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.

Parotidectomy: A Ten Year Experience with Fine Needle Aspiration and Frozen Section Biopsy Correlation

During the years 1980 through 1990, 247 patients underwent parotidectomy at our institution for the removal of primary parotid lesions. Charts were reviewed in an effort to document the distribution of pathology in patients undergoing parotidectomy and the histopathology from each case was organized and tallied by virtue of the final specific diagnoses. An additional goal of this study was to evaluate the efficacy of pre-operative fine-needle aspiration biopsy (FNAB) and frozen section pathology in accurately predicting final histopathology. In our series, 86.7% of lesions were found to be benign and 13.3% were malignant in nature. When compared to final pathologic findings, FNAB yielded a diagnostic accuracy rate of 89.3% with a 2.1% false negative rate with regards to pre-operative detection of malignancy. Frozen section biopsy was found to have a diagnostic accuracy of 94.1% and also demonstrated a 2.1% false-negative rate. We believe these studies are indeed complementary to each other, as reflected in the 96.2% diagnostic accuracy achieved with a combination of FNAB and frozen section biopsy information. This report will review the patterns of misdiagnosis for each modality of diagnostic testing and present the parotid histopathology found over a 10-year period.

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.

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.

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.

Aural Full and Otogenic Pain Redux

Program Description:

Otogenic pain and aural fullness can be some of the more frustrating chief complaints to work up and address. Many patients with this complaint are frustrated with lack of diagnosis and treatment. This leads to multiple visits in search of the answer to their affliction. In this miniseminar, our panel of experts will continue their discussion on how to evaluate and treat these difficult patients. Paradigms for management of these patients will be discussed. Case presentations will highlight proper workup and management of these confusing cases. Sponsored by the Otology and Neurotology Education Committee.

Educational Objectives:

(1) Describe pathologies that may cause otogenic pain or aural fullness. (2) Conduct workup paradigms to avoid missing potentially dangerous processes. (3) Examine possible treatments for the various pathologies.

Sudden Sensorineural Hearing Loss: What Every Otolaryngologist Should Know

Program Description:

Idiopathic sudden sensorineural hearing loss (ISSHL) has no known etiology. However, numerous studies have addressed this important problem. This miniseminar, sponsored by the American Academy of Otolaryngology—Head and Neck Foundation (AAO-HNSF) Otology and Neurotology Education Committee, will summarize existing literature with regard to the evaluation and treatment of ISSHL. We will review AAO-HNSF guidelines, studies on the efficacy of steroids, antivirals, hyperbaric oxygen, and other treatments. Lastly, we will discuss treatment options when hearing does not recover.

Educational Objectives:

(1) Implement the recommended evaluation of patients with sudden hearing loss. (2) Recognize the benefits of oral versus intratympanic steroids for sudden hearing loss. (3) Analyze the utility of nonsteroidal treatments when steroids and other modalities fail.

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.

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.

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 .

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.

Surgical duration of cochlear implantation in an academic university-based practice

OBJECTIVE

Establish the time to safely and efficiently perform cochlear implantation (CI) in a university-based academic center.

STUDY DESIGN

Case series with chart review.

SETTING

Academic neurotologic referral center.

PATIENTS

424 patients who underwent CI surgery between 2002 and 2010.

INTERVENTION

Unilateral, bilateral or revision CI using commercially available devices approved for use in the United States.

MAIN OUTCOME MEASURES

mean surgical duration (SD) and mean total operative room time (TORT).

RESULTS

Overall mean SD for all 424 patients was 83 ± 30 min (min) whereas the mean TORT was 135 ± 56 min. The mean SD for unilateral CI was 84 ± 18 min for the first implant and 82 ± 22 min for the second implant (p=0.55). The SD for primary and revision CI was 83 ± 18 min and 85 ± 36 min, respectively (p=0.51). The mean SD for pediatric and adult CI was 83 ± 21 min and 83 ± 18 min, respectively (p=0.92). The mean SD without resident assistance was 74 ± 14 min whereas with the assistance of a resident the mean SD was 84 ± 20 min (p=0.02). When ossification was encountered the mean SD was 90 ± 32 min compared to 82 ± 19 min when absent (p<0.001). An association was found between TORT or SD, and the year of surgery, presence of ossification and the involvement of an assistant.

CONCLUSION

In a university-based academic center, CI surgery can be safely and efficiently performed, supporting future cost-effectiveness analysis of its current practice.

