Otosclerosis: relationship of spiral ligament hyalinization to sensorineural hearing loss

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 Radiologic Imaging in Otosclerosis

Purpose of Review

To review the role of imaging in otosclerosis with an emphasis on pre- and post-operative imaging evaluation.

Recent Findings

Pre-operative CT imaging can help define the extent of bone involvement in otosclerosis and may help avoid surgical complications due to variant anatomy or unsuspected alternative causes of conductive hearing loss. In patients with recurrent hearing loss after surgery, CT imaging can clarify prosthesis position and re-assess anatomy.

Summary

CT imaging complements otologic exam and audiometry findings in patients with suspected otosclerosis, for pre-operative planning, and post-operative assessment for patients with recurrent symptoms.

Contributions of Contemporary Human Temporal Bone Histopathology to Clinical Otology

Contemporary techniques have greatly enhanced the contributions of human temporal bone (HTB) histopathology to our understanding of the mechanisms of human otologic disease and disease treatment. Herein, we review some of the most salient contributions of this research to disease management. The field of HTB histopathology is challenged by limited resources as applies to trained investigators, infrastructure, and well-equipped laboratories. This research provides insights into clinical otology that cannot be obtained by any other means. Measures should be taken to preserve and extend the contributions of HTB research.

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.

Controversies in the Evaluation and Management of Otosclerosis

Controversies have been associated with the etiology, diagnosis, evaluation, and management of otosclerosis since Valsalva first described stapes fixation as a cause of hearing loss. Although the exact mechanism of the bone remodeling associated with otosclerosis remains uncertain, stapedotomy has been accepted as the surgical treatment of most patients with stapedial otosclerosis. There remains a disparity of opinion, however, regarding the role of preoperative imaging, surgical technique, implant selection, and medical therapy for cochlear otosclerosis. In addition, opinions vary regarding the optimal postoperative care of patients undergoing stapedotomy and a patient's ability to participate in activities that may result in barotrauma.

Connexin 26 Immunohistochemistry in Temporal Bones With Cochlear Otosclerosis

HYPOTHESIS

Connexin-26 (Cx26) expression is diminished in the spiral ligament of subjects with hearing loss and cochlear otosclerosis (CO).

BACKGROUND

Human temporal bone (HTB) studies have demonstrated that CO is associated with hyalinization of the spiral ligament. We hypothesize that hyalinization is associated with a loss of fibrocytes with a consequent decline in Cx26 expression. Cx26 and Connexin-30 (Cx30) encode gap junction proteins expressed in supporting cells of the organ of Corti, the spiral limbus, stria vascularis, and in fibrocytes of the spiral ligament. These gap junctions are critical for potassium recycling and maintenance of the endocochlear potential. Diminished expression of these proteins would likely be associated with hearing dysfunction.

METHODS

Histopathology and clinical characteristics of 45 HTB specimens with CO and spiral ligament hyalinization were reviewed. Those with sensorineural or mixed hearing loss but normal or near-normal hair cell counts were analyzed with light microscopy, and Cx26-immunoreactive (IR) signal was qualitatively assessed.

RESULTS

H&E staining demonstrated hyalinization in the spiral ligament and loss of type II and type III fibrocytes. Cx26-IR was diminished throughout the cochlea affected with CO compared with normal controls.

CONCLUSIONS

Cx26-IR reduction in the spiral ligament of subjects with CO likely plays a role in hearing loss.

Imaging Review of the Temporal Bone: Part II. Traumatic, Postoperative, and Noninflammatory Nonneoplastic Conditions

The first part of this review of the temporal bone discussed anatomy of the temporal bone as well as inflammatory and neoplastic processes in the temporal bone region (1). This second part will first discuss trauma to the temporal bone and posttraumatic complications. The indications for common surgical procedures performed in the temporal bone and their postoperative imaging appearance are then presented. Finally, a few noninflammatory nonneoplastic entities involving the temporal bone are reviewed. They are relatively uncommon diagnoses compared with infectious or inflammatory diseases. However, because patients present with symptoms that are either common (hearing loss) or distinctive (sensorineural hearing loss in a child), they are important for the radiologist to be aware of and recognize.

