Publications by authors named "Marlan R Hansen"

135 Publications

Photograftable Zwitterionic Coatings Prevent and Adhesion to PDMS Surfaces.

ACS Appl Bio Mater 2021 Feb 22;4(2):1283-1293. Epub 2021 Jan 22.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa 52242, United States.

Due to its attractive mechanical properties and biocompatibility, poly(dimethyl)siloxane (PDMS) is widely used in the fabrication of biomedical materials. On the other hand, PDMS is also prone to adsorption of both proteins and bacteria, making PDMS implants susceptible to infection. Herein, we examine the use of durably cross-linked zwitterionic coatings for PDMS surfaces to mitigate bacterial adhesion. Using a single-step photografting technique, poly(sulfobetaine methacrylate) (pSBMA) and poly(carboxybetaine methacrylate) (pCBMA) thin films were covalently attached to PDMS substrates. The abilities of these coatings to resist the adhesion of and were tested under both wet and droplet conditions, as well as in subcutaneous and transcutaneous implantation models using Sprague-Dawley rats. Zwitterionic thin films effectively reduced bacterial adhesion in both and conditions. This was particularly true for pCBMA-coated materials, which exhibited significant reduction in bacterial adhesion and growth with respect to and for all conditions as well as the ability to resist bacterial growth on PDMS implants. The results of this study suggest that a simple and durable photografting process can be used to produce polymer thin films capable of preventing infection of implantable medical devices.
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http://dx.doi.org/10.1021/acsabm.0c01147DOI Listing
February 2021

Timing of Acoustic Hearing Changes After Cochlear Implantation.

Laryngoscope 2021 Dec 9. Epub 2021 Dec 9.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa, U.S.A.

Objectives/hypothesis: To determine the timing of acoustic hearing changes among hearing preservation Cochlear implant (CI) recipients. To determine differences in hearing outcomes based on device type and demographic factors. To determine if there is a relationship between the extent of early hearing loss after CI and the subsequent rate of continued hearing loss.

Study Design: Prospective, single subject study.

Methods: Two hundred and eleven subjects who received a hearing preservation CI were included in the study-80 Nucleus Hybrid L24 (Cochlear), 47 422/522 (Cochlear), 24 S8 (Cochlear), 14 S12 (Cochlear), 6 SRW (Cochlear), 21 SLIM J (Advanced Bionics), and 19 Flex (Med-EL). Of these, 127 were included in the subsequent analyses. Audiometric thresholds (low frequency pure-tone-averages) were collected and compared pre and postoperatively.

Results: Long-term hearing preservation rates were 65% (52/80) for L24, 83% (20/24) for S8, 79% (11/14) for S12, 83% (5/6) for SRW, 54% (25/47) for 422/522, 91% (21/23) for SLIM J, and 84% (16/19) for Flex. Hearing loss was not related to device type (P = .9105) or gender (P = .2169). Older subjects (age ≥65) had worse hearing outcomes than younger subjects after initial device activation (age <65, P = .0262). There was no significant difference in rate of hearing loss over time between older and younger patients (P = .0938). Initial postoperative hearing loss was not associated with the rate of long-term hearing loss.

Conclusions: Long-term low frequency hearing preservation is possible for CI recipients and is not associated with gender or device type. Rate of hearing loss over time is not dependent on patient age. Early hearing loss after CI does not predict the rate of long-term hearing loss.

Level Of Evidence: 3 Laryngoscope, 2021.
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http://dx.doi.org/10.1002/lary.29984DOI Listing
December 2021

Access and Polarization Electrode Impedance Changes in Electric-Acoustic Stimulation Cochlear Implant Users with Delayed Loss of Acoustic Hearing.

J Assoc Res Otolaryngol 2022 Feb 22;23(1):95-118. Epub 2021 Oct 22.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA.

Acoustic hearing can be preserved after cochlear implant (CI) surgery, allowing for combined electric-acoustic stimulation (EAS) and superior speech understanding compared to electric-only hearing. Among patients who initially retain useful acoustic hearing, 30-40 % experience a delayed hearing loss that occurs 3 or more months after CI activation. Increases in electrode impedances have been associated with delayed loss of residual acoustic hearing, suggesting a possible role of intracochlear inflammation/fibrosis as reported by Scheperle et al. (Hear Res 350:45-57, 2017) and Shaul et al. (Otol Neurotol 40(5):e518-e526, 2019). These studies measured only total impedance. Total impedance consists of a composite of access resistance, which reflects resistance of the intracochlear environment, and polarization impedance, which reflects resistive and capacitive properties of the electrode-electrolyte interface as described by Dymond (IEEE Trans Biomed Eng 23(4):274-280, 1976) and Tykocinski et al. (Otol Neurotol 26(5):948-956, 2005). To explore the role of access and polarization impedance components in loss of residual acoustic hearing, these measures were collected from Nucleus EAS CI users with stable acoustic hearing and subsequent precipitous loss of hearing. For the hearing loss group, total impedance and access resistance increased over time while polarization impedance remained stable. For the stable hearing group, total impedance and access resistance were stable while polarization impedance declined. Increased access resistance rather than polarization impedance appears to drive the increase in total impedances seen with loss of hearing. Moreover, access resistance has been correlated with intracochlear fibrosis/inflammation in animal studies as observed by Xu et al. (Hear Res 105(1-2):1-29, 1997) and Tykocinski et al. (Hear Res 159(1-2):53-68, 2001). These findings thus support intracochlear inflammation as one contributor to loss of acoustic hearing in our EAS CI population.
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http://dx.doi.org/10.1007/s10162-021-00809-zDOI Listing
February 2022

Development and Characterization of an Electrocochleography-Guided Robotics-Assisted Cochlear Implant Array Insertion System.

Otolaryngol Head Neck Surg 2021 Oct 5:1945998211049210. Epub 2021 Oct 5.

iotaMotion, Inc, Iowa City, Iowa, USA.

Objective: Electrocochleography (ECochG) is increasingly being used during cochlear implant (CI) surgery to detect and mitigate insertion-related intracochlear trauma, where a drop in ECochG signal has been shown to correlate with a decline in hearing outcomes. In this study, an ECochG-guided robotics-assisted CI insertion system was developed and characterized that provides controlled and consistent electrode array insertions while monitoring and adapting to real-time ECochG signals.

