Three-dimensional quantification of fibrosis and ossification after cochlear implantation via virtual re-sectioning: Potential implications for residual hearing

Hearing preservation may be achieved initially in the majority of patients after cochlear implantation, however, a significant proportion of these patients experience delayed hearing loss months or years later. A prior histological report in a case of delayed hearing loss suggested a potential cochlear mechanical origin of this hearing loss due to tissue fibrosis, and older case series highlight the frequent findings of post-implantation fibrosis and neoosteogenesis though without a focus on the impact on residual hearing. Here we present the largest series (N = 20) of 3-dimensionally reconstructed cochleae based on digitally scanned histologic sections from patients who were implanted during their lifetime. All patients were implanted with multichannel electrodes via a cochleostomy or an extended round window insertion. A quantified analysis of intracochlear tissue formation was carried out via virtual re-sectioning orthogonal to the cochlear spiral. Intracochlear tissue formation was present in every case. On average 33% (SD 14%) of the total cochlear volume was occupied by new tissue formation, consisting of 26% (SD 12%) fibrous and 7% (SD 6%) bony tissue. The round window was completely covered by fibro-osseous tissue in 85% of cases and was associated with an obstruction of the cochlear aqueduct in 100%. The basal part of the basilar membrane was at least partially abutted by the electrode or new tissue formation in every case, while the apical region, corresponding with a characteristic frequency of < 500 Hz, appeared normal in 89%. This quantitative analysis shows that after cochlear implantation via extended round window or cochleostomy, intracochlear fibrosis and neoossification are present in all cases at anatomical locations that could impact normal inner ear mechanics.

Histopathology of the Clarion cochlear implant electrode positioner in a human subject

A Silastic electrode positioner was introduced by the Advanced Bionics Corporation in 1999 and it was designed to achieve a perimodiolar position of the stimulating electrode. The positioner was voluntarily recalled in the United States in July 2002 due to an apparent higher risk of bacterial meningitis in patients in whom the electrode positioner had been placed. A detailed histopathologic study of the positioner in the human has not previously been published. The histopathologic findings in a 74-year-old woman who underwent bilateral cochlear implantation using the positioner are presented. Findings include a large track caused by the combined electrode and its positioner with considerable disruption of the basilar membrane and osseous spiral lamina. Although there was a fibrous sheath around the electrode and positioner at the cochleostomy in both ears, this fibrous sheath did not extend deeply into the cochlea except at the apical end of the electrode beyond the positioner. This resulted in a large fluid space around and between the positioner and electrode within the cochlea and presumably in fluid continuity with the cerebrospinal fluid space. Possible clinical implications are discussed.

Morphometric analysis of age-related changes in the human basilar membrane

The histopathologic correlates of presbycusis suggest several categories, including degeneration of sensory cells, neurons, or the stria vascularis. Lack of clear-cut histopathologic changes in some cases has suggested an "indeterminate category"; however, several studies have suggested that a disorder of the basilar membrane (BM) may underlie indeterminate presbycusis. The objective of the present study was to quantify age-related changes in the human BM and correlate them with audiometric patterns. Under high-resolution light microscopy, BM thickness was calculated, and the number of tympanic mesothelial cells (TMCs) lining the BM was counted, at 4 cochlear locations in 92 temporal bones. The control group (n = 80) included subjects from 10 decades of age with normal hearing and/or histopathologic findings. The indeterminate group (n = 12) consisted of elderly patients (ages 64 to 91 years) with hearing loss and no apparent histopathologic changes. Age-related BM thickening was seen in both groups, but only in the most basal cochlear region. The BM thickness in the indeterminate group was not significantly different from that of age-matched controls. Counts of TMCs showed age-related decreases in all cochlear regions in both groups; however, TMC counts in the indeterminate group were not different from those of age-matched controls. The results suggest that BM histopathology is not a common cause of presbycusis. Although age-related BM thickening, seen in both groups, could contribute to hearing loss, the extreme basal region, to which the thickening was confined, is not tested in routine audiometry.

Histopathology and molecular genetics of hearing loss in the human

Hearing loss is among the most common disabilities of man. It has been estimated that over 70 million individuals in the world are hearing impaired with pure tone averages greater than 55 dB. A genetic etiology is thought to be responsible for over half of early onset hearing loss and at least one third of late onset hearing loss. In this review, examples of the histopathology of the inner ear in known genetic syndromes in the human will be presented in order to provide a structural basis for understanding molecular mechanisms of development and maintenance in the inner ear, and to serve the essential function of validating the applicability of animal genetic models of hearing loss to the human condition.

Histopathology of cochlear implants in humans

The insertion of an intrascalar electrode array during cochlear implantation causes immediate damage to the inner ear and may result in delayed onset of additional damage that may interfere with neuronal stimulation. To date, there have been reports on fewer than 50 temporal bone specimens from patients who had undergone implantation during life. The majority of these were single-channel implants, whereas the majority of implants inserted today are multichannel systems. This report presents the histopathologic findings in temporal bones from 8 individuals who in life had undergone multichannel cochlear implantation, with particular attention to the type and location of trauma and to long-term changes within the cochlea. The effect of these changes on spiral ganglion cell counts and the correlation between speech comprehension and spiral ganglion cell counts were calculated. In 4 of the 8 cases, the opposite, unimplanted ear was available for comparison. In 3 of the 4 cases, there was no significant difference between the spiral ganglion cell counts on the implanted and unimplanted sides. In addition, in this series of 8 cases, there was an apparent negative correlation between residual spiral ganglion cell count and hearing performance during life as measured by single-syllable word recognition. This finding suggests that abnormalities in the central auditory pathways are at least as important as spiral ganglion cell loss in limiting the performance of implant users.

