Effect of monopolar and bipolar electric stimulation on survival and size of human spiral ganglion cells as studied by postmortem histopathology

The spiral ganglion cell (SGC) is the target of electrical stimulation in cochlear implants. This study is designed to test the hypothesis that chronic electrical stimulation tends to preserve SGCs in implanted hearing-impaired ears. A total of 26 pairs of temporal bones were studied from 26 individuals who in life suffered bilateral profound hearing impairment that was symmetric (in degree of impairment and etiology) across ears and then underwent unilateral cochlear implantation. The subjects were divided in two groups by stimulus configuration: bipolar (n = 16) or monopolar (n = 10). The temporal bones were prepared for histological review by standard methods and two measures of SGC status were made by cochlear segment: count and maximal cross-sectional area. Within-subject comparison of the measures between the implanted-stimulated and the unimplanted ears showed: (1) for both stimulus configurations, the mean (across subjects and segments) of the count difference (implanted ear - unimplanted ear) was significantly less than zero; (2) the mean (across subject) count difference for cochlear segments I, II and III (segments with electrode contacts in the implanted ear) was significantly less negative than the mean difference for cochlear segment IV (no electrode in implanted ear) for bipolar but not for monopolar stimulation; (3) neither implantation-stimulation nor stimulus configuration significantly influenced the measures of maximum cross-sectional cell area. The SGC count results are consistent with the hypothesis that implantation results in a propensity across the whole cochlea for SGCs to degenerate and with chronic bipolar stimulation ameliorating this propensity in those cochlear segments with electrodes present.

Interaural comparison of spiral ganglion cell counts in profound deafness

OBJECTIVES

This study is designed to measure the degree to which spiral ganglion cell (SGC) survival in the left and right ears is similar in profoundly hearing-impaired human patients with symmetric (right/left) etiology and sensitivity. This is of interest because a small difference between ears would imply that one ear could be used as a control ear in temporal bone studies evaluating the impact on SGC survival of a medical intervention in the other ear.

MATERIALS AND METHODS

Forty-two temporal bones from 21 individuals with bilaterally symmetric profound hearing impairment were studied. Both ears in each individual were impaired by the same etiology. Rosenthal's canal was reconstructed in two dimensions and segmental and total SGCs were counted. Correlation analysis and t-tests were used to compare segmental and total counts of left and right ears. Statistical power calculations illustrate how the results can be used to estimate the effect size (right/left difference in SGC count) that can be reliably identified as a function of sample size.

RESULTS

Left counts (segmental and total) were significantly correlated with those in the right ears (p < 0.01) and the coefficients of determination for segments 1 to 4 and total count were respectively 0.64, 0.91, 0.93, 0.91 and 0.98. The hypothesis that mean segmental and total counts of right and left are the same could not be rejected by paired t-test.

CONCLUSION

The variance in the between-ear difference across the temporal bones studied indicates that useful effect sizes can be reliably identified using subject numbers that are practical for temporal bone studies. For instance, there is 95% likelihood that an interaural difference in SGC count of approximately 1000 cells associated with a treatment/manipulation of one ear will be reliably detected in a bilaterally-symmetric profound hearing loss population of temporal bones from approximately 10 subjects.

The histopathology of revision cochlear implantation

The current study evaluates histopathologic changes in the temporal bones of 4 human subjects who underwent revision cochlear implantation. Specimens were removed at autopsy, fixed and prepared for histological study by standard techniques. Specimens were serially sectioned, reconstructed by two-dimensional methods, and the tracks of the initial and revision cochlear-implant electrodes identified. The tracks were of three types: a 'common track' (shared by the reimplantation electrode and initial electrode), 'two tracks' (where the reimplantation electrode was in a different track than that of the initial electrode) and 'one track' (where the reimplantation electrode extended beyond the initial electrode, forming a single track). Associated histopathologic findings (new bone formation, fibrosis or inflammatory cells, and cochlear fluid) were evaluated for the three types of tracks. In all 4 subjects, the insertion depth of the revision cochlear implant was deeper than that of the initial cochlear implant. The primary track of the initial implantation did not interfere with insertion of a revision cochlear implant, and the trajectory of the revision electrode did not always follow the primary track. In cochlear segments with a common track or two tracks, the mean (across-subject) percent area of the extraelectrode cochlear duct filled with abnormal (new bone or fibrotic) tissue (43.2%) was significantly greater than the mean percent area occupied by fluid (13.4%; t = 3.12, d.f. = 19.9, p = 0.003).

