Functional Outcomes and Postoperative Cerebral Venous Sinus Thrombosis after Translabyrinthine Approach for Vestibular Schwannoma Resection: A Radiographic Demonstration of Anatomic Predictors.

Introduction While regarded as an effective surgical approach to vestibular schwannoma (VS) resection, the translabyrinthine (TL) approach is not without complications. It has been postulated that postoperative cerebral venous sinus thrombosis (pCVST) may occur as a result of injury and manipulation during surgery. Our objective was to identify radiologic, surgical, and patient-specific risk factors that may be associated with pCVST. Methods The Institutional Review Board (IRB) approval was obtained and the medical records of adult patients with VS who underwent TL craniectomy at University Hospitals Cleveland Medical Center between 2009 and 2019 were reviewed. Demographic data, radiographic measurements, and tumor characteristics were collected. Outcomes assessed included pCVST and the modified Rankin score (mRS). Results Sixty-one patients ultimately met inclusion criteria for the study. Ten patients demonstrated radiographic evidence of thrombus. Patients who developed pCVST demonstrated shorter internal auditory canal (IAC) to sinus distance (mean: 22.5 vs. 25.0 mm, p = 0.044) and significantly smaller petrous angles (mean: 26.3 vs. 32.7 degrees, p = 0.0045). Patients with good mRS scores (<3) appeared also to have higher mean petrous angles (32.5 vs. 26.8, p = 0.016). Koos' grading and tumor size, in our study, were not associated with thrombosis. Conclusion More acute petrous angle and shorter IAC to sinus distance are objective anatomic variables associated with pCVST in TL surgical approaches.

Vision Deterioration and Hydrocephalus: Rare Presentations of Vestibular Schwannoma and Evolution of Management.

Introduction The incidence of vestibular schwannoma is reported as 12 to 54 new cases per million per year, increasing over time. These patients usually present with unilateral sensorineural hearing loss, tinnitus, or vertigo. Rarely, these patients present with symptoms of hydrocephalus or vision changes. Objective The study aimed to evaluate the surgical management of vestibular schwannoma at a single institution and to identify factors that may contribute to hydrocephalus, papilledema, and the need for pre-resection diversion of cerebrospinal fluid. Patients and Methods A retrospective review examining the data of 203 patients with vestibular schwannoma managed with surgical resection from May 2008 to May 2020. We stratified patients into five different groups to analyze: tumors with a diameter of ≥40 mm, clinical evidence of hydrocephalus, and of papilledema, and patients who underwent pre-resection cerebrospinal fluid (CSF) diversion. Results From May 2008 to May 2020, 203 patients were treated with surgical resection. Patients with tumors ≥40 mm were more likely to present with visual symptoms ( p < 0.001). Presentation with hydrocephalus was associated with larger tumor size ( p < 0.001) as well as concomitant visual symptoms and papilledema ( p < 0.001). Patients with visual symptoms presented at a younger age ( p = 0.002) and with larger tumors ( p < 0.001). Conclusion This case series highlights the rare presentation of vision changes and hydrocephalus in patients with vestibular schwannoma. We recommend urgent CSF diversion for patients with visual symptoms and hydrocephalus, followed by definitive resection. Further, vision may still deteriorate even after CSF diversion and tumor resection.

Sex-specific enlarged vestibular aqueduct morphology and audiometry.