Study Design: Experimental research.

Setting: A research laboratory and animal testing facility.

Methods: A proof-of-concept benchtop study evaluated the ability of the system to detect simulated ECochG signal changes and robotically adapt the insertion. Additionally, the ECochG-guided insertion system was evaluated in a pilot in vivo sheep study to characterize the signal-to-noise ratio and amplitude of ECochG recordings during robotics-assisted insertions. The system comprises an electrode array insertion drive unit, an extracochlear recording electrode module, and a control console that interfaces with both components and the surgeon.

Results: The system exhibited a microvolt signal resolution and a response time <100 milliseconds after signal change detection, indicating that the system can detect changes and respond faster than a human. Additionally, animal results demonstrated that the system was capable of recording ECochG signals with a high signal-to-noise ratio and sufficient amplitude.

Conclusion: An ECochG-guided robotics-assisted CI insertion system can detect real-time drops in ECochG signals during electrode array insertions and immediately alter the insertion motion. The system may provide a surgeon the means to monitor and reduce CI insertion-related trauma beyond manual insertion techniques for improved CI hearing outcomes.
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http://dx.doi.org/10.1177/01945998211049210DOI Listing
October 2021

Audiology findings in patients with teprotumumab associated otologic symptoms.

Am J Ophthalmol Case Rep 2021 Dec 16;24:101202. Epub 2021 Sep 16.

Department of Ophthalmology and Visual Sciences, University of Iowa Hospitals and Clinics, Iowa City, USA.

Purpose: To report a case series of subjective and objective hearing function changes associated with teprotumumab treatment for thyroid eye disease.

Observations: A 74-year-old female with a history of Graves' disease with thyroid eye disease was treated with teprotumumab. She had a history of bilateral tinnitus and noticed a subjective improvement in her tinnitus after the second infusion. Audiology testing obtained before, during, and after completion of infusions showed symmetric and rapidly progressive worsening of the patient's sensorineural hearing loss. In contrast, a 42-year-old male with a history of Grave's disease endorsed worsening intermittent tinnitus and low-pitched hearing loss after initiation of teprotumumab. Audiology testing before, during, and after completion of infusions showed stable and normal hearing function bilaterally.

Conclusion And Importance: This case series highlights the importance of objective testing in patients prior to and after teprotumumab initiation as subjective hearing changes may not accurately reflect objective hearing function. In addition, this report suggests that teprotumumab may play a role in potentiating sensorineural hearing loss.
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http://dx.doi.org/10.1016/j.ajoc.2021.101202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8452766PMC
December 2021

Bilateral hearing aid use is feasible in patients with well-preserved hearing who struggle to acclimate to combined electro-acoustic (hybrid) stimulation.

Int J Audiol 2021 Sep 6:1-5. Epub 2021 Sep 6.

Departments of Otolaryngology - Head & Neck Surgery, University of Iowa, Iowa City, IA, USA.

Objective: This report presents a case study of a patient who resumed bilateral hearing aid use after nearly four years of limited progress and subjective dissatisfaction with a hybrid cochlear implant device.

Design: Case study.

Study Sample: One patient.

Results: The patient's post-operative objective and subjective abilities with bilateral hearing aids were better than with a hybrid cochlear implant and contralateral hearing aid.

Conclusions: Although the benefits of combined acoustic and electric hearing have been well-documented, this report presents a solution for those with well-preserved hearing and poor hybrid cochlear implant performance: returning to bilateral hearing aid use.
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http://dx.doi.org/10.1080/14992027.2021.1971312DOI Listing
September 2021

NeuriteNet: A convolutional neural network for assessing morphological parameters of neurite growth.

J Neurosci Methods 2021 11 2;363:109349. Epub 2021 Sep 2.

Dept of Neuroscience, University of Texas-Austin, 100 E. 24th St., Austin, TX 78712, USA. Electronic address:

Background: During development or regeneration, neurons extend processes (i.e., neurites) via mechanisms that can be readily analyzed in culture. However, defining the impact of a drug or genetic manipulation on such mechanisms can be challenging due to the complex arborization and heterogeneous patterns of neurite growth in vitro. New Method: NeuriteNet is a Convolutional Neural Network (CNN) sorting model that uses a novel adaptation of the XRAI saliency map overlay, which is a region-based attribution method. NeuriteNet compares neuronal populations based on differences in neurite growth patterns, sorts them into respective groups, and overlays a saliency map indicating which areas differentiated the image for the sorting procedure.

Results: In this study, we demonstrate that NeuriteNet effectively sorts images corresponding to dissociated neurons into control and treatment groups according to known morphological differences. Furthermore, the saliency map overlay highlights the distinguishing features of the neuron when sorting the images into treatment groups. NeuriteNet also identifies novel morphological differences in neurons cultured from control and genetically modified mouse strains. Comparison with Existing Methods: Unlike other neurite analysis platforms, NeuriteNet does not require manual manipulations, such as segmentation of neurites prior to analysis, and is more accurate than experienced researchers for categorizing neurons according to their pattern of neurite growth.

Conclusions: NeuriteNet can be used to effectively screen for morphological differences in a heterogeneous group of neurons and to provide feedback on the key features distinguishing those groups via the saliency map overlay.
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http://dx.doi.org/10.1016/j.jneumeth.2021.109349DOI Listing
November 2021

Advances in hearing preservation in cochlear implant surgery.

Curr Opin Otolaryngol Head Neck Surg 2021 Oct;29(5):385-390

Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.

Purpose Of Review: Advancements in cochlear implant surgical approaches and electrode designs have enabled preservation of residual acoustic hearing. Preservation of low-frequency hearing allows cochlear implant users to benefit from electroacoustic stimulation, which improves performance in complex listening situations, such as music appreciation and speech understanding in noise. Despite the relative high rates of success of hearing preservation, postoperative acoustic hearing outcomes remain unpredictable.

Recent Findings: Thin, flexible, lateral wall arrays are preferred for hearing preservation. Both shortened and thin, lateral wall arrays have shown success with hearing preservation and the optimal implant choice is an issue of ongoing investigation. Electrocochleography can monitor cochlear function during and after insertion of the electrode array. The pathophysiology of hearing loss acutely after cochlear implant may differ from that involved in delayed hearing loss following cochlear implant. Emerging innovations may reduce cochlear trauma and improve hearing preservation.