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.

Prevention of postoperative cerebrospinal fluid leaks with multilayered reconstruction using titanium mesh-hydroxyapatite cement cranioplasty after translabyrinthine resection of acoustic neuroma

OBJECT

Several prophylactic surgical methods have been tried to prevent CSF leakage after translabyrinthine resection of acoustic neuroma (TLAN). The authors report an improvised technique for multilayer watertight closure using titanium mesh-hydroxyapatite cement (HAC) cranioplasty in addition to dural substitute and abdominal fat graft after TLAN.

METHODS

The study was limited to 42 patients who underwent TLAN at University Hospitals Case Medical Center using this new technique from 2006 to 2012. Systematic closure of the surgical wound in layers using temporalis fascia, dural substitute, dural sealant, adipose graft, titanium mesh, and then HAC was performed in each case. Temporalis muscle and eustachian tube obliteration were not used. The main variables studied were patient age, tumor size, tumor location, cosmetic outcome, length of hospitalization, and the incidence of CSF leak, pseudomeningocele, and infection.

RESULTS

Excellent cosmetic outcome was achieved in all patients. There were no cases of postoperative CSF rhinorrhea, incisional CSF leak, or meningitis. Cosmetic results were comparable to those achieved using HAC alone. This cost-effective technique used only a third of the HAC required for traditional closure in which the entire mastoid defect is filled with cement, predisposing to infection. Postoperative CT and MRI showed excellent bony contouring and dural reconstitution, respectively.

CONCLUSIONS

The authors report on successful use of titanium mesh-HAC cranioplasty in preventing postoperative CSF leak after TLAN in all cases in their series. The titanium mesh provides a well-defined anatomical dissection plane that would make reoperation easier than working through scarred soft tissue. The mesh bolsters the fat graft and keeps HAC out of direct contact with mastoid air cells, thereby reducing the risk of infection. The cement cranioplasty does not preclude subsequent implantation of a bone-anchored hearing aid.

Cochlear implantation outcomes in patients with far advanced otosclerosis

OBJECTIVES

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

HYPOTHESIS

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

STUDY DESIGN

Retrospective chart review.

SETTING

Academic neurotologic tertiary referral center.

PATIENTS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

Subcutaneous emphysema after otologic surgery: a case report

Subcutaneous emphysema of the head and neck after otologic surgery is exceedingly rare. The mechanism relates to the intimate relationship of the temporomandibular joint to the external auditory canal. We present a rare case of subcutaneous emphysema after otologic surgery for ear disease. An astute clinical index of suspicion coupled with prompt treatment can help minimize morbidity and improve patient outcomes.

MEMS capacitive accelerometer-based middle ear microphone

The design, implementation, and characterization of a microelectromechanical systems (MEMS) capacitive accelerometer-based middle ear microphone are presented in this paper. The microphone is intended for middle ear hearing aids as well as future fully implantable cochlear prosthesis. Human temporal bones acoustic response characterization results are used to derive the accelerometer design requirements. The prototype accelerometer is fabricated in a commercial silicon-on-insulator (SOI) MEMS process. The sensor occupies a sensing area of 1 mm × 1 mm with a chip area of 2 mm × 2.4 mm and is interfaced with a custom-designed low-noise electronic IC chip over a flexible substrate. The packaged sensor unit occupies an area of 2.5 mm × 6.2 mm with a weight of 25 mg. The sensor unit attached to umbo can detect a sound pressure level (SPL) of 60 dB at 500 Hz, 35 dB at 2 kHz, and 57 dB at 8 kHz. An improved sound detection limit of 34-dB SPL at 150 Hz and 24-dB SPL at 500 Hz can be expected by employing start-of-the-art MEMS fabrication technology, which results in an articulation index of approximately 0.76. Further micro/nanofabrication technology advancement is needed to enhance the microphone sensitivity for improved understanding of normal conversational speech.

Hearing preservation in Guinea pigs with long-standing endolymphatic hydrops

HYPOTHESIS

Interruption of the excitotoxic and inflammatory pathways implicated in endolymphatic hydrops (ELH)-associated hearing loss (HL) should afford hearing protection at the neuronal level.

BACKGROUND

Previous work in our laboratory in the mouse model of ELH shows that dimethyl sulfoxide (DMSO), an anti-inflammatory solvent, can slow the progression of HL before neuronal degeneration occurs. Riluzole, a glutamate release inhibitor, may provide synergistic benefit. This study was designed to quantify the effects of DMSO and riluzole in a long-term model.