OBJECTIVE: Enlargement of the vestibular aqueduct (EVA) is one of the most common congenital malformations in pediatric patients presenting with sensorineural or mixed hearing loss. The relationship between vestibular aqueduct (VA) morphology and hearing loss across sex is not well characterized. This study assesses VA morphology and frequency-specific hearing thresholds with sex as the primary predictor of interest. MATERIALS AND METHODS: A retrospective, longitudinal, and repeated-measures study was used. 47 patients at an academic tertiary care center with hearing loss and a record of CT scan of the internal auditory canal were candidates, and included upon meeting EVA criteria after confirmatory measurements of vestibular aqueduct midpoint and operculum widths. Audiometric measures included pure-tone average and frequency-specific thresholds. RESULTS: Of the 47 patients (23 female and 24 male), 79 total ears were affected by EVA; the median age at diagnosis was 6.60 years. After comparing morphological measurements between sexes, ears from female patients were observed to have a greater average operculum width (3.25 vs. 2.70 mm for males, p = 0.006) and a greater average VA midpoint width (2.80 vs. 1.90 mm for males, p = 0.004). After adjusting for morphology, male patients' ears had pure-tone average thresholds 17.6 dB greater than female patients' ears (95% CI, 3.8 to 31.3 dB). CONCLUSIONS: Though females seem to have greater enlargement of the vestibular aqueduct, this difference does not extend to hearing loss. Therefore, our results indicate that criteria for EVA diagnoses may benefit from re-evaluation. Further exploration into morphological and audiometric discrepancies across sex may help inform both clinician and patient expectations.

Long-term outcomes of endolymphatic sac shunting with local steroids for Meniere's disease.

OBJECTIVES: To evaluate the long-term efficacy of endolymphatic sac shunt techniques with and without local steroid administration. STUDY DESIGN: Retrospective case series and patient survey. SETTING: Tertiary university hospital. PATIENTS: Meniere's disease (MD) patients that failed medical therapy and subsequently underwent an endolymphatic sac shunt procedure. All patients had definitive or probable MD and at least 18-months of follow-up. INTERVENTIONS: Three variations on endolymphatic sac decompression with shunt placement were performed: Group A received no local steroids, Group B received intratympanic dexamethasone prior to incision, and Group C received dexamethasone via both intratympanic injection and direct endolymphatic sac instillation. MAIN OUTCOME MEASURE(S): Vertigo control, hearing results, and survey responses. RESULTS: Between 2002 and 2013, 124 patients with MD underwent endolymphatic sac decompression with shunt placement. 53 patients met inclusion criteria. Groups A, B, and C had 6 patients, 20 patients, and 27 patients, respectively. Mean follow-up was 56months. Vertigo control improved in 66%, 83%, and 93% of Groups A, B, and C. Functional level improved for Group B (-2.0) and Group C (-2.2) but was unchanged in Group A. Pure-tone average and speech discrimination scores changed by +22dB and -30%, +6dB and -13%, and +6dB and -5% in Groups A, B, and C. The long-term hearing results were significantly better with steroids (Groups B and C) according to the AAO-HNS 1995 criteria but did not meet significance on non-parametric testing. CONCLUSIONS: Endolymphatic sac shunt procedures may benefit from steroid instillation at the time of shunt placement.

Treatment of ear and bone disease in the Phex mouse mutant with dietary supplementation.

HYPOTHESIS: Phosphorus and vitamin D (calcitriol) supplementation in the Phex mouse, a murine model for endolymphatic hydrops (ELH), will improve otic capsule mineralization and secondarily ameliorate the postnatal development of ELH and sensorineural hearing loss (SNHL). BACKGROUND: Male Phex mice have X-linked hypophosphatemic rickets (XLH), which includes osteomalacia of the otic capsule. The treatment for XLH is supplementation with phosphorus and calcitriol. The effect of this treatment has never been studied on otic capsule bone and it is unclear if improving the otic capsule bone could impact the mice's postnatal development of ELH and SNHL. METHODS: Four cohorts were studied: 1) wild-type control, 2) Phex control, 3) Phex prevention, and 4) Phex rescue. The control groups were not given any dietary supplementation. The Phex prevention group was supplemented with phosphorus added to its drinking water and intraperitoneal calcitriol from postnatal day (P) 7-P40. The Phex rescue group was also supplemented with phosphorus and calcium but only from P20 to P40. At P40, all mice underwent auditory brainstem response (ABR) testing, serum analysis, and temporal bone histologic analysis. Primary outcome was otic capsule mineralization. Secondary outcomes were degree of SNHL and presence ELH. RESULTS: Both treatment groups had markedly improved otic capsule mineralization with less osteoid deposition. The improved otic capsule mineralized did not prevent the development of ELH or SNHL. CONCLUSION: Supplementation with phosphorus and calcitriol improves otic capsule bone morphology in the Phex male mouse but does not alter development of ELH or SNHL.