Summary: Hearing preservation is possible using soft surgical techniques and electrode arrays designed to minimize cochlear trauma; however, a subset of patients suffer from partial to total loss of acoustic hearing months to years following surgery despite evidence of residual apical hair cell function. Early investigations in robotic-assisted insertion and dexamethasone-eluting implants show promise.
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http://dx.doi.org/10.1097/MOO.0000000000000742DOI Listing
October 2021

Antifouling and Mechanical Properties of Photografted Zwitterionic Hydrogel Thin-Film Coatings Depend on the Cross-Link Density.

ACS Biomater Sci Eng 2021 09 4;7(9):4494-4502. Epub 2021 Aug 4.

Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, United States.

Zwitterionic polymer networks have shown promise in reducing the short- and long-term inflammatory foreign body response to implanted biomaterials by combining the antifouling properties of zwitterionic polymers with the mechanical stability provided by cross-linking. Cross-link density directly modulates mechanical properties (i.e., swelling behavior, resistance to stress and strain, and lubricity) but theoretically could reduce desirable biological properties (i.e., antifouling) of zwitterionic materials. This work examined the effect of varying poly(ethylene glycol) dimethacrylate cross-linker concentration on protein adsorption, cell adhesion, equilibrium swelling, compressive modulus, and lubricity of zwitterionic thin films. Furthermore, this work aimed to determine the appropriate balance among each of these mechanical and biologic properties to produce thin films that are strong, durable, and lubricious, yet also able to resist biofouling. The results demonstrated nearly a 20-fold reduction in fibrinogen adsorption on zwitterionic thin films photografted on polydimethylsiloxane (PDMS) across a wide range of cross-link densities. Interestingly, either at high or low cross-link densities, increased levels of protein adsorption were observed. In addition to fibrinogen, macrophage and fibroblast cell adhesion was reduced significantly on zwitterionic thin films, with a large range of cross-link densities, resulting in low cell counts. The macrophage count was reduced by 30-fold, while the fibroblast count was reduced nearly 10-fold on grafted zwitterionic films relative to uncoated films. Increasing degrees of cell adhesion were noted as the cross-linker concentration exceeded 50%. As expected, increased cross-link density resulted in a reduced swelling but greater compressive modulus. Notably, the coefficient of friction was dramatically reduced for zwitterionic thin films compared to uncoated PDMS across a broad range of cross-link densities, an attractive property for insertional implants. This work identified a broad range of cross-link densities that provide desirable antifouling effects while also maintaining the mechanical functionality of the thin films.
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http://dx.doi.org/10.1021/acsbiomaterials.1c00852DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8441969PMC
September 2021

Interaction of micropatterned topographical and biochemical cues to direct neurite growth from spiral ganglion neurons.

Hear Res 2021 09 21;409:108315. Epub 2021 Jul 21.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, United States; Department of Neurosurgery, University of Iowa, Iowa City, IA 52242, United States. Electronic address:

Functional outcomes with neural prosthetic devices, such as cochlear implants, are limited in part due to physical separation between the stimulating elements and the neurons they stimulate. One strategy to close this gap aims to precisely guide neurite regeneration to position the neurites in closer proximity to electrode arrays. Here, we explore the ability of micropatterned biochemical and topographic guidance cues, singly and in combination, to direct the growth of spiral ganglion neuron (SGN) neurites, the neurons targeted by cochlear implants. Photopolymerization of methacrylate monomers was used to form unidirectional topographical features of ridges and grooves in addition to multidirectional patterns with 90 angle turns. Microcontact printing was also used to create similar uni- and multi-directional patterns of peptides on polymer surfaces. Biochemical cues included peptides that facilitate (laminin, LN) or repel (EphA4-Fc) neurite growth. On flat surfaces, SGN neurites preferentially grew on LN-coated stripes and avoided EphA4-Fc-coated stripes. LN or EphA4-Fc was selectively adsorbed onto the ridges or grooves to test the neurite response to a combination of topographical and biochemical cues. Coating the ridges with EphA4-Fc and grooves with LN lead to enhanced SGN alignment to topographical patterns. Conversely, EphA4-Fc coating on the grooves or LN coating on the ridges tended to disrupt alignment to topographical patterns. SGN neurites respond to combinations of topographical and biochemical cues and surface patterning that leverages both cues enhance guided neurite growth.
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http://dx.doi.org/10.1016/j.heares.2021.108315DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8419132PMC
September 2021

Zwitterionic Photografted Coatings of Cochlear Implant Biomaterials Reduce Friction and Insertion Forces.

Otol Neurotol 2021 Dec;42(10):1476-1483

Department of Otolaryngology-Head and Neck Surgery.

Hypothesis: Application of photografted zwitterionic coatings to cochlear implant (CI) biomaterials will reduce friction and insertion forces.

Background: Strategies to minimize intracochlear trauma during implantation of an electrode array are critical to optimize outcomes including preservation of residual hearing. To this end, advances in thin-film zwitterionic hydrogel coatings on relevant biomaterials may show promise, in addition to the potential of these materials for decreasing the intracochlear foreign body response.

Methods: Using a recently designed one-step process, thin-film coatings derived from zwitterionic sulfobetaine methacrylate (SBMA) were photopolymerized and photografted to the surface of polydimethylsiloxane (PDMS, silastic) samples and also to CI arrays from two manufacturers. Fluorescein staining and scanning electron microscopy with energy-dispersive X-ray spectroscopy verified and characterized the coatings. Tribometry was used to measure the coefficient of friction between uncoated and coated PDMS and synthetic and biological tissues. Force transducer measurements were obtained during insertion of uncoated (n = 9) and coated (n = 9) CI electrode arrays into human cadaveric cochleae.

Results: SBMA thin-film coating of PDMS resulted in >90% reduction in frictional coefficients with steel, ceramic, and dermal tissue from guinea pigs (p < 0.0001). We employed a novel method for applying covalently bonded, durable, and uniform coating in geographically selective areas at the electrode array portion of the implant. Image analysis confirmed uniform coating of PDMS systems and the CI electrode arrays with SBMA polymer films. During insertion of electrode arrays into human cadaveric cochleae, SBMA coatings reduced maximum force by ∼40% during insertion (p < 0.001), as well as decreasing force variability and the overall work of insertion.

