Histologic variants in otosclerosis

Automated detection of otosclerosis with interpretable deep learning using temporal bone computed tomography images

Objective

This study aimed to develop an automated detection schema for otosclerosis with interpretable deep learning using temporal bone computed tomography images.

Methods

With approval from the institutional review board, we retrospectively analyzed high-resolution computed tomography scans of the temporal bone of 182 participants with otosclerosis (67 male subjects and 115 female subjects; average age, 36.42 years) and 157 participants without otosclerosis (52 male subjects and 102 female subjects; average age, 30.61 years) using deep learning. Transfer learning with the pretrained VGG19, Mask RCNN, and EfficientNet models was used. In addition, 3 clinical experts compared the system's performance by reading the same computed tomography images for a subset of 35 unseen subjects. An area under the receiver operating characteristic curve and a saliency map were used to further evaluate the diagnostic performance.

Results

In prospective unseen test data, the diagnostic performance of the automatically interpretable otosclerosis detection system at the optimal threshold was 0.97 and 0.98 for sensitivity and specificity, respectively. In comparison with the clinical acumen of otolaryngologists at P < 0.05, the proposed system was not significantly different. Moreover, the area under the receiver operating characteristic curve for the proposed system was 0.99, indicating satisfactory diagnostic accuracy.

Conclusion

Our research develops and evaluates a deep learning system that detects otosclerosis at a level comparable with clinical otolaryngologists. Our system is an effective schema for the differential diagnosis of otosclerosis in computed tomography examinations.

Interest of computer tomography in the study of prognostic factors of otosclerosis

BACKGROUND

Otosclerosis is a primary osteodystrophy of the otic capsule that causes stapedo-vestibular ankylosis. Its diagnosis is suspected on the basis of clinical and audiometric elements, basically in the presence of conductive hearing loss with a normal eardrum. The CT-scan is an essential examination for the preoperative evaluation of otosclerosis. The aim of our study was to evaluate the use of CT-scanning in predicting the functional outcome of otosclerosis surgery by correlating postoperative audiometric results and preoperative CT findings.

METHODS

We conducted a retrospective study at the ENT Department in association with the Medical Imaging Department of our hospital, over a period of 8 years, from January 2014 to December 2022 and involving 90 patients (104 ears).

RESULTS

The average age of our patients was 40 years with extremes ranging from 22 to 61 years. We noted a sex ratio of 0.38. The preoperative CT-scan showed signs of otosclerosis in 87% of the cases and infra-radiological forms in 13% of the cases. Veillon stage II was the most frequent radiological stage encountered with a percentage of 48%. A good audiometric evolution, defined by a closure of postoperative Air Bone Gap (ABG ≤ 20 dB) and by an improvement of Bone Conduction (BC gain ≥ 0), was recorded in 86 cases (82.7%) for ABG and in 84 cases (80.8%) for BC gain. Scanographic predictive factors of poor postoperative outcome for ABG and BC gain were: advanced stages (Veillon stage III and IV), endosteal effraction, and round window involvement. According to multivariate analysis, only the extent of otosclerotic foci was directly and independently associated with the postoperative audiometric outcome.

CONCLUSION

The CT-scan is an essential examination in the preoperative evaluation of otosclerosis. It allows a positive diagnosis to be made and evaluate the extension of otosclerosis. Moreover, thanks to the analysis of the extent of the otosclerosis foci, mainly by the Veillon classification, the CT-scan allows to predict the postoperative audiometric prognosis.

Measurement of stapes footplate thickness using ultra-high-resolution computed tomography: stapes axial plane correlates better with otosclerosis than lateral semicircular canal plane

BACKGROUND, AIMS

Stapes footplate thickness measurement using ultra-high-resolution CT has been described only in the lateral semicircular canal plane. The purpose of this study was to compare stapes footplate thickness between the lateral semicircular canal and stapes axial planes in patients with otosclerosis compared to controls.

MATERIAL AND METHODS

We performed a retrospective single-center study of patients undergoing high-resolution temporal bone CT. Two radiologists measured stapes footplate thickness in both the lateral semicircular canal and stapes axial planes.

RESULTS

Between February 2020 and October 2022, we collected 81 ears from 49 patients (75% of women; mean age 51.22 ± 16.6 years, 17 otosclerosis, and 64 controls). In the stapes axial plane, there was a significant anterior thickening in otosclerosis patients (Reader 1: 0.52 ± 0.12 [0.3-0.7] vs. 0.41 ± 0.08 [0.3-0.6], p = 0.001; Reader 2: 0.54 ± 0.06 [0.5-0.7] vs. 0.39 ± 0.08 [0.2-0.6], P < 0.001) compared to controls. These differences were not significant using the lateral semicircular canal plane.

CONCLUSION

The stapes footplate was thickened at its AC in otosclerosis patients using only the stapes axial plane.

SIGNIFICANCE

We propose to use the stapes axial plane instead of the lateral semicircular canal plane when analyzing the stapes.

SMARCA4 mutation causes human otosclerosis and a similar phenotype in mice

BACKGROUND

Otosclerosis is a common cause of adult-onset progressive hearing loss, affecting 0.3%-0.4% of the population. It results from dysregulation of bone homeostasis in the otic capsule, most commonly leading to fixation of the stapes bone, impairing sound conduction through the middle ear. Otosclerosis has a well-known genetic predisposition including familial cases with apparent autosomal dominant mode of inheritance. While linkage analysis and genome-wide association studies suggested an association with several genomic loci and with genes encoding structural proteins involved in bone formation or metabolism, the molecular genetic pathophysiology of human otosclerosis is yet mostly unknown.

METHODS

Whole-exome sequencing, linkage analysis, generation of CRISPR mutant mice, hearing tests and micro-CT.

RESULTS

Through genetic studies of kindred with seven individuals affected by apparent autosomal dominant otosclerosis, we identified a disease-causing variant in SMARCA4, encoding a key component of the PBAF chromatin remodelling complex. We generated CRISPR-Cas9 transgenic mice carrying the human mutation in the mouse SMARCA4 orthologue. Mutant Smarca4+/E1548K mice exhibited marked hearing impairment demonstrated through acoustic startle response and auditory brainstem response tests. Isolated ossicles of the auditory bullae of mutant mice exhibited a highly irregular structure of the incus bone, and their in situ micro-CT studies demonstrated the anomalous structure of the incus bone, causing disruption in the ossicular chain.

CONCLUSION

We demonstrate that otosclerosis can be caused by a variant in SMARCA4, with a similar phenotype of hearing impairment and abnormal bone formation in the auditory bullae in transgenic mice carrying the human mutation in the mouse SMARCA4 orthologue.

Brazilian Society of Otology task force - Otosclerosis: evaluation and treatment

OBJECTIVES

To review and provide evidence-based recommendations for the diagnosis and treatment of otosclerosis.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on otosclerosis were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: 1) Diagnosis - audiologic and radiologic; 2) Treatment - hearing AIDS, pharmacological therapy, stapes surgery, and implantable devices - bone-anchored devices, active middle ear implants, and Cochlear Implants (CI).

CONCLUSIONS

The pathophysiology of otosclerosis has not yet been fully elucidated, but environmental factors and unidentified genes are likely to play a significant role in it. Women with otosclerosis are not at increased risk of worsening clinical condition due to the use of contraceptives or during pregnancy. Drug treatment has shown little benefit. If the patient does not want to undergo stapedotomy, the use of hearing aids is well indicated. Implantable systems should be indicated only in rare cases, and the CI should be indicated in cases of profound deafness.