METHODS

Guinea pigs with surgically induced ELH were sorted into 3 groups: riluzole+DMSO (Group 1), DMSO alone (Group 2), and untreated controls (Group 3). Animals in Groups 1 and 2 received daily injections of the study drug(s). All animals underwent auditory-evoked brainstem response evaluation every 4 weeks until 24 weeks, when they were sacrificed. Cochleae were preserved; spiral ganglion density was quantified. Animals without hydrops were excluded from the study as surgical failures.

RESULTS

Animals from all groups developed unilateral HL. At the end of the experiment, HL was significantly lower in Group 1 relative to Group 3 (p = 0.049) and trended toward lower in Group 2 relative to Group 3 (p = 0.097). Groups 1 and 2 were not different (p = 0.311). At the cellular level, there is no evidence of neuronal degeneration in either treated group, whereas there is a significant neuronal degeneration in the untreated group.

CONCLUSION

These results confirm the hearing protection observed with DMSO in short-term studies. However, unlike the previous study, which showed no additive benefit to riluzole, the combined treatment group in this study showed a hearing-protective effect at 24 weeks. This indicates a potential additive benefit conferred by riluzole toward long-term hearing protection. The study also finds evidence of statistically significant neuronal protection with both treatment groups. Overall, study provides additional evidence that DMSO and riluzole may preserve or slow the long-term progression of ELH-associated HL.

Otology/Neurotology

Program Description: The temporal bone is the home to and neighbor of a variety of critical neural and vascular structures that are at risk for injury during otologic surgery involving the middle ear and mastoid cavity. Their injury can have devastating consequences including hearing loss, facial nerve injury, central nervous system injury, or stroke. The challenge to the otologic surgeon is to eradicate disease, to preserve structure and function, and to avoid injury. Being prepared to handle expected and unexpected situations is the key to success for otologic or any other surgery. In this miniseminar, a panel of experts will specifically review: 1) How to avoid cholesteatoma recurrence; 2) strategies to prevent facial nerve injury; 3) what to do when the brain is injured; 4) avoiding and managing vascular injury; 5) what to do when the unexpected occurs during routine stapes surgery. The goal of the panel is to provide the tools necessary to become a more effective otologic surgeon and guidance for how to handle a variety of potential complications that may be encountered during routine ear surgery.

Educational Objectives: 1) Understand surgical principles and techniques to avoid FN, vascular, and CNS injury during otologic surgery. 2) Understand strategies to effect total removal of cholesteatoma and minimize its recurrence. 3) Understand the state-of-the-art approaches to minimizing and addressing complications of stapes surgery.

A novel method of translabyrinthine cranioplasty using hydroxyapatite cement and titanium mesh: a technical report

We report a novel technique for closure using titanium mesh cranioplasty in addition to hydroxyapatite cement and abdominal fat graft for acoustic neuroma. We reviewed 15 patients who underwent translabyrinthine craniectomy for resection of acoustic neuroma. Hearing loss was documented prior to surgical procedure. Over 2 years, patients underwent titanium mesh and hydroxyapatite cranioplasty with abdominal fat graft. Participants included seven men and eight women, age range 38 to 65. Main outcome measures included cosmetic outcome and incidence of cerebrospinal fluid (CSF) leak. The lesion was right-sided in seven patients and left-sided in eight. Cosmetic outcome was excellent in all. There were no cases of CSF leak. Closure used one-third the hydroxyapatite required for traditional closure. Our technique yields cosmetic results equivalent to hydroxyapatite cement alone and a comparable incidence of CSF leakage without leaving a drain in place postoperatively. The technique is easy to adopt, is more cost-effective than hydroxyapatite cement cranioplasty alone, offers greater ease of access for reoperation, and does not preclude later implantation of bone-anchored hearing aid.

Cavernous Malformation of the Trochlear Nerve: Case Report and Review of the Literature on Cranial Nerve Cavernomas

BACKGROUND AND IMPORTANCE:

Cavernous malformations (CMs) arising intrinsically to the cisternal segment of the trochlear nerve are extremely rare. This case of a trochlear nerve cavernous angioma is the third to be reported in the neurosurgical literature and the first to be resected by a middle fossa approach.