IgG4-related disease causing facial nerve and optic nerve palsies: Case report and literature review.

IgG4-related disease (IgG4-RD) is increasingly being recognized as an entity effecting the head and neck region. Although most commonly seen with salivary gland or paranasal sinus involvement, IgG4-RD may also involve the temporal bone and skull base. We report a rare care of a 61-year-old female with IgG4-RD presenting as synchronous lesions of the middle ear and middle cranial fossa with polyneuropathy of cranial nerves II, VI, and VII. Initial histopathological evaluation of her resected ear mass suggested a benign inflammatory process but no specific diagnosis. Her symptoms progressed over 10months prompting re-evaluation of the specimen and consideration of the IgG4-RD diagnosis. Key pathologic features included prominent lymphoplasmacytic population, storiform fibrosis, obliterative phlebitis, and IgG4 specific staining. The patient was treated with high-dose intravenous and oral steroids but was transitioned to azathioprine secondary to steroid-induced myopathy. Radiographic studies before and after treatment reveal marked improvement of the intracranial and extracranial disease. Correspondingly, her cranial neuropathies resolved. A high degree of clinical suspicion is necessary to diagnosis IgG4-RD. The diagnosis can be supported by elevated serum IgG, elevated IgG index, and pathognomonic histopathological findings. Primary treatment is with corticosteroids. However, immunotherapy using azathioprine or rituximab can be utilized in recurrent disease or patients with steroid intolerance.

Meniere's disease.

Meniere's disease (MD) is a disorder of the inner ear that causes vertigo attacks, fluctuating hearing loss, tinnitus and aural fullness. The aetiology of MD is multifactorial. A characteristic sign of MD is endolymphatic hydrops (EH), a disorder in which excessive endolymph accumulates in the inner ear and causes damage to the ganglion cells. In most patients, the clinical symptoms of MD present after considerable accumulation of endolymph has occurred. However, some patients develop symptoms in the early stages of EH. The reason for the variability in the symptomatology is unknown and the relationship between EH and the clinical symptoms of MD requires further study. The diagnosis of MD is based on clinical symptoms but can be complemented with functional inner ear tests, including audiometry, vestibular-evoked myogenic potential testing, caloric testing, electrocochleography or head impulse tests. MRI has been optimized to directly visualize EH in the cochlea, vestibule and semicircular canals, and its use is shifting from the research setting to the clinic. The management of MD is mainly aimed at the relief of acute attacks of vertigo and the prevention of recurrent attacks. Therapeutic options are based on empirical evidence and include the management of risk factors and a conservative approach as the first line of treatment. When medical treatment is unable to suppress vertigo attacks, intratympanic gentamicin therapy or endolymphatic sac decompression surgery is usually considered. This Primer covers the pathophysiology, symptomatology, diagnosis, management, quality of life and prevention of MD.

Successful endovascular management of venous sinus thrombosis complicating trans-labyrinthine removal of vestibular schwanomma.

Cerebral venous sinus thrombosis (CVST) is a rare complication of surgical treatment of vestibular schwanomma. We present a rare case of extensive venous sinus thrombosis after trans-labyrinthine approach that was refractory to systemic anti-coagulation. Mechanical aspiration thrombectomy was utilized to re-canalize the venous sinuses and resulted in successful resolution of neurological symptoms. Indications of utilizing endovascular approaches are discussed that will enable skull base surgeons to address this uncommon yet potentially fatal complication.

Bilateral Sequential Cochlear Implantation in Patients With Enlarged Vestibular Aqueduct (EVA) Syndrome.