[Revision surgery after stapedectomy]

Revision stapes surgery is considered to be significantly more demanding than primary stapes surgery, both in terms of the indication and the surgical approach. This article reviews common indications for revision after stapedectomy as well as the surgical approaches and intraoperative findings. A distinction is made between revision surgeries, which are usually carried out because of conductive hearing loss a long time after stapes surgery, and acute or subacute revisions that become necessary in the immediate postoperative course. With the shortening of postoperative observation times under inpatient conditions as a result of increasing economization and the associated shift of the immediate postoperative phase to the outpatient setting, the recognition of postoperative irregularities is also becoming increasingly important for otorhinolaryngologists in private practice, even if they do not perform these highly specialized interventions themselves.

Paediatric Type 1 Tympanoplasty: Comparison of Full Thickness Tragal Cartilage Versus Temporalis Fascia Graft-A Randomised Controlled Trial

Tympanic membrane perforation in children usually appears as a sequel of middle ear infection. This study was conducted to compare the anatomical and functional outcomes of cartilage and temporalis fascia graft in type 1 tympanoplasty in Paediatric population.

DESIGN

A hospital based randomized controlled trial.

SETTING

A tertiary care institute of central India.

SUBJECTS

All consecutive paediatric patients between 5 and 18 years of either sex attending ENT OPD and Paediatric OPD fulfilling inclusion criteria were included in the study. Anatomical and functional results of total 90 patients who underwent tympanoplasty were analyzed. These patients were divided into two groups depending on the graft material used. The cartilage group and the temporalis fascia group each comprising of 45 patients respectively.

METHODS

All patients underwent Type I tympanoplasty under general anaesthesia and with a post auricular approach. The surgeries were performed by senior surgeons. The graft success rate of the cartilage group (91.1%) was higher than the fascia group (84.44%) but the difference was not statistically significant (p = 0.449). The air bone gap closure was slightly better with temporalis fascia group than with cartilage group but the overall functional success rate in both the groups was not statistically significant.Cartilage and fascia grafts yield similar results for hearing gain and graft success rate in paediatric tympanoplasty.

Comparison of Short-Term Hearing Outcome in Stapedotomy Using either Vein or Fat (Adipose Tissue) as Sealing Material

Introduction Otosclerosis is a common cause of conductive hearing loss in the adult population that is caused by fixation of the stapes footplate. Cochlear otosclerosis may also present with sensorineural or mixed hearing loss. Surgery is the definitive treatment of choice and, during the procedure, sealing of the oval window with autologous tissue graft around the stapes prosthesis has been routinely done to improve hearing outcome and to mitigate postoperative complications.

Objective To evaluate the efficacy of two different types of autologous tissue (vein or fat) grafts as oval window sealing materials in stapedotomy in improving short-term hearing outcomes.

Methods In our study, 70 patients with otosclerosis who underwent primary stapedotomy were included. They were divided into group 1 (vein graft) and group 2 (fat graft) based on the type of sealing material used. All patients were followed-up at the end of 3 months, undergoing an audiometric examination to assess the hearing outcome.

Results A total of 80% (n = 28) of the patients in group1 had an air-bone gap (ABG) closure < 10dB, and, in group 2, 85.7% had an ABG closure < 10 dB; this difference was found to be statistically insignificant. A total of 42.9% (n = 15) of the patients in group 1 and of 31.4% (n = 11) in group 2 had a significant improvement in bone conduction, while 14.3% (n = 5) of the patients in group 1 and 17.1% (n = 6) in group 2 had worsening of average bone conduction postoperatively, which was found to be statistically insignificant.

Conclusion Both vein and fat grafts had comparable effects on hearing outcomes when used as sealing materials in stapedotomy.

Cellular voids in the pathogenesis of otosclerosis

BACKGROUND

Otosclerosis is a common ear disease that causes fixation of the stapes and conductive hearing impairment. However, the pathogenesis of otosclerosis is still unknown. Otosclerosis could be associated with the unique bony environment found in the otic capsule. Normal bone remodelling is almost completely absent around the inner ear after birth allowing degenerative changes and dead osteocytes to accumulate. High levels of inner ear anti resorptive osteoprotegerin (OPG) is most likely responsible for this capsular configuration. Studies have demonstrated how osteocyte lifespan variation creates occasional clusters of dead osteocytes, so-called cellular voids, at otosclerotic predilection sites in the human otic capsule. These cellular voids have been suggested as possible starting points of otosclerosis.

AIM

To describe the cellular viability in otosclerotic lesions and compare it to that of cellular voids.

MATERIALS AND METHODS

The study was based on unbiased stereological quantifications in undecalcified human temporal bones with otosclerosis.

RESULTS

Osteocyte viability was found to vary within the otosclerotic lesions. Furthermore, the results presented here illustrate that inactive otosclerotic lesions consist of mainly dead interstitial bone, much like cellular voids.

CONCLUSIONS AND SIGNIFICANCE

Focal degeneration in the otic capsule may play an important role in the pathogenesis of otosclerosis.

Missed Radiological Diagnosis of Otosclerosis in High-Resolution Computed Tomography of the Temporal Bone-Retrospective Analysis of Imaging, Radiological Reports, and Request Forms

Objectives: Several studies reported low detection rates of otosclerosis in high-resolution computed tomography (HRCT), especially when the scans were reviewed by non-specialized general radiologists. In the present study, we conducted a retrospective review of the detection of otosclerosis in HRCT by general radiologists and the impact of inadequately filled radiological request forms on the detection rate. Methods: Retrospective analysis of hospital records, HRCT reports, and radiological referral notes of 40 patients who underwent stapedotomy surgery for otosclerosis. HRCT imaging data sets were retrospectively reviewed by a blinded experienced neuroradiologist, whose reading served as the gold standard. Results: General radiologists reading HRCT scans had an overall detection rate of otosclerosis of 36.1% in this cohort (13 of 36 available HRCT reports). The neuroradiologist had a much higher detection rate of 82.5% (33 of 40 cases). Interobserver agreement between the general radiologists and the subspecialist neuroradiologist was poor (Cohen’s kappa κ = 0.26). General radiologists missed the diagnosis in 15 of the 33 CT-positive scans, corresponding to a missed diagnosis rate of 45.4%. There was a highly significant association between a missed diagnosis and the lack of an explicitly mentioned clinical suspicion of otosclerosis in the request forms (Pearson’s chi-squared test, p < 0.005). Conclusion: The diagnosis of otosclerosis is frequently missed by radiologists on HRCT scans of the temporal bone in a clinical setting. Possible reasons include a relative lack of experience of general radiologists with temporal bone imaging as well as the failure of clinicians to unambiguously communicate their suspicion of otosclerosis.

Radiological parameters and audiometric findings in otosclerosis: is there any relationship?

OBJECTIVE

The role of high-resolution computed tomography scans in otosclerosis remains uncertain. There is a debate over the relationship between radiological and audiometric findings among patients.

METHOD

Pre-operative audiometry and high-resolution computed tomography findings from 40 ears with surgically confirmed otosclerosis were compared. High-resolution computed tomography scan data regarding the characteristics of the disease foci, the endosteal extension and the occurrence of internal auditory canal diverticula were obtained. The influence of each radiological variable on the simple pure tone average, the high-frequency pure tone average and the bone-conduction pure tone average were investigated.