Conclusion: Thin-film SBMA photografted coatings on PDMS and electrode arrays significantly reduce frictional coefficients and insertional forces in cadaveric cochleae. These encouraging findings support that thin-film zwitterionic coating of CI electrode arrays may potentially reduce insertional trauma and thereby promote improved hearing and other long-term outcomes.
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http://dx.doi.org/10.1097/MAO.0000000000003288DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8595522PMC
December 2021

The biological underpinnings of radiation therapy for vestibular schwannomas: Review of the literature.

Laryngoscope Investig Otolaryngol 2021 Jun 30;6(3):458-468. Epub 2021 Mar 30.

Department of Otolaryngology-Head & Neck Surgery University of Iowa Hospitals & Clinics Iowa City Iowa USA.

Objective: Radiation therapy is a mainstay in the treatment of numerous neoplasms. Numerous publications have reported good clinical outcomes for primary radiation therapy for Vestibular Schwannomas (VS). However, there are relatively few pathologic specimens of VSs available to evaluate post-radiation, which has led to a relative dearth in research on the cellular mechanisms underlying the effects of radiation therapy on VSs.

Methods: Here we review the latest literature on the complex biological effects of radiation therapy on these benign tumors-including resistance to oxidative stress, mechanisms of DNA damage repair, alterations in normal growth factor pathways, changes in surrounding vasculature, and alterations in immune responses following radiation.

Results: Although VSs are highly radioresistant, radiotherapy is often successful in arresting their growth.

Conclusion: By better understanding the mechanisms underlying these effects, we could potentially harness such mechanisms in the future to potentiate the clinical effects of radiotherapy on VSs.

Level Of Evidence: N/A.
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http://dx.doi.org/10.1002/lio2.553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8223465PMC
June 2021

Genetic Causes of Hearing Loss in a Large Cohort of Cochlear Implant Recipients.

Otolaryngol Head Neck Surg 2021 Jun 22:1945998211021308. Epub 2021 Jun 22.

Department of Otolaryngology-Head & Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.

Understanding genetic causes of hearing loss can determine the pattern and course of a patient's hearing loss and may also predict outcomes after cochlear implantation. Our goal in this study was to evaluate genetic causes of hearing loss in a large cohort of adults and children with cochlear implants. We performed comprehensive genetic testing on all patients undergoing cochlear implantation. Of the 459 patients included in the study, 128 (28%) had positive genetic testing. In total, 44 genes were identified as causative. The top 5 genes implicated were (20, 16%), (13, 10%), (10, 8%), (9, 7%), and (7, 5%). Pediatric patients had a higher diagnostic rate. This study lays the groundwork for future studies evaluating the relationship between genetic variation and cochlear implant performance.
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http://dx.doi.org/10.1177/01945998211021308DOI Listing
June 2021

Residual Hair Cell Responses in Electric-Acoustic Stimulation Cochlear Implant Users with Complete Loss of Acoustic Hearing After Implantation.

J Assoc Res Otolaryngol 2021 04 4;22(2):161-176. Epub 2021 Feb 4.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA.

Changes in cochlear implant (CI) design and surgical techniques have enabled the preservation of residual acoustic hearing in the implanted ear. While most Nucleus Hybrid L24 CI users retain significant acoustic hearing years after surgery, 6-17 % experience a complete loss of acoustic hearing (Roland et al. Laryngoscope. 126(1):175-81. (2016), Laryngoscope. 128(8):1939-1945 (2018); Scheperle et al. Hear Res. 350:45-57 (2017)). Electrocochleography (ECoG) enables non-invasive monitoring of peripheral auditory function and may provide insight into the pathophysiology of hearing loss. The ECoG response is evoked using an acoustic stimulus and includes contributions from the hair cells (cochlear microphonic-CM) as well as the auditory nerve (auditory nerve neurophonic-ANN). Seven Hybrid L24 CI users with complete loss of residual hearing months after surgery underwent ECoG measures before and after loss of hearing. While significant reductions in CMs were evident after hearing loss, all participants had measurable CMs despite having no measurable acoustic hearing. None retained measurable ANNs. Given histological data suggesting stable hair cell and neural counts after hearing loss (e.g., Quesnel et al. Hear Res. 333:225-234. (2016)), the loss of ECoG and audiometric hearing may reflect reduced synaptic input. This is consistent with the theory that residual CM responses coupled with little to no ANN responses reflect a "disconnect" between hair cells and auditory nerve fibers (Fontenot et al. Ear Hear. 40(3):577-591. 2019). This "disconnection" may prevent proper encoding of auditory stimulation at higher auditory pathways, leading to a lack of audiometric responses, even in the presence of viable cochlear hair cells.
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http://dx.doi.org/10.1007/s10162-021-00785-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7943691PMC
April 2021

Electrodiagnostic testing in acute facial palsy: Outcomes and comparison of methods.

Laryngoscope Investig Otolaryngol 2020 Oct 10;5(5):928-935. Epub 2020 Sep 10.

Department of Otolaryngology-Head and Neck Surgery Johns Hopkins University School of Medicine Baltimore Maryland USA.

Objective: To study the relationship between various electrodiagnostic modalities in acute facial palsy.

Setting: Academic tertiary care center.

Patients: One-hundred and six patients who presented with traumatic or non-traumatic acute facial paralysis (House-Brackmann, HB, grade 6/6) between 2008 and 2017 and underwent acute electrodiagnostic testing.

Intervention: Electroneurography (ENoG) using nasolabial fold (NLF) or nasalis muscle (NM) methods, and volitional electromyography (EMG) in all patients.

Main Outcome Measures: Percent degeneration of ipsilateral facial nerve compound muscle action potentials (CMAP) on NLF- and NM-ENoG, presence or absence of muscle unit potentials (MUPs) on EMG.

Results: Extent of facial nerve degeneration measured by NLF- and NM-ENoG were highly correlated ( = 0.85,  < .01) on each test and on serial testing. NLF- and NM-ENoG concordantly diagnosed ≥90% degeneration in 44 patients (80%), of whom 32 patients were diagnosed to have 100% degeneration by both methodologies. Absence of MUPs on EMG was 63% sensitive and 92% specific for ≥90% degeneration on ENoG, with a positive predictive value of 90%. For patients with Bell's palsy, percent degeneration on ENoG was also correlated to HB score at 1 year. Surgical decompression resulted in mean HB scores of 2.2 and 3.0 for patients with Bell's palsy and trauma, respectively.

