Ultra Long-Term Audiometric Outcomes in the Treatment of Vestibular Schwannoma With the Middle Cranial Fossa Approach.

OBJECTIVE: Define the long-term audiometric outcomes of vestibular schwannomas treated using the middle cranial fossa (MCF) approach. STUDY DESIGN: Retrospective records review. SETTING: University-based tertiary referral center. PATIENTS: Patients undergoing treatment of small vestibular schwannomas using the MCF approach. INTERVENTION(S): MCF exposure and treatment of small vestibular schwannomas. MAIN OUTCOME MEASURE(S): Demographic and audiometric variables were assessed. RESULTS: Thirteen subjects demonstrated audiometric data for review. The average time between surgery and the most recent audiometric testing was 14 years (range 10-18 yr). The mean baseline pure-tone average (PTA) was 36 dB HL and the most recent PTA was 59 dB HL in the operated ear. The mean baseline PTA was 16 dB HL and the most recent PTA was 37 dB HL in the nonoperated ear. The mean change from baseline to most recent follow-up was a threshold elevation of 22 and 19 dB HL in the operated and nonoperated ears, respectively. The mean baseline speech discrimination score (SDS) was 83% and the most recent SDS was 73% in the operated ear. The mean baseline SDS was 98% and the most recent SDS was 94% in the nonoperated ear. The mean changes from baseline to most recent follow-up were 10 and 0% SDS depression in the operated and nonoperated ears, respectively. The rates of changes in PTA and SDS were not statistically different between the operated and nonoperated ears. CONCLUSIONS: Surgically preserved hearing is maintained in the majority of patients more than 10 years following surgery. PTA and SDS changes were similar between the ipsilateral and contralateral ears.

Intraoperative Electrocochleographic Characteristics of Auditory Neuropathy Spectrum Disorder in Cochlear Implant Subjects.

Auditory neuropathy spectrum disorder (ANSD) is characterized by an apparent discrepancy between measures of cochlear and neural function based on auditory brainstem response (ABR) testing. Clinical indicators of ANSD are a present cochlear microphonic (CM) with small or absent wave V. Many identified ANSD patients have speech impairment severe enough that cochlear implantation (CI) is indicated. To better understand the cochleae identified with ANSD that lead to a CI, we performed intraoperative round window electrocochleography (ECochG) to tone bursts in children (n = 167) and adults (n = 163). Magnitudes of the responses to tones of different frequencies were summed to measure the "total response" (ECochG-TR), a metric often dominated by hair cell activity, and auditory nerve activity was estimated visually from the compound action potential (CAP) and auditory nerve neurophonic (ANN) as a ranked "Nerve Score". Subjects identified as ANSD (45 ears in children, 3 in adults) had higher values of ECochG-TR than adult and pediatric subjects also receiving CIs not identified as ANSD. However, nerve scores of the ANSD group were similar to the other cohorts, although dominated by the ANN to low frequencies more than in the non-ANSD groups. To high frequencies, the common morphology of ANSD cases was a large CM and summating potential, and small or absent CAP. Common morphologies in other groups were either only a CM, or a combination of CM and CAP. These results indicate that responses to high frequencies, derived primarily from hair cells, are the main source of the CM used to evaluate ANSD in the clinical setting. However, the clinical tests do not capture the wide range of neural activity seen to low frequency sounds.

Treatment of Lateral Skull Base and Posterior Cranial Fossa Lesions Utilizing the Extended Middle Cranial Fossa Approach.

OBJECTIVE: Define the indications and outcomes for subjects undergoing treatment utilizing the extended middle cranial fossa approach (EMCF). STUDY DESIGN: Retrospective records review. SETTING: University-based tertiary referral center. PATIENTS: Subjects undergoing treatment of posterior cranial fossa (PCF) lesions. INTERVENTION(S): EMCF exposure and treatment of the indicating PCF lesion. MAIN OUTCOME MEASURE(S): Demographic, audiometric, and cranial nerve functioning variables were assessed. RESULTS: Thirty-five subjects who underwent an EMCF exposure were identified over a 12-year period. The most common indication was meningioma (18; 51%) followed by schwannomas (six, 17%), and vascular lesions (five, 14%). Preoperative cranial nerve complaints were common (32, 94%) as were objective cranial nerve abnormalities on physical examination (21; 60%). Preoperative audiometric data from subjects with hearing demonstrated good functioning including pure-tone average (PTA) (21.7 ±â€Š15.6 dB HL) and word understanding scores (95.1 ±â€Š7.4%). Most (34, 97%) subjects had intact facial nerve function. The average length of stay was 11.6 days (median = 9). Cranial neuropathies were common postoperatively with 27 (79%) subjects demonstrating some objective cranial nerve dysfunction, the most common of which was trigeminal nerve hypesthesia (21, 61.7%). Subjects with identifiable pre- and postoperative audiometric data and preoperative hearing demonstrated small declines in the four-tone average (16.2 dB) and word recognition scores (22.4%). Two subjects (6%) had new profound hearing loss postoperatively. CONCLUSIONS: The EMCF approach can provide safe and effective exposure of the anterior PCF.