Otopathology in a case of type I Waardenburg's syndrome

We report a case of type I Waardenburg's syndrome that provides insight into the etiopathogenesis of sensorineural hearing loss (SNHL) in this syndrome. The subject, a 76-year-old woman with type I Waardenburg's syndrome (dystopia canthorum, heterochromia irides, and white hair), had congenital low-frequency SNHL in her right ear only, which had remained relatively stable throughout her life. Blood leukocyte DNA studies revealed a PAX-3 mutation with a 1 base pair C-to-A substitution in exon 5 at base 602. Light microscopic studies of the right cochlea showed intact neurosensory structures in only the lower basal turn, with the remainder of the cochlea showing absence of melanocytes, absence of stria vascularis, missing hair cells, dysmorphogenesis of the tectorial membrane, and lack of peripheral processes of the spiral ganglion cells. There was pathological alteration of the vestibular dark cells with marked reduction of melanocytes associated with these dark cells. The left inner ear was normal, with a full complement of neurosensory structures, including melanocytes. Because the PAX-3 gene is involved in neural crest development and melanocytes migrate from the neural crest to the ear, the findings in this case are consistent with the hypothesis that defective melanocyte migration or defective melanocyte function results in defective development of the stria vascularis (and perhaps other structures of the ear), leading to SNHL.

Temporal bone histopathologic and genetic studies in Mohr-Tranebjaerg syndrome (DFN-1)

OBJECTIVE

To describe the temporal bone histopathologic and genetic abnormalities in a case of Mohr-Tranebjaerg syndrome.

BACKGROUND

Mohr-Tranebjaezrg syndrome (DFN-1) is an X-linked, recessive, syndromic hearing loss, characterized by postlingual sensorineural hearing loss with onset in childhood, followed in adult life by progressive dystonia, spasticity, dysphagia, and optic atrophy. The syndrome is caused by mutations in the DDP (deafness/dystonia peptide) gene, which are thought to result in mitochondrial dysfunction with subsequent neurodegeneration. The temporal bone pathologic changes in this syndrome have not been reported.

METHODS

Hearing loss developed in the patient at age 4, blindness at age 48, and dystonia at age 57. Genetic studies on peripheral blood showed a l51delT mutation in his DDP gene. He died at age 66. The right temporal bone was subjected to light microscopy and polymerase chain reaction-based analysis of the DDP gene sequence.

RESULTS

There was near complete loss of spiral ganglion cells with loss of nearly all peripheral and central processes. Only 1,765 spiral ganglion cells remained (8.5% of mean normal for age). The organ of Corti (including hair cells), stria vascularis, and spiral ligament were preserved. There was also a severe loss of Scarpa's ganglion cells with preservation of vestibular hair cells. The population of geniculate and trigeminal ganglion cells appeared normal. Sequence analysis from temporal bone DNA showed the 15ldelT DDP gene mutation.

CONCLUSION

Sensorineural hearing loss in Mohr-Tranebjaerg syndrome is the result of a postnatal, progressive, severe auditory neuropathy.

Histologic Studies of the Posterior Stapediovestibular Joint in Otosclerosis

OBJECTIVE

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

BACKGROUND

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

METHODS

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

RESULTS AND CONCLUSIONS

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

Histopathology of residual and recurrent conductive hearing loss after stapedectomy

HYPOTHESIS

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Prevalence and ultrastructural morphology of axosomatic synapses on spiral ganglion cells in humans of different ages

Axosomatic synapses were found on human spiral ganglion cells (HSGCs). Ultrastructural characterization and calculation of the prevalence of these synapses were performed by electron microscopic semi-serial sections of both type I and type II HSGCs, in specimens from subjects of ages 1 day, 14 days, 21 years and 51 years. Synapses on type I HSGCs were extremely rare. In contrast, axosomatic synapses were present on approximately 50% of type II HSGCs of a young adult. This prevalence seemed to vary by age. Thus, no synapses were found in a 1-day old neonate, few in a 14-day old, and on approximately 15% of the type II SGCs from a 51-year old specimen. The origin of the nerve fibers synapsing on the type II HSGCs could not be determined. In view of the fact that some of the fibers projected from the intraganglionic spiral bundle, which is known to contain olivocochlear efferents, these fibers may represent an efferent pathway to the spiral ganglion. However, since there was morphological evidence of more than one type of nerve fiber synapsing on type II HSGCs, other neural origins must be considered. Although the physiological function of these synapses is unknown, they may mediate pre-synaptic neural modulation of the type II HSGCs at the level of the spiral ganglion.

Hearing preservation in acoustic neuroma surgery: middle fossa versus retrosigmoid approach

OBJECTIVE

To compare the results of the middle fossa approach with those of the retrosigmoid approach in acoustic neuroma hearing preservation surgery.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary care facility.