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Depth of electrode insertion and postoperative performance in humans with cochlear implants: a histopathologic study

The depth of electrode insertion of a multichannel cochlear implant has been suggested as a clinical variable that may correlate with word recognition using the implant. The current study evaluates this relationship using the human temporal bone collection at the Massachusetts Eye and Ear Infirmary. Twenty-seven temporal bones of subjects with cochlear implants were studied. Temporal bones were removed at autopsy, fixed and prepared for histological study by standard techniques. Specimens were then serially sectioned, and reconstructed by two-dimensional methods. Three measures of length were made from each subject's reconstruction: (1) depth of insertion (DI) of the cochlear implant electrode array, from the round window to the array's apical tip; (2) inserted length (IL) from the cochleostomy to the apical tip of the array, and (3) cochlear duct length (CDL) from the round window to the helicotrema. The active electrode length (AEL) was defined as the distance between the most apical and most basal electrodes of the array. Stepwise regression was used to identify whether subsets of six metrics associated with insertion depth (DI, DI/AEL, DI/CDL, IL, IL/AEL and IL/CDL), duration of deafness, sound-processing strategy, potential for central impairment and age at implantation accounted for significant across-subject variance in the last recorded NU-6 word score measured during each subject's life. Age at implantation and potential for central impairment account for significant percentages of the across-subject variance in NU-6 word scores for the 27 subjects studied. None of the insertion metrics accounted for significant performance variance, even when the variance associated with the other variables was controlled. These results, together with those of previous studies, are consistent with a relatively weak association between electrode insertion depth and speech reception.

Analysis of intracochlear new bone and fibrous tissue formation in human subjects with cochlear implants

OBJECTIVES

In this study we aimed to evaluate new bone and new fibrous tissue formation in the inner ear following cochlear implantation.

METHODS

Twelve temporal bones from patients who underwent cochlear implantation during life were prepared for histologic study. The specimens were reconstructed by both 2-dimensional and 3-dimensional methods. These reconstructions were used to calculate the total volume and distribution of new bone and new fibrous tissue in the cochlea, the number of spiral ganglion cells, and other histopathologic parameters. Clinical data, including the last-recorded word recognition scores, were obtained from the patients' medical records.

RESULTS

New bone and new fibrous tissue were found in all 12 specimens, particularly at the site of cochleostomy. There was a significant correlation between overall damage to the lateral cochlear wall and the total volume of intracochlear new tissue (Spearman rho = .853; p = .0004). The total volume of new tissue did not correlate with word recognition scores or spiral ganglion cell counts.

CONCLUSIONS

These preliminary results suggest that the degree of damage to the lateral cochlear wall may play an important role in influencing the amount of new tissue formation following cochlear implantation. Intracochlear new tissue does not appear to be an important determinant of performance as measured by word recognition scores or the total number of remaining spiral ganglion cells.

Anatomy of the round window and hook region of the cochlea with implications for cochlear implantation and other endocochlear surgical procedures

HYPOTHESIS

The goal of this study was to create a three-dimensional model of the anatomy of the hook region to identify the optimal site for cochleostomy in cochlear implant surgery.

BACKGROUND

The anatomy of the hook region is complex, and spatial relationships can be difficult to evaluate using two-dimensional histological slides or cadaveric temporal bones.

METHODS

The right temporal bone of a 14-year-old adolescent boy was used to create a three-dimensional model. Sections containing the round window membrane (RWM) and surrounding cochlear structures were stained, digitized, and imported into a general purpose three-dimensional rendering and analysis software program (Amira, version 4.1). Three-dimensional models of the RWM, basilar membrane, osseous spiral lamina, spiral ligament, cochlear aqueduct, inferior cochlea vein, scala media, ductus reuniens, scala vestibuli, scala tympani, and surrounding bone were generated. The relationship between these structures and the RWM and adjacent otic capsule was evaluated. Histological sections from a different temporal bone were also analyzed. This temporal bone was sectioned in a plane perpendicular to the axis corresponding to the surgical view of the RWM, seen through the facial recess.

