwent HRCT scan before surgery (slice thickness of 0.6 to 1 mm). Stapedotomy was performed in 99% of cases.

MAIN OUTCOME MEASURES

High-resolution computed tomographic scan results were categorized as positive, doubtful, or negative. We classified a CT scan as positive for otosclerosis when a hypodense focus was seen around the otic capsule. Preoperative and postoperative air- and bone-conduction thresholds were collected.

RESULTS

Of 209 HRCT scans, 84.2% were classified positive, 8.6% doubtful, and 7.2% negative. In all patients with positive CT scan, otosclerosis was confirmed in surgery. Among 15 negative cases, we found 4 minor malformations and 1 fracture of the stapes. Footplate incidents (mobilized, floating, or fractured footplate; 5.3%) occurred significantly more frequently when an HRCT scan was negative or doubtful (p = 0.05). Mean preoperative air-bone gap was 27.7 dB (standard deviation, 10). Mean postoperative air-bone gap was within 10 dB in 65% and within 20 dB in 92% of cases. Greater than 10 dB deterioration of bone-conduction thresholds occurred in 2% of cases. Mean preoperative and postoperative bone-conduction thresholds were significantly lower in cases of round window obliteration, pericochlear, or internal auditory canal hypodensities (p < 0.005 and p < 0.0001, respectively).

CONCLUSION

In our series, the sensitivity of HRCT scan to otosclerosis was 95.1%. Hypodense otosclerotic foci were mostly localized at the anterior part of footplate. Negative or doubtful cases were associated with the highest incidence of stapes footplate complications. Foci involving otic capsule, internal auditory canal, or round window led to a significantly higher risk of sensorineural hearing loss.

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.

Histopathology of nonotosclerotic stapes fixations

HYPOTHESIS

Different diseases without exact histopathologic classification can cause stapes ankylosis.

BACKGROUND

Otosclerosis is a complex bone remodeling disorder of the otic capsule due to persisting measles virus infection and consecutive inflammatory reaction. In fact, clinical and demographic features of otosclerosis have reference to stapes ankylosis. In the clinical practice, otosclerosis and stapes ankylosis are incorrect synonyms.

METHODS

Nonotosclerotic stapes footplates (n = 284) removed during stapedectomy were analyzed histologically. Otosclerosis was excluded during the histologic preselection (n = 437). Total RNA was extracted, and measles virus-specific reverse-transcriptase-polymerase chain reaction was performed.

RESULTS

Nonotosclerotic stapes ankylosis was associated with total absence of measles virus RNA. Six main types of nonotosclerotic stapes fixations could be distinguished histologically: annular calcification (n = 152; 53.5%), globular fibrosis (n = 49; 17.25%), lymphocytic infiltration (n = 31; 10.9%), hemosiderosis (n = 22; 7.75%), granulomas (n = 17; 6%) and amyloidosis (n = 13; 4.6%). Fragmentation of nonotosclerotic stapes footplates was infrequent (7%) during stapes surgery. Only 1 floating footplate (0.35%) was reported.

CONCLUSION

Two thirds of nonotosclerotic stapes footplates represented complete pathologic bone remodeling. Unlike otosclerosis, nonotosclerotic stapes fixations were characterized by basic histopathologic findings without organ specificity that can also be identified in case of different diseases. Prevalence of nonotosclerotic stapes ankylosis is approximately 30 to 40% among stapes fixation cases. The long-term prognosis and surgical considerations theoretically differ from those of otosclerosis.

Fisch's reversal steps stapedotomy: when to use it?

OBJECTIVE

To determine that the use of Fisch's reversal steps stapedotomy is recommended only when the visible portion of the footplate is blue in all its points before removing the stapes superstructure.

STUDY DESIGN

Prospective study.