PATIENTS

Patients of the otology service with acoustic neuromas and useful hearing. Fifteen intracanalicular tumors were removed via a middle fossa approach and matched with 15 intracanalicular tumors removed via the retrosigmoid approach. Four additional patients with larger tumors were operated on via the middle fossa approach and matched with patients having similar tumors removed via the retrosigmoid approach.

MAIN OUTCOME MEASURES

The 1994 Committee on Hearing and Equilibrium guidelines for the evaluation of hearing preservation in acoustic neuroma were applied. Facial nerve results were graded according to the House-Brackmann grading scale 3 months postoperatively.

RESULTS

In the group operated on by the middle fossa approach, the average preoperative pure-tone threshold average (PTA) was 23 dB with a word recognition score (WRS) of 79%, and the postoperative PTA averaged 49 dB with a mean WRS of 56%. In the group operated on by the retrosigmoid approach, the mean preoperative PTA was 16 dB with a WRS of 95% and a postoperative PTA value of 62 dB and WRS of 51% (hearing preservation rate of 47%). The middle fossa patients had an average change in PTA of 19 dB and an average change in WRS of 20% (hearing preservation rate of 57%). Overall, the retrosigmoid patients had an average change in PTA of 42 dB and an average change in WRS of 40%. The average change in PTA for larger tumors removed via the middle fossa approach was 32 dB, whereas all matched retrosigmoid patients lost all hearing. The rate of cerebrospinal fluid leak and facial nerve outcomes were similar between the two groups. The retrosigmoid group had a higher rate of postoperative headache.

CONCLUSIONS

Compared with the retrosigmoid approach, the middle fossa approach for hearing preservation surgery yields better hearing results for intracanalicular tumors and also has a lower incidence of postoperative headache.

Outcomes assessment for chronic otitis media: the Chronic Ear Survey

Analysis of outcomes in chronic otitis media has in the past been limited to audiological measurement or physical examination. The Chronic Ear Survey (CES) is an instrument to measure the impact of chronic otitis media and its treatment. The survey provides information regarding total ear-specific health, as well as subscore information regarding activity restriction, symptoms, and medical resource usage attributable to chronic otitis media Application of the CES to a prospective, nonrandomized series of 147 patients revealed that patients with chronic otitis media have significantly decreased CES scores compared with unaffected controls and that surgical intervention provides a significant improvement in ear-specific outcomes.

Validation of outcomes survey for adults with chronic suppurative otitis media

Currently, there is no valid, disease-specific outcomes measure to evaluate health impact and treatment effectiveness for patients with chronic suppurative otitis media (CSOM). The Chronic Ear Survey (CES) is a new, disease-specific outcomes measure for CSOM that was administered in a prospective manner to 91 patients with CSOM. It was then validated according to established criteria for reliability, validity, and sensitivity to clinical change by correlation with objective data and self-assessment questionnaires such as the Hearing Handicap Inventory for Adults (HHIA) and the generic 36-Item Short-Form Health Survey (SF-36). Significant correlations between subscale scores of the CES and audiometric data and between subscale scores of the HHIA and SF-36 were found. The standardized response mean for the CES total score was 0.42, indicating moderate sensitivity to clinical change. Overall, results demonstrated that the CES is a reliable and valid instrument for investigation of health status and health-related quality-of-life outcomes.

Pattern of degeneration of the spiral ganglion cell and its processes in the C57BL/6J mouse

Although degeneration of spiral ganglion cells has been described as a histopathologic correlate of hearing loss both in animals and humans, the pattern and sequence of this degeneration remain controversial. Degeneration of hair cells and of spiral ganglion cells and their dendritic processes was evaluated in the C57BL/6J mouse, in which there is a genetically determined progressive sensorineural loss starting in the high frequencies that is similar to the pattern commonly seen in the human. Auditory function was evaluated by brainstem evoked responses, and degeneration of hair cells, ganglion cells and their dendrites was evaluated histologically at 3, 8, 12 and 18 months of age. Progressive loss of auditory sensitivity was correlated with the loss of outer and inner hair cells and spiral ganglion cells and their dendritic processes. In addition, dendritic counts were consistently lower at a distal location in the osseous spiral lamina (i.e. near the organ of Corti) than at a proximal location (i.e. near the spiral ganglion), and the difference between the number of distal dendrites and the number of proximal dendrites tended to be greater with advancing age. These observations suggest an age-related progressive retrograde degeneration of spiral ganglion cells. Thus, in degenerating cochleas, some remaining spiral ganglion cells may have no distal dendritic processes near the organ of Corti. This may have implications for successful stimulation of the cochlear neuron in cochlear implantation.

Osteomyelitis, lateral sinus thrombosis, and temporal lobe infarction caused by infection of a percutaneous cochlear implant

OBJECTIVE

Cochlear implantation has become a routine operation in the last 10 years. The most common soft tissue complications with transcutaneous cochlear implants include infection or necrosis of the flap and extrusion of the implant and device failure. The most common complication reported with percutaneous devices include minor skin irritations at the pedestal site, retraction of skin from the pedestal site, and loosening of screws that retain the pedestal. We describe one case of lateral sinus thrombosis and secondary temporal lobe infarction caused by infection of a screw anchoring the percutaneous pedestal of an Ineraid implant.