RESULTS

The anteroinferior margin of the RWM or adjacent otic capsule was identified as the site for a cochleostomy that will avoid damage to critical cochlear structures and allow implantation directly into the scala tympani. The model can be downloaded from: https://research.meei.harvard.edu/otopathology/3dmodels.

CONCLUSION

This three-dimensional model has implications for surgical procedures to the inner ear that aim to minimize insertional trauma.

Clinical investigation and mechanism of air-bone gaps in large vestibular aqueduct syndrome

OBJECTIVES

Patients with large vestibular aqueduct syndrome (LVAS) often demonstrate an air-bone gap at the low frequencies on audiometric testing. The mechanism causing such a gap has not been well elucidated. We investigated middle ear sound transmission in patients with LVAS, and present a hypothesis to explain the air-bone gap.

METHODS

Observations were made on 8 ears from 5 individuals with LVAS. The diagnosis of LVAS was made by computed tomography in all cases. Investigations included standard audiometry and measurements of umbo velocity by laser Doppler vibrometry (LDV) in all cases, as well as tympanometry, acoustic reflex testing, vestibular evoked myogenic potential (VEMP) testing, distortion product otoacoustic emission (DPOAE) testing, and middle ear exploration in some ears.

RESULTS

One ear with LVAS had anacusis. The other 7 ears demonstrated air-bone gaps at the low frequencies, with mean gaps of 51 dB at 250 Hz, 31 dB at 500 Hz, and 12 dB at 1,000 Hz. In these 7 ears with air-bone gaps, LDV showed the umbo velocity to be normal or high normal in all 7; tympanometry was normal in all 6 ears tested; acoustic reflexes were present in 3 of the 4 ears tested; VEMP responses were present in all 3 ears tested; DPOAEs were present in 1 of the 2 ears tested, and exploratory tympanotomy in 1 case showed a normal middle ear. The above data suggest that an air-bone gap in LVAS is not due to disease in the middle ear. The data are consistent with the hypothesis that a large vestibular aqueduct introduces a third mobile window into the inner ear, which can produce an air-bone gap by 1) shunting air-conducted sound away from the cochlea, thus elevating air conduction thresholds, and 2) increasing the difference in impedance between the scala vestibuli side and the scala tympani side of the cochlear partition during bone conduction testing, thus improving thresholds for bone-conducted sound.

CONCLUSIONS

We conclude that LVAS can present with an air-bone gap that can mimic middle ear disease. Diagnostic testing using acoustic reflexes, VEMPs, DPOAEs, and LDV can help to identify a non-middle ear source for such a gap, thereby avoiding negative middle ear exploration. A large vestibular aqueduct may act as a third mobile window in the inner ear, resulting in an air-bone gap at low frequencies.

Otopathology in Mohr-Tranebjaerg syndrome

BACKGROUND

Mohr-Tranebjaerg syndrome (MTS) is an X-linked, recessive, syndromic sensorineural hearing loss (HL) characterized by onset of deafness in childhood followed later in adult life by progressive neural degeneration affecting the brain and optic nerves. MTS is caused by mutations in the DDP/TIMM8A gene, which encodes for a 97 amino acid polypeptide; this polypeptide is a translocase of the inner mitochondrial membrane.

OBJECTIVES

To describe the otologic presentation and temporal bone histopathology in four affected individuals with MTS.

MATERIAL AND METHODS

All four subjects belonged to a large, multigenerational Norwegian family and were known to carry a frame shift mutation in the TIMM8A gene. Temporal bones were removed at autopsy and studied by light microscopy. Cytocochleograms were constructed for hair cells, stria vascularis, and cochlear neuronal cells. Vestibular neurons were also counted.