OBJECTIVES: To analyze audiometric outcomes after bilateral cochlear implantation in patients with isolated enlarged vestibular aqueduct (EVA) syndrome and associated incomplete partition (IP) malformations. Secondary objective was to analyze rate of cerebrospinal fluid (CSF) gusher in patients with IP-EVA spectrum deformities and compare this with the existing literature. STUDY DESIGN: Retrospective chart review. METHODS: Thirty-two patients with EVA syndrome who received unilateral or bilateral cochlear implants between June 1999 and January 2014 were identified in the University Hospitals Case Medical Center cochlear implant database. Isolated EVA (IEVA) and Incomplete Partition Type II (IP-II) malformations were identified by reviewing high-resolution computed tomography (HRCT) imaging. Demographic information, age at implantation, surgical details, postimplantation audiometric data including speech reception thresholds (SRT), word, and sentence scores were reviewed and analyzed. Intra- and postoperative complications were analyzed as well and compared with the literature. RESULTS: Seventeen patients (32 implanted ears) had pediatric cochlear implantation for EVA-associated hearing loss. Data from 16 controls (32 implanted ears) were used to compare audiometric and speech outcomes of EVA cohort. Mean age at implantation was 6.8 years for EVA cohort and 6.0 years for controls. There was no statistically significant difference in long-term postoperative SRT, monaurally aided word scores, and binaurally tested word scores between pediatric EVA group and controls. The EVA patients had a long-term mean sentence score of 85.92%. A subset of EVA patients implanted at mean age of 3.18 years (n = 15 ears) had similar audiometric outcomes to another control group with Connexin 26 mutations (n = 20 ears) implanted at a similar age. Further subset analysis revealed no significant differences in age at implantation, SRT, and word scores in patients with IEVA and IP-II malformation. There was no significant association between size of vestibular aqueduct and age at implantation. There was no CSF gusher or other intra- or postoperative complications reported in our series. CONCLUSION: Bilateral sequential cochlear implantation can be performed safely in patients with EVA. Audiometric outcomes are excellent and comparable to pediatric cochlear implant patients with no malformations. CSF gusher rates can be minimized by trans-round window approach. Further long-term studies are needed to identify differences within IP-EVA spectrum deformities, audiometric outcomes, and proportions of EVA patients who will need cochlear implantation for hearing rehabilitation.

Retrosigmoid versus translabyrinthine approach to acoustic neuroma resection: A comparative cost-effectiveness analysis.

OBJECTIVES/HYPOTHESIS: Approach-specific economic data of acoustic neuroma (AN) resection is lacking. The purpose of this study was to analyze and compare adjusted total hospital costs, hospital and intensive care unit (ICU) length of stay (LOS), and associated factors in AN patients undergoing resection by translabyrinthine (TL) approach versus retrosigmoid (RS) approach. STUDY DESIGN: Retrospective chart review. METHODS: A total of 113 patients with AN undergoing TL (N = 43) or RS (N = 70) surgical resection between 1999 and 2012 were analyzed. Data including age, health status, preoperative hearing, tumor size, postoperative complications, hospital, ICU LOS, and disposition after discharge were collected from medical records and compared between both groups. Cost data was obtained from the hospital finance department and adjusted based on the Consumer Price Index for 2013. RESULTS: There were no significant differences in demographic data, preoperative hearing, preoperative health status, or postoperative complication rate. Total hospital LOS and ICU LOS were significantly longer in the RS compared to the TL group (4.3 ± 3.6 vs. 2.6 ± 1.1 days; P < 0.001, and 1.5 ± 1.1 vs. 1.0 ± 0.5 days; P = 0.015, respectively). Tumors were larger in RS compared to the TL group (2.1 ± 1.0 cm vs. 1.5 ± 0.7 cm, respectively; P = 0.002). When patients were stratified by tumor size < or ≥ 2 cm, the total hospital LOS remained greater in the RS group in both subgroups (< and ≥ 2 cm, P < 0.001, and P = 0.031, respectively). However, there was no difference in the total ICU LOS between both subgroups. The adjusted mean total hospital cost was higher in the RS compared to the TL group ($25,069 ± 14,968 vs. $16,799 ± 5,724; P < 0.001). The adjusted mean total hospital cost was greater in the RS group with tumor < 2 cm (P < 0.001) but not significantly different in patients with tumors ≥ 2 cm. Univariate analysis showed that greater tumor size, poorer preoperative health status, the presence of major postoperative complications, and the RS approach were independently significantly associated with higher total hospital LOS (P = 0.001, P = 0.009, P = 0.001, and P < 0.001, respectively) and a higher adjusted total hospital cost (P < 0.001, P = 0.002, P = 0.014, and P < 0.001, respectively). CONCLUSION: Hospital LOS and total adjusted costs are significantly less for patients undergoing translabyrinthine acoustic neuroma resection compared to the retrosigmoid approach. Many factors appear to influence these differences. Economic considerations in addition to tumor characteristics and surgeon preference should be considered in future acoustic neuroma resections. LEVEL OF EVIDENCE: 2c.