CLINICAL PRESENTATION:

The authors present a case of a 31-year-old woman with progressive left-sided headache and left hemisensory symptoms, whose magnetic resonance imaging showed a solid enhancing tumor in the left ambient cistern at the level of the midbrain-pontine junction causing significant brainstem compression. Intraoperatively, a left trochlear nerve cavernous angioma circumferentially enveloping the nerve was visualized. The angioma was microsurgically resected by a middle fossa approach under frameless stereotactic guidance. Gross total resection of the intrinsic trochlear nerve lesion was achieved, although the trochlear nerve could not be preserved intact.

CONCLUSION:

CMs should be considered in a possible differential diagnosis of cisternal trochlear nerve tumors. Surgical resection remains the standard of care, and is indicated for relief of compressive symptoms and prevention of future bleeds. Postoperative diplopia often persists; however, resolution of diplopia reported in the literature can be attributed to either regeneration after direct surgical repair of the sacrificed nerve or a spontaneous adaptation over time.

Contemporary perspectives on the pathophysiology of Meniere's disease: implications for treatment

PURPOSE OF REVIEW

Meniere's disease is characterized by episodic vertigo, fluctuating hearing loss, aural fullness and tinnitus. Endolymphatic hydrops, found on post-mortem examination, is the histologic hallmark. Recent research suggests that endolymphatic hydrops results from cytochemical perturbations of unknown etiology that lead to disturbance of the normal endolymphatic fluid homeostasis. This consequent hydropic state or the associated cytochemical perturbations appears to create a neurotoxic environment that ultimately leads to spiral ganglion cell death likely via the apoptotic mechanism. This review highlights some of the recent advances in the understanding of the pathophysiology of endolymphatic hydrops and progressive cochleovestibular deterioration, with emphasis placed on its potential therapeutic implications.

RECENT FINDINGS

Recent evidence supports that endolymphatic hydrops is possibly an epiphenomenon, and is preceded by perturbation of the normal ionic transport regulatory mechanisms. Furthermore, chronic cochleovestibular deterioration appears to be the result of an excitotoxic response to chronic hydrops. A recently described animal model, the Phex mouse, carrying a mutation in the Phex Hyp-Duk gene, provides a novel insight to genetically regulated postnatal endolymphatic hydrops and a useful tool to expand our understanding.

SUMMARY

Despite encouraging recent advances, there are considerable challenges that remain in the development of targeted therapeutic interventions that may offer new avenues of neuroprotection in known cases of Meniere's disease. These advances will hopefully provide pharmacotherapeutic interventions aimed at preventing progressive cochleovestibular dysfunction.

Pharmacological protection of hearing loss in the mouse model of endolymphatic hydrops

OBJECTIVES/HYPOTHESIS

Excitotoxic and related inflammatory injury are implicated in the spiral ganglion degeneration seen with Meniere's disease and endolymphatic hydrops (ELH). Excitotoxicity is initiated with glutamate elevation and associated with downstream increases in reactive oxygen species resulting in inflammation-mediated neuronal degeneration. This study tests the hypothesis that interruption of the initial and/or downstream aspects of excitotoxicity should provide hearing protection in ELH-associated hearing loss.

STUDY DESIGN

This study tests whether riluzole, a glutamate release inhibitor, and dimethylsulfoxide (DMSO), an anti-inflammatory and antioxidant solvent with favorable properties at the level of glutamate receptors, can protect against early-stage hearing loss in a mouse model of ELH.

METHODS

The Phex(Hyp-Duk) mouse spontaneously develops ELH and postnatal hearing loss. Starting at postnatal day 6 (P6), daily injections of riluzole + DMSO or just DMSO were administered. Untreated mutants served as controls. At P21, P25, and P30, hearing function was assessed by recording auditory brainstem responses. A cochlear function index was developed to assess global cochlear function at each time point.

RESULTS

Compared to no treatment, DMSO provided significant hearing protection (P < .05). The riluzole + DMSO also showed protection, but it was statistically indistinguishable from DMSO alone; a synergistic increase in protection with riluzole was not observed.

CONCLUSIONS

This study demonstrates pharmacological hearing protection in an animal model of ELH. The results support the assertion that inflammatory (reactive oxygen species) injury, which is part of the excitotoxic pathway, contributes to the development of ELH-associated hearing loss.