RESULTS

All four subjects developed progressive HL in early childhood, becoming profoundly deaf by the age of 10 years. All four developed language, and at least one subject used amplification in early life. Audiometric evaluation in two subjects showed 80- to 100-dB HL by the age of 10 years. The subjects died between the ages of 49 and 67. The otopathology was strikingly similar in that all bones examined showed near-total loss of cochlear neuronal cells and severe loss of vestibular neurons. When compared with age-matched controls, there was 90% to 95% loss of cochlear neurons and 75% to 85% loss of vestibular neurons.

CONCLUSIONS

We infer that the HL in MTS is likely to be the result of a postnatal and progressive degeneration of cochlear neurons and that MTS constitutes a true auditory neuropathy. Our findings have implications for clinical diagnosis of patients with MTS and management of the HL.

Quantitative evaluation of new bone and fibrous tissue in the cochlea following cochlear implantation in the human

The formation of new bone and fibrous tissue in the human inner ear following cochlear implantation was evaluated by computer-assisted 3-D reconstruction. Seven temporal bones from patients who in life had undergone cochlear implantation were prepared for histological study with the implant in situ. The specimens were sectioned in the axial plane at a thickness of 20 microm. At least every tenth section was digitally reconstructed in three dimensions and volumes of new bone and fibrous tissue were calculated per millimeter length of the cochlea. New bone and fibrous tissue were found in all seven specimens, particularly at the cochleostomy site. In addition, new bone and fibrous tissue had extended to variable lengths along the track of the cochlear implant and in some cases extended beyond the distal end of the implanted electrode. This methodology provides a quantitative tool for evaluation of new bone and fibrous tissue in the inner ear following implantation. This should assist in correlating psychophysical and speech perception tests with intracochlear pathology, evaluating both electrode design and the techniques of preserving residual auditory function.

Revision mastoidectomy

The first three priorities in surgery for chronic otitis media are (1) the elimination of progressive disease to produce a safe and dry ear, (2) modification of the anatomy of the tympanomastoid compartment to prevent recurrent disease, and (3) reconstruction of the hearing mechanism. The indications for revision following mastoidectomy for chronic otitis media thus involve failure to achieve any of these goals, including recurrent cholesteatoma, recurrent suppuration, recurrent perforation, or recurrent or residual conductive hearing loss. The focus of this article is the management of recurrent cholesteatoma or suppuration; that is, failure to achieve either of the first two priorities.

Cochleosaccular dysplasia associated with a connexin 26 mutation in keratitis-ichthyosis-deafness syndrome

OBJECTIVE

The objective of this study was to characterize the temporal bone phenotype associated with a mutation of GJB2 (encoding connexin 26).

STUDY DESIGN

The authors conducted correlative clinical, molecular genetic, and postmortem histopathologic analysis.

METHODS

The study subject was a male infant with keratitis-ichthyosis-deafness (KID) syndrome. We performed a nucleotide sequence analysis of GJB2 and a histopathologic analysis of the temporal bones.

RESULTS

The subject was heterozygous for G45E, a previously reported KID syndrome mutation of GJB2. The primary inner ear abnormality was dysplasia of the cochlear and saccular neuroepithelium.

CONCLUSIONS

GJB2 mutations can cause deafness in KID syndrome, and possibly in other GJB2 mutant phenotypes, by disrupting cochlear differentiation.

Results after revision stapedectomy with malleus grip prosthesis

Revision stapedectomy with a malleus grip prosthesis is a technically challenging otologic procedure. The prosthesis is usually longer and extends deeper into the vestibule than a conventional stapes prosthesis, creating the potential to affect the vestibular sense organs. The prosthesis also bypasses the ossicular joints, which are thought to play a role in protecting the inner ear from large changes in static pressure within the middle ear. The prosthesis is in close proximity to the tympanic membrane, thus increasing the risk for its extrusion. We reviewed our experience with revision stapedectomy with the Schuknecht Teflon-wire malleus grip prosthesis in 36 ears with a mean follow-up of 23 months. The air-bone gap was closed to within 10 dB in 16 ears (44%) and to within 20 dB in 26 ears (72%). The incidence of postoperative sensorineural hearing loss was 8% (3 ears). There were no dead ears. Extrusion of the prosthesis occurred in 1 case (3%). Nearly 50% of patients reported various degrees of vertigo or disequilibrium during the first 3 weeks after surgery. These vestibular symptoms resolved by 6 weeks in all but 1 case. We did not find evidence of damage to the inner ear due to the length of the prosthesis or due to the potential for direct transmission of changes in static pressures within the middle ear to the labyrinth. Our results are similar to those published in the literature for malleus attachment stapedectomy and conventional revision incus stapedectomy.