Otopathology in Osteogenesis Imperfecta

BACKGROUND

Osteogenesis Imperfecta (OI) is a genetic disorder of connective tissue matrix. OI is caused by mutations that affect type I collagen. The hearing loss in OI is characterized by onset in early adulthood and can be conductive, sensorineural, or mixed.

OBJECTIVES

To describe the temporal bone histopathology in 9 individuals with OI.

MATERIALS AND METHODS

Four adult, 1 pediatric, and 4 infant specimens were identified. Temporal bones were removed at autopsy and studied using light microscopy.

RESULTS

All adults and 1 pediatric specimen showed otosclerotic lesions. The findings included examples of clinical, histologic, and cochlear otosclerosis. The temporal bones of infants showed delayed ossification of the endochondral layer of bone and of the ossicles. There were no infant specimens with otosclerotic lesions.

CONCLUSION

Hearing loss in OI may be the result of clinical or cochlear otosclerosis. Fracture or atrophy of the ossicles may also be present in OI. A third unidentified mechanism of hearing loss may lead to cochlear degeneration. The described findings of otosclerotic lesions have implications for the observed heterogeneity of hearing loss patterns and for the surgical management of hearing loss in OI.

Third-generation bisphosphonates for treatment of sensorineural hearing loss in otosclerosis

OBJECTIVE

To evaluate hearing outcomes in patients treated with third generation bisphosphonates for otosclerosis-related sensorineural hearing loss (SNHL).

HYPOTHESIS

Otosclerosis is a disease of abnormal bone remodeling in the otic capsule. In recent years, third generation bisphosphonates, with more powerful anti-resorptive properties and increased bone affinity, have demonstrated effectiveness in the treatment of osteoporosis and other metabolic bone diseases. We hypothesized that newer generation bisphosphonates, such as risedronate and zoledronate, would be effective in slowing the progression of SNHL in patients with otosclerosis.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral center, ambulatory care.

INTERVENTIONS

Risedronate or zoledronate administration.

MAIN OUTCOME MEASURES

Bone conduction pure tone threshold averages (PTAs) and word recognition (WR) scores were examined for each ear before and after bisphosphonate treatment. Criteria for significant change were defined as greater than 10 decibels in PTA or between 4% and 18% in WR based on binomial variance.

RESULTS

All 10 patients had audiometric progression of SNHL in the pretreatment monitoring interval and 12 ears met criteria for significant progression. All 10 patients (19 ears) showed at least no significant progression of SNHL (i.e., stabilization) at an average follow-up of 13 months. Two patients (3 ears) showed improvement by defined audiometric criteria. There were no major complications.

CONCLUSION

Treatment with zoledronate or risedronate stabilized progressive SNHL related to otosclerosis in this small group of patients. Further evaluation of third-generation bisphosphonate treatments is warranted.

Cochlear implantation outcomes in patients with far advanced otosclerosis

OBJECTIVES

To compare hearing outcomes in patients with far advanced otosclerosis (FAO) undergoing cochlear implantation to an age-matched group of controls, to describe the effects of cochlear ossification on hearing, and to review the adverse effects of implantation in patients with FAO.

HYPOTHESIS

Hearing performance in patients with FAO after cochlear implantation is comparable to similarly treated postlingually deafened adults without FAO. Ossification or retrofenestral otosclerosis does not predict poor hearing outcomes. Modiolar-hugging technology reduces postoperative facial nerve stimulation.

STUDY DESIGN

Retrospective chart review.

SETTING

Academic neurotologic tertiary referral center.

PATIENTS

Thirty patients with FAO, who metaudiological criteria for cochlear implantation, were compared to 30 age-matched controls, postlingually deafened by non-otosclerotic causes.

MAIN OUTCOME MEASURES

Audiometric pre- and postoperative speech reception threshold, word, and sentence scores were analyzed. The presence of retrofenestral findings on computed tomography or intraoperative cochlear ossification were noted.

RESULTS

In the FAO group, radiographic abnormalities were noted in 26.4% of patients. Intraoperative ossification requiring drillout was seen in 29.4% of patients. None developed postoperative facial nerve stimulation. There was no difference between the FAO and control groups in the mean short-term and long-term postoperative speech reception threshold, word, and sentence scores (P = .77). The presence of radiographic abnormalities did not predict hearing outcome. Intraoperative cochlear ossification was not associated with worse short-term word and sentence scores (P = .58 and 0.79, respectively), and for the long-term hearing outcome (P = .24).