MATERIALS AND METHODS

This study started on January 2007 and ended on June 2007, when the statistical data reached significance. Fifty patients with otosclerosis were examined. Four otosclerosis were excluded from the study following the exclusion criteria indicated by Fisch (obliterative otosclerosis and narrow oval niche). Finally, 46 otosclerosis patients were considered for the study. For all patients, stapedotomy procedures using the reversal steps technique by Fisch were planned. The study group was divided into 2 groups (A and B) on the basis of the footplate color before removing the stapes superstructure. Group A included otosclerosis with blue footplate (n = 34). Group B included otosclerosis with white footplate (n = 12). We estimated whether the reversal steps stapedotomy proposed by Fisch significantly avoids incus complications (luxation and subluxation) and stapes footplate complications (luxation and fracture) both in blue and white otosclerosis.

MAIN OUTCOME MEASURES

Footplate color, incidence of complications.

RESULTS

The footplate fenestration had not caused fractures or luxation of footplate in both groups. The fracture of the anterior crus had caused 5 footplate complications (2 luxations and 3 fractures) in Group B, but none in Group A. This difference was significant. In Group A, we had no subluxation/luxation of the incus. In Group B, we had 3 incus subluxations. This difference was significant.

CONCLUSION

The use of Fisch's reversal steps stapedotomy is recommended only when the visible portion of the footplate, before removing the stapes superstructure, is blue in all its points, that is, "blue otosclerosis," because only in this case that the original idea of Fisch avoids incus and footplate complications. When the visible portion of the footplate, before removing the stapes superstructure, is white in all or in most of its points, that is, "white otosclerosis," the reversal steps technique by Fisch is not recommended because it does not avoid incus luxation/subluxation and footplate complications (fracture and luxation of the anterior half).

High-resolution computed tomography in the diagnosis of otosclerosis in Taiwan

BACKGROUND

Otosclerosis is rare in Asians, and the clinical role of imaging remains controversial. We sought to clarify the tomographic findings of otosclerosis in Taiwanese patients and determine the value and necessity of high-resolution computed tomography (HRCT) of the temporal bone in diagnosing the disease in Taiwan.

METHODS

This retrospective study enrolled 22 patients (24 ears) with clinically, surgically and pathologically confirmed otosclerosis. All subjects underwent HRCT of the temporal bone; the images were then reviewed at workstations. The control group consisted of 15 patients.

RESULTS

HRCT was positive in 46% of the clinically, surgically and pathologically confirmed otosclerotic ears. Patients with a positive imaging study had a smaller preoperative air-bone gap and a significantly shorter duration of the disease. The duration of the disease also tended to be greater in patients with a larger preoperative air-bone gap.

CONCLUSION

HRCT has high specificity (100%) but low sensitivity (46%) for the diagnosis of otosclerosis in Taiwanese patients despite progress in radiology. The low image positive rate we found, compared with that in Western literature, may stem from a greater percentage of inactive otosclerosis.

Taste disturbance after stapes surgery--clinical and experimental study

CONCLUSION

Most of the clinical cases experienced taste disturbance after stapes surgery, and in a few cases this disturbance persisted for a long time. The animal experiment suggested the role of geniculate ganglion (GG) cells in nerve generation.

OBJECTIVES

To clinically examine taste disorder and its recovery after stapes surgery and experimentally demonstrate a role of GG.

PATIENTS AND METHODS

Taste function after preservation of chorda tympani nerve (CTN) in stapes surgery was prospectively investigated with a questionnaire and electrogustometry (EGM). Further, expression of neurotrophic factors in GG after injury of CTN was examined by in situ hybridization histochemistry (ISSH) and RT-PCR.

RESULTS

Among the cases, 15/18 (83.3%) were associated with taste disturbance and 6/18 (33.3%) were associated with tongue numbness 2 weeks after surgery; however, the symptoms ceased in 14/18 cases (77.8%). Two weeks after surgery, the EGM threshold was found to be elevated in 15/18 cases (83.3%), while in 10/18 cases (55.6%), it did not decrease until 1 year after surgery. Expression of ISSH and amplified bands of BDNF and GFR increased at 7 and 14 days after nerve injury in ipsilateral GGs and also increased at 7 days on the contralateral side.