Reconstruction Outcomes Following Lateral Skull Base Resection.

OBJECTIVE: Compare reconstruction outcomes for various lateral skull base closure techniques. STUDY DESIGN: Retrospective medical records review. SETTING: University-based tertiary referral center. PATIENTS: Patients who underwent resections of tumors involving the lateral skull base requiring reconstruction beyond primary closure. INTERVENTION(S): Reconstructive techniques, from rotational flaps to free tissue transfer. MAIN OUTCOME MEASURE(S): Outcome data including wound complications, cerebrospinal fluid (CSF) leakage, and need for surgical revision were tabulated. RESULTS: Eighty-six patients underwent lateral skull base tumor resection and reconstruction. Procedures were primarily lateral temporal bone resections but also included subtotal temporal bone, total temporal bone, and infratemporal fossa resections. Cutaneous malignancy was the most common resection indication (83%) and the temporalis rotational flap was the most commonly employed reconstructive option (30%). When free tissue transfer techniques were used, the radial forearm, anterolateral thigh, and latissimus dorsi were the most frequent donor sites. Patients with T2 disease were more likely to undergo temporalis flaps, whereas patients with T4 disease were more likely to undergo free flap reconstruction. Major complications were uncommon (∼8%), the most frequent being stroke (∼3%). The postoperative wound complication rate was approximately 45%. The majority involved minor dehiscences and were managed conservatively. Patients with T4 disease were more likely to have wound complications (p < 0.05). Radial forearm free flaps were less likely to have wound complications when compared with other reconstruction techniques (p < 0.05). CONCLUSIONS: Many factors go into planning lateral skull base reconstruction. Free flaps were more often used for T4 disease. Radial forearm free flaps tended to have lower wound complication rates when compared with other techniques.

Middle Cranial Fossa (MCF) Approach Without the Use of Lumbar Drain for the Management of Spontaneous Cerebral Spinal Fluid (CSF) Leaks.

OBJECTIVE: To determine the efficacy and morbidity of repairing spontaneous cerebrospinal fluid (CSF) leaks with the middle cranial fossa (MCF) approach without the use of a lumbar drain (LD), as perioperative use of LD remains controversial. STUDY DESIGN: Retrospective review from 2003 to 2015. SETTING: University of Iowa Hospitals and Clinics and Indiana University Health Center. PATIENTS: Those with a confirmed lateral skull base spontaneous CSF leaks and/or encephaloceles. INTERVENTION: MCF approach for repair of spontaneous CSF leak and/or encephalocele without the use of lumbar drain. Assessment of patient age, sex, body mass index (BMI), and medical comorbidities. MAIN OUTCOME MEASURE: Spontaneous CSF leak patient characteristics (age, sex, BMI, obstructive sleep apnea) were collected. Length of stay (LOS), hospital costs, postoperative complications, CSF leak rate, and need for LD were calculated. RESULTS: Sixty-five operative MCF repairs were performed for spontaneous CSF leaks on 60 patients (five had bilateral CSF leaks). CSF diversion with LD was used in 15 of 60 patients, mostly before 2010. After 2010, only three of 44 patients (6.7%) had postoperative otorrhea requiring LD. The use of LD resulted in significantly longer LOS (3.6 ±â€Š1.6 versus 8.7 ±â€Š2.9 d) and hospital costs ($29,621). There were no postoperative complications in 77% (50 of 65) of cases. Three cases required return to the operating room for complications including frontal subdural hematoma (1), subdural CSF collection (1), and tension pneumocephalus (1). No patients experienced long-term neurologic sequelae or long-term CSF leak recurrence with an average length of follow-up of 19.5 months (range 3-137 mo). The average patient BMI was 37.5 ±â€Š8.6 kg/m. The average age was 57.5 ±â€Š11.4 years and 68% were female. Obstructive sleep apnea was present in 43.3% (26 of 60) of patients. CONCLUSION: The morbidity of the MCF craniotomy for repair of spontaneous CSF leaks is low and the long-term efficacy of repair is high. Universal use of perioperative lumbar drain is not indicated and significantly increases length of stay and hospital costs. Obesity and obstructive sleep apnea are highly associated with spontaneous CSF leaks.