Surgical induction of endolymphatic hydrops by obliteration of the endolymphatic duct

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal model of the condition and an important correlate for human Meniere's disease. In 1965, Robert Kimura and Harold Schuknecht first described an intradural approach for obstruction of the endolymphatic duct (Kimura 1965). Although effective, this technique, which requires penetration of the brain's protective covering, incurred an undesirable level of morbidity and mortality in the animal subjects. Consequently, Andrews and Bohmer developed an extradural approach, which predictably produces fewer of the complications associated with central nervous system (CNS) penetration.(Andrews and Bohmer 1989)

The extradural approach described here first requires a midline incision in the region of the occiput to expose the underlying muscular layer. We operate only on the right side. After appropriate retraction of the overlying tissue, a horizontal incision is made into the musculature of the right occiput to expose the right temporo-occipital suture line. The bone immediately inferio-lateral the suture line (Fig 1) is then drilled with an otologic drill until the sigmoid sinus becomes visible. Medial retraction of the sigmoid sinus reveals the operculum of the endolymphatic duct, which houses the endolymphatic sac. Drilling medial to the operculum into the area of the endolymphatic sac reveals the endolymphatic duct, which is then packed with bone wax to produce obstruction and ultimately ELH.

In the following weeks, the animal will demonstrate the progressive, fluctuating hearing loss and histologic evidence of ELH.

Spiral ganglion loss outpaces inner hair cell loss in endolymphatic hydrops

OBJECTIVES/HYPOTHESIS

Neuronal toxicity is thought to be important in Meniere's disease and experimental endolymphatic hydrops (ELH). This study quantifies the relationship between neuronal degeneration and hair cell degeneration in ELH to evaluate the hypothesis that a primary neural insult would yield greater loss in the spiral ganglion than at the inner hair cell level.

STUDY DESIGN

Following induction and histopathologic confirmation of endolymphatic hydrops in guinea pigs, the degree of hydrops, spiral ganglion loss, and hair cell degeneration were quantified and compared.

METHODS

Guinea pigs with surgically induced unilateral hydrops were sacrificed and their cochleas preserved. Hydrops severity and spiral ganglion density were quantified using automated methods. Hair cells were counted manually. Values were normalized against the contralateral ear to create loss indexes.

RESULTS

Inner hair cell (IHC) loss at the apex is significantly lower than corresponding neuronal loss. IHC loss at the base is also lower than neuron loss, although not significantly. Regression analysis shows a significant, positive correlation between neuron loss severity and IHC loss severity at the apex, but not at the base. There is no correlation between hydrops severity and inner hair cell loss.

CONCLUSIONS

By confirming that spiral ganglion loss is more severe than hair cell loss, and that hair cell loss appears to worsen with neuronal degeneration, this study supports the theory that neuronal toxicity is the primary insult in ELH-related disorders, such as Meniere's disease, and may provide the basis for designing treatment strategies.

Characterization of Ossicular Chain Vibration at the Umbo: Implications for a Middle Ear Microelectromechanical System Design

We propose the use of a microelectromechanical system (MEMS) accelerometer as a middle ear microphone for future totally implantable cochlear prostheses. The MEMS accelerometer would be attached to the umbo to detect and convert the natural bone vibration that occurs in response to external sounds into an electrical signal that represents the acoustic information. The signal could be further processed to stimulate cochlear implant electrodes. To determine the feasibility of our proposal, we conducted a study to investigate whether the characteristics of umbo vibration along two orthogonal axes—one axis being perpendicular to the tympanic membrane and the other axis being parallel to the tympanic membrane plane but orthogonal to the long process of the malleus—differ significantly enough to compromise the sensing performance of the proposed accelerometer should a position misalignment occur during the implant procedure. We used laser Doppler vibrometry to measure the displacement of the umbo along the two orthogonal axes in 4 cadaveric temporal bones at multiple frequencies within the audible spectrum. We found that the peak-to-peak displacement frequency response along both axes was nearly flat from 250 Hz to 1 kHz, and it gradually rolled off with a slope of approximately −20 dB and −40 dB per decade above 1 kHz and 4 kHz, respectively. At each frequency, the displacement exhibited a linear function of the input sound level with a slope of 20 dB per decade. A comparison of measurements along the two axes indicated a similar frequency response, with an average amplitude difference of 20%. The characterization data suggest that the performance of a miniature ossicular vibration-sensing device attached on the umbo would not be degraded in the event of a position misalignment. The data also indicate that a MEMS accelerometer needs to achieve a resolution of i g /√ Hz to detect normal conversation.