Gene expression analysis of human otosclerotic stapedial footplates

Otosclerosis is a complex disease that results in a common form of conductive hearing loss due to impaired mobility of the stapes. Stapedial motion becomes compromised secondary to invasion of otosclerotic foci into the stapedio-vestibular joint. Although environmental factors and genetic causes have been implicated in this process, the pathogenesis of otosclerosis remains poorly understood. To identify molecular contributors to otosclerosis we completed a microarray study of otosclerotic stapedial footplates. Stapes footplate samples from otosclerosis and control patients were used in the analysis. One-hundred-and-ten genes were found to be differentially expressed in otosclerosis samples. Ontological analysis of differentially expressed genes in otosclerosis provides evidence for the involvement of a number of pathways in the disease process that include interleukin signaling, inflammation and signal transduction, suggesting that aberrant regulation of these pathways leads to abnormal bone remodeling. Functional analyses of genes from this study will enhance our understanding of the pathogenesis of this disease.

Clinical and genetic analysis of two Tunisian otosclerosis families

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

The coding polymorphism T263I in TGF-β1 is associated with otosclerosis in two independent populations

Otosclerosis is a progressive hearing loss characterized by an abnormal bone homeostasis of the otic capsule that leads to stapes fixation. Although its etiology remains unknown, otosclerosis can be considered a complex disease. Transforming growth factor-beta 1 (TGF-beta1) was chosen for a case-control association study, because of several non-genetic indications of involvement in otosclerosis. Single nucleotide polymorphism (SNP) analysis in a large Belgian-Dutch sample set gave significant results (P = 0.0044) for an amino acid changing SNP, T263I. Analysis of an independent French population replicated this association with SNP T263I (P = 0.00019). The results remained significant after multiple testing correction in both populations. Haplotype analysis and the results of an independent effect test using the weighted haplotype (WHAP) computer program in both populations were both compatible with SNP T263I being the only causal variant. The variant I263 is under-represented in otosclerosis patients and hence protective against the disease. Combining the data of both case-control groups for SNP T263I with a Mantel-Haenszel estimate of common odds ratios gave a very significant result (P = 9.2 x 10(-6)). Functional analysis of SNP T263I with a luciferase reporter assay showed that the protective variant I263 of TGF-beta1 is more active than the WT variant T263 (P = 1.6 x 10(-6)). On the basis of very low P-values, replication in an independent population and a functional effect of the protective variant, we conclude that TGF-beta1 influences the susceptibility for otosclerosis, and that the I263 variant is protective against the disease.

Histopathology of ossicular grafts and implants in chronic otitis media

OBJECTIVES

We describe the histopathology of ossicular grafts and implants so as to provide insight into factors that may influence functional results after surgery for chronic otitis media.

METHODS

Histopathologic observations were made on 56 cases: 50 surgical specimens and 6 temporal bone cases in which the graft was sectioned in situ.

RESULTS AND CONCLUSIONS

Autogenous malleus, incus, and cortical bone grafts behaved in a similar manner and maintained their morphological size, shape, and contour for extended periods of time, at least up to 30 years. These histopathologic observations support the continued use of autograft ossicular and cortical bone grafts for middle ear reconstruction. Cartilage grafts developed chondromalacia with resulting loss of stiffness and showed a tendency to undergo resorption. Synthetic prostheses made of porous plastic (Plastipore, Polycel) elicited foreign body giant cell reactions with various degrees of biodegradation of the implants. Prostheses made of hydroxyapatite and Bioglass were enveloped by a lining of connective tissue and mucosal epithelium. The Bioglass material was broken down into small fragments and partially resorbed by a host response within the middle ear. These results warrant caution in the use of prostheses made of porous plastic or Bioglass.

Vestibular-Evoked Myogenic Potentials in Patients With Otosclerosis Using Air- and Bone-Conducted Tone-Burst Stimulation

OBJECTIVE

Otosclerosis is a progressive disease with a remodeling process causing ossicular malformation and conductive hearing loss. The aim of this study was to investigate whether vestibular-evoked myogenic potential (VEMP) correlates with the progression of otosclerosis.