Histopathology of human cochlear implants: correlation of psychophysical and anatomical measures

The cadavaric temporal bones of five subjects who underwent cochlear implantation during life (2 Nucleus and 3 Ineraid) were analyzed using two-dimensional (2D) reconstruction of serial sections to determine the number of surviving spiral ganglion cells (SGCs) in the region of each electrode of the implanted arrays. The last psychophysical threshold and maximum-comfortable sensation level measured for each electrode were compared to their respective SGC count to determine the across-electrode psychophysical variance accounted for by the SGC counts. Significant correlations between psychophysical measures and SGC counts were found in only two of the five subjects: one Nucleus implantee (e.g., r=-0.71; p<0.001 for threshold vs. count) and one Ineraid implantee (e.g., r=-0.86; p<0.05 for threshold vs. count). A three-dimensional (3D) model of the implanted cochlea was formulated using the temporal-bone anatomy of the Nucleus subject for whom the 2D analysis did not result in significant correlations between counts and psychophysical measures. Predictions of the threshold vs. electrode profile were closer to the measured profile for the 3D model than for the 2D analysis. These results lead us to hypothesize that 3D techniques will be required to asses the impact of peripheral anatomy on the benefit patients derive from cochlear implantation.

Cochlin immunostaining of inner ear pathologic deposits and proteomic analysis in DFNA9 deafness and vestibular dysfunction

Seven missense mutations and one in-frame deletion mutation have been reported in the coagulation factor C homology (COCH) gene, causing the adult-onset, progressive sensorineural hearing loss and vestibular disorder at the DFNA9 locus. Prevalence of COCH mutations worldwide is unknown, as there is no systematic screening effort for late-onset hearing disorders; however, to date, COCH mutations have been found on four continents and the possibility of COCH playing an important role in presbycusis and disorders of imbalance has been considered. Cochlin (encoded by COCH) has also been shown as a major target antigen for autoimmune sensorineural hearing loss. In this report, we present histopathology, immunohistochemistry and proteomic analyses of inner ear tissues from post-mortem DFNA9 temporal bone samples of an individual from a large Dutch kindred segregating the P51S mutation and adult human unaffected controls, and wild-type (+/+) and Coch null (-/-) knock-out mice. DFNA9 is an inner ear disorder with a unique histopathology showing loss of cellularity and aggregation of abundant homogeneous acellular eosinophilic deposits in the cochlear and vestibular labyrinths, similar to protein aggregation in well-known neurodegenerative disorders. By immunohistochemistry on the DFNA9 temporal bone sections, we have shown cochlin staining of the characteristic cochlear and vestibular deposits, indicating aggregation of cochlin in the same structures in which it is normally expressed. Proteomic analysis identified cochlin as the most abundant protein in mouse and human cochleae. The high-level expression and stability of cochlin in the inner ear, even in the absence and severe atrophy of the fibrocytes that normally express COCH, are shown through these studies and further elucidate the pathobiologic events occurring in DFNA9 leading to hearing loss and vestibular dysfunction.

Efficient method for the proteomic analysis of fixed and embedded tissues

Formalin-fixed and paraffin-embedded (FFPE) tissues present a particular challenge for proteomic analysis. Yet, most of the archived tissues in hospitals and tissue banks worldwide are only available in this form. We have developed conditions for removal of the embedding medium and protein digestion, such that informative tryptic peptides are released from fixed proteins which are suitable for analysis by liquid chromatography-mass spectrometry (LC-MS). We demonstrate that the peptide identifications made by this approach compare favorably to those made from matched fresh frozen tissue. Moreover, we demonstrate that a high level of sequence coverage can be observed for proteins of interest.