Ipsilateral single stage conversion from BAHA to cochlear implant.

Profound unilateral sensorineural hearing loss is an indication for the placement of a bone anchored hearing aid. In a few unfortunate patients who later develop contralateral hearing loss, a cochlear implant becomes a good option. We present our experience in these cases and discuss our technique for single stage conversion from a bone anchored hearing aid to a cochlear implant.

Endolymphatic sac tumors.

Endolymphatic sac tumors (ELST) are slow-growing, locally aggressive, low-grade malignancies that originate from the epithelium of the endolymphatic duct and sac. ELST often present with sensorineural hearing loss, tinnitus, and vertigo, which may mimic Meniere disease. Large tumors may present with additional cranial neuropathies. Management is primarily via microsurgical excision. Radiation therapy has a limited role for residual or unresectable disease. Early detection may enable hearing preservation techniques. ELST have an association with von Hippel-Lindau disease.

Predictive factors and outcomes of cochlear implantation in patients with connexin 26 mutation: a comparative study.

PURPOSE: To compare hearing outcomes in patients with connexin 26 (Cx 26) mutations undergoing cochlear implantation to age matched controls and to examine whether age at implantation, gender and type of mutation were correlated with hearing outcome. MATERIALS AND METHODS: Retrospective chart review of 21 patients with Cx 26 mutations that underwent cochlear implantation compared to 18 age-matched controls. Patients' characteristics, type of mutation and pre- and postoperative short and long-term hearing thresholds, word and sentence scores were analyzed. RESULTS: There was no statistically significant difference between the Cx 26 and control group in the mean short term and mean long term post-operative pure tone averages (PTA), speech reception thresholds (SRT), word and sentence scores. Gender, age at implantation and type of connexin 26 mutation did not predict hearing outcomes. CONCLUSIONS: In patients with connexin 26 mutation, cochlear implantation provides an effective mean of auditory habilitation. Mutational status, age and gender do not seem to predict hearing outcomes.

A Genetic Murine Model of Endolymphatic Hydrops: The Phex Mouse.

Animal models of endolymphatic hydrops (ELH) provide critical insight into the pathophysiology of Meniere's disease (MD). A new genetic murine model, called the Phex mouse, circumvents prior need for a time and cost-intensive surgical procedure to create ELH. The Phex mouse model of ELH, which also has X-linked hypophosphatemic rickets, creates a postnatal, spontaneous, and progressive ELH whose phenotype has a predictable decline of vestibular and hearing function reminiscent of human MD. The Phex mouse enables real-time histopathologic analysis to assess diagnostic and therapeutic interventions as well as further our understanding of ELH's adverse effects. Already the model has validated electrocochleography and cervical vestibular evoked myogenic potential as useful diagnostic tools. New data on caspase activity in apoptosis of the spiral ganglion neurons may help target future therapeutic interventions. This paper highlights the development of the Phex mouse model and highlights its role in characterizing ELH.