Conclusions: NM-ENoG may be a valid and comparable method to NLF-ENoG for predicting the recovery of facial nerve function in acute paralysis. Absence of MUPs on EMG is a specific measure of severe degeneration and highly predictive of candidacy for surgical decompression.

Level Of Evidence: Level 3.
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http://dx.doi.org/10.1002/lio2.458DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7585247PMC
October 2020

Unilateral Cochlear Implants for Severe, Profound, or Moderate Sloping to Profound Bilateral Sensorineural Hearing Loss: A Systematic Review and Consensus Statements.

JAMA Otolaryngol Head Neck Surg 2020 10;146(10):942-953

Department of Otorhinolaryngology and Auditory and Voice Surgery, University of Tokyo Hospital, Tokyo, Japan.

Importance: Cochlear implants are a treatment option for individuals with severe, profound, or moderate sloping to profound bilateral sensorineural hearing loss (SNHL) who receive little or no benefit from hearing aids; however, cochlear implantation in adults is still not routine.

Objective: To develop consensus statements regarding the use of unilateral cochlear implants in adults with severe, profound, or moderate sloping to profound bilateral SNHL.

Design, Setting, And Participants: This study was a modified Delphi consensus process that was informed by a systematic review of the literature and clinical expertise. Searches were conducted in the following databases: (1) MEDLINE In-Process & Other Non-Indexed Citations and Ovid MEDLINE, (2) Embase, and (3) the Cochrane Library. Consensus statements on cochlear implantation were developed using the evidence identified. This consensus process was relevant for the use of unilateral cochlear implantation in adults with severe, profound, or moderate sloping to profound bilateral SNHL. The literature searches were conducted on July 18, 2018, and the 3-step Delphi consensus method took place over the subsequent 9-month period up to March 30, 2019.

Main Outcomes And Measures: A Delphi consensus panel of 30 international specialists voted on consensus statements about cochlear implantation, informed by an SR of the literature and clinical expertise. This vote resulted in 20 evidence-based consensus statements that are in line with clinical experience. A modified 3-step Delphi consensus method was used to vote on and refine the consensus statements. This method consisted of 2 rounds of email questionnaires and a face-to-face meeting of panel members at the final round. All consensus statements were reviewed, discussed, and finalized at the face-to-face meeting.

Results: In total, 6492 articles were identified in the searches of the electronic databases. After removal of duplicate articles, 74 articles fulfilled all of the inclusion criteria and were used to create the 20 evidence-based consensus statements. These 20 consensus statements on the use of unilateral cochlear implantation in adults with SNHL were relevant to the following 7 key areas of interest: level of awareness of cochlear implantation (1 consensus statement); best practice clinical pathway from diagnosis to surgery (3 consensus statements); best practice guidelines for surgery (2 consensus statements); clinical effectiveness of cochlear implantation (4 consensus statements); factors associated with postimplantation outcomes (4 consensus statements); association between hearing loss and depression, cognition, and dementia (5 consensus statements); and cost implications of cochlear implantation (1 consensus statement).

Conclusions And Relevance: These consensus statements represent the first step toward the development of international guidelines on best practices for cochlear implantation in adults with SNHL. Further research to develop consensus statements for unilateral cochlear implantation in children, bilateral cochlear implantation, combined electric-acoustic stimulation, unilateral cochlear implantation for single-sided deafness, and asymmetrical hearing loss in children and adults may be beneficial for optimizing hearing and quality of life for these patients.
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http://dx.doi.org/10.1001/jamaoto.2020.0998DOI Listing
October 2020

Transmastoid and Transtemporal Drainage of Petrous Apicitis with Otitis Media.

Ann Otol Rhinol Laryngol 2021 Mar 8;130(3):314-318. Epub 2020 Aug 8.

Department of Otolaryngology-Head and Neck Surgery, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.

Background: Petrous apicitis (PA) is a serious infection involving the apical portion of the petrous temporal bone. The classic triad of purulent otorrhea, ipsilateral abducens nerve palsy and retroorbital pain is rarely seen due to early detection and widespread use of antibiotics. Medical management is the primary treatment modality with surgery reserved for cases of recalcitrant petrous apex abscess.

Methods And Results: We presented a case of PA with previously untreated otitis media. After multidisciplinary evaluation, the patient was initially treated with intravenous antibiotics followed by drainage of the abscess using a combined transmastoid and middle cranial fossa (MCF) approach. The patient recovered well with no recurrence of the infection based on imaging and symptoms.

Discussion: While a variety of different surgical approaches can be used in treatment of PA, we recommend the MCF approach in cases where access to the anterior petrous apex may be challenging via transcanal or transmastoid approach.
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http://dx.doi.org/10.1177/0003489420949591DOI Listing
March 2021

Evaluation of Insertion Forces and Cochlea Trauma Following Robotics-Assisted Cochlear Implant Electrode Array Insertion.

Otol Neurotol 2020 06;41(5):631-638

Department of Otolaryngology-Head & Neck Surgery, University of Iowa Hospitals and Clinics.

Hypothesis: The objective was to evaluate the effect of cochlear implant (CI) insertion technique on electrode insertion forces and intracochlear trauma. We hypothesize that robotics-assisted insertions will reduce insertion forces and intracochlear trauma compared with manual insertions.

Background: Variability in CI outcomes exists across patients, implant centers, surgeons, and electrode types. While surgical techniques that reduce electrode insertion trauma are well established, insertion trauma remains one contributing factor to variability in CI outcomes. Previous work demonstrates that micromechanically controlled insertion tools reduce both maximum insertion forces and insertion variability compared with manual insertions.

Methods: CI electrode insertions were performed either by hand (n = 12) or utilizing a robotics-assisted tool (n = 12) in fresh frozen, human cadaveric cochleae using electrodes from four different CI manufacturers. Electrodes array insertion forces were additionally evaluated in benchtop cochlea models. Following cadaveric insertions, samples were imaged via high resolution x-ray microscopy to evaluate electrode position and intracochlear trauma events based on a modified Eshraghi scale.