On the Horizon: Cochlear Implant Technology.

Cochlear implantation and cochlear implants (CIs) have a long history filled with innovations that have resulted in the high-performing device's currently available. Several promising technologies have been reviewed in this article, which hold the promise to drive performance even higher. Remote CI programming, totally implanted devices, improved neural health and survival through targeted drug therapy and delivery, intraneural electrode placement, electroacoustical stimulation and hybrid CIs, and methods to enhance the neural-prosthesis interface are evolving areas of innovation reviewed in this article.

Cost of cholesteatoma care at a tertiary medical center.

OBJECTIVE: Estimate the available direct cost of cholesteatoma care in a university practice. STUDY DESIGN: Retrospective review of both physician and hospital financial data during a recent 3-year period. SETTING: University-based tertiary referral medical system. PATIENTS: Adults (≥ 18 yr old) with cholesteatoma. INTERVENTION(S): Financial information associated with both physician and hospital encounters were analyzed in a deidentified manner. MAIN OUTCOME MEASURE(S): Frequency and type of encounter, charges, collections, and payers were tabulated. RESULTS: Approximately 949 physician encounters (817 clinic, 130 surgical, and 2 inpatient) among 344 patients resulted in greater than $700, 000 in charges and greater than $211,000 in receipts (≈ 30% rate of collection). The average physician charge per patient per year was approximately $1,600. About 259 hospital encounters among 171 patients resulted in greater than $1.8 million in charges and greater than $520,000 in receipts (≈ 28% collection rate). The average hospital charge per patient per year was ∼$10,000. For physician encounters, managed care (37%) and Medicare (25%) were the most common payers, whereas 17% were uninsured. For hospital encounters, managed care (28%) and Medicare (14%) were the most common payers, whereas 24% were uninsured. CONCLUSION: The direct cost of care for patients with cholesteatoma is significant. The current treatment paradigm for this chronic disorder results in repeated health care system access and associated direct (and unmeasured indirect) expenses. Future treatment paradigms should be designed to improve disease-specific quality of life while mitigating this financial impact.

A gerbil model of sloping sensorineural hearing loss.

OBJECTIVE: The goal of the overall project is to develop knowledge about cochlear physiology during cochlear implantation and develop procedures for assessing its status during hearing preservation surgery. As a step toward this goal, for this study, we established an animal model of sloping high frequency sensorineural hearing loss that mimics the hearing condition of candidates for combined electric-acoustic stimulation. METHODS: Mongolian gerbils were exposed to band-pass noise using various cutoff frequencies, intensities, exposure times, and survival times. Hearing loss was assessed in far-field recording using preexposure and postexposure auditory brainstem responses (ABRs), and in acute, near-field recordings of the cochlear microphonic and compound action potential from an electrode on the round window. Anatomic loss of hair cells was assessed from dissections. RESULTS: Postexposure ABRs and near-field recordings from the round window revealed sensorineural hearing loss that varied with the overall noise exposure. Loss of hair cells ranged from relatively sparse to large areas of complete absence depending on the noise exposure. Cases with high intensity (120 dB SPL) and long exposure times (3 h) showed sloping patterns of hearing loss with profound high-frequency loss and mild-to-moderate low-frequency loss. These cases showed complete loss of hair cells in the basal cochlea and preserved hair cells in the apical cochlea. The frequencies comprising the slope in the ABRs and the location of the transition zone between preserved and lost hair cells varied according to the cutoff frequency used. CONCLUSION: We were able to reliably induce sensorineural hearing loss and loss of hair cells in the gerbil that is comparable to candidates for hearing preservation surgery. This model can be used to evaluate the effects of electrode introduction in a system with a hearing condition similar to that in cases of hearing preservation operations.

Imaging characteristics of children with auditory neuropathy spectrum disorder.