Characterization of ossicular chain vibration at the umbo: implications for a middle ear microelectromechanical system design

We propose the use of a microelectromechanical system (MEMS) accelerometer as a middle ear microphone for future totally implantable cochlear prostheses. The MEMS accelerometer would be attached to the umbo to detect and convert the natural bone vibration that occurs in response to external sounds into an electrical signal that represents the acoustic information. The signal could be further processed to stimulate cochlear implant electrodes. To determine the feasibility of our proposal, we conducted a study to investigate whether the characteristics of umbo vibration along two orthogonal axes-one axis being perpendicular to the tympanic membrane and the other axis being parallel to the tympanic membrane plane but orthogonal to the long process of the malleus-differ significantly enough to compromise the sensing performance of the proposed accelerometer should a position misalignment occur during the implant procedure. We used laser Doppler vibrometry to measure the displacement of the umbo along the two orthogonal axes in 4 cadaveric temporal bones at multiple frequencies within the audible spectrum. We found that the peak-to-peak displacement frequency response along both axes was nearly flat from 250 Hz to 1 kHz, and it gradually rolled off with a slope of approximately -20 dB and -40 dB per decade above 1 kHz and 4 kHz, respectively. At each frequency, the displacement exhibited a linear function of the input sound level with a slope of 20 dB per decade. A comparison of measurements along the two axes indicated a similar frequency response, with an average amplitude difference of 20%. The characterization data suggest that the performance of a miniature ossicular vibration-sensing device attached on the umbo would not be degraded in the event of a position misalignment. The data also indicate that a MEMS accelerometer needs to achieve a resolution of 35 i g/sqrt[Hz] to detect normal conversation.

Studies of MEMS Acoustic Sensors as Implantable Microphones for Totally Implantable Hearing-Aid Systems

There is a need for high-quality implantable microphones for existing semiimplantable middle-ear hearing systems and cochlear prosthesis to make them totally implantable, thus overcoming discomfort, inconvenience, and social stigma. This paper summarizes and compares the results of an in-vitro study on three design approaches and the feasibility of using microelectromechanical system acoustic sensors as implantable microphones to convert the umbo vibration directly into a high-quality sound signal. The requirements of sensors were selected including the ability to withstand large body shocks or sudden changes of air pressure. Umbo vibration characteristics were extracted from literature and laboratory measurement data. A piezoelectric vibration source was built and calibrated to simulate the umbo vibration. Two laboratory models of the acoustic sensor were studied. The model-A device, using electrets-microphone as the sensor, was designed and tested in the laboratory and on temporal bones. The results verify that the laboratory measurement is consistent with the temporal bone characterization and achieves a near flat frequency response with a minimum detectable signal of a 65-dB sound-pressure-level (SPL) at 1 kHz. The model-B sensor was then designed to increase the sensitivity and provide an easy mounting on umbo. The model-B device can detect 40-dB SPL sound in the 1-2 kHz region, with 100-Hz channel bandwidth. The results of model-A and model-B displacement sensors and the acceleration sensor are summarized and compared. A preliminary design of the implantable displacement sensor for totally implantable hearing-aid systems is also presented.

Management of anterior inferior cerebellar artery aneurysms: an illustrative case and review of literature

Aneurysms of the anterior inferior cerebellar artery (AICA) are relatively rare among intracranial aneurysms. They can occur in 1 of 3 regions of the AICA: 1) craniocaudal (high or low riding), 2) mediolateral-premeatal (proximal), and 3) meatal-postmeatal (distal). The management strategies for treatment differ according to the location and configuration of the aneurysm. The existing body of neurosurgical literature contains articles published on aneurysms arising from the AICA near the basilar artery (BA), intracanalicular/meatal aneurysms, and distal AICA. Several therapeutic options exist, encompassing microsurgical and endovascular techniques. The authors describe a case of treatment involving a large BA-AICA aneurysm approached via exposure of the presigmoid dura using a retromastoid suboccipital craniectomy and partial petrosectomy. Treatment of these lesions requires detailed knowledge of the anatomy, and an anatomical overview of the AICA with its arterial loops and significant branches is presented, including a discussion of the internal auditory (labyrinthine) artery, recurrent perforating arteries, subarcuate artery, and cerebellosubarcuate artery. The authors discuss the various surgical approaches (retromastoid, far lateral, subtemporal, and transclival) with appropriate illustrations, citing the advantages and disadvantages in accessing these AICA lesions in relation to these approaches. The complications of these different surgical techniques and possible clinical effects of parent artery occlusion during AICA surgery are highlighted.