STUDY DESIGN

Case report.

SETTING

Tertiary referral center.

CONCLUSIONS

Intracranial complications of a percutaneous bone-anchored pedestal may occur with little prodrome. Computed tomography (CT) scan of the pedestal and bone anchoring screws may be indicated if local evidence of infection persists.

Training the physician-scholar in otolaryngology-head and neck surgery

The Resident Education Committee of the Society of University Otolaryngologists constructed a questionnaire for young academic otolaryngologist-head and neck surgeons to better understand their training background and to garner their opinions concerning adequacy or deficiencies in various aspects of that training. The questionnaire was mailed to 145 individuals who were in academic posts for 5 years or fewer in 1997. There was an overall response rate of 88.3%. Of the 128 respondents, 89% identified additional training, most commonly a clinical fellowship, in preparation for an academic career. The median number of hours per week devoted to professionally related activity was 61, of which two thirds was spent in direct patient care. The most common source of funds to pursue research activities was intradepartmental resources. Most individuals were satisfied with their jobs, although one quarter were considering leaving academic practice within the year. The single most important reason motivating selection of an academic career was a desire to teach. Details of the specific training and competencies and recommendations for improvement in resident training were obtained. Specific recommendations were generated for improving the training of future academic otolaryngologists; these recommendations include clarity of job description, a single track for clinical training for academicians and nonacademicians, more training in pertinent skills including research training, protected time for research, and amelioration of some of the downsides of academic life.

Standardized format for depicting hearing preservation results in the management of acoustic neuroma

The Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery recently published guidelines for reporting hearing preservation in the treatment of acoustic neuromas. These suggestions included pretreatment and posttreatment pure-tone hearing thresholds, word recognition scores, and hearing classification. We present a standardized reporting format that addresses the Committee's recommendations and displays individual patient audiologic data as a simple, concise plot of posttreatment hearing results. To illustrate the use of the recommended format, preoperative and postoperative hearing data from our institution are reported. Such reporting criteria will facilitate comparative reviews of studies of hearing preservation after surgical or radiotherapeutic management of acoustic neuromas, while providing specific data for individual patient outcome analysis.

Delayed intracranial abscess after acoustic neuroma surgery: a report of two cases

OBJECTIVE

The use of antibiotics before and after surgery has made infectious complications of neurotologic surgery rare. The neurosurgical literature cites a rate of postoperative meningitis between 1% and 2% for "clean" cases and 1.5% to 2.5% for "clean contaminated" cases, such as cerebrospinal fluid contact with the middle ear or mastoid. Reports of infections after neurotologic procedures are rare in the otologic literature. In this report, two patients with brain abscess occurring in a delayed fashion after surgery are described.

STUDY DESIGN

The study design was a retrospective chart review and case report.

SETTING

The study was conducted at a tertiary referral center.

RESULTS

Patient 1 underwent a suboccipital craniotomy for removal of an acoustic neuroma and had an uneventful postoperative recovery. Three months after surgery, he reported mild unsteadiness. Examination revealed mild ataxia, which led to repeat magnetic resonance imaging (MRI) and a diagnosis of cerebellar abscess. Patient 2 underwent translabyrinthine removal of an acoustic neuroma complicated by postoperative Pseudomonas aeruginosa meningitis, which responded promptly to intravenous antibiotics. Fifteen months after surgery, he visited a neurologist after having a seizure and was treated with anticonvulsants. After a second episode of seizure, imaging studies showed a temporal lobe abscess.

CONCLUSIONS

The signs of intracranial abscess may be subtle and can occur weeks or months after surgery, requiring vigilance and a high index of suspicion for diagnosis. A change in postoperative symptoms after acoustic neuroma surgery should signal further investigation using MRI with gadolinium.

Does otosclerosis occur only in the temporal bone?

HYPOTHESIS

Otosclerosis does not occur outside the temporal bone.

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Prevention of hearing loss in experimental pneumococcal meningitis by administration of dexamethasone and ketorolac

Pneumococcal meningitis remains a significant cause of morbidity, particularly sensorineural hearing loss. Recent literature has suggested that a vigorous host immune response to Streptococcus [corrected] pneumoniae is responsible for much of the neurologic sequelae, including deafness, after bacterial meningitis. This study used a rabbit model of hearing loss in experimental pneumococcal meningitis to evaluate the therapeutic effect of two anti-inflammatory agents, dexamethasone and ketorolac, coadministered with ampicillin. Both adjunctive drugs minimized or prevented sensorineural hearing loss compared with placebo. Dexamethasone, administered 10 min before ampicillin, was particularly effective in minimizing mean hearing threshold change compared with placebo for both clicks (dexamethasone: 6.7-dB sound pressure level [SPL] vs. placebo: 33. 4-dB SPL, P=.0078) and 10-kHz tone bursts (dexamethasone: 8.4-dB SPL vs. placebo: 53.4-dB SPL, P=.0003). These findings support the beneficial role of anti-inflammatory agents in reducing the incidence of hearing loss from pneumococcal meningitis, especially if therapy is instituted early in the course of infection.