CONCLUSIONS

In patients with FAO, effective and safe hearing rehabilitation can be accomplished with cochlear implantation.

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).

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.

Surgical and Medical Treatment of Hearing Loss in Mixed Otosclerosis

Objectives:

We assessed the effect of using preoperative sodium fluoride (NaF) on the difficulty of working with the footplate during stapedectomy and its effect on the postsurgical hearing gain in patients with mixed otosclerosis (ie, otosclerosis and/or otospongiosis).

Methods:

There were 2 groups of patients with mixed otosclerosis. The experimental group was made up of patients with an active focus of the disease; they received NaF for 6 months and then underwent stapedectomy. The control group was made up of patients with an inactive focus of the disease; they underwent stapedectomy without administration of NaF.

Results:

The difference between the study groups in the degree of difficulty in extracting the footplate was not found to be statistically significant. Both groups had hearing gains in bone and air conduction. The level of posttreatment hearing gain in the group exposed to NaF was greater than that in the nonexposed group.

Conclusions:

Sodium fluoride administered to patients with mixed otosclerosis and an active focus of disease does not increase the difficulty of working with the footplate during stapedectomy, and it increases the hearing gain after the procedure.

CT grading of otosclerosis

BACKGROUND AND PURPOSE

The CT grading system for otosclerosis was proposed by Symons and Fanning in 2005. The purpose of this study was to determine if this CT grading system has high interobserver and intraobserver agreement.

MATERIALS AND METHODS

All 997 petrous bone CTs performed between December 2000 and September 2007 were reviewed. A total of 81 subjects had CT evidence of otosclerosis on at least 1 side; 68 (84%) had bilateral disease. Because otosclerosis was clinically suspected in both ears of all 81 subjects even if CT evidence was only unilateral, both petrous bones (162 in total) were included. Two blinded neuroradiologists independently graded disease severity using the Symons/Fanning grading system: grade 1, solely fenestral; grade 2, patchy localized cochlear disease (with or without fenestral involvement) to either the basal cochlear turn (grade 2A), or the middle/apical turns (grade 2B), or both the basal turn and the middle/apical turns (grade 2C); and grade 3, diffuse confluent cochlear involvement (with or without fenestral involvement). One reviewer repeat-graded the petrous bone CTs to determine intraobserver agreement with a 7-month intervening delay to mitigate recall bias.

RESULTS

There were 154 agreements (95%) comparing the first grading of reviewer 1 with that of reviewer 2 (kappa = 0.93). When the repeat 7-month delayed grading of reviewer 1 was compared with that of reviewer 2, there were 151 (93%) agreements (kappa = 0.90). Therefore, mean interobserver agreement was excellent (mean kappa = 0.92). There were 155 agreements (96%) comparing the original grading of reviewer 1 with the delayed grading (kappa = 0.94), demonstrating excellent intraobserver agreement.

CONCLUSIONS

A recently published CT grading for otosclerosis on the basis of location of involvement yielded excellent interobserver and intraobserver agreement.

Selective activation of nuclear factor kappa B in the cochlea by sensory and inflammatory stress

Damage response pathways triggered by mechanical stress might reasonably be expected to be conserved throughout evolution. However, using a nuclear factor kappa B (NF-kappaB) reporter mouse we show here that this phylogenetically recent transcription factor plays a major role in the response to mechanosensory stress in the mammalian inner ear. The protective action of NF-kappaB is exerted in neither sensory nor non-sensory epithelial cells, but rather in connective tissue cells within the spiral ligament and spiral limbus. In the spiral ligament, predominantly type I fibrocytes are activated following noise exposure, whereas type II fibrocytes are activated following systemic inflammatory stress. Immune-mediated and acoustic trauma-mediated hearing loss syndromes in humans may in part result from the vulnerability of type II and type I fibrocytes to systemic inflammatory stress and acoustic trauma, respectively. Unexpected cell-specific and stress-specific NF-kappaB activation found in the inner ear in this in vivo study suggest that this approach may have wide applications in demonstrating similar specializations of stress responses in other tissues, including the brain.

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.

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.