RESULTS

Cases with endosteal extension (p = 0.047) and a higher number of affected sites within the otic capsule had a worse bone-conduction pure tone average, although it was only significant for the latter (p = 0.006). Those without concomitant retrofenestral disease (p = 0.019) had better simple pure tone average.

CONCLUSION

The number of sites of involvement and concomitant retrofenestral disease seem to significantly impact audiometric findings in otosclerosis.

[Role of computed tomography in the preoperative diagnosis of otosclerosis]

BACKGROUND

Otosclerosis is an osteodystrophy of the otic capsule and presents with progressive conductive hearing loss. Imaging studies, especially computed tomography (CT) and cone-beam CT, have gained increased relevance in the diagnosis of otosclerosis.

OBJECTIVE

This study investigated whether there is a correlation between the extent of otosclerosis in high-resolution or cone-beam CT and hearing loss in pure-tone audiometry.

MATERIALS AND METHODS

Based on an existing classification of otosclerotic foci, a classification was established. Preoperative CT scans of patients undergoing stapedotomy between 2015 and 2019 were evaluated and classified by two independent otorhinolaryngologists. The preoperative pure-tone audiograms were analysed and compared to the results of CT.

RESULTS

A total of 168 CT studies (i.e., 168 ears) in 156 patients with intraoperatively confirmed otosclerosis were included in our study. A correlation between the extent of the otosclerotic focus or the calculated scores and hearing loss in pure-tone audiometry (air conduction, bone conduction and air-bone-gap) could not be proven.

CONCLUSION

Preoperative CT is not obligatory. However, preoperative imaging using CT or cone-beam CT can be helpful to confirm the diagnosis and exclude other middle or inner ear pathologies as well as in planning of the surgical procedure in the overall context of otoscopy and audiometry. A correlation with the degree of hearing impairment could not be demonstrated and remains unclear.

Feasibility of CBCT in Diagnosing Otosclerosis by Measuring CBCT Bone Density: A Preliminary Study

The aim of this study was to measure cone beam computed tomography (CBCT) derived bone density of 6 anatomic points around the otic capsule in preoperative assessment of patients with clinically suspected otosclerosis, and to compare these densities with control group. CBCT images of 21 patients (34 ears, the otosclerosis group) with surgically confirmed otosclerosis and 26 patients (52 normal ears, the control group) were evaluated in this prospective study. Six regions of interest (ROI) were set manually around the otic capsule with the slice thickness of 0.3 mm. The mean CBCT bone density these regions were measured and compared in the case and control groups. In the case group, the mean CBCT bone density at the fissula ante fenestram (FAF) was significantly lower than the control group. Moreover, at the 4 points of the other ROIs (3-6) CBCT bone densities were significantly lower in the case group compared to the control group (p < 0.01). In this group, among 13 bilateral otosclerosis, 22 ears had conductive hearing loss (CHL), 4 ears had mixed hearing loss (MHL) and among 8 unilateral otosclerosis, 5 ears had CHL, 3 ears had MHL. Our study showed the mean CBCT bone density of ROIs 1 and 6 were correlated with the average air-bone gap in the bilateral and unilateral otosclerosis group, respectively. Quantitative evaluation of CBCT with a slice thickness of 0.3 mm can be used as a suitable tool for diagnosis and follow-up of otosclerosis in temporal bone.

Prognostic factors influencing postoperative air-bone gap in stapes surgery

Objective

Otosclerosis is an osteodystrophic disease of the otic capsule, determining conductive or mixed hearing loss, which can be successfully treated with stapedotomy. The aim of the present multicentric retrospective study was to identify prognostic factors related to better auditory outcomes in stapes surgery.

Methods

581 patients affected by otosclerosis were submitted to stapedotomy under local anaesthesia in two different hospitals. Both Teflon and titanium prostheses were adopted.

Results

A statistically significant decrease of postoperative air-conduction thresholds and air-bone gap (ABG) values was seen, whereas the mean bone-conduction threshold did not differ from the preoperative condition. Among the various parameters investigated, the prosthetic material, duration of surgery and intraoperative detection of unexpected anatomical anomalies of the middle ear were found to be related to lower postoperative ABG values.

Conclusions

All the previously mentioned parameters played a significant role in determining the postoperative auditory outcomes and can therefore be considered prognostic factors for the success of the stapedotomy.

CT scan findings impact on hearing thresholds in otosclerosis: A study of 108 patients

Background

The relationship between the location of otosclerotic zones and hearing thresholds has been evaluated in several studies and has generated different conflicting reports. This study was carried out in order to evaluate the relationship between otosclerotic zones extension on CT scan and pure tone audiometry (PTA) thresholds, before and after stapedotomy. Materials and Methods: 108 patients with a positive surgical diagnosis of otosclerosis, operated by the same surgeon, were enrolled in this retrospective study, performed in a tertiary referral hospital between 2015 and 2018.

Results

PTA thresholds were significantly poorer in cases of extensive otosclerosis (peri cochlear, peri vestibular, or internal auditory canal hypodensities, p = 0,001). However, for cases with hypodensity extending to the endosteum of cochlea (Type III), we have noted a significant improvement in postoperative PTA thresholds (Mean AC (air conduction) = 32,8 ± 8,16/62,97 ± 12,28 dB), Mean BC (bone conduction) = 18,3 ± 8,56/26,25 ± 15,93 dB). Conclusions: In our study, extensive and multifocal otosclerosis lesions had a statistically significant negative impact on postoperative AC and BC threshold; however, type III lesions tend to be associated with a very good prognosis.

Cochlear Implantation in Advanced Otosclerosis: Pitfalls and Successes

Purpose of Review

This review will highlight recent outcome-based evidence guiding decision making for cochlear implantation in advanced otosclerosis, related complications, and technical surgical considerations in otosclerosis and the obstructed cochlea.

Recent Findings

Cochlear implantation in advanced otosclerosis results in consistent, excellent auditory outcomes with improvement in both objective speech recognition scores and subjective quality of life measures. Facial nerve stimulation may occur at higher rates in otosclerosis cochlear implant recipients. Cochlear implantation in the setting of luminal obstruction in osteosclerotic patients may be managed with altered surgical technique to achieve successful auditory improvements. Pre-operative imaging with high resolution CT or MRI may help anticipate intraoperative challenges and post-operative complications in cochlear implantation.

Summary

Cochlear implantation is an established, successful treatment for profound hearing loss in advanced otosclerosis. Surgeon knowledge of outcomes, complications, and potential surgical challenges is important to appropriately counsel patients regarding auditory rehabilitation options in advanced otosclerosis.

Histopathologic Analysis of Temporal Bones With Otosclerosis Following Cochlear Implantation

OBJECTIVE

Analyze changes in osteoneogenesis and fibrosis following cochlear implant (CI) surgery in patients with otosclerosis and compare differences based on insertion technique.

BACKGROUND

When advanced otosclerotic disease extends to the otic capsule, severe and profound sensorineural hearing loss necessitates consideration of a cochlear implant. Histopathological analysis of the human temporal bone after implantation in the patient with otosclerosis may reveal important variables that predict CI success.

METHODS

Histopathological evaluation of archival human temporal bones from subjects with a history of CI for cochlear otosclerosis. A total of 17 human temporal bones (HTB) were analyzed, 13 implanted, and 4 contralateral non-implanted controls.