DESIGN

Fifteen patients with otosclerosis (21 ears) without operation and 10 healthy subjects (20 ears) underwent VEMP test using air-conducted (AC) and bone-conducted (BC) tone-burst stimulation.

SETTING

Tertiary referral university hospital.

RESULTS

In 21 unoperated otosclerotic ears, 5 ears (24%) showed present AC-VEMPs, and 16 ears had absent AC-VEMPs. Conversely, 16 ears (76%) displayed present BC-VEMPs and 5 ears with absent BC-VEMPs. In those with both AC- and BC-VEMPs, none of them showed air-bone gap greater than 30 dB; in those with absent AC-VEMPs but present BC-VEMPs, 27% of the ears had air-bone gap greater than 30 dB; and in those with absence of both AC- and BC-VEMPs, 80% of the ears revealed air-bone gap greater than 30 dB. Thus, a significant relationship existed among the presence of AC-VEMPs, BC-VEMPs, and magnitude of conductive hearing loss.

CONCLUSION

The presence of an AC-VEMP may indicate an earlier stage of otosclerosis, although absent BC-VEMP infers a later stage. Restated, AC-VEMPs may complement the results obtained with BC-VEMPs to classify the stage of otosclerosis.

Otosclerosis: etiopathogenesis and histopathology

Otosclerosis is a disease of the bony labyrinth manifesting clinically as a progressive conductive hearing loss, a mixed-type hearing loss, or a sensorineural hearing loss. The age of onset of the hearing loss caused by otosclerosis is principally between 15 and 40 years. Although histopathological inner ear changes due to otosclerosis have been very well documented, the true etiopathogenesis of the disease has yet to be described despite intensive research. Both genetic and environmental factors have been implicated, however.

Computed tomography in the diagnosis of otosclerosis

OBJECTIVES

To identify the main tomographic findings of otosclerosis and to evaluate the usefulness of high-resolution computed tomography as a diagnostic method for this osteodystrophy.

STUDY DESIGN AND SETTING

A prospective and multicenter study consisting of computed tomography (CT) of the temporal bone was conducted on 54 patients with a clinical and surgical diagnosis of otosclerosis. Twenty-two patients were included in the control group.

RESULTS

The CT scan was positive in 87% of the patients. The tomographic findings were mainly bilateral and fenestral foci were more prevalent.

CONCLUSIONS

CT showed a high rate of positivity, mainly for fenestral lesions. Foci anterior to the oval window were the most prevalent in this population.

SIGNIFICANCE

CT is useful as a diagnostic method and therapeutic indicator of otosclerosis.

EBM RATING

B-3b.

Osteoprotegrin knockout mice demonstrate abnormal remodeling of the otic capsule and progressive hearing loss

OBJECTIVES

The otic capsule, when compared with other bones in the body, is unique in that it undergoes no significant remodeling of bone after development. We previously demonstrated that osteoprotegerin (OPG), which inhibits formation and function of osteoclasts, is produced at high levels in the inner ear of normal mice and secreted into the perilymph from where it diffuses into the surrounding otic capsule bone through a lacunocanalicular system. To test our hypothesis that the high level of OPG may be important in the inhibition of otic capsule remodeling, we studied the light microscopic histology of the otic capsule in OPG knockout mice for evidence of abnormal remodeling of bone. We also tested the hearing in OPG knockout mice to determine whether OPG and its influence on surrounding bone is important for auditory function.

METHODS

Temporal bone histopathology and pathophysiology were compared in homozygous OPG knockout mice and C57BL/6 (B6) mice, the background strain for the knockouts. Auditory function in age-matched animals from each group was evaluated at approximately 4-week intervals from 8 to 21 weeks using frequency-specific auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE). After each of the last three evaluations, the cochleae from one mouse of each group were harvested, processed, and examined by light microscopy.