Cochlear Implantation of Patients with Far-Advanced Otosclerosis

OBJECTIVE

This current single-subject, repeated-measures study was to describe our experience with 30 patients who had been diagnosed with "far-advanced otosclerosis" and who were included in our program of cochlear implants. We analyzed the history of the patients and their families before implantation, the surgical findings, and the performance over a follow up of 3 years.

MATERIAL AND METHODS

All patients met one or more of the after criteria: 1) previous surgical intervention as a treatment of their otosclerosis; 2) signs of pericochlear hypodensities in high resolution computed tomography (HRCT) scans; and 3) family precedents of otosclerosis. All underwent standard surgical cochlear implantation.

RESULTS

In 78% of the cases, a stapedectomy had previously been realized. Cochlear otosclerosis could be appreciated in HRCT in 78% of the patients. A family history of otosclerosis was found in 40%, and 33.3% of patients had familial precedents of nonfilial hypoacusis. The mean results in the two-syllable test were 20% preimplantation, 54% 6 months after implantation, and 52%, 62%, 54% at 1, 2, and 3 years after implantation. In the CID sentence test, they were in the order of 32% preimplantation and of 64% at 6 months, 66% after 1 year, of 68% after 2 years, and reaching 72% after 3 years. No complications related to the surgery were detected.

CONCLUSION

Patients diagnosed with far-advanced otosclerosis have a good prognosis with cochlear implantation comparable to that of other patients in whom postlingual implants are performed.

Paget disease and sensorineural hearing loss associated with spiral ligament degeneration

HYPOTHESIS

Previously unreported cystic degeneration of the spiral ligament in cases of Paget disease.

BACKGROUND

About 70% of cases of Paget disease involve the skull, with hearing affected in approximately 50% of these. The hearing impairment may be sensorineural, mixed, or, rarely, only conductive. The etiology and pathogenesis of the hearing loss are not yet understood, and reports in the literature are inconsistent regarding the pathologic changes responsible for sensorineural hearing loss. Of six pairs of temporal bones from patients with Paget disease in the temporal bone collection of a research institution, two pairs have abnormalities not previously associated with sensorineural hearing loss or Paget disease. We report the histopathologic findings in these temporal bones.

METHODS

The temporal bones were fixed in formalin, decalcified in ethylenediaminetetraacetic acid, embedded in celloidin, and sectioned in the horizontal plane at a thickness of 20 microm. Every 10th section was stained with hematoxylin-eosin and mounted on glass slides. The sections were examined by light microscopy.

RESULTS

Cystic degeneration of the spiral ligament, primarily in the basal segment, was found in both cases. Endolymphatic hydrops and a small endolymphatic sac with calcification of the perisaccular tissue were found in one case.

CONCLUSIONS

Cystic degeneration of the spiral ligament has not been previously reported and may be unique to Paget disease. This is consistent with recent literature showing a previously unsuspected role of the spiral ligament in sensorineural hearing loss.

Cochlear implantation in 53 patients with otosclerosis: demographics, computed tomographic scanning, surgery, and complications

OBJECTIVES

To collect data from a large number of cochlear implant recipients with otosclerosis and to make an assessment of these patients' clinical characteristics, computed tomographic scans, surgical findings, and complications, and to quantify the occurrence of postoperative facial nerve stimulation.

STUDY DESIGN

Retrospective multicenter study.

PATIENTS

Fifty-three patients with otosclerosis from four cochlear implant centers in the United Kingdom and The Netherlands were reviewed. Sixty surgical procedures were performed in these patients: 57 devices were placed in 56 ears.

RESULTS

The computed tomographic imaging demonstrated retrofenestral (cochlear) otosclerotic lesions in the majority of patients. Although not statistically significant, the extent of otosclerotic lesions on the computed tomographic scan as categorized in three types tends to be greater in patients with rapidly progressive hearing loss, in patients in whom there is surgically problematic insertion of the electrode array, and in patients with facial nerve stimulation. In four patients, revision surgery had to be performed. Twenty of 53 (38%) patients experienced facial nerve stimulation at various periods postoperatively.

CONCLUSION

Cochlear implant surgery in patients with otosclerosis can be challenging, with a relatively high number of partial insertions and misplacements of the electrode array demanding revision surgery. A very high proportion of patients experienced facial nerve stimulation mainly caused by the distal electrodes. This must be discussed with patients preoperatively.