Hearing and vertigo outcomes after congenital labyrinthine cholesteatoma resection.

Congenital labyrinthine cholesteatoma can cause varying degrees of hearing loss and vertigo. Hearing preservation is not always possible when treatment involves total labyrinthectomy. Since 1969, there have been several case reports and case series documenting hearing preservation following surgical treatment of congenital labyrinthine cholesteatoma. However, none of the case reports or case series documents the patients' vestibular complaints after surgery. Herein, we report a case series of four patients who were treated with the goal of hearing preservation and resolution of vertigo after partial or complete removal of the bony labyrinth for congenital inner ear cholesteatoma. We will also discuss possible explanations for the mechanisms of preservation of hearing and vestibular function with a review of the current literature.

A mouse model validates the utility of electrocochleography in verifying endolymphatic hydrops.

Endolymphatic hydrops (ELH) is a disorder of the inner ear that causes tinnitus, vertigo, and hearing loss. An elevated ratio of the summating potential (SP) to the action potential (AP) measured by electrocochleography has long been considered to be the electrophysiological correlate of ELH-related clinical conditions, such as Meniere's disease, but in vivo confirmation and correlation between an elevated SP/AP ratio and ELH has not yet been possible. Confirming this relationship will be important to show that elevated SP/AP ratio is indeed diagnostic of ELH. Here, we sought to confirm that an elevated SP/AP ratio is associated with ELH and test the hypothesis that severity of ELH and hearing loss would also correlate with the SP/AP ratio in vivo using the Phex(Hyp-Duk)/Y mouse model of postnatal ELH. In addition, we describe a minimally invasive approach for electrocochleography in mice. Auditory brainstem responses and electrocochleography data were collected from controls and Phex(Hyp-Duk)/Y mutants at postnatal day 21 and the mice (all male) were euthanized immediately for cochlear histology. Our results show that (1) the SP/AP ratio was significantly elevated in mice with histological ELH compared to controls, (2) the SP/AP ratio was not correlated with the severity of histological ELH or hearing loss, and (3) the severity of hearing loss correlated with the severity of histological ELH. Our study demonstrates that an elevated SP/AP ratio is diagnostic of ELH and that the severity of hearing loss is a better predictor of the severity of ELH than is the SP/AP ratio.

Translabyrinthine resection of small intracanalicular acoustic tumor.

This case is an example of a translabyrinthine resection of a small intracanalicular acoustic tumor. The patient is a 69-year-old right-handed woman with complaints of progressive incapacitating vertigo and right-sided hearing loss worsening over the past 3 years. She had normal facial nerve function with imaging demonstrating progressive increase in size of a small right-sided acoustic tumor. A translabyrinthine approach was performed, and the mass was resected completely. Facial nerve function remained normal immediately after surgery. The video can be found here: http://youtu.be/27ARlLLSbKE .

Petroclival meningiomas: an update on surgical approaches, decision making, and treatment results.