A mouse model with postnatal endolymphatic hydrops and hearing loss

Endolymphatic hydrops (ELH), hearing loss and neuronal degeneration occur together in a variety of clinically significant disorders, including Meniere's disease (MD). However, the sequence of these pathological changes and their relationship to each other are not well understood. In this regard, an animal model that spontaneously develops these features postnatally would be useful for research purposes. A search for such a model led us to the Phex Hyp-Duk mouse, a mutant allele of the Phex gene causing X-linked hypophosphatemic rickets. The hemizygous male (Phex Hyp-Duk/Y) was previously reported to exhibit various abnormalities during adulthood, including thickening of bone, ELH and hearing loss. The reported inner-ear phenotype was suggestive of progressive pathology and spontaneous development of ELH postnatally, but not conclusive. The main focuses of this report are to further characterize the inner ear phenotype in Phex Hyp-Duk/Y mice and to test the hypotheses that (a) the Phex Hyp-Duk/Y mouse develops ELH and hearing loss postnatally, and (b) the development of ELH in the Phex Hyp-Duk/Y mouse is associated with obstruction of the endolymphatic duct (ED) due to thickening of the surrounding bone. Auditory brainstem response (ABR) recordings at various times points and histological analysis of representative temporal bones reveal that Phex Hyp-Duk/Y mice typically develop adult onset, asymmetric, progressive hearing loss closely followed by the onset of ELH. ABR and histological data show that functional degeneration precedes structural degeneration. The major degenerative correlate of hearing loss and ELH in the mutants is the primary loss of spiral ganglion cells. Further, Phex Hyp-Duk/Y mice develop ELH without evidence of ED obstruction, supporting the idea that ELH can be induced by a mechanism other than the blockade of longitudinal flow of endolymphatic fluid, and occlusion of ED is not a prerequisite for the development of ELH in patients.

A laboratory study on a capacitive displacement sensor as an implant microphone in totally implant cochlear hearing aid systems

A totally implant cochlear hearing aids system, integrating an implant microphone, interface electronics, a speech processor, a stimulator, and cochlear electrodes, can overcome the uncomfortable, inconvenient, and stigma problems associated with the conventional and semi-implantable hearing aids. This paper presents a laboratory feasibility study on the use of an electret condenser microphone (ECM) displacement sensor, serving as an implant microphone, and combined with a spring coupler to directly sense the umbo acoustic vibration. The umbo vibration characteristics were extracted from literature to determine the coupler and sensor requirements. A laboratory model was built to simulate the vibration source and experimentally study the transmission coefficient. Experimental data demonstrate that by using a 5 N/m stiffness spring, the umbo vibration amplitude as high as 67% can be transmitted to the sensor. Measurement of the sensor system on the temporal bone was also made. The minimum detectable sound pressure level (SPL) at 1 kHz is 41 and 67 dB for laboratory and 38 and 64 dB for temporal bone measurement for 1 and 388 Hz bandwidth, respectively. Better performance was achieved in a higher frequency. Results and analysis of this study can be used as a guideline for the future design of displacement sensors as implant microphones.

Inflammatory pseudotumor of the middle ear masquerading as Bell's palsy

We describe the case of a 28-year-old woman who presented with an acute dense left facial paralysis. Magnetic resonance imaging demonstrated enhancement of the labyrinthine portion of the facial nerve, and Bell's palsy was the presumed initial diagnosis. After 2 months without recovery despite receiving steroid and antiviral therapy, the patient underwent further workup. Computed tomographic scan demonstrated a mass lesion adjacent to the tympanic portion of the facial nerve, and electromyography showed active denervation and prominent fibrillation potentials. Surgical excision of the tumor was performed with decompression and sparing of the facial nerve. Histologically, the tumor proved to be an inflammatory pseudotumor (IPT). At the 3-year follow-up, the patient had an improvement in her facial nerve function, progressing to a House-Brackman grade III. An IPT can masquerade as Bell's palsy with sudden complete facial paralysis. Failure to obtain even slight recovery in Bell's palsy should prompt further workup, including appropriate imaging, to assess for a mass lesion. Confusion of an IPT with a nerve-based tumor on frozen section and imaging could lead to inappropriate resection and cable grafting of the facial nerve. Therefore, the relationship between an IPT and facial nerve paralysis is vital and must be recognized for treatment and to maximize postoperative facial nerve function.