Results: Electrode array insertions performed by robotics-assisted system showed significantly lower insertion forces and variability. Manual electrode array insertions had a significantly higher overall trauma score of 3.1 ± 2.0 compared with 0.9 ± 1.0 for robotics-assisted insertions. Robotics-assisted insertions had higher rate of basilar membrane elevations while manual insertions showed higher rates of severe trauma events.

Conclusions: The robotic-assisted insertion system reduced trauma events associated with CI electrode insertions in cadaveric cochleae compared with manual insertions. Surgical devices which help to precisely and more consistently insert electrodes may improve CI outcomes and hearing preservation.
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http://dx.doi.org/10.1097/MAO.0000000000002608DOI Listing
June 2020

Effects of Neurod1 Expression on Mouse and Human Schwannoma Cells.

Laryngoscope 2021 01 21;131(1):E259-E270. Epub 2020 May 21.

Department of Otolaryngology, University of Lowa, Lowa City, Lowa, U.S.A.

Objectives: The objective was to explore the effect of the proneuronal transcription factor neurogenic differentiation 1 (Neurod1, ND1) on Schwann cells (SC) and schwannoma cell proliferation.

Methods: Using a variety of transgenic mouse lines, we investigated how expression of Neurod1 effects medulloblastoma (MB) growth, schwannoma tumor progression, vestibular function, and SC cell proliferation. Primary human vestibular schwannoma (VS) cell cultures were transduced with adenoviral vectors expressing Neurod1. Cell proliferation was assessed by 5-ethynyl-2'-deoxyuridine (EdU) uptake.

Study Design: Basic science investigation.

Results: Expression of Neurod1 reduced the growth of slow-growing but not fast-growing MB models. Gene transfer of Neurod1 in human schwannoma cultures significantly reduced cell proliferation in dose-dependent way. Deletion of the neurofibromatosis type 2 (Nf2) tumor-suppressor gene via Cre expression in SCs led to increased intraganglionic SC proliferation and mildly reduced vestibular sensory-evoked potentials (VsEP) responses compared to age-matched wild-type littermates. The effect of Neurod1-induced expression on intraganglionic SC proliferation in animals lacking Nf2 was mild and highly variable. Sciatic nerve axotomy significantly increased SC proliferation in wild-type and Nf2-null animals, and expression of Neurod1 reduced the proliferative capacity of both wild-type and Nf2-null SCs following nerve injury.

Conclusion: Expression of Neurod1 reduces slow-growing MB progression and reduces human SC proliferation in primary VS cultures. In a genetic mouse model of schwannomas, we find some effects of Neurod1 expression; however, the high variability indicates that more tightly regulated Neurod1 expression levels that mimic our in vitro data are needed to fully validate Neurod1 effects on schwannoma progression.

Level Of Evidence: NA Laryngoscope, 131:E259-E270, 2021.
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http://dx.doi.org/10.1002/lary.28671DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7772964PMC
January 2021

Nucleus Hybrid S12: Multicenter Clinical Trial Results.

Laryngoscope 2020 10 25;130(10):E548-E558. Epub 2020 Mar 25.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa.

Objectives/hypothesis: The use of a short 10-mm/10-electrode cochlear implant to preserve low-frequency residual hearing was investigated. This report describes the 12-month outcomes of this multicenter clinical trial.

Study Design: Single-subject design.

Methods: Twenty-eight subjects with low-frequency hearing at or better than 60 dB HL at 500 Hz and severe high-frequency hearing loss were implanted with a Nucleus Hybrid S12 implant in their poorer ear. Speech perception in quiet using Consonant-Nucleus-Consonant (CNC) words and sentences in noise using AzBio sentences was collected pre- and postoperatively at 3, 6, and 12 months. Subjective reporting using the Speech, Spatial, and Qualities of Hearing Scale (SSQ) questionnaire was also collected pre- and postoperatively.

Results: Functional hearing preservation was accomplished in 96% of subjects. At 3 and 6 months, 86% of the 28 subjects had maintained functional hearing. By 12 months, 23 out of 27 subjects (85%) had maintained functional hearing (one subject with functional hearing at 6 months withdrew from the study prior to the 12-month visit). Speech perception results demonstrated that 81% of the participants on CNC words and 77% with AzBio sentences in noise had significant improvements using their everyday listening condition at 12 months compared to preoperative performance with bilateral hearing aids. Furthermore, preoperative to 12 months postoperative subjective ratings showed significant improvements for the SSQ.

Conclusions: This study demonstrates that a high degree of hearing preservation enabling acoustic-electric hearing and improvement in speech understanding in quiet and in noise can be accomplished using a short-electrode 10-mm cochlear implant.

Level Of Evidence: 2c Laryngoscope, 130:E548-E558, 2020.
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http://dx.doi.org/10.1002/lary.28628DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7728297PMC
October 2020

Pilot Evaluation of Sheep as In Vivo Model for Cochlear Implantation.

Otol Neurotol 2020 06;41(5):596-604

Department of Otolaryngology-Head and Neck Surgery, University of Iowa.

Objectives: The rise in the use of cochlear implants (CIs) has continued to fuel research aimed at improving surgical approaches and the preservation of residual hearing. Current in vivo models involve small animals not suitable for evaluating full-sized CIs nor are prohibitively expensive nonhuman primates. The objective of this study was to develop and evaluate an in vivo model of cochlear implantation in sheep.

Methods: Eight adult, female sheep were implanted with full-sized CIs from three manufacturers using a retrofacial approach to the round window. Partial electrode insertions were performed to a depth of 10 to 12 mm before closure. Round window electrocochleography (ECoG) and auditory brainstem responses (ABR) were conducted during and after surgery. Following a 30-day implantation, cochleae were explanted and imaged using both x-ray microscopy and histology.

Results: The surgery was well tolerated although limited complications were observed in three of eight sheep. Electrode insertions were up to 12 mm before insertion resistance noted. ECoG and ABR responses were reduced postimplantation, reflecting changes in cochlear mechanics due to the presence of the implant, and/or insertion trauma. Histological and radiological image analysis showed the presence of intracochlear fibrosis as well as one instance of tip fold-over.