RESULTS

Histopathological studies revealed extensive osteoneogenesis and fibrosis which was more prominent at the cochleostomy insertion site in the basal turn of the cochlea often obliterating the scala tympani in the basal turn, and in some cases extending to the scala media and scala vestibuli. Cochlear hydrops was nearly universal in these cases. This contrasted with the round window insertion, which exhibited minimal osteoneogenesis within the cochlear duct. In addition, in the contralateral, unimplanted control ears, there was otosclerosis at the stapes footplate, fissula ante fenestrum but no osteoneogenesis within the cochlear duct.

CONCLUSION

Cochleostomy approach to CI insertion in otosclerosis patients is associated with significant fibrosis, osteoneogenesis, and cochlear hydrops. A round window insertion technique can be utilized to help minimize these histopathologic findings whenever feasible.

Stapes and Stapes Revision Surgery: Preoperative Air-Bone Gap Is a Prognostic Marker

OBJECTIVE

Stapes surgery is considered an effective treatment in otosclerosis, but controversy remains regarding predictors of surgical outcome.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

One hundred sixty three cases of stapes surgery between 2012 and 2019 were reviewed.

MAIN OUTCOME MEASURES

Primary outcome measures were relative hearing improvement (relHI), defined as preoperative minus postoperative air conduction divided by preoperative air-bone gap (ABG), as well as relative ABG closure (relABGc), defined as preoperative ABG minus postoperative ABG divided by preoperative ABG. Univariate and multivariate linear regression analyses were performed to determine independent predictors for these outcomes.

RESULTS

Higher preoperative bone conduction (BC) and primary surgery (compared with revision) were independently associated with increased relHI (p = 0.001 and p = 0.004, respectively). Lower preoperative BC, higher preoperative ABG, primary surgery, and age were independently associated with increased relABGc (p = 0.0030, p < 0.001, p = 0.0214, and p = 0.0099, respectively). Sex did not predict surgical outcome. In patients with less than 20 dB preoperative ABG, likelihood of negative relABGc was increased (compared with 20-30 dB or >30 dB preoperative ABG, p = 0.0292, Fisher's exact test). This tendency was not significant for relHI (p = 0.074).

CONCLUSIONS

Our findings demonstrate that calculating HI and ABGc in relation to preoperative ABG can reliably predict outcomes of stapes surgery. Both primary and revision stapes surgery are effective treatment options, but relative improvement is higher in primary cases. Preoperative BC, preoperative ABG, and age predict surgical outcomes as well. Otosclerosis patients with low preoperative ABG, especially less than 20 dB, should be counseled and selected cautiously regarding stapes surgery.

Internal Auditory Canal Diverticula in Children: A Congenital Variant

OBJECTIVES/HYPOTHESIS

Internal auditory diverticula in adults have been found to exist independent of otosclerosis, and in the presence of otosclerosis. We sought to determine the prevalence of internal auditory canal (IAC) diverticula in a pediatric cohort, to assess whether IAC diverticula are a risk factor for hearing loss, and the co-occurrence of otic capsule hypoattenuation.

STUDY DESIGN

Retrospective review.

METHODS

A single-site retrospective review of high-resolution temporal bones computed tomography (CT) scans including the presence and size of diverticula and hypoattenuation of the otic capsule. Demographic, imaging, and audiometric data were collected and descriptively analyzed. Bivariate analysis of collected variables was conducted. Comparisons between sides in unilateral cases were also performed.

RESULTS

16/600 (2.7%; 95% CI [2.0%, 3.4%]) were found to have IAC diverticula. Six were bilateral. Thirty-one patients (5.2%) were found to have hypoattenuation of the otic capsule. There were no coincident cases of IAC diverticulum and hypoattenuation of the otic capsule. There was no association between the presence of IAC diverticula and age (P = .13). In six patients with unilateral diverticula, pure tone average (P = .42), and word recognition (P = .27) scores were not significantly different when compared to the normal, contralateral side.

CONCLUSIONS

The prevalence of IAC diverticula in children is lower than the prevalence in adults. IAC diverticula in children likely represent congenital variants of temporal bone anatomy. Similar to adult populations, there is evidence that IAC diverticula in children are likely not an independent risk factor for hearing loss.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1683-E1687, 2021.

Measurement of stapes footplate thickness in otosclerosis by ultra-high-resolution computed tomography

BACKGROUND

Ultra-high-resolution computed tomography (U-HRCT) utilizes a 1024 × 1024 matrix with 0.25-mm section thickness, offering better spatial resolution than conventional multi-detector row CT to detect anatomic data for otologic surgery.

AIMS

We examined stapes footplate thickness using U-HRCT in relation to stapedotomy to predict the difficulty of the surgical procedure.

MATERIALS AND METHODS

Subjects were 12 otosclerosis patients and 25 controls who underwent diagnostic U-HRCT. A profile curve (Hounsfield units) was used to measure stapes footplate thickness along a perpendicular line across the stapes footplate in a plane parallel to the lateral semicircular canal.

RESULTS

Footplate thickness was smaller at the midpoint than just before the anterior crus and just after the posterior crus. Interobserver variability was lowest at the midpoint, where foot plate thickness was significantly greater in the affected ear in otosclerosis patients compared with controls (0.60 ± 0.09 mm vs 0.46 ± 0.04 mm; p < .001). Otosclerosis patients were detected using U-HRCT with a high area under the curve. Difficulty in the stapes opening procedure correlated with stapes footplate thickness.

CONCLUSIONS

Footplate thickness on U-HRCT correlated with temporal bone anatomy and corresponded to surgical difficulty. Significance: U-HRCT-derived anatomic data is useful for evaluating the stapes.

Internal Auditory Canal Diverticula among Pediatric Patients: Prevalence and Assessment for Hearing Loss and Anatomic Associations

BACKGROUND AND PURPOSE

Internal auditory canal diverticula are focal lucencies along the anterior-inferior aspect of the internal auditory canal fundus. Studies in adults report conflicting data on the etiology and clinical relevance of this finding. We would expect a pediatric study to help elucidate the significance of internal auditory canal diverticula. The primary goals of this study were to determine the temporal bone CT prevalence of diverticula among pediatric patients and to assess possible hearing loss and anatomic associations.

MATERIALS AND METHODS

For this retrospective study including 283 pediatric temporal bone CTs, 4 neuroradiologists independently assessed for diverticula. Discrepancies were resolved by consensus. One neuroradiologist assessed for an enlarged vestibular aqueduct, labyrinthine dysplasia, cochlear cleft, and otospongiosis. Patient demographics, audiologic data, and pertinent clinical history were recorded. One-way analysis of variance and the Fisher exact test were used to assess possible associations between diverticula and specific patient characteristics.

RESULTS

Diverticula were observed in 42/283 patients (14.8%) and were more commonly bilateral. There was no significant association with age, sex, hearing loss, enlarged vestibular aqueduct, labyrinthine dysplasia, or cochlear cleft. A statistically significant association was observed with otospongiosis (P = .013), though only 1 study patient had this disease.

CONCLUSIONS

Internal auditory canal diverticula are a common finding on pediatric temporal bone CT. In the absence of clinical or imaging evidence for otospongiosis, diverticula likely fall within the range of a normal anatomic variation. Familiarity with these findings may prevent neuroradiologists from recommending unnecessary additional testing in pediatric patients with isolated internal auditory canal diverticula.

Histopathologic Characteristics of Internal Auditory Canal Diverticula

HYPOTHESIS

We hypothesize that internal auditory canal (IAC) diverticula occur independent of otosclerosis as demonstrated by temporal bone histopathology.