Correlation of acoustic threshold measures and spiral ganglion cell survival in severe to profound sensorineural hearing loss: implications for cochlear implantation

In a temporal bone study of 26 ears from 13 patients who, in life, had severe sensorineural hearing loss, the segmental and total spiral ganglion cell (SGC) counts were correlated with hearing thresholds and with the difference between hearing thresholds in the two ears, the age at death, the duration of deafness, and the duration of hearing loss. A statistically significant correlation was found between the interaural differences in total SGC counts and the interaural difference in pure tone averages for 3, 4, and 5 frequencies. The total SGC count was higher in the ear with the better residual hearing in 11 of 12 cases. Approximately 41% of the variability in interaural difference in pure tone average was explained by the difference in SGC counts. The findings would suggest that in a given individual, selection of the ear with better residual hearing for cochlear implantation is likely to result in accessing a higher number of residual SGCs. This, in turn, may result in better speech recognition with the implant.

Mutations in a novel cochlear gene cause DFNA9, a human nonsyndromic deafness with vestibular dysfunction

DFNA9 is an autosomal dominant, nonsyndromic, progressive sensorineural hearing loss with vestibular pathology. Here we report three missense mutations in human COCH (previously described as Coch5b2), a novel cochlear gene, in three unrelated kindreds with DFNA9. All three residues mutated in DFNA9 are conserved in mouse and chicken Coch, and are found in a region containing four conserved cysteines with homology to a domain in factor C, a lipopolysaccharide-binding coagulation factor in Limulus polyphemus. COCH message, found at high levels in human cochlear and vestibular organs, occurs in the chicken inner ear in the regions of the auditory and vestibular nerve fibres, the neural and abneural limbs adjacent to the cochlear sensory epithelium and the stroma of the crista ampullaris of the vestibular labyrinth. These areas correspond to human inner ear structures which show histopathological findings of acidophilic ground substance in DFNA9 patients.

Dense innervation of Deiters' and Hensen's cells persists after chronic deefferentation of guinea pig cochleas

Innervation of Deiters' and Hensen's cells has been described in the organ of Corti of several mammalian species and has been suggested to arise from the olivocochlear (OC) efferent system (Wright and Preston [1976] Acta Otolaryngol. 82:41-47). In the present study, antineurofilament immunostaining was used to reveal these outer supporting cell fibers (OSCFs) in the normal guinea pig. In control ears, OSCFs were absent in the basal half of the cochlea but increased in number steadily toward the apex, peaking at values of over 1,200 fibers/mm. These values indicate a far more profuse innervation of supporting cells than has been described previously, suggesting that most OSCFs were not stained in previous immunohistochemical studies. Chronic cochlear deefferentation was used to test whether OSCFs are part of the OC system. The OC bundle was transected unilaterally, and the animals were allowed to survive for 4-8 weeks. Completeness of deefferentation was assessed by using acetylcholinesterase staining of the brainstem and measurement of the density of OC fascicles in the cochlea. By using these metrics, unilateral deefferentation was nearly complete in three animals. In successfully deefferented cases, the OSCF innervation density was not statistically different from control values. We conclude that the vast majority of OSCFs are not of OC origin. We speculate that they may be branches of type II afferent fibers to outer hair cells and that a smaller population of OSCFs with different morphology and immunoreactivity may arise from the OC system.

Single-channel to multichannel conversions in adult cochlear implant subjects

OBJECTIVE

This study aimed to compare open-set speech perception of single-channel with multichannel cochlear implants in the same ear of postlingually deafened adults.

STUDY DESIGN

The study design was a retrospective case and literature review.

SETTING

The study was conducted at a tertiary referral center with an associated veterans administration hospital.

PATIENTS

Postlingually deafened adults with at least 6 months of experience with a single-channel cochlear implant were studied.

INTERVENTION

Replacement of a single-channel with a multichannel cochlear implant in the same ear was performed.

MAIN OUTCOME MEASURES

Open-set word and sentence perception scores at least 6 months after single-channel implantation and multichannel reimplantation were measured.

RESULTS

Six of six patients had substantial improvement in open-set speech recognition after reimplantation of the same ear.

CONCLUSIONS

Removal of a functioning single-channel implant and replacement with a multichannel device are appropriate in postlingually deafened adults who desire better speech recognition.

Nucleus 22 cochlear implantation results in postmeningitic deafness

Cochlear implant surgery was performed on 13 patients with postmeningitic deafness (seven adults, six children). Two adults and two children (30.8%) had severe labyrinthitis ossificans requiring radical "drill-out." Five of 13 (38.5%) had some bone growth requiring partial drill-out, and four of 13 (30.8%) had normal insertion with no drill-out. Hearing results for patients with no bone growth were similar to nonmeningitic patients; three of four (75%) had open-set speech recognition. Performance of patients with total drill-out was poor; "auditory only" performance was limited to detection and pattern perception of speech, and no patients had open-set speech recognition. Results for patients with partial drill-out were similar to results in patients with no bone growth. Labyrinthitis ossificans not only presents surgical challenges to cochlear implantation but may also adversely affect hearing outcome.