OBJECT: Petroclival meningiomas remain a formidable challenge for neurosurgeons because of their location deep within the skull base and proximity to eloquent neurovascular structures. Various skull base approaches have been used in their treatment, and deciding which is the optimal one remains controversial. Attempts at achieving gross- or near-total resections are associated with an increased rate of morbidity and mortality. As adjunctive treatment options such as stereotactic radiosurgery have been developed and become widely available, there has been a trend toward accepting subtotal resections in an effort to minimize neurological morbidity. This paper reviews a recent series of patients with petroclival meningiomas and highlights current management trends and important considerations useful in surgical decision making. METHODS: The records of patients with large (> 3 cm) petroclival meningiomas surgically treated by the senior author over the past 5 years were reviewed. The clinical results are presented as examples of the surgical approaches available for approaching these tumors, and treatment options are reviewed. RESULTS: Of 196 meningiomas surgically treated during the study period, 8 lesions in 8 patients met the study criteria. Overall clinical results were excellent, with no death or major morbidity. Intracranial gross- or near-total resection (Simpson Grade 1, 2, or 3) was achieved in 5 patients (67%). New cranial nerve deficits occurred in 3 patients (37%) and were more common in patients in whom a subtotal resection was performed (2 of 3 cases). A variety of surgical approaches were used. Important considerations determining the best approach include the location of the tumor relative to the internal auditory canal, the presence of preoperative hearing loss, and the location of the tumor relative to the tentorium. CONCLUSIONS: Achieving gross- or near-total resections of large petroclival meningiomas remains achievable and should be the primary goal of surgical treatment. A retrosigmoid craniotomy remains a workhorse surgical approach for most petroclival tumors of any size. Tumors that are medial to the internal auditory canal and span both middle and posterior cranial fossae are often best treated with a combined transpetrosal approach, which is especially true if there is a preoperative hearing deficit.

Meningoencephalocele of the temporal bone: pictorial essay on transmastoid extradural-intracranial repair.

PURPOSE: A spontaneous meningoencephalocele of the temporal bone may present with effusion in the middle ear, a cerebrospinal fluid leak, hearing loss, or rarely otitic meningitis. Repair of spontaneous encephaloceles in the temporal bone has been performed using transmastoid and transcranial middle fossa approaches or a combination of the two with varied results. The authors present a technical paper on the transmastoid extradural intracranial approach for the management of temporal lobe encephaloceles. MATERIALS/METHODS: Case reports and cadaver dissections are used to provide a pictorial essay on the technique. Advantages and disadvantages compared with alternative surgical approaches are discussed. RESULTS: Traditional transmastoid approaches are less morbid compared with a transcranial repair as they avoid brain retraction. However, in the past, there has been a higher risk of graft failure and hearing loss due to downward graft migration and a potential need for ossicular disarticulation. For the appropriate lesion, the transmastoid extradural intracranial approach lesion offers a stable meningoencephalocele repair without the comorbidity of brain retraction. CONCLUSION: The authors describe a transmastoid extradural intracranial technique via case reports and cadaver dissections for the repair of spontaneous meningoencephalocele defects larger than 2 cm. This approach provides more support to the graft compared to the conventional transmastoid repair.

Characterization of neuronal cell death in the spiral ganglia of a mouse model of endolymphatic hydrops.

HYPOTHESIS: Spiral ganglion neurons (SGN) in the Phex male mouse, a murine model of postnatal endolymphatic hydrops (ELH) undergo progressive deterioration reminiscent of human and other animal models of ELH with features suggesting apoptosis as an important mechanism. BACKGROUND: Histologic analysis of the mutant's cochlea demonstrates ELH by postnatal Day (P) 21 and SGN loss by P90. The SGN loss seems to occur in a consistent topographic pattern beginning at the cochlear apex. METHODS: SGN were counted at P60, P90, and P120. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), quantitative PCR, and immunohistochemical analyses of activated caspase-3, caspase-8, and caspase-9 were performed on cochlear sections obtained from mutants and controls. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling assay (TUNEL) was carried out on 2 mutants and 2 controls. RESULTS: Corrected SGN counts in control mice were greater in the apical turn of the cochleae at P90 and P120, respectively (p < 0.01). Increased expression of activated caspase-3, caspase-8, and caspase-9 was seen in the mutant. At later time points, activated caspase expression gradually declined in the apical turns and increased in basal turns of the cochlea. Quantitative and semiquantitative PCR analysis confirmed increased expression of caspase-3, caspase-8, and caspase-9 at P21 and P40. TUNEL staining demonstrated apoptosis at P90 in the apical and basal turns of the mutant cochleae. CONCLUSION: SGN degeneration in the Phex /Y mouse seems to mimic patterns observed in other animals with ELH. Apoptosis plays an important role in the degeneration of the SGN in the Phex male mouse.