BACKGROUND

Diverticula at the anterior-inferior aspect of the IAC have been described histologically in the setting of cavitary otosclerosis. Recent radiographic studies show the prevalence of IAC diverticula that is higher than what can be accounted for by cavitary otosclerosis alone.

METHODS

We examined hematoxylin and eosin temporal bone histopathology slides with otosclerosis involving the IAC. We also examined bones from normal hearing subjects with normal histologic findings. Temporal bones were included if donors were more than 18 years of age at time of death and adequate horizontal cuts were available to evaluate the area of interest.

RESULTS

IAC diverticula were found in 33 of 47 (70%) temporal bones with IAC otosclerosis and in 5 of 20 (25%) normal temporal bones. The difference in mean pure tone averages (PTA) in the normal temporal bones with (PTA 7.3 ± 7) and without (PTA 8 ± 2) diverticula was not statistically significant (p = 0.86).

CONCLUSION

IAC diverticula which have been previously demonstrated to occur in the setting of cavitary otosclerosis can also occur independent from otosclerosis. Subjects with diverticula but without other temporal bone pathology have normal hearing thresholds.

Sensitivity of High-Resolution Computed Tomography in Otosclerosis Patients undergoing Primary Stapedotomy

OBJECTIVE

To determine the incidence of abnormal otospongiotic or otosclerotic findings on high-resolution computed tomography (HRCT) as read by local radiologists in patients with surgically-confirmed otosclerosis.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary-referral private otology-neurotology practice.

PATIENTS

Adults (>18 years old) with surgically-confirmed otosclerosis between 2012 and 2017 with a HRCT performed preoperatively.

INTERVENTION

Preoperative HRCT then stapedotomy.

MAIN OUTCOME MEASURES

Positive identification and location of radiographic otosclerosis as reported by the local radiologist. We then correlated the CT with surgical location as documented at time of surgery. Audiometry, demographic data, intraoperative findings, and surgical technique were secondarily reviewed.

RESULTS

Of the 708 stapes surgeries were performed during the study time frame. Preoperative HRCT scans were available for 68 primary stapedotomy surgeries performed in 54 patients. Otosclerosis was reported in 20/68 (29.4%). Following a negative report by the local radiologist, a re-review by the surgeon and/or collaborating neuroradiologist confirmed otosclerosis in 12/48 additional cases (25.0%). There was an overall sensitivity of 47.1%. Intraoperatively, cases with negative reads tended to have more limited localization at the ligament (8.7%) or anterior crus (39.1%), compared with positive reads, which demonstrated more extensive involvement, with bipolar foci (30.0%) or diffuse footplate manifestations (20.0%) more common. Acoustic reflexes were characteristically absent.

CONCLUSIONS

While HRCT may aid in the diagnosis of otosclerosis and rule out concomitant pathology in certain cases of clinical uncertainty or unexplained symptoms, its sensitivity for otosclerosis remains low. HRCT should not be relied upon to diagnose routine fenestral otosclerosis.

Involvement of the Internal Auditory Canal in Subjects With Cochlear Otosclerosis: A Less Acknowledged Third Window That Affects Surgical Outcome

OBJECTIVE

To investigate the effects of cavitating lesions involving the internal auditory canal (IAC) in subjects with cochlear otosclerosis with regard to poststapedotomy hearing outcome.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

A retrospective chart review of 134 subjects with otosclerosis treated from January 2011 to June 2017 at Seoul National University Bundang Hospital was conducted. Sixteen subjects (23 ears) with temporal bone computed tomography (TBCT)-confirmed cochlear otosclerosis who underwent stapedotomy were included in the study.

MAIN OUTCOME MEASURES

Pure tone audiometry (PTA) (i.e., air and bone conduction; AC and BC, respectively) thresholds and air-bone gap (ABG), measured at 6 months postoperatively were compared between cochlear otosclerosis with and without IAC involvement (IAC group and non-IAC group, respectively).

RESULTS

A total of 14 of 23 ears showed involvement of the IAC. There were no significant differences in age, side of otosclerosis, or preoperative hearing threshold between the two groups. The mean postoperative AC and BC thresholds and ABG of the IAC group were significantly poorer (45.7 dB, 33.8 dB, and 11.8 dB, respectively) than those of the nonIAC group (24.1 dB, 20.0 dB, and 4.1 dB, respectively).

CONCLUSIONS

Cochlear otosclerosis with cavitating lesions involving the IAC showed significantly poorer postoperative audiological outcomes than those without any cavitating lesion. Cavitation extending to the IAC may act as a third window providing a route for sound energy shunting, and thus precluding successful hearing outcome in some subjects with cavitating otosclerosis after stapedotomy.

Hearing Improvement After Type III Tympanoplasty: A Prospective Observational Study

To analyse the postoperative hearing results of patients undergoing type III tympanoplasty using sculptured homologous spur cartilage. This prospective study included 156 patients of chronic otitis media (COM), between the ages 10-60 years. All cases underwent type III tympanoplasty with ossiculoplasty using homologous spur cartilage. The study sample of 156 patients contained 107 cases of mucosal type and 49 cases of squamosal type COM. Type III A tympanoplasty was done for 71 cases and type III B tympanoplasty was done for 85. Pure tone audiometry (PTA) was done pre and postoperatively, in all the cases. The patients were followed up for 6 months postoperatively. The average preoperative mean air-bone-gap (ABG) was 43.64 dB, whereas in type III A cases it was 39.7 dB and in type III B it was 46.9 dB. The mean ABG at 6th month follow up was 18.9 dB in the study group. In type III A cases, mean ABG was 15.2 dB and in type III B cases it was 22.11 dB. Homogenous spur cartilage graft can be used for ossicular chain reconstruction with the advantage of very low extrusion rate, technically easy to perform with less risk of residual disease.

The Size of Internal Auditory Canal Diverticula Is Unrelated to Degree of Hearing Loss

OBJECTIVES

To explore the relationship between hearing loss and the internal auditory canal (IAC) diverticula. To determine whether diverticula exist within or medial to the otic capsule and the prevalence in a control population.

METHODS

Retrospective review of adult patients with radiologic evidence of an IAC diverticulum, no evidence of otosclerosis, and audiometric testing. Analyzed degree of hearing loss and width, length, height, and volume of diverticulum. Hounsfield unit (HU) measurements lateral and medial to the diverticulum.

RESULTS

Pure tone average (PTA), air-bone gap, and WRS (word recognition score) did not correlate with length, width, height, and volume of the diverticula. In patients with a unilateral diverticulum, there was no difference in mean PTA or WRS when comparing the diverticulum and nondiverticulum sides. Mean HU lateral to the diverticulum (2104 HU) was found to be significantly higher than medial to the diverticulum (1818 HU). There is a 5.6% prevalence of IAC diverticula in patients who underwent high-resolution computed tomography (CT) scans for chronic sinusitis (control group).

CONCLUSION

These data support the notion that hearing loss in this population is a product of sampling bias. The size of IAC diverticula does not correlate with the degree of hearing loss, and there is no statistically significant association between sensorineural hearing loss (SNHL) and the presence of an IAC diverticulum. IAC diverticula may exist medial to, rather than within, the otic capsule given the significant difference in mean HUs medial and lateral to the diverticula.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1011-1015, 2020.