Molecular Changes Associated With the Endolymphatic Hydrops Model

HYPOTHESIS

Hearing loss and cochlear degeneration in the guinea pig model of endolymphatic hydrops (ELH) results, in part, from toxic levels of excitatory amino acids (EAAs) such as glutamate, which in turn leads to changes in the expression of genes linked to intracellular glutamate homeostasis and apoptosis, leading to neuronal cell death.

BACKGROUND

EAAs have been shown to play a role in normal auditory signal transmission in mammalian cochlea, but have also been implicated in neurotoxicity when levels are elevated. Changes in the expression of specific genes involved in the glutamatergic and apoptotic pathway would serve as evidence for excitotoxicity linked to elevated levels of glutamate.

METHODS

Guinea pigs underwent surgical obliteration of the endolymphatic duct, and then a timed harvest of the treated (right) and control (left) cochlea and subsequent quantification of gene expression via real-time quantitative polymerase chain reaction.

RESULTS

Quantitative polymerase chain reaction data show significant upregulation of glutamate aspartate transporter and neuronal nitric oxide synthase mRNA levels 3 weeks postsurgery and Caspase 3 mRNA levels 1 week postsurgery. No significant changes were detected in glutamine synthetase expression levels.

CONCLUSION

Upregulation of genes involved in glutamate homeostasis and the apoptotic pathway in animals treated with endolymphatic duct obstruction (usually associated with secondary ELH) support the hypothesis that EAAs may play a role in the pathophysiology of ELH-related cochlear injury. Inhibitors to these pathways can be useful for the study of new avenues to delay or prevent ELH-related hearing loss.

Evaluation and Management of Endolymphatic Sac and Duct Tumors

The endolymphatic sac tumor is a slow-growing, locally aggressive neoplasm that originates from the epithelium of the endolymphatic sac and duct. Disease progression can lead to profound sensorineural hearing loss, posterior fossa invasion, brainstem compression, drop metastasis, and eventual death. Early diagnosis and surgical attention are the primary objectives in the management of patients who have endolymphatic sac tumor. This article describes the latest rationale and techniques for hearing preservation surgery and a review of the latest developments surrounding this disease entity.

Optimization of ribonucleic acid detection from archival Guinea pig temporal bone specimens

HYPOTHESIS

The choice of ribonucleic acid (RNA) isolation protocol coupled with modifications to RNA extraction and detection procedures may result in a more reliable method to detect gene expression in archived temporal bones.

BACKGROUND

A large number of archival temporal bones exist. Retrospective analysis of these specimens using techniques of RNA extraction will greatly enrich our understanding of the pathophysiology of specific otologic diseases. However, archival human temporal bones are aged and embedded in paraffin or celloidin, rendering isolation and manipulation of nucleic acid in preserved specimens difficult, especially as it pertains to RNA degradation. Despite some reports of moderate success in the recent past, RNA isolation and gene expression using polymerase chain reaction (PCR) analysis continues to be challenging and unreliable. Archival guinea pig temporal bone specimens were used to develop and optimize a protocol for RNA extraction and gene expression analysis using PCR and quantitative PCR methods. The genes amplified comprise housekeeping genes and genes associated with the glutamate pathway.

METHODS

Archival celloidin-embedded guinea pig temporal bones were collected from the senior author's collection of experimental hydropic inner ear specimens. RNA from this tissue was extracted using the protocol described previously in 16animals and using a modified trizol extraction technique in 10 animals. Gene expression analysis was performed on the extracted RNA. Analysis included two housekeeping genes, GAPDH and 18S, as well as three mediators of the glutamate pathway, glutamate aspartate transporter, glutamate synthetase, and inducible nitric oxide synthase.

RESULTS

Compared with the standard extraction protocol, the trizol-based extraction technique showed greater reliability and reproducibility of RNA detection. The housekeeping gene GAPDH or 18S was detected in 7 of 36 attempts with the standard protocol versus 9 of 9 using the modified extraction method (P < 0.001). The gene of interest, glutamate aspartate transporter, was detected in 3 of 26 attempts with the standard protocol versus 12 of 13 attempts using the modified extraction method (P < 0.001). Quantification of messenger RNA levels was then achieved using quantitative PCR methods.

CONCLUSION

Improved reliability for detection of gene expression and demonstration of reproducibility were accomplished by modification of RNA extraction technique and standard reverse transcriptase PCR protocol. In addition, we also showed that gene expression from archival material can be quantified by real-time PCR.