Spiral ligament and stria vascularis changes in cochlear otosclerosis: effect on hearing level

OBJECTIVE

To investigate the effect of changes within the spiral ligament and stria vascularis on hearing in cochlear otosclerosis, we examined spiral ligament hyalinization, stria vascularis atrophy, and sensory hearing loss in cochlear otosclerosis and described changes in ion transport molecule expression.

STUDY DESIGN

Retrospective.

SETTING

Tertiary referral center.

PATIENTS

Thirty-two cochleae from 24 temporal bone donors with histologic evidence of cochlear otosclerosis, including spiral ligament hyalinization.

INTERVENTION

Audiography.

MAIN OUTCOME MEASURES

Measurements of spiral ligament width, stria vascularis, and bone-conduction thresholds were compared by the amount of hyalinization. Expression of the ion transport molecules Na,K-ATPase, connexin 26, and carbonic anhydrase II were assessed by immunohistochemical techniques.

RESULTS

Hyalinization most often involved the posterior basal turn (88%) and the posterior middle turn (27%). Spiral ligament hyalinization correlated significantly with stria vascularis atrophy in the posterior middle turn of the cochlea (rho = -0.63, p < 0.01). There was a trend toward a significant association in the posterior basal turn (rho = -0.31, p < 0.08). Bone-conduction thresholds at 2,000 and 4,000 Hz were significantly associated with the amount of stria vascularis atrophy (rho = -0.44, -0.40, p < 0.05). In addition, we observed decreased immunostaining for both carbonic anhydrase II with Type I fibrocytes and Na,K-ATPase with stria vascularis and Type II and Type IV fibrocytes of the spiral ligament in cochlear otosclerosis sections compared with normal cochlea. Na,K-ATPase staining within the stria vascularis was further decreased in the presence of spiral ligament hyalinization. No significant differences were seen with connexin 26 immunostaining. However, immunostaining results were somewhat inconsistent.

CONCLUSION

These data suggest that spiral ligament structure and function are essential for stria vascularis survival. In addition, dampened expression of ion transport molecules within the spiral ligament and stria vascularis may disrupt potassium ion recycling, resulting in loss of endocochlear potential and sensory hearing loss.

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.

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.

[Evidence of otospongiosis obtained by computerized tomography. Does it compromise the post-stapedectomy auditory gain?]

To study the influence of tomographic otospongiosis/otosclerosis on the audiometric gain after stapedectomy, we evaluated 34 patients (mean age 39.9 years, S.D. 9.8) with otosclerosis and mixed hearing loss. We performed Computed Tomography (CT) with densitometry before stapedectomy and audiometry before and 4 weeks after the surgery. CT results were classified as compatible or not for otospongiosis (< 1000 UH) or for otosclerosis (> 2000 UH). According to the affected turns of the cochlea, the studies were classified in 3 groups. In 43% of the patients the CT showed otospongiosis. After stapedectomy, air conduction thresholds of the low (125-500 Hz), middle (500-2000 Hz) and high frequency bands (2000-8000 Hz) and for the air/bone gap were similar for the ears with or without otospongiosis (p > 0.05, ANOVA). However, patients with otospongiosis in all the cochlea showed the lowest audiometric gain for the high frequency band (p < 0.05 ANOVA). Evidence of otospongiosis evaluated just by CT has a low impact on the audiometric outcome after stapedectomy.

Cochlear otosclerosis 30 years after stapedectomy confirmed by CT, MRI

A 64-year-old Japanese male patient, status post-stapedectomy, presented with progressive, bilateral SNHL of 30 years' duration. CT showed extensive demineralization of the otic capsule, suggestive of otospongiotic change in both ears. There were no hyperostotic lesions found, which would have been suggestive of otosclerotic change. MRI showed a morphologically intact membranous labyrinth in both ears, with no obstruction of the cochlear lumen. It was concluded that the patient has progressive otospongiotic change of the otic capsule, but no otosclerotic change.