Cochlear implantation in far-advanced otosclerosis: hearing results and complications

Severe forms of otosclerosis known as far-advanced otosclerosis (FAO) can lead to severe to profound sensorineural hearing loss and can justify cochlear implantation. Because of the pathophysiology of otosclerosis, patients implanted for FAO may experience an increased rate of complications, such as facial nerve stimulation or electrode dislocation, and may have poorer hearing outcomes than expected. This retrospective study aimed to compare cochlear implantation hearing outcomes, surgical difficulties and complications in FAO patients versus non-FAO patients. Moreover, we evaluated whether high resolution computed tomography (CT scan) findings were predictive of perioperative problems, complications and hearing outcomes. FAO patients were diagnosed based on medical history, examination and CT scan. Thirty-five ears from FAO patients were compared to 38 control ears. Audiometric results were assessed at least 12 months after implantation by pure tone average, speech reception threshold, monosyllabic and disyllabic word recognition score (WRS) and Central Institute for the Deaf (CID) sentences test. Complications and surgical difficulties were compiled. CT scan findings were categorised within 3 grades of otosclerotic extension. No significant difference was found between FAO and non-FAO hearing outcomes, except that monosyllabic WRS were lower for FAO patients, especially those who underwent previous stapedotomy. Facial nerve symptomatology occurred in 8.6% of FAO patients; among these, one required explantation-reimplantation surgery. 86% of FAO implanted patients had retrofenestral extension on CT. These were associated with poorer disyllabic WRS (51% vs 68%, p < 0.05) than those with only fenestral involvement. Although not significant, high grade of severity on CT tended to be associated with surgical difficulties and complications. Cochlear implantation in FAO patients is an effective treatment technique. Though the overall complication rate is low, it tends to be higher in cases of severe extension on CT. Patient counselling should be adjusted accordingly.

A Biochemical Analysis of the Stapes

BACKGROUND Otosclerosis is a primary disease of the bony labyrinth. In the course of otosclerosis, abnormal resorption and recalcification of the endochondral layer of the temporal bone is observed. The otosclerotic process most commonly develops in the anterior part of the oval window. MATERIAL AND METHODS We analyzed stapes superstructures from 4 patients undergoing surgery for otosclerosis. The first step involved tissue assessment under a scanning electron microscope. The resulting images were analyzed in terms of morphological changes. The stapes superstructure was then divided into small "ossicles", including fragments from the closest vicinity of the stapes footplate and a fragment of the head of the stapes. This material was examined using a scanning electron microscope with a unit for chemical analysis in microareas. RESULTS Chemical analysis confirms the appearance of considerable quantities of the following elements: carbon, oxygen, potassium, and calcium, and the appearance of small quantities of sodium and magnesium. Based on a detailed analysis of the chemical composition, these fragments could represent a calcium phosphate compound from the following system: CaO-P₂O₅-H₂O. Fragments of the superstructure from the region closest to the base of the stapes demonstrated a considerably larger presence of carbon, oxygen, and nitrogen, which most likely suggests an increased metabolic process in this region. CONCLUSIONS Our analysis revealed an increased metabolic activity in the closest vicinity of the otosclerotic focus, the fissula ante fenestram. The increased metabolism correlated with the bone tissue changes seen on scanning electron microscopy.

Otosclerosis: anatomical distribution of otosclerotic loci analyzed by high-resolution computed tomography

PURPOSE

To clarify the anatomical distribution of otosclerotic loci in otosclerosis.

METHODS

Ninety-five patients with surgically confirmed uni- or bilateral otosclerosis were enrolled into the study. Hypodense areas observed in the otic capsule by high-resolution computed tomography (HRCT) were defined as otosclerotic loci. The location and number of lesions were examined, and the probability of lesion overlap and correlation with age/hearing parameters (air and bone conduction threshold, air-bone gaps) were tested.

RESULTS

Otosclerotic loci were confirmed by HRCT in 77 out of 115 operated ears. The three commonly affected sites were the anterior part of the oval window (ant-OW), anterior part of the internal auditory canal (ant-IAC), and pericochlear area (PCochA), with lesions detected in 96.1%, 46.8%, and 26.0% of ears, respectively. Only the ant-OW area was affected in 48.1% of the ears; the ant-IAC in 3.9%; and PCochA in none with significant differences (p < 0.01). The ant-OW lesions preferentially overlapped with ant-IAC (44.6%) than PCochA lesions (27.0%) (p < 0.05). Among double sites diseases, triple sites diseases occurred more commonly in the ant-OW + PCochA group (80%) than ant-OW + ant-IAC group (48.5%) (p < 0.05). There was no correlation between a number of lesions and age/hearing parameters.

CONCLUSIONS

Based on the probability of lesion overlap, otosclerotic lesions may initiate at ant-OW followed by ant-IAC and later PCochA. Although the number of lesions showed no immediate correlation with hearing level or age, anatomical stage of the disease estimated by the location and the number of otosclerotic loci could be useful in predicting the future hearing status.

Immunohistochemical analysis of Otic Capsule Osteogenesis in the Palmerston North Autoimmune Mouse

Autoimmunity and the immune complex disease associated with it have been hypothesized to be the cause of several idiopathic diseases of the inner ear—including the new bone formation associated with otic capsule osteogenesis and otosclerosis. The Palmerston North (PN) autoimmune mouse strain, which exhibits both spontaneous systemic autoimmune disease and otic capsule bone formation, has been proposed as a model relating these two disease processes. To investigate the potential role of immunopathologic processes in PN otic capsule lesion formation, inner ears from PN mice were immunostained for the presence of IgG and complement (C3), two immunologic markers involved in the development of the vascular and perivascular changes associated with immune complex deposition. Both systemic autoimmune disease and otic capsule bony lesions were confirmed in all animals. However, immunohistochemical analyses did not establish a direct relationship between the two conditions as complement was absent in all lesions and IgG stained positive in only one instance. These results suggest that immune complex deposition is not directly involved in the otic capsule lesions of the PN mouse, and alternate mechanisms relating autoimmune disease and otic capsule osteogenesis must be explored.

Significance of internal auditory canal diverticula in ears with otosclerosis

BACKGROUND

Diverticula in the internal auditory canal (IAC) have been reported in ears with otosclerosis.

OBJECTIVE

We evaluated hearing levels and vascular activity in ears with otosclerosis with and without IAC diverticula and clarify the significance of IAC diverticula.

MATERIALS AND METHODS

Sixty-one ears from 54 patients who underwent stapes surgery for otosclerosis [fenestral (48 ears) and retrofenestral (13 ears) groups] were included in the present study. Preoperative hearing levels on pure tone audiometry (PTA) and intraoperative measurements of blood flow were compared between the groups.

RESULTS

A total of 24 of 61 ears (39.3%) showed IAC diverticula, significantly higher than the frequency in ears without otosclerosis (3.7%). No significant differences in air- and bone-conduction thresholds on PTA were evident between ears with and without IAC diverticula in each group. Ears without IAC diverticula tended to show higher blood flow in the area anterior to the oval window than ears with IAC diverticula, but the difference was not significant.

CONCLUSIONS

The incidence of the IAC diverticula in otosclerosis was significantly higher than in cases without otosclerosis. The existence of IAC diverticula was not evidently related to the severity of the disease from the perspective of hearing level and vascular activity.