RESULTS

Osteoprotegerin knockout mice demonstrated abnormal remodeling of bone within the otic capsule with multiple foci showing osteoclastic bone resorption and formation of new bone. Such changes were not seen in the age-matched B6 controls. The active bone remodeling process in the knockout animals showed many similarities to otosclerosis seen in human temporal bones. Over the time period that we monitored, auditory function was significantly and progressively compromised in the knockout animals relative to B6 controls. At the earliest age of test (8 wk), the loss was apparent as a mild, high-frequency reduction in sensitivity by ABR. In contrast, DPOAE losses in the knockouts were substantial even at 8 weeks, and by 21 weeks, these losses exceeded our equipment limits. Results of ABR testing showed hearing sensitivity changes in the animals of the background strain were confined largely to the high frequencies, whereas OPG knockouts demonstrated substantial low-frequency shifts in addition to those at high frequencies.

CONCLUSIONS

The histopathological and pathophysiological findings in OPG knockout mice support the hypothesis that OPG is important in the inhibition of bone remodeling within the otic capsule and the maintenance of normal auditory function. This mouse may provide a valuable animal model of human otosclerosis.

Monogenic nonsyndromic otosclerosis: audiological and linkage analysis in a large Greek pedigree

OBJECTIVE

The aim of our study was to characterize the hearing impairment in a large multigenerational Greek family with autosomal dominant nonsyndromic otosclerosis and to perform genetic linkage analysis to known otosclerosis loci and collagen genes. In addition, we looked for mutations in the NOG gene to rule out congenital stapes ankylosis syndrome.

METHODS

Audiological analysis of the affected persons was based on multiple linear regression (MLR) analysis and construction of age-related typical audiograms (ARTA). Genotyping of microsatellite DNA polymorphisms for known otosclerosis (OTSC) loci or collagen genes and linkage analysis using the MLINK computer program were performed. The coding region of the NOG gene was screened for mutations by direct DNA sequencing.

RESULTS

The hearing loss in this family appears in childhood as conductive, but soon becomes mixed. Because the additional sensorineural component is progressive, this finally has lead to a pure sensorineural hearing loss in some family members, as the conductive component is masked. Audiological analysis showed an age-independent conductive component and a progressive frequency-specific sensorineural component. Linkage analysis excluded linkage to the four known otosclerosis loci (OTSC1, OTSC2, OTSC3, and OTSC5), as well as to the COL1A1 and COL1A2 genes. Mutation analysis of the coding region of the NOG gene did not reveal any disease causing mutation.

CONCLUSIONS

This study represents the first description of a detailed audiological analysis in a large pedigree segregating otosclerosis as a monogenic autosomal dominant trait. Exclusion of the four known otosclerosis loci in this family shows that monogenic otosclerosis is a genetically heterogeneous disease involving at least five different genes. A mutation in the NOG gene is not the underlying molecular mechanism of the early onset otosclerosis segregating in this family.

Three-dimensional regular arrangement of the annular ligament of the rat stapediovestibular joint

The stapes footplate articulates with the vestibular window through the annular ligament. This articulation is known as the stapediovestibular joint (SVJ). We investigated the ultrastructure of adult rat SVJ and report here on the characteristic ultrastructure of the corresponding annular ligament. Transmission electron microscopy showed that this annular ligament comprises thick ligament fibers consisting of a peripheral mantle of microfibrils and an electron-lucent central amorphous substance that is regularly arranged in a linear fashion, forming laminated structures parallel to the horizontal plane of the SVJ. Scanning electron microscopy revealed that transverse microfibrils cross the thick ligament fibers, showing a lattice-like structure. The annular ligament was vividly stained with elastica van Gieson's stain and the Verhoeff's iron hematoxylin method. Staining of the electron-lucent central amorphous substance of the thick ligament fibers by the tannate-metal salt method revealed an intense electron density. These results indicate that the annular ligament of the SVJ is mainly composed of mature elastic fibers.

Late Failure of Cochlear Implantation Resulting From Advanced Cochlear Otosclerosis: Surgical and Programming Challenges

OBJECTIVE

The objective of this study was to discuss cochlear implantation in the setting of severe cochlear otosclerosis and review programming challenges in a patient whose performance is deteriorating as a result of advancing disease.

STUDY DESIGN

We conducted a case report and literature review.