Histopathology of the Peripheral Vestibular System after Cochlear Implantation in the Human

OBJECTIVES

The objective of this study was to describe the histology of the peripheral vestibular system in temporal bones from patients who in life had undergone cochlear implantation and to correlate the findings with previous reports of vestibular dysfunction after cochlear implantation. This is the first quantitative report of the impact of implantation on the vestibular neuronal end organ. METHODSThere were 19 temporal bones available for histologic study. Of these, 17 were suitable for the description of the morphology of the membranous labyrinth, 8 for counting Scarpa's ganglion cells, and 6 for measuring the densities of vestibular hair cells. The bones were fixed, cut, and stained according to previously published methods. Preferably, the implanted electrode was left in situ. Vestibular hair cells were counted with Nomarski's optics.

RESULTS

Differences in Scarpa's ganglion cell counts and hair cell densities between the implanted and nonimplanted sides were not statistically significant. In 59% of the implanted bones, the cochlea was hydropic, and in the majority of these bones the saccule was collapsed.

CONCLUSION

Cochlear implantation does not cause deafferentation of the peripheral vestibular system. Cochlear hydrops accompanied by saccular collapse is common and may cause attacks of vertigo of delayed onset, similar to Ménière's syndrome as previously reported in several clinical series. Hydrops could be caused by obstruction of endolymphatic flow in the ductus reuniens or in the hook portion of the cochlea or by damage to the lateral cochlear wall caused by implantation.

Histopathology of the inner ear relevant to cochlear implantation

The most common forms of severe hearing loss and deafness are related to morphological changes in the cochlea. Many individuals with such forms of hearing disorders have received cochlear implants. It has been assumed that preservation of spiral ganglion cells is important for success of cochlear implants. Preservation of ganglion cells is negatively correlated with the duration of the hearing loss. It has, however, not been possible to reveal a relationship between the degree of survival of spiral ganglion cells and performance of cochlear implants. It is important to understand the histopathological changes that follow cochlear implantation. Insertion of cochlear implants may cause trauma to the basilar membrane, the spiral lamina, and the spiral ligament. Rupture of the basilar membrane may occur. Over time, new bone forms at the cochleostomy and along the implant track. Further investigation is necessary to evaluate the causes of variability of behavioral measures of performance.

Carcinoid Tumor of the Middle Ear: Clinical Features, Recurrences, and Metastases

OBJECTIVE

Present four new cases of carcinoid tumor of the middle ear, two of which developed late recurrences and regional metastases. Review the literature to identify the clinical features, rate of recurrence, and incidence of metastasis of carcinoid tumor of the middle ear.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral hospital.

PATIENTS

Eligibility criteria consist of a diagnosis of carcinoid tumor of middle ear.

INTERVENTION

Surgical excision of primary and metastatic disease.

MAIN OUTCOME MEASURE

Clinical characteristics, rate of recurrence, and incidence of metastasis of carcinoid tumor of the middle ear.

RESULTS

Forty-six patients with carcinoid tumor of the middle ear are included in this report, 42 patients were identified from a review of the literature, and 4 new patients are presented. The most common presenting symptom was hearing loss. Surgical excision was the treatment with radical mastoidectomy being the most common procedure. Ten (22%) patients developed locally recurrent disease, and four (9%) developed regional metastases.

CONCLUSIONS

Carcinoid tumor of the middle ear is an infrequent cause of a middle ear mass, with only 46 cases published. Despite previous assertions of benignancy, the findings of this study suggest that carcinoid tumor of the middle ear is indeed a potential low-grade malignancy with documented metastatic potential. Almost all middle ear adenomatous tumors ("adenoma" and "carcinoid") show evidence of neuroendocrine differentiation, and so at least some middle ear carcinoids ("adenomas") appear to represent well-differentiated neuroendocrine carcinomas. Presentation and symptoms are consistent with a middle ear mass and rarely include carcinoid syndrome. Surgical treatment is recommended and tailored to the extent of disease. Patients with carcinoid tumor of the middle ear require indefinite follow-up for possible recurrence or metastasis.

Pathophysiology of Meniere's syndrome: are symptoms caused by endolymphatic hydrops?