Retrospective Review of Otic Capsule Contour and Thickness in Patients with Otosclerosis and Individuals with Normal Hearing on CT

BACKGROUND AND PURPOSE

Otosclerosis is commonly identified on CT as a focus of hypodensity in the otic capsule anterior to the oval window. However, otosclerosis can have a sclerotic phase approximating the density of normal bone, making diagnosis challenging. This study assesses differences in otic capsule contour and thickness anterolateral to the anterior margin of the oval window in patients with otosclerosis compared with individuals with normal hearing.

MATERIALS AND METHODS

Axial CT of 104 ears with clinically diagnosed otosclerosis and 108 consecutive ears of audiometrically normal individuals were retrospectively reviewed. Two radiologists independently evaluated the pattern of otosclerosis, otic capsule contour, and bone thickness on standardized axial images at the level of the oval window and cochleariform process. Measurements were made from the posterolateral margin of the cochlea to the apex of the otic capsule convex contour just anterolateral to the anterior margin of the oval window. In the absence of a convex contour, the sulcus between the oval window and the cochleariform process was identified, and measurement to the depth of the sulcus was used. Receiver operating characteristic analysis determined the best cutoff value of otic capsule thickness.

RESULTS

Mean otic capsule thickness (2 SDs) was 3.08 (0.93) mm and 1.82 (0.31) mm in patients with otosclerosis and individuals with normal hearing, respectively (P < .001), with excellent interobserver agreement. Otic capsule thickness of >2.3 mm had 96.2% sensitivity, 100% specificity, 100% positive predictive value, and 96.4% negative predictive value for otosclerosis. A bulging/convex contour of the otic capsule had 68.3% sensitivity, 98.1% specificity, 97.3% positive predictive value, and 76.3% negative predictive value.

CONCLUSIONS

Patients with otosclerosis have significantly thicker bone abutting the oval window than individuals with normal hearing.

Otosclerosis in a nonendemic population: Utility of CT scan and correlation with audiometry and surgical outcome

The incidence of otosclerosis in nonendemic patients is low, and preoperative diagnosis can be challenging. The aim of this study was to evaluate computed tomography (CT) findings in patients with otosclerosis and determine their correlation with audiometric findings and surgical outcome in a nonendemic population. We retrospectively reviewed 17 patients from August 2011 to August 2013 with surgically confirmed otosclerosis who underwent preoperative high-resolution CT scans and pre- and postoperative audiometry. Otosclerotic foci were identified on the scans. The density ratio of these foci was calculated and compared with pre- and postoperative audiometric parameters. One patient with Paget disease was excluded from the study. A total of 19 ears were operated on and included in the data analysis. CT scans were normal in 4 ears (21.1%). Hypodense lesions were detected in the remaining 15 (78.9%) ears and the region of interest mapped out. The density ratio was obtained between the hypodense area and adjacent normal labyrinthine bone. No statistically significant correlation was found between the density ratio and any of the audiometric parameters tested (p > 0.05). The diagnosis of otosclerosis in nonendemic areas is challenging. A preoperative CT scan can be useful when otosclerotic foci are present. However, the density ratio of the otosclerotic foci did not correlate with audiometric parameters or surgical outcome.

Stapes surgery in patients with a small air-bone gap

The objective of this study was to determine hearing outcomes in patients undergoing stapes surgery with a preoperative air-bone gap (ABG) <21.25 dB. Patients with a unilateral or bilateral preoperative ABG <21.25 dB undergoing primary stapes surgery were identified from a database of all stapes surgeries performed in a tertiary center over 15 years. A total of 254 ears met the inclusion criteria. The primary outcome measure was the degree of closure of the preoperative ABG. A secondary outcome measure was improvement in bone-conduction thresholds at 4 kHz. All patients underwent stapes surgery under local anesthesia. Ossicular reconstruction was achieved using a SMart 360 nitinol fluoroplastic piston (Gyrus ACMI, Inc.; Southborough, Mass.), and complete posterior crurotomy was performed with a KTP laser. Hearing was assessed with clinical voice testing immediately postoperatively and with pure-tone audiometry at 6 weeks postoperatively. A total of 248 ears (97.6%) demonstrated ABG closure to <10 dB. Bone-conduction thresholds showed an increase in 114 (44.9%), no change 74 (29.1%), and a decrease in 66 (26.0%). There is a slight increase in the risk of stapes mobilization in ears with a small ABG when compared to those with larger ABGs; however, this can be overcome by using a laser-assisted technique in combination with good surgical experience. The benefit in terms of hearing aid avoidance and the restoration of symmetrical hearing is both achievable and significant for the patient.

Impact of Imaging in Management of Otosclerosis

The use of imaging in otosclerosis for diagnosis, preoperative assessment, and follow-up has the potential to give the clinician an additional tier of patient evaluation and validation of diagnosis. Before stapes surgery, imaging may help avoid unnecessary middle ear explorations in nonotosclerotic cases, prevent potential complications, and assist in appropriate patient counseling regarding management expectations. Postoperatively, following unsuccessful air-bone gap closure in stapes surgery or conductive hearing deterioration following initial successful closure of the air bone gap, imaging can be used to determine the prosthesis position in the middle ear.

Bilateral Vestibulopathy Due to Severe Cochlear Otosclerosis: A Well-Known Condition Without Any Favorable Solution

Bilateral vestibulopathy is a rare condition. It is one of the most difficult balance problems to treat because nearly all patients experience long-term unsteadiness. In this report, a 39-year-old woman gradually developing chronic dizziness and instability due to bilateral vestibulopathy as a result of progressive severe cochlear otosclerosis was presented with review of the literature.

Prevalence of Internal Auditory Canal Diverticulum and Its Association with Hearing Loss and Otosclerosis

BACKGROUND AND PURPOSE

Focal low-attenuation outpouching or diverticulum at the anterolateral internal auditory canal is an uncommon finding on CT of the temporal bone. This finding has been described as cavitary otosclerosis in small case reports and histology series. The purpose of this study was to establish the prevalence of internal auditory canal diverticulum and its association with classic imaging findings of otosclerosis and/or hearing loss.

MATERIALS AND METHODS

Temporal bone CT scans of 807 patients, obtained between January 2013 and January 2016, were retrospectively reviewed to identify internal auditory canal diverticula and/or classic imaging findings of otosclerosis. Clinical evaluations for hearing loss were reviewed for patients with internal auditory canal diverticula and/or otosclerosis.

RESULTS

Internal auditory canal diverticula were found in 43 patients (5%); classic otosclerosis, in 39 patients (5%); and both findings, in 7 patients (1%). Most temporal bones with only findings of internal auditory canal diverticula (91%) demonstrated hearing loss, with 63% of this group demonstrating sensorineural hearing loss. The hearing loss classification distribution was significantly different (P < .01) from that in the classic otosclerosis group and in the group with both diverticula and otosclerosis.

CONCLUSIONS

Internal auditory canal diverticula are not uncommon on CT examinations of the temporal bone and most commonly occur without classic imaging findings of otosclerosis. These lesions are associated with sensorineural hearing loss, and referral for hearing evaluation may be appropriate when present.

Lack of Evidence for Nonotosclerotic Stapes Fixation in Human Temporal Bone Histopathology

HYPOTHESIS

Nonotosclerotic stapes fixation does not represent a significant cause of stapes ankylosis in patients undergoing stapedectomy; the vast majority have otosclerosis.