SETTING

Tertiary care medical center. PATIENTS, INTERVENTION, AND RESULTS: A case is presented of a 66-year-old man with otosclerosis who initially had good benefit from a cochlear implant but gradually lost benefit even with reimplantation. Imaging studies demonstrated severely distorted otic capsule anatomy from cochlear otosclerosis.

CONCLUSIONS

Advancing cochlear otosclerosis can result in a severely thinned and distorted otic capsule. Although cochlear implantation is generally beneficial in cochlear otosclerosis, implantation in certain severe cases may be complicated as a result of difficulties with cerebrospinal fluid leak, programming challenges, and other potential hazards that can occur with a distorted anatomy.

Questioning the Relationship between Cochlear Otosclerosis and Sensorineural Hearing Loss: A Quantitative Evaluation of Cochlear Structures in Cases of Otosclerosis and Review of the Literature

BACKGROUND

The literature provides conflicting information regarding the prevalence and cause of sensorineural hearing loss (HL) in individuals with otosclerosis.

OBJECTIVE

The purpose of this study was to further evaluate the association between involvement of the cochlear endosteal layer with otosclerosis and sensorineural HL.

STUDY DESIGN

Retrospective case review.

METHODS

Temporal bones and audiograms from five individuals with otosclerosis were evaluated. The cochlear elements were quantified. The location and extent of the cochlear element loss was correlated with the location and extent of endosteal involvement with otosclerosis.

RESULTS

A reduction in the population of cochlear elements was observed in most individuals; however, the reduction was not proportional to the extent of endosteal involvement with otosclerosis. The cochlear elements remained normal adjacent to some areas of endosteal involvement with otosclerosis. One individual with extensive cochlear otosclerosis had normal hearing and predominantly normal cochlear elements.

CONCLUSION

This study demonstrates a variable amount of degeneration of the cochlear elements in individuals with otosclerotic involvement of the endosteum. The reduction in the population of cochlear elements was not related to the extent and location of endosteal involvement with otosclerosis. These findings suggest that factors that limit the effect of otosclerotic endosteal involvement on the cochlear elements or processes that effect the cochlear elements directly and are independent of bone involvement may be present.

Correlation of CT analysis and audiometry in Japanese otosclerosis

OBJECTIVE

To determine the extent of audiometric correlation with CT findings.

METHODS

Forty-four patients (82 ears) with surgically confirmed otosclerosis underwent preoperative CT examination. Based on the computed tomography (CT) findings, the ears were classified into five groups as follows: Group A, the group with no pathological CT findings; Group B1, the group with demineralization localized in the region of the fissula antefenestram; Group B2, the group with demineralization extending towards the cochleariform process from the anterior region of the oval window; Group B3, the group with extensive demineralization surrounding the cochlea; and Group C, the group with thick anterior and posterior calcified plaques.

RESULTS

There were 32 ears (39.0%) in Group A, 21 ears (25.6%) in Group B1, 16 ears (19.5%) in Group B2, 7 ears (8.5%) in Group B3, and 6 ears (7.3%) in Group C. The mean bone conduction levels were greater in the order of the extent of demineralization: Groups A, B1-B3 suggesting positive relationship between the cochlear function and the degree of labyrhinthine otosclerosis.

CONCLUSION

A good correlation between the preoperative CT findings and audiometry findings suggests that CT with a slice intervals between 0.5 and 1mm could provide useful informations in assuming the extent of otosclerosis in the inner ear.