BACKGROUND

The association of Meniere's syndrome with endolymphatic hydrops has led to the formation of a central hypothesis: many possible etiologic factors lead to hydrops, and hydrops in turn generates the symptoms. However, this hypothesis of hydrops as being the final common pathway has not been proven conclusively.

SPECIFIC AIM

To examine human temporal bones with respect to the role of hydrops in causing symptoms in Meniere's syndrome. If the central hypothesis were true, every case of Meniere's syndrome should have hydrops and every case of hydrops should show the typical symptoms.

METHODS

Review of archival temporal bone cases with a clinical diagnosis of Meniere's syndrome (28 cases) or a histopathologic diagnosis of hydrops (79 cases).

RESULTS

All 28 cases with classical symptoms of Meniere's syndrome showed hydrops in at least one ear. However, the reverse was not true. There were 9 cases with idiopathic hydrops and 10 cases with secondary hydrops, but the patients did not exhibit the classic symptoms of Meniere's syndrome. A review of the literature revealed cases with asymptomatic hydrops (similar to the current study), as well as cases where symptoms of Meniere's syndrome existed during life but no hydrops was observed on histology. We also review recent experimental data where obstruction of the endolymphatic duct in guinea pigs resulted in cytochemical abnormalities within fibrocytes of the spiral ligament before development of hydrops. This result is consistent with the hypothesis that hydrops resulted from disordered fluid homeostasis caused by disruption of regulatory elements within the spiral ligament.

CONCLUSION

Endolymphatic hydrops should be considered as a histologic marker for Meniere's syndrome rather than being directly responsible for its symptoms.

Effect of cochlear implantation on residual spiral ganglion cell count as determined by comparison with the contralateral nonimplanted inner ear in humans

It is generally assumed that at least a minimal number of spiral ganglion cells is essential for successful speech perception with a cochlear implant. Although the insertion of a multichannel cochlear implant frequently results in loss of residual hearing in the implanted ear, this outcome does not imply that significant damage to residual populations of spiral ganglion cells has occurred. The purpose of the current study was to compare spiral ganglion cell counts in implanted and nonimplanted cochleas in 11 patients for whom both temporal bones were available and in whom a multichannel cochlear implant had been placed unilaterally. The temporal bones were processed for light microscopy by standard techniques. The cochleas were reconstructed by 2-dimensional methods. Spiral ganglion cell counts of the implanted and nonimplanted sides were compared by a paired t-test (2-tailed). The mean spiral ganglion cell counts for implanted and nonimplanted ears were not statistically different in the most basal three segments of the cochlea. However, the mean spiral ganglion cell count in segment 4 (apical segment) and the mean total spiral ganglion cell count were lower in the implanted cochleas than in the nonimplanted cochleas (p < .01). The results of this study suggest a modest decrease in the total spiral ganglion cell count in the implanted ears as compared to the nonimplanted ears, principally in the apical segment. Possible interpretations of this finding are discussed.

Is word recognition correlated with the number of surviving spiral ganglion cells and electrode insertion depth in human subjects with cochlear implants?

OBJECTIVES/HYPOTHESIS

Speech perception scores using cochlear implants have ranged widely in all published series. The underlying determinants of success in word recognition are incompletely defined. Although it has been assumed that residual spiral ganglion cell population in the deaf ear may play a critical role, published data from temporal bone specimens from patients have not supported this hypothesis. The depth of insertion of a multichannel cochlear implant has also been suggested as a clinical variable that may be correlated with word recognition. In the current study these correlations were evaluated in 15 human subjects.

STUDY DESIGN

Retrospective review of temporal bone histopathology.

METHODS

Temporal bones were fixed and prepared for histological study by standard techniques. Specimens were then serially sectioned and reconstructed by two-dimensional methods. The spiral ganglion cells were counted, and the depth of insertion of the cochlear implant as measured from the round window was determined. Correlation analyses were then performed between the NU6 word scores and spiral ganglion cell counts and the depth of insertion.