Conclusions: The use of sheep presents a feasible live-animal model to study cochlear implantations. Full-sized implants as well as surgical techniques can be evaluated on functional outcomes such as ABR and ECoG as well as histological markers for residual hearing including intracochlear fibrosis. Use of this model and surgical approach has potential to evaluate CIs and surgical techniques in both the acute and chronic setting.
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http://dx.doi.org/10.1097/MAO.0000000000002587DOI Listing
June 2020

Intracochlear fibrosis and the foreign body response to cochlear implant biomaterials.

Laryngoscope Investig Otolaryngol 2019 Dec 13;4(6):678-683. Epub 2019 Nov 13.

Department of Otolaryngology-Head & Neck Surgery University of Iowa Hospitals and Clinics Iowa City Iowa.

Objective: To report current knowledge on the topic of intracochlear fibrosis and the foreign body response following cochlear implantation (CI).

Methods: A literature search was performed in PubMed to identify peer-reviewed articles. Search components included "cochlear implant," "Foreign body response (FBR)," and "fibrosis." Original studies and review articles relevant to the topic were included.

Results: Ninety peer-reviewed articles describing the foreign body response or intracochlear fibrosis following CI were included.

Conclusions: Intracochlear fibrosis following CI represents a significant limiting factor for the success of CI users. Several strategies have been employed to mitigate the foreign body response within the cochlea including drug delivery systems and modifications in surgical technique and electrode design. A better understanding of the FBR has the potential to improve CI outcomes and the next generation of cochlear prostheses.
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http://dx.doi.org/10.1002/lio2.329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6929576PMC
December 2019

An Osseous Destructive Mass of the Infratemporal Fossa.

JAMA Otolaryngol Head Neck Surg 2020 02;146(2):194-195

Department of Otolaryngology-Head and Neck Surgery, Carver College of Medicine, University of Iowa, Iowa City.

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http://dx.doi.org/10.1001/jamaoto.2019.3390DOI Listing
February 2020

Long-term audiologic outcomes after cochlear implantation for single-sided deafness.

Laryngoscope 2020 07 11;130(7):1805-1811. Epub 2019 Nov 11.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa, U.S.A.

Objectives: To evaluate the long-term audiometric outcomes, sound localization abilities, binaural benefits, and tinnitus assessment of subjects with cochlear implant (CI) after a diagnosis of unilateral severe-to-profound hearing loss.

Method: The study group consisted of 60 (mean age 52 years, range 19-84) subjects with profound hearing loss in one ear and normal to near-normal hearing in the other ear who underwent CI. Data analysis included pre- and postoperative Consonant-Nucleus-Consonant (CNC) Word scores, AzBio Sentence scores, pure tone thresholds, sound localization, and Iowa Tinnitus Handicap Questionnaire scores.

Results: Preoperative average duration of deafness was 3.69 years (standard deviation 4.31), with an average follow-up time of 37.9 months (range 1-87). CNC and AzBio scores significantly improved (both P < 0.001) postoperatively among the entire cohort, and there was much heterogeneity in outcomes with respect to deafness etiology subgroup analysis. Sound localization abilities tended to improve longitudinally in the entire cohort. Binaural benefits using an adaptive Hearing in Noise Test test showed a significant (P < 0.001) improvement with head shadow effect. Utilizing the Iowa Tinnitus Handicap Questionnaire, there was significant improvement in social, physical, and emotional well-being (P = 0.011), along with hearing abilities (P = 0.001).

Conclusions: This case series is the largest cohort of CI SSD subjects to date and systematically analyzes their functional outcomes. Subjects have meaningful improvement in word understanding, and sound localization tends to gradually improve over time. Binaural benefit analysis showed significant improvement with head shadow effect, which likely provides ease of listening.

Level Of Evidence: 4 Laryngoscope, 130:1805-1811, 2020.
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http://dx.doi.org/10.1002/lary.28358DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8588258PMC
July 2020

Electrical stimulation induces synaptic changes in the peripheral auditory system.

J Comp Neurol 2020 04 6;528(6):893-905. Epub 2019 Nov 6.

Department of Otolaryngology & Head-Neck Surgery, Eye & ENT Hospital of Fudan University, Shanghai, China.

Since a rapidly increasing number of neurostimulation devices are used clinically to modulate specific neural functions, the impact of electrical stimulation on targeted neural structure and function has become a key issue. In particular, the specific effect of electrical stimulation via a cochlear implant (CI) on inner hair cell (IHC) synapses remains unclear. Importantly, CI candidacy has recently expanded to include patients with partial hearing loss. Unfortunately, some CI recipients experience progressive hearing loss after activation of electrical stimulation. The mechanism(s) accounting for loss of residual hearing following electrical stimulation is unknown. Here normal-hearing guinea pigs were implanted with customized CIs. Intracochlear electrical stimulation with an intensity equal to or above electrically evoked compound action potential (ECAP) threshold decreased the excitability of auditory nerve. Furthermore, the number of synapses between IHCs and the afferent spiral ganglion neurons (SGNs) also decreased after electrical stimulation with higher intensities. However, no significant change was observed in the packing density and perikaryal area of SGNs as well as the quantity of hair cells. These results carry important implications for use of CIs in patients with residual hearing and for an increasing number of patients treated with other neurostimulation devices. Notably, the results were based on acute electrical stimulation. Considering the complex interaction between CIs and targeted tissues, it is urgent to conduct further research to clarify whether the similar changes could be induced by chronic electrical stimulation.
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http://dx.doi.org/10.1002/cne.24802DOI Listing
April 2020

Auditory synaptopathy, auditory neuropathy, and cochlear implantation.

Laryngoscope Investig Otolaryngol 2019 Aug 1;4(4):429-440. Epub 2019 Jul 1.

Department of Otolaryngology-Head and Neck Surgery University of Iowa Carver College of Medicine Iowa City Iowa U.S.A.