Etidronate for the Neurotologic Symptoms of Otosclerosis: Preliminary Study

The efficacy of etidronate, a Bisphosphonate, was assessed as a treatment for the inner ear symptoms of otosclerosis in a retrospective case review of 896 patients diagnosed with otosclerosis, with primary complaints of dizziness, hearing loss, tinnitus or Meniere's syndrome. The diagnosis of otosclerosis was based on small-pixel computed tomography of the temporal bones. Of the 896 patients placed on an etidronate protocol, 545 were followed for more than six months and were analyzed. The symptomatic response to etidronate, as well as audiologic and computerized rotary chair results were used in the assessment. Patients who were previously on sodium fluoride were separately analyzed. In this preliminary study etidronate appeared to be an effective treatment for the neurotologic symptoms of otosclerosis. Prospective blinded efficacy studies of the bisphosphonates in the treatment of otosclerosis should be undertaken.

Ultrastructure of otic capsule sclerosis in Palmerston North autoimmune mice

PURPOSE

Numerous temporal bone studies have reported a correlation between systemic autoimmune disease and osteogenic lesions within the inner ear. However, little is known of the cellular mechanisms that relate these two disease processes. The Palmerston North (PN) autoimmune strain mouse exhibits both spontaneous systemic autoimmune disease and otic capsule sclerotic lesions that are similar in many ways to those reported in humans. This suggests the PN mouse is a potential model in which to study the cellular events responsible for immune-related otic capsule lesions. Therefore, an evaluation of the fine structure of the PN modiolus was conducted to better understand these matrix changes of the inner ear.

MATERIALS AND METHODS

Inner ears were collected from 15 PN mice at ages from 17 to 24 months and prepared for electron microscopy. The ears were ultrastructurally evaluated to characterize the lesions and their associated cytoarchitecture.

RESULTS

The sclerotic lesions consisted of an electron-dense mass that appeared lobulated or layered, usually adjacent to the modiolar bone and blood vessels. Immediately surrounding the lesions were activated fibroblasts and fine fibrillar material in the extracellular space between them. The sclerotic foci often were apposed to normal modiolar bone that never appeared degraded.

CONCLUSIONS

The similarities between these bony lesions and known human otic capsule diseases suggests parallel processes are involved. Thus, further study of the PN inner ear may provide insight into the cellular events that underlie otic capsule and other temporal bone alterations in systemic autoimmune diseases.

Osteogenesis imperfecta: clinical symptoms and update findings in computed tomography and tympano-cochlear scintigraphy

Osteogenesis imperfecta (OI) is an autosomal-dominantly inherited connective tissue disorder characterized by abnormal bone fragility combined with blue sclerae. The association of OI with hearing impairment is commonly known as Van der Hoeve-de Kleyn syndrome. Besides typical symptoms we here report on findings by high resolution CT and by high resolving scintigraphy of the labyrinthine capsule in 3 families (9 patients) with OI, which resemble those in otosclerosis (OS): In 4 of 6 cases with OI and mixed hearing loss, severely decreased peri-cochlear bone density was established by CT. In these cases, increased bone metabolism could be revealed by high resolving tympano-cochlear scintigraphy (TCS) in the cochlear region. In 2 patients with mixed hearing loss and 3 cases without hearing impairment or with slight conductive hearing loss, bone alteration was not detectable by CT and TCS. These results raise the question whether OI and OS lead to similar labyrinthine bone alterations, based on different aetiologies or whether these diseases may co-exist, OS being part of OI.