OBJECTIVE: To identify and define the imaging characteristics of children with auditory neuropathy spectrum disorder (ANSD). DESIGN: Retrospective medical records review and analysis of both temporal bone computed tomographic (CT) and magnetic resonance images (MRI) in children with a diagnosis of ANSD. SETTING: Tertiary referral center. PATIENTS: One hundred eighteen children with the electrophysiologic characteristics of ANSD with available imaging studies for review. INTERVENTIONS: Two neuroradiologists and a neurotologist reviewed each study, and consensus descriptions were established. MAIN OUTCOME MEASURES: The type and number of imaging findings were tabulated. RESULTS: Sixty-eight (64%) MRIs revealed at least 1 imaging abnormality, whereas selective use of CT identified 23 (55%) with anomalies. The most prevalent MRI findings included cochlear nerve deficiency (n = 51; 28% of 183 nerves), brain abnormalities (n = 42; 40% of 106 brains), and prominent temporal horns (n = 33, 16% of 212 temporal lobes). The most prevalent CT finding from selective use of CT was cochlear dysplasia (n = 13; 31%). CONCLUSION: Magnetic resonance imaging will identify many abnormalities in children with ANSD that are not readily discernable on CT. Specifically, both developmental and acquired abnormalities of the brain, posterior cranial fossa, and cochlear nerves are not uncommonly seen in this patient population. Inner ear anomalies are well delineated using either imaging modality. Because many of the central nervous system findings identified in this study using MRI can alter the treatment and prognosis for these children, we think that MRI should be the initial imaging study of choice for children with ANSD.

In silico analysis of 2085 clones from a normalized rat vestibular periphery 3' cDNA library.

The inserts from 2400 cDNA clones isolated from a normalized Rattus norvegicus vestibular periphery cDNA library were sequenced and characterized. The Wackym-Soares vestibular 3' cDNA library was constructed from the saccular and utricular maculae, the ampullae of all three semicircular canals and Scarpa's ganglia containing the somata of the primary afferent neurons, microdissected from 104 male and female rats. The inserts from 2400 randomly selected clones were sequenced from the 5' end. Each sequence was analyzed using the BLAST algorithm compared to the Genbank nonredundant, rat genome, mouse genome and human genome databases to search for high homology alignments. Of the initial 2400 clones, 315 (13%) were found to be of poor quality and did not yield useful information, and therefore were eliminated from the analysis. Of the remaining 2085 sequences, 918 (44%) were found to represent 758 unique genes having useful annotations that were identified in databases within the public domain or in the published literature; these sequences were designated as known characterized sequences. 1141 sequences (55%) aligned with 1011 unique sequences had no useful annotations and were designated as known but uncharacterized sequences. Of the remaining 26 sequences (1%), 24 aligned with rat genomic sequences, but none matched previously described rat expressed sequence tags or mRNAs. No significant alignment to the rat or human genomic sequences could be found for the remaining 2 sequences. Of the 2085 sequences analyzed, 86% were singletons. The known, characterized sequences were analyzed with the FatiGO online data-mining tool (http://fatigo.bioinfo.cnio.es/) to identify level 5 biological process gene ontology (GO) terms for each alignment and to group alignments with similar or identical GO terms. Numerous genes were identified that have not been previously shown to be expressed in the vestibular system. Further characterization of the novel cDNA sequences may lead to the identification of genes with vestibular-specific functions. Continued analysis of the rat vestibular periphery transcriptome should provide new insights into vestibular function and generate new hypotheses. Physiological studies are necessary to further elucidate the roles of the identified genes and novel sequences in vestibular function.

Assessment of differential gene expression in vestibular epithelial cell types using microarray analysis.

Current global gene expression techniques allow the evaluation and comparison of the expression of thousands of genes in a single experiment, providing a tremendous amount of information. However, the data generated by these techniques are context-dependent, and minor differences in the individual biological samples, methodologies for RNA acquisition, amplification, hybridization protocol and gene chip preparation, as well as hardware and analysis software, lead to poor correlation between the results. One of the significant difficulties presently faced is the standardization of the protocols for the meaningful comparison of results. In the inner ear, the acquisition of RNA from individual cell populations remains a challenge due to the high density of the different cell types and the paucity of tissue. Consequently, laser capture microdissection was used to selectively collect individual cells and regions of cells from cristae ampullares followed by extraction of total RNA and amplification to amounts sufficient for high throughput analysis. To demonstrate hair cell-specific gene expression, myosin VIIA, calmodulin and alpha9 nicotinic acetylcholine receptor subunit mRNAs were amplified using reverse transcription-polymerase chain reaction (RT-PCR). To demonstrate supporting cell-specific gene expression, cyclin-dependent kinase inhibitor p27kip1 mRNA was amplified using RT-PCR. Subsequent experiments with alpha9 RT-PCR demonstrated phenotypic differences between type I and type II hair cells, with expression only in type II hair cells. Using the laser capture microdissection technique, microarray expression profiling demonstrated 408 genes with more than a five-fold difference in expression between the hair cells and supporting cells, of these 175 were well annotated. There were 97 annotated genes with greater than a five-fold expression difference in the hair cells relative to the supporting cells, and 78 annotated genes with greater than a five-fold expression difference in the supporting cells relative to the hair cells.