Cochlear implantation has become the standard-of-care for adults and children with severe to profound hearing loss. There is growing evidence that qualitative as well as quantitative deficits in the auditory nerve may affect cochlear implant (CI) outcomes. Auditory neuropathy spectrum disorder (ANSD) is characterized by dysfunctional transmission of sound from the cochlea to the brain due to defective synaptic function or neural conduction. In this review, we examine the precise mechanisms of genetic lesions causing ANSD and the effect of these lesions on CI outcomes. Reviewed data show that individuals with lesions that primarily affect the cochlear sensory system and the synapse, which are bypassed by the CI, have optimal CI outcomes. Individuals with lesions that affect the auditory nerve show poor performance with CIs, likely because neural transmission of the electrical signal from the CI is affected. We put forth a nuanced molecular classification of ANSD that has implications for preoperative counseling for patients with this disorder prior to cochlear implantation. We propose that description of ANSD patients should be based on the molecular site of lesion typically derived from genetic evaluation (synaptopathy vs. neuropathy) as this has implications for expected CI outcomes. Improvements in our understanding of genetic site of lesions and their effects on CI function should lead to better CI outcomes, not just for individuals with auditory neuropathy, but all individuals with hearing loss.
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http://dx.doi.org/10.1002/lio2.288DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6703118PMC
August 2019

Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion: Effect of Micro-mechanical Control on Limiting Pressure Trauma.

Otol Neurotol 2019 07;40(6):736-744

Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado.

Hypothesis: Use of micro-mechanical control during cochlear implant (CI) electrode insertion will result in reduced number and magnitude of pressure transients when compared with standard insertion by hand.

Introduction: With increasing focus on hearing preservation during CI surgery, atraumatic electrode insertion is of the utmost importance. It has been established that large intracochlear pressure spikes can be generated during the insertion of implant electrodes. Here, we examine the effect of using a micro-mechanical insertion control tool on pressure trauma exposures during implantation.

Methods: Human cadaveric heads were surgically prepared with an extended facial recess. Electrodes from three manufacturers were placed both by using a micro-mechanical control tool and by hand. Insertions were performed at three different rates: 0.2 mm/s, 1.2 mm/s, and 2 mm/s (n = 20 each). Fiber-optic sensors measured pressures in scala vestibuli and tympani.

Results: Electrode insertion produced pressure transients up to 174 dB SPL. ANOVA revealed that pressures were significantly lower when using the micro-mechanical control device compared with insertion by hand (p << 0.001). No difference was noted across electrode type or speed. Chi-square analysis showed a significantly lower proportion of insertions contained pressure spikes when the control system was used (p << 0.001).

Conclusion: Results confirm previous data that suggest CI electrode insertion can cause pressure transients with intensities similar to those elicited by high-level sounds. Results suggest that the use of a micro-mechanical insertion control system may mitigate trauma from pressure events, both by reducing the amplitude and the number of pressure spikes resulting from CI electrode insertion.
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http://dx.doi.org/10.1097/MAO.0000000000002164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6578873PMC
July 2019

Neuronal Migration Generates New Populations of Neurons That Develop Unique Connections, Physiological Properties and Pathologies.

Front Cell Dev Biol 2019 24;7:59. Epub 2019 Apr 24.

Department of Biology, University of Iowa, Iowa City, IA, United States.

Central nervous system neurons become postmitotic when radial glia cells divide to form neuroblasts. Neuroblasts may migrate away from the ventricle radially along glia fibers, in various directions or even across the midline. We present four cases of unusual migration that are variably connected to either pathology or formation of new populations of neurons with new connectivities. One of the best-known cases of radial migration involves granule cells that migrate from the external granule cell layer along radial Bergman glia fibers to become mature internal granule cells. In various medulloblastoma cases this migration does not occur and transforms the external granule cell layer into a rapidly growing tumor. Among the ocular motor neurons is one unique population that undergoes a contralateral migration and uniquely innervates the superior rectus and levator palpebrae muscles. In humans, a mutation of a single gene ubiquitously expressed in all cells, induces innervation defects only in this unique motor neuron population, leading to inability to elevate eyes or upper eyelids. One of the best-known cases for longitudinal migration is the facial branchial motor (FBM) neurons and the overlapping inner ear efferent population. We describe here molecular cues that are needed for the caudal migration of FBM to segregate these motor neurons from the differently migrating inner ear efferent population. Finally, we describe unusual migration of inner ear spiral ganglion neurons that result in aberrant connections with disruption of frequency presentation. Combined, these data identify unique migratory properties of various neuronal populations that allow them to adopt new connections but also sets them up for unique pathologies.
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http://dx.doi.org/10.3389/fcell.2019.00059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6491807PMC
April 2019

A mouse model of cochlear implantation with chronic electric stimulation.

PLoS One 2019 18;14(4):e0215407. Epub 2019 Apr 18.

Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA, United States of America.

Objectives: Cochlear implants provide an effective treatment option for those with severe hearing loss, including those with preserved low frequency hearing. However, certain issues can reduce implant efficacy including intracochlear tissue response and delayed loss of residual acoustic hearing. We describe a mouse model of cochlear implantation with chronic electric stimulation that can be used to study cochlear implant biology and related pathologies.

Methods: Twelve normal hearing adult CBA/J mice underwent unilateral cochlear implantation and were evenly divided into one group receiving electric stimulation and one not. Serial impedance and neural response telemetry (NRT) measurements were made to assess implant functionality. Functionality was defined as having at least one electrode with an impedance ≤ 35 kOhms. Mouse cochleae were harvested for histology and 3D x-ray microscopy 21 days post-operatively, or, in case the implant was still functional, at a later time point when the implant failed. A separate experiment measured the hearing preservation rate in 7 adult CBA/J mice undergoing unilateral cochlear implantation with serial auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE).

Results: Implants maintained functionality for a mean of 35 days in the non-stimulated group and 19.8 days in the stimulated group. Reliable NRT and behavioral responses to electric stimulation were recorded. A robust intracochlear peri-implant tissue response with neo-ossification was seen in all cochleae. Six of seven mice maintained intact low frequency hearing up to 6 weeks following cochlear implantation.

Conclusions: We demonstrate the feasibility of cochlear implantation and behaviorally significant electric stimulation in the mouse, with the potential for hearing preservation. This model may be combined with established mouse models of hearing loss and the large genetic and molecular research toolkit unique to the mouse for mechanistic and therapeutic investigations of cochlear implant biology.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0215407PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472764PMC
January 2020

Does the intracochlear position of an electrode array impact performance?

Laryngoscope 2019 09 25;129(9):1962-1963. Epub 2019 Mar 25.

Department of Otolaryngology-Head and Neck Surgery, the University of Iowa, Iowa City, Iowa, U.S.A.

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http://dx.doi.org/10.1002/lary.27944DOI Listing
September 2019
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