Patterns of neural degeneration in the human cochlea and auditory nerve: implications for cochlear implantation

Although the identity of all the variables that may influence speech recognition after cochlear implantation is unknown, the degree of preservation of spiral ganglion cells is generally considered to be of primary importance. A series of experiments in our laboratories, directed at quantification of surviving spiral ganglion cells in the profoundly deaf, evaluation of the predictive value of a variety of clinical parameters, and the evaluation of the consequences of implantation in the inner ear, is summarized. Histologic study of the inner ears of patients who were deafened during life demonstrated that the cause of deafness accounted for 57% of the variability of spiral ganglion cell counts. Spiral ganglion cell counts were highest in individuals deafened by aminoglycoside toxicity or sudden idiopathic deafness and lowest in those deafened by postnatal viral labyrinthitis, congenital or genetic deafness, or bacterial meningitis. Study of the determinants of degeneration of the spiral ganglion revealed that degeneration is most severe in the basal compared with the apical turn and more severe when both inner and outer hair cells are absent. Unlike the findings in some experimental animal studies, no survival advantage of type II ganglion cells could be identified. There was a strong negative correlation between the degree of bony occlusion of the cochlea and the normality of the spiral ganglion cell count. However, even in specimens in which there was severe bony occlusion, significant numbers of spiral ganglion cells survived. A strong positive correlation between the diameter of the cochlear, vestibular, and eighth cranial nerves with the total spiral ganglion cell count (p < 0.001) was found. This would suggest that modern imaging techniques may be used to predict residual spiral ganglion cell population in cochlear implant candidates. Trauma from implantation of the electrode array was studied in both cadaveric human temporal bone models and temporal bones from individuals who received implants during life. A characteristic pattern of damage to the lateral cochlear wall and basilar membrane was identified in the upper basal turn. New bone formation and perielectrode fibrosis was common after cochlear implantation. Despite this significant trauma and reaction, there is no firm evidence that further degeneration of the spiral ganglion can be predicted as a consequence.

Revision stapedectomy: intraoperative findings, results, and review of the literature

Seventy-four revision stapedectomies performed consecutively over 10 years (1986 to 1995) were reviewed retrospectively. The most common intraoperative findings were incus erosion, prosthesis displacement, and oval window closure. Incus erosion was more frequently associated with multiple revisions. The postoperative results were reported using the conventional method (postoperative air minus preoperative bone) as well as the guidelines recently published by the American Academy of Otolaryngology--Head and Neck Surgery (postoperative air minus postoperative bone), with success rates of postoperative air-bone gap closure to within 10 dB after revision surgery of 51.6% and 45.6%, respectively. Patients with persistent conductive hearing loss (large residual air-bone gaps) after primary stapedectomy had poorer postrevision hearing results. Sensorineural hearing loss (defined as a drop in bone pure-tone average of more than 10 dB) occurred in four cases (5.4%). The number of revision surgeries, variations in operative techniques using laser or drill, and the ossicle to which the prosthesis was attached did not statistically affect the postoperative air-bone gaps. These results were compared with previously published data.

Efficacy of tympanomastoid surgery for control of infection in active chronic otitis media

The efficacy of surgery in controlling infection in 272 tympanomastoidectomy procedures for chronic otitis media (COM) was assessed by means of a four-point rating scale that incorporated both symptoms and signs, such as the presence or absence of otorrhea and granulation tissue. Of the 272 procedures, 170 were performed for COM with cholesteatoma and 102 were for active COM with granulation tissue but no cholesteatoma. Forty-seven percent were primary procedures, and 53% were revisions. Minimum follow-up was 12 months for all cases, with a mean of 30 months. Adequate control of infection occurred in 248 (91%) of the 272 cases. Of the 24 cases (9%) that developed persistent infection, 10 were controlled with a combination of oral and topical antibiotics and/or delayed skin grafting in the office. Thus overall satisfactory control of infection was achieved in 258 of 272 cases (95%). The outcome was influenced by the diagnostic category of COM: COM with cholesteatoma did significantly better than COM with granulation tissue (P = 0.02). The outcome was not influenced by the following variables: primary versus revision surgery, canal wall-up versus canal wall-down surgery, and extent of disease. The results suggest that active COM with granulation tissue may be more difficult to control than COM with cholesteatoma.

Morphologic evidence for innervation of Deiters' and Hensen's cells in the guinea pig

The presence of nerve fibers and terminals among Deiters' and Hensen's cells of the organ of Corti of the adult guinea pig is demonstrated using immunostaining for synaptophysin and neurofilaments, acetylcholinesterase histochemistry, and transmission electron microscopy. These nerve terminals appeared to form chemical synapses with Deiters' and Hensen's cells. Nerve fibers and synapses were more common in the apical as compared to the basal cochlea. The terminals were often present on basal appendages of Hensen's cells, which were rich in mitochondria and often contained a Golgi apparatus and dense core vesicles. Electron microscopy and immunostaining for neurofilaments showed that most Hensen's cells in the apical cochlea received innervation. Few of the nerve fibers and terminals were positive for acetylcholinesterase, which suggests that they were not collaterals of cholinergic olivocochlear fibers. The density of these fibers, as shown by immunohistochemistry for neurofilaments, was far greater than previous reports of GABA-ergic fibers, which suggests that they were not GABA-ergic olivocochlear fibers. The role of such fibers and synapses with supporting cells of the outer hair cell area is unknown. Determination of the origins and functions of these fibers will provide new insights into cochlear structure and function.