RESULTS

The segmental and total spiral ganglion cell counts were not significantly correlated (P > .50) with NU6 word scores for the 15 subjects. Statistically significant correlations were not achieved by separate analysis of implant types. Similarly, no significant correlation between the depth of insertion of the electrode array and postoperative NU6 word score was identified for the group.

CONCLUSION

Although it is unlikely that the number of residual spiral ganglion cell counts is irrelevant to the determination of word recognition following cochlear implantation, there are, clearly, other clinical variables not yet identified that play an important role in determining success with cochlear implantation.

Is word recognition correlated with the number of surviving spiral ganglion cells and electrode insertion depth in human subjects with cochlear implants?

OBJECTIVES/HYPOTHESIS

Speech perception scores using cochlear implants have ranged widely in all published series. The underlying determinants of success in word recognition are incompletely defined. Although it has been assumed that residual spiral ganglion cell population in the deaf ear may play a critical role, published data from temporal bone specimens from patients have not supported this hypothesis. The depth of insertion of a multichannel cochlear implant has also been suggested as a clinical variable that may be correlated with word recognition. In the current study these correlations were evaluated in 15 human subjects.

STUDY DESIGN

Retrospective review of temporal bone histopathology.

METHODS

Temporal bones were fixed and prepared for histological study by standard techniques. Specimens were then serially sectioned and reconstructed by two-dimensional methods. The spiral ganglion cells were counted, and the depth of insertion of the cochlear implant as measured from the round window was determined. Correlation analyses were then performed between the NU6 word scores and spiral ganglion cell counts and the depth of insertion.

RESULTS

The segmental and total spiral ganglion cell counts were not significantly correlated (P > .50) with NU6 word scores for the 15 subjects. Statistically significant correlations were not achieved by separate analysis of implant types. Similarly, no significant correlation between the depth of insertion of the electrode array and postoperative NU6 word score was identified for the group.

CONCLUSION

Although it is unlikely that the number of residual spiral ganglion cell counts is irrelevant to the determination of word recognition following cochlear implantation, there are, clearly, other clinical variables not yet identified that play an important role in determining success with cochlear implantation.

Pathology and Pathophysiology of Idiopathic Sudden Sensorineural Hearing Loss

BACKGROUND

The cause and pathogenesis of idiopathic sudden sensorineural hearing loss remain unknown. Proposed theories include vascular occlusion, membrane breaks, and viral cochleitis.

AIMS

To describe the temporal bone histopathology in 17 ears (aged 45-94 yr) with idiopathic sudden sensorineural hearing loss in our temporal bone collection and to discuss the implications of the histopathologic findings with respect to the pathophysiology of idiopathic sudden sensorineural hearing loss.

METHODS

Standard light microscopy using hematoxylin and eosin-stained sections was used to assess the otologic abnormalities.

RESULTS

Hearing had recovered in two ears and no histologic correlates were found for the hearing loss in both ears. In the remaining 15 ears, the predominant abnormalities were as follows: 1) loss of hair cells and supporting cells of the organ of Corti (with or without atrophy of the tectorial membrane, stria vascularis, spiral limbus, and cochlear neurons) (13 ears); 2) loss of the tectorial membrane, supporting cells, and stria vascularis (1 ear); and 3) loss of cochlear neurons only (1 ear). Evidence of a possible vascular cause for the idiopathic sudden sensorineural hearing loss was observed in only one ear. No membrane breaks were observed in any ear. Only 1 of the 17 temporal bones was acquired acutely during idiopathic sudden sensorineural hearing loss, and this ear did not demonstrate any leukocytic invasion, hypervascularity, or hemorrhage within the labyrinth, as might be expected with a viral cochleitis.

DISCUSSION

The temporal bone findings do not support the concept of membrane breaks, perilymphatic fistulae, or vascular occlusion as common causes for idiopathic sudden sensorineural hearing loss. The finding in our one case acquired acutely during idiopathic sudden sensorineural hearing loss as well as other clinical and experimental observations do not strongly support the theory of viral cochleitis.

CONCLUSION

We put forth the hypothesis that idiopathic sudden sensorineural hearing loss may be the result of pathologic activation of cellular stress pathways involving nuclear factor-kappaB within the cochlea.