BACKGROUND

Nonotosclerotic stapes fixation has been proposed as the diagnosis in 30 to 40% of patients undergoing stapedectomy (after excluding rare congenital, systemic, and syndromic causes of stapes fixation and tympanosclerosis). This finding was based on the histopathologic evaluation of total stapedectomy surgical specimens. Since these specimens do not include the surrounding otic capsule, the histopathologic evidence of otosclerosis may be missed.

METHODS

Human temporal bone specimens from patients who underwent stapes mobilization, stapedotomy, or stapedectomy during life were evaluated for histologic evidence of otosclerosis. Patients with a history of temporal bone trauma, tympanosclerosis, and congenital, systemic, or syndromic causes of stapes fixation were excluded. Therefore, most temporal bone donors carried a clinical diagnosis of otosclerosis.

RESULTS

Two hundred ten specimens from three temporal bone collections were independently evaluated. Otosclerosis was found on histology in 99% (207/210). Therefore, the incidence of nonotosclerotic stapes fixation was 1% (3/210). In two of the three patients who did not have otosclerosis, the contralateral temporal bone had otosclerosis on histopathologic evaluation. These patients may have had otosclerosis in the footplate only (which was removed at the time of surgery and not available for review).

CONCLUSION

Nonotosclerotic stapes fixation is not likely a distinct pathologic classification from otosclerosis. Most patients diagnosed with nonotosclerotic stapes fixation likely have otosclerosis, but do not have otosclerotic foci in the stapes itself.

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.

Factors affecting postoperative outcome in otosclerosis patients: Predictive role of audiological and clinical features

OBJECTIVE

Factors affecting postoperative hearing results of patients with otosclerosis were analyzed.

METHODS

Included were 191 patients with otosclerosis in whom 234 primary stapes surgeries were performed from August 1991 to December 2011 by one surgeon in three tertiary hospitals. Evaluation of factors affecting postoperative hearing thresholds at individual frequencies were performed by logistic regression analysis.

RESULTS

Closure of the air-bone gap (ABG) after surgery was good at 2kHz, but poor at 4kHz and frequencies under 1kHz. In addition, improvement at 8kHz was worse than that at any other frequency. Multivariate logistic regression analysis by the stepwise method showed that under the mean preoperative ABG (odds ratio [OR]=2.42), unilaterality (OR=2.53) and male sex (OR=2.65) were significantly better prognostic factors at 250Hz. At 500Hz, under mean preoperative ABG (OR=2.56) was the significantly better factor. No significant factors were found at 1kHz. Cochlear otosclerosis (OR=3.57) was a significantly worse prognostic factor at 2kHz. Under mean preoperative ABG (OR=2.82) and younger age (OR=1.03) were significantly better prognostic factors at 4kHz. At 8kHz, worse preoperative air conduction threshold (OR=1.96) was a significantly better prognostic factor.

CONCLUSION

Preoperative ABG, preoperative air conduction threshold, cochlear otosclerosis, male sex, laterality and age were significant prognostic factors for postoperative hearing outcome in otosclerosis patients. Especially, preoperative ABG was a significant prognostic factor at multiple frequencies. We suppose that patients with larger preoperative ABG have some other otosclerotic lesions outside the oval window niche.

Dynamic properties of human stapedial annular ligament measured with frequency-temperature superposition

Stapedial annular ligament (SAL) is located at the end of human ear ossicular chain and provides a sealed but mobile boundary between the stapes footplate and cochlear fluid. Mechanical properties of the SAL directly affect the acoustic-mechanical transmission of the middle ear and the changes of SAL mechanical properties in diseases (e.g., otosclerosis) may cause severe conductive hearing loss. However, the mechanical properties of SAL have only been reported once in the literature, which were obtained under quasi-static condition (Gan, R. Z., Yang, F., Zhang, X., and Nakmali, D., 2011, "Mechanical Properties of Stapedial Annular Ligament," Med. Eng. Phys., 33, pp. 330-339). Recently, the dynamic properties of human SAL were measured in our lab using dynamic-mechanical analyzer (DMA). The test was conducted at the frequency range from 1 to 40 Hz at three different temperatures: 5 °C, 25 °C, and 37 °C. The frequency-temperature superposition (FTS) principle was applied to extend the testing frequency range to a much higher level. The generalized Maxwell model was employed to describe the constitutive relation of the SAL. The storage shear modulus G' and the loss shear modulus G" were obtained from seven specimens. The mean storage shear modulus was 31.7 kPa at 1 Hz and 61.9 kPa at 3760 Hz. The mean loss shear modulus was 1.1 kPa at 1 Hz and 6.5 kPa at 3760 Hz. The dynamic properties of human SAL obtained in this study provide a better description of the damping behavior of soft tissues than the classic Rayleigh type damping, which was widely used in the published ear models. The data reported in this study contribute to ear biomechanics and will improve the accuracy of finite element (FE) model of the human ear.

The pathologic basis of facial nerve stimulation in otosclerosis and multi-channel cochlear implantation

HYPOTHESIS

Unintentional electrical stimulation of the facial nerve by cochlear implants occurs when advanced otosclerosis invades the endosteum of both the upper basal turn of the cochlea (UBTC) and the facial nerve canal (FNC) and all the bone between these 2 structures.

BACKGROUND

A complication of cochlear implantation is facial nerve stimulation (FNS) known to be more common in otosclerosis. Otosclerotic involvement of the enchondral bone of the otic capsule results in areas of bone resorption, new bone formation, vascular proliferation, and a connective tissue stroma. This may reduce impedance, shunting current to the facial nerve. The cause of FNS has not been fully elucidated, and remarkable differences in FNS rates have been reported using different types of electrode arrays.

METHODS

Thirteen implanted temporal bones from 11 patients with otosclerosis, 10 with straight, and 3 with perimodiolar electrodes, were histologically processed after death. The data were analyzed using Fisher's exact test.

RESULTS

In the straight electrode group (n = 10), only those subjects with temporal bones showing involvement by otosclerosis of the UBTC and of FNC endosteum and the bone between these 2 structures (n = 4; 40%) showed FNS during life (p = 0.005), which was consistent with the location of problematic electrodes during life. None of the cases in the perimodiolar group had FNS even with endosteal involvement by otosclerosis.

CONCLUSION

FNS is a common complication of cochlear implantation in patients with otosclerosis and occurs most commonly with straight electrode implants where the endosteum of both UBTC and FNC and the intervening bone are otosclerotic.

Anatomopathology of the superstructure of the stapes in patients with otosclerosis

Introduction Otosclerosis is a disease that causes bone resorption and deposition in the auditory structures, leading to deafness. Many studies have evaluated the histopathology of the stapes footplate in this disease (osteoblasts, osteoclasts, vascular proliferation, fibroblasts, and histiocytes), but we found no studies in the literature involving the histology of the superstructure of the stapes.

Objectives To perform an analysis under optical microscopy of histopathologic findings of the superstructure of the stapes from patients with otosclerosis.

Methods A contemporary cross-sectional cohort study of pathology analysis of superstructures of the stapes of patients with otosclerosis.

Results Fifteen superstructures of stapes in patients with otosclerosis operated in our service and four stapes of cadavers used for dissection (controls) were evaluated. No areas of bone resorption or deposition or presence of osteoclasts and osteoblasts in the superstructure of the stapes were found. However, we found in the more distal portions of the crura areas with prominent cementitious lines and woven bone, which was different than the mature trabecular bone found in the head of the stapes or in the controls.

Conclusion There were histologic changes in the superstructure of the stapes in patients with otosclerosis operated in our service.