Techniques for human temporal bone removal: information for the scientific community

Human temporal bones provide an irreplaceable resource for study of the pathology and pathophysiology of disorders of hearing, balance, taste, and facial nerve function. Additional specimens are needed to study disorders for which there are few human specimens; to increase the number of specimens for a given disorder to understand the natural variability and expression of the disease entity; to evaluate the accuracy of otologic diagnoses and the efficacy of otologic treatment modalities; to apply newly available scientific methods, including immunohistochemistry and molecular biologic or molecular genetic techniques; and to teach the anatomy of the human ear and modern otologic surgical techniques. This article provides information for the scientific community concerning techniques for temporal bone and auditory brain stem removal, including intracranial and extracranial approaches and methods to minimize postmortem autolysis and cosmetic defects. Close collaboration between physicians and funeral directors will maximize the yield and utility of these valuable specimens for scientific inquiry and training.

A gene for non-syndromic autosomal dominant progressive postlingual sensorineural hearing loss maps to chromosome 14q12-13

We report a novel locus responsible for postlingual progressive sensorineural hearing loss (designated DFNA9) that maps to chromosome 14q12-13. A large kindred with autosomal dominant transmission of non-syndromic hearing loss was clinically studied. Hearing in affected individuals deteriorated at approximately 20 years of age and progressed to anacusis in the fifth decade. A random genome-wide search using polymorphic short tandem repeats demonstrated linkage with D14S121 (maximum two point LOD score = 6.19, theta = 0). Haplotype analysis of recombination events defined a 9 cM disease interval, between D14S252 and D14S49.

Morphologic evidence for three cell types in the human spiral ganglion

Although two types of spiral ganglion cells (large type I and smaller type II) have classically been described by anatomic studies in both animal and human spiral ganglion, there is physiologic and morphologic evidence for subtypes of the large type I ganglion cell. In addition, in the animal and human, a variety of morphologic differences based on cytoplasmic content, myelinization, immunostaining and morphometric analysis have suggested more than one variety of type I ganglion cell. Light and electron microscopic serial sections of the spiral ganglion in two human specimens in the basal, middle and upper middle turns were pooled for morphometric analysis of the cell area, nuclear area and axon diameter. Analysis of variance, bivariate scatter plots and multivariate cluster analysis provided evidence for 3 types of ganglion cells in the human spiral ganglion: large, intermediate and small, varying from each other significantly on the basis of cell area. It was suggested, based on the morphologic findings and prevalence of the cell types, that the large and intermediate cells were subtypes of the classic type I spiral ganglion cell, whereas the small ganglion cell was consistent with the classically described type II ganglion cell.

Tubal and tympanic openings of the peritubal cells: implications for cerebrospinal fluid otorhinorrhea

Cerebrospinal fluid otorhinorrhea after surgery for cerebellopontine angle tumors may persist despite obliteration of the mastoid, middle ear, and tympanic orifice of the eustachian tube. In this study, histologic sections of 120 adult temporal bones were examined by light microscopy to determine the incidence of peritubal pneumatization and to demonstrate the frequency of tubal and tympanic openings of the peritubal cells. The results of this study suggest that the pathway for these persistent cerebrospinal fluid leaks may be via the peritubal cells that open directly into the eustachian tube anterior to its tympanic orifice. Peritubal pneumatization was present in 78 (65%) of the temporal bones. Of the 57 specimens in which the openings of the peritubal cells could be identified, in 52 (91%), the cells opened into the eustachian tube anterior to its tympanic orifice, and in only five (9%), they opened into the middle ear. The overall incidence of tubal openings in this study was 59%. In 13 temporal bones (21%), the tubal opening were at a distance of > 5 mm anterior to the tympanic orifice of the eustachian tube. Therefore, cerebrospinal leak may persist through these tubal openings despite obliteration of the mastoid, middle ear, and tympanic orifice of the eustachian tube. A case of persistent cerebrospinal fluid leak in which extensive peritubal pneumatization was demonstrated by computed tomography scan is presented. Successful control of the leak was obtained only after the tubal openings of these cells several millimeters anterior to the tympanic orifice were obliterated.

Vestibular symptoms in otosclerosis--correlation of otosclerotic involvement of vestibular apparatus and Scarpa's ganglion cell count

Although several histopathologic studies have shown otosclerotic involvement of the vestibular apparatus in patients with otosclerosis, the pathogenesis of vestibular symptoms in otosclerosis remains unknown. A quantitative study of Scarpa's ganglion was performed in 217 temporal bones from 118 subjects with otosclerosis. Review of clinical records revealed an incidence of vestibular symptoms in 11.9% of these subjects. Scarpa's ganglion cell counts in temporal bones of subjects with otosclerosis and vestibular symptoms were lower than counts in temporal bones of subjects with otosclerosis but without vestibular symptoms and those of normal subjects. This difference in Scarpa's ganglion cell counts, adjusted for age, between the group with otosclerosis and vestibular symptoms and a group of normal subjects was highly significant (p = 0.0015), whereas the difference in Scarpa's ganglion cell count between a group with otosclerosis but without vestibular symptoms and a group of normal subjects was not significant (p = 0.53). There was also a significant correlation between elevation of the average bone-conduction threshold and the presence of vestibular symptoms in these subjects (p = 0.041). The endosteum of the perilymphatic space of the vestibule and the endosteum of the canal for the superior vestibular nerve or its cribrose area were the two most common sites of involvement by otosclerosis. However, there was no significant correlation between the presence of vestibular symptoms and otosclerotic involvement of any single site or the number of involved sites. Histologic examination of the vestibular nerve fibers and end organs subjacent to otosclerotic foci demonstrated no obvious degenerative changes. Thus our findings appear to suggest that the vestibular symptoms present in patients with otosclerosis are more common in patients with elevated bone conduction thresholds and are correlated with degeneration of the vestibular nerve, which appears to be independent of the severity of otosclerotic involvement of the vestibular end organs.