Otosclerosis: the University of Minnesota temporal bone collection

A study of 1452 human temporal bones revealed a previously unpublished material of 144 bones with otosclerosis. After exclusion of infants and individuals of races other than white, the incidence of otosclerosis was 12.75%. Of the bones with otosclerosis, 56.1% belonged to men and 43.9% to women. The incidence of clinical and histologic otosclerosis was practically the same for men (44.7% to 55.3%) as for women (47% to 53%). However, the incidence of bilateral otosclerosis was higher in women (88.9%) than in men (65.2%). Bilateral otosclerosis was present in 75.6%, whereas it was unilateral in 24.4%. Sixty-six (66) ears (45.8%) had clinical otosclerosis, whereas 78 (54.2%) had histologic otosclerosis--frequently unifocal lesions. The most common site was anterior to the oval window (117 ears, 81.25%), followed by round window niche (52 ears, 36.11%), apical and medial cochlear wall (31 ears, 21.52%), and anterior wall of the internal auditory canal (27 ears, 18.75%). The activity of lesions was directly related to their size. Smaller lesions were predominantly inactive, whereas medium and larger lesions were predominantly active. There was a positive correlation when the size of the lesions, activity, and degree of cochlear endosteal involvement were compared with bone conduction thresholds (37 cases). Correlations between size and activity, and between activity and associated sensorineural hearing loss did not necessarily follow the sequence of an initial active stage (spongiotic) to a final inactive one (sclerotic). Comparison of cases of otosclerosis with equivalent age groups of the normal population yielded worse bone conduction thresholds for the otosclerosis cases only in the age group 60 to 69 years and older. Comparison of average bone conduction thresholds between bones with one site of endosteal involvement (28.26 dB HL) revealed no significant differences. Bones with two or more sites of endosteal involvement had significant differences. Bones with two or more sites of endosteal involvement had significantly worse bone conduction thresholds (62 dB HL). The overall results are not suggestive of an association of sensorineural hearing loss with otosclerosis without stapedial fixation.

Cochlear otosclerosis: statistical analysis of relationship of spiral ligament hyalinization to hearing loss

This paper presents an analysis of the relationship of the amount of hyalinization of the spiral ligament, secondary to cochlear otosclerosis (spongiosis), to the amount of hearing loss. This relationship was previously studied by Parahy and Linthicum. It was found that the larger the amount of hyalinization, the greater the hearing loss. This hyalinization is a measure of the amount of toxic enzymes being excreted into the inner ear fluid. These enzymes are suspected to affect the metabolic function of the hair cells.

Reduction of spiral ganglion neurons in the aging canine with hearing loss

The middle and inner ears of 16 dogs, from 1.5 to 17 years of age, with differing degrees of suspected hearing loss were examined. Auditory function was assessed subjectively, and electrophysiologically by recording brainstem auditory-evoked responses (BAER) to click stimuli. Ossicular chains and stapediovestibular articulations were evaluated macroscopically and by light microscopy for evidence of bony ankylosis; no abnormalities were found. A determination of spiral ganglion packing density revealed a loss of spiral ganglion cells in all areas of the cochlea in dogs of the deaf group and in the upper and lower basal region of dogs from the hearing impaired group. The largest losses of spiral ganglion cells in the deaf group were located in the upper and lower basal region. The deaf group's density was reduced to 44% (upper basal) 15% (lower basal) of the normal hearing group. The largest spiral ganglion cell loss for dogs in the hearing impaired group occurred in the lower basal region where the density was reduced to 40% of the normal hearing group. These morphological findings in the aging canine are consistent with a peripheral nerve hearing loss.

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

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

Otosclerosis and sensorineural hearing loss: a histopathologic study

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

Otosclerosis and otospongiosis: clinical and histological comparisons

The simultaneous occurrence of otosclerosis and otospongiosis in the same lesion is well documented. The logical sequence of events would seem to be softening and destruction of the bone by the otospongiotic lesion, which is subsequently converted to otosclerosis. Examination of 46 temporal bones has led us to further classify the lesion as: 1. an active lesion, both otospongiotic and otosclerotic, 2. an inactive lesion, also both otosclerotic and otospongiotic, or 3. a fibrous lesion. Hyalinization of the spiral ligament only occurs adjacent to active otospongiotic or very large otosclerotic lesions. If the lesion adjacent to the spiral ligament is inactive, there is no hyalinization. It seems illogical that a hyalinized spiral ligament will return to normal when the lesion changes from active otospongiosis to inactive otosclerosis. Otospongiotic and otosclerotic lesions are found side by side at the periphery of lesions, and both are adjacent to normal bone. These findings have implications concerning the mode of action of sodium fluoride and other medications that are under evaluation for the control of the sensorineural hearing loss due to otosclerosis.

Histologic evaluation of temporal bones with cochlear implants

Ectopic bone in the scala tympani is characteristic of cochlear otosclerosis and meningitis, which are the two most frequent etiologies of deafness in cochlear implant patients. The ectopic bone in a multiple-electrode implanted bone is probably caused by disease (syphilis) rather than by the electrode or electrical stimulation. The sensory elements being stimulated by intracochlear electrodes probably are the ganglion cells.