Tomografia computadorizada no diagnóstico da otosclerose fenestral

OBJETIVO: Identificar os principais achados tomográficos da otosclerose fenestral e avaliar a utilidade da tomografia computadorizada de alta resolução (TCAR), como método diagnóstico dessa osteodistrofia. FORMA DE ESTUDO: Estudo prospectivo multicêntrico com tomografia computadorizada (TC) de ossos temporais. MATERIAL E MÉTODO: 54 pacientes com diagnóstico clínico e cirúrgico de otosclerose. Foi realizada uma análise tomográfica, em que foi avaliada a sensibilidade da TC no diagnóstico radiológico da otosclerose fenestral, sendo verificados os principais sítios de lesões dessa doença, como também a sua bilateralidade e simetria. Foram incluídos neste estudo 22 pacientes submetidos à TC de ossos temporais para investigação de outras afecções otológicas, que constituíram o grupo controle. RESULTADOS: A TC foi positiva em 87% dos pacientes (77% das orelhas). Os achados tomográficos foram bilaterais na maioria dos casos (78,7%), e o foco fenestral mais prevalente foi o foco anterior à janela oval (FAJO). CONCLUSÕES: A TC apresentou um alto índice de positividade e o FAJO foi o foco mais prevalente nessa população, podendo ser considerado um achado tomográfico altamente sugestivo de otosclerose.

Why is otosclerosis of low prevalence in Japanese?

OBJECTIVE

This study aimed to clarify the reasons why clinical otosclerosis, a very common disease among Caucasians, is not prevalent among Japanese.

STUDY DESIGN

The incidence, site, activity, and volume of otosclerotic foci were examined in 1011 temporal bone sections from 507 Japanese individuals.

SETTING

This study was prepared at the temporal bone laboratory, Fukushima Medical University, Fukushima.

RESULTS

Otosclerotic foci were observed in 2.56% of individuals and in 1.48% of the ears. The most common site of involvement was anterior to the oval window region, but this was only in 38.9% of the ears with otosclerotic foci. The otosclerotic foci were not involved in the stapediovestibular articulation or the endosteal layer of the otic capsule in any ears. An active change of the otosclerotic focus was seen in 33.3% of ears with otosclerosis. The volume of otosclerotic foci at the site anterior to the oval window region was less than 0.8 mm3 in 5 out of 7 ears.

CONCLUSION

The incidence of histologic otosclerosis among Japanese seemed to be almost the same as that among Caucasians. Three reasons why clinical otosclerosis was not as prevalent among Japanese as among Caucasians are suggested: low incidence of involvement of foci anterior to the oval window, low activity, and small lesion without involvement of the footplate and/or membranous labyrinth of the inner ear.

Round window atresia and its effect on sound transmission

OBJECTIVE

To document isolated round window atresia and to discuss its impact on current theories of inner ear function.

PATIENTS AND STUDY DESIGN

Retrospective analysis of isolated round window atresia suggesting an autosomal dominant inheritance pattern and review of current concepts of cochlear macromechanics.

SETTING

Tertiary referral center.

RESULTS

The unexpected finding of isolated round window atresia in two female patients of the same family was confirmed intraoperatively as well as postoperatively using high-resolution computed tomography. The current audiograms and the review of the literature highlight a mixed, but predominantly conductive, hearing impairment with thresholds at 30 to 40 dB. Implying that there is no pressure release mechanism for inner ear fluid displaced by the stapes footplate, a total conductive hearing loss would be expected.

CONCLUSIONS

The rare finding of round window atresia can be overlooked at surgery because of insufficient exposure of the round window niche. High-resolution computed tomography confirms the round window obliteration. It seems that an alternative way of cochlear stimulation takes place besides the concept of fluid bulk shifting. Surgery seems not to guarantee favorable results.

Histologic changes on stapedial footplate in otosclerosis. Correlations between histologic activity and clinical findings

OBJECTIVE

To quantify the relationship between the stage of histologic changes of the stapedial footplate in otosclerosis and the magnitude of preoperative hearing loss, tinnitus, vestibular disorder, and postoperative improvement of hearing.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

The study included 97 patients (ears) (69 female and 28 male patients), with conductive or mixed hearing loss who were operated on for otosclerosis. The criterion for including a patient in the study was otosclerosis established by tympanoscopy and confirmed by histologic examination of a piece of the stapedial footplate.

MAIN OUTCOME MEASURES

By the histologic features of the stapedial footplate fragments, the stage of the otosclerotic lesion was classified as spongiotic, fibrotic, or sclerotic. The patients were carefully matched for sex, age, duration of hearing impairment, presence of tinnitus, and vestibular symptoms. Preoperative and postoperative air-conduction and bone-conduction thresholds were calculated as an average of four frequencies (0.5, 1, 2, and 4 kHz). Analysis was subsequently carried out on the preoperative and postoperative air-bone gap and bone-conduction threshold improvement.