Vestibular neurectomy: retrosigmoid-intracanalicular versus retrolabyrinthine approach

Selective vestibular neurectomy is an effective treatment for intractable vertigo of peripheral vestibular origin when preservation of hearing is a goal. The retrolabyrinthine and retrosigmoid-intracanalicular approaches have been used predominantly at our institutions over the last 10 years. The results and complications of these two techniques were compared. No significant differences were found between hearing results in these two patient groups. The retrosigmoid-internal auditory can approach yielded better control of recurrent episodic vertigo, as well as superior ablation of postoperative ice-water caloric responses (p < 0.05). Surgical complications, including the incidence of cerebrospinal fluid leakage (greater in retrolabyrinthine approach) and postoperative headache (more prevalent in retrosigmoid approach), were also analyzed. To further evaluate the results of this study, data were reanalyzed and compared with previously published reports of selective vestibular nerve section.

Correlation of hearing loss and radiologic dimensions of vestibular schwannomas (acoustic Neuromas)

A retrospective analysis was performed of puretone audiograms, speech-discrimination scores, and gadolinium-enhanced magnetic resonance imaging scans of 75 patients with vestibular schwannomas (acoustic neuroma). Sensorineural hearing loss was analyzed for low frequencies (250-500 Hz), midfrequencies (1,000-2,000 Hz), and high frequencies (4,000-8,000 Hz). The largest tumor diameter in the cerebellopontine angle and the lateral extent of invasion by tumor into the internal auditory canal were calculated from magnetic resonance images. There were statistically significant correlations between the largest tumor diameter and the severity of low-frequency sensorineural hearing loss (p = 0.001). However, no significant correlations were found between the following: largest tumor diameter and the severity of mid-frequency or high-frequency sensorineural hearing loss or speech-discrimination scores and lateral extent of invasion of the internal auditory canal and sensorineural hearing loss at all frequencies or speech-discrimination scores (p > or = 0.05). The findings suggest that nerve compression is not the only cause of hearing loss in vestibular schwannoma.

The use of the temporoparietal fascial flap in temporal bone reconstruction

After routine canal wall down mastoidectomy, local muscle flaps with and without bone paté, cartilage and fascia are the standard techniques available to otologists wishing to obliterate the mastoid and reconstruct the external auditory canal. Reconstructive options for temporal bone defects after extirpative surgery for cancer, osteoradionecrosis, and revision surgery for chronic granulomatous otitis media, however, are few. Although the neighboring temporoparietal fascia flap (TPFF), based on the superficial temporal vessels, has been frequently employed for auricular reconstruction, its versatility in temporal bone reconstruction has not been widely explored. The TPFF has recently been employed at our institution in 11 patients who presented with a variety of reconstructive problems, including defects after temporal bone resection, surgery for malignant otitis externa, and revision mastoid surgery. Follow-up in these patients ranged from 1 to 43 months (average 18.4 months) and surgical objectives of achieving a dry mastoid bowl, fully epithelialized canal, and/or reduction of mastoid cavity volume was attained in 100% of cases. The TPFF offers many advantages to the otologic surgeon when faced with reconstruction dilemmas that center around a poorly vascularized mastoid cavity and temporal bone. The TPFF is a reliable source of local well-vascularized tissue that is extremely pliable and facilitates both hearing and nonhearing preservation temporal bone reconstruction.

Patterns of degeneration in the human cochlear nerve

The patterns of neural degeneration of the spiral ganglion were studied in 12 human pathologic specimens and 2 normal neonatal specimens. Morphometric analysis of spiral ganglion cells included the maximum cross-sectional areas of both large (type 1) and small (type II) spiral ganglion cells. The organ of Corti in segments corresponding to the spiral ganglion, was evaluated for the presence or absence of inner (IHC) and outer (OHC) hair cells and supporting cells. The relationship between degeneration of spiral ganglion cells and degeneration in the organ of Corti, the age, sex, duration of deafness, cochlear location and delay between death and fixation was evaluated statistically. Both primary and secondary degeneration of the spiral ganglion were more severe in the basal than apical half of the cochlea. Degeneration of the spiral ganglion was most severe when both IHCs and OHCs were absent in the organ of Corti. No survival advantage was identified for type II ganglion cells as has been previously reported. That is, there was no correlation between the degree of degeneration of the spiral ganglion and the prevalence of type II ganglion cells. In fact, there was more severe degeneration of type II cells when the corresponding organ of Corti was severely degenerated. These findings in the human were compared with animal models of degeneration of the spiral ganglion, and the implications for cochlear implantation were discussed.