RESULTS

With regard to the histologic stage of otosclerotic lesions, tinnitus and vestibular disorders were present more frequently in patients with the sclerotic type of lesion. The type of otosclerotic lesion had no significant influence on the mean preoperative air-conduction threshold, bone-conduction threshold, and air-bone gap or on postoperative air-conduction threshold and bone-conduction threshold, but the postoperative air-bone gap was higher in patients with the fibrotic type of otosclerotic lesion and was highest in patients with the spongiotic type of otosclerotic lesion (p < 0.01).

CONCLUSIONS

Tinnitus, vestibular disorders, and better postoperative closure of the air-bone gap are present more frequently in patients with a sclerotic type of otosclerotic lesion on the stapedial footplate.

Experience with Stapedectomy in a Developing Country: A Review of 200 Cases

Since stapedectomy was first performed in 1956, many innovations have been described. We retrospectively analyzed 200 cases of stapedectomy that had been performed with standard otologic instruments. Of the 200 patients, 54 (27.0%) had significant sensory deafness associated with footplate fixation. In most cases, the footplate was partially removed (stapedotomy group); in the remainder, the footplate was removed in its entirety or subtotally (stapedectomy group). Of the 200 patients, 163 were available for short-term follow-up. The air-bone gap was closed to within 10 dB in roughly 83% of both groups. Although long-term follow-up was possible in only a limited number of cases, we believe that an experienced otologist working with standard equipment and a basic operating microscope can obtain satisfactory stapedectomy results with minimal complications.

Incidence and characteristics of otosclerosis in the Japanese population

OBJECTIVE

Otosclerosis is thought to be quite an uncommon disease in Japan. However, in recent years the incidence of this disease seems to have increased. Here we report about the characteristics and incidence of this disease in the Japanese population who underwent stapes surgery in our department.

METHODS

A total of 80 patients (115 ears), who underwent stapes surgery by a single surgeon in 21 years and 8 months were included in this study.

RESULTS

The incidence of clinical otosclerosis was found to be 0.22% among the outpatients with ear disease. During the first half of the period, the ratio of stapes surgery/tympanoplasty was less than 0.05. While, during the second half of this period, this ratio had increased to 0.08. The average number of stapes surgery performed in the first half period was 3.7 ears/year, and that in the second half was 6.8 ears/year. In contrast to otosclerosis in Caucasians, pure tone threshold in lower frequencies was much higher than that of higher frequencies (except for 8000 Hz). However, the improvement of the threshold after surgery was not so different from that reported in Caucasians.

CONCLUSIONS

Taken together, the present results clearly demonstrate that the incidence of otosclerosis in Japan has been increasing. Moreover the rise in the slope of the conduction curve at higher frequencies may be a reflection of the pathological characteristics of otosclerosis in Japanese population, which is less invasive and has limited otosclerotic foci in the temporal bone.

Cartilage interposition in ossiculoplasty with hydroxylapatite prostheses: a histopathologic study in the guinea pig

In this experimental animal study, a cartilage disk was interposed between a synthetic middle ear prosthesis and the tympanic membrane in guinea pigs to investigate its effect on the extrusion process of the implant. Two groups of guinea pigs were studied. One group consisted of animals in which the prosthesis was directly in contact with the tympanic membrane, and the other group consisted of animals in which a cartilage disk had been inserted between the head of the prosthesis and the tympanic membrane. Before histologic processing, in situ inspection was performed with an operating microscope. After fixation and embedding, light microscopic and transmission electron microscopic examination were performed. We studied the histopathologic aspects of the tympanic membrane with regard to the protrusion and extrusion processes of the middle ear implant. In this experimental model, protrusion and extrusion of a hydroxylapatite middle ear prosthesis was greatly reduced by interposition of a cartilage disk. Further clinical evaluation of these experimental results is needed in the human middle ear.