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IEEE Transactions on Bio-medical... Jun 2024In cochlear implant users with residual acoustic hearing, compound action potentials (CAPs) can be evoked by acoustic (aCAP) or electric (eCAP) stimulation and recorded...
OBJECTIVE
In cochlear implant users with residual acoustic hearing, compound action potentials (CAPs) can be evoked by acoustic (aCAP) or electric (eCAP) stimulation and recorded through the electrodes of the implant. We propose a novel computational model to simulate aCAPs and eCAPs in humans, considering the interaction between combined electric-acoustic stimulation that occurs in the auditory nerve.
METHODS
The model consists of three components: a 3D finite element method model of an implanted cochlea, a phenomenological single-neuron spiking model for electric-acoustic stimulation, and a physiological multi-compartment neuron model to simulate the individual nerve fiber contributions to the CAP.
RESULTS
The CAP morphologies closely resembled those known from humans. The spread of excitation derived from eCAPs by varying the recording electrode along the cochlear implant electrode array was consistent with published human data. The predicted CAP amplitude growth functions largely resembled human data, with deviations in absolute CAP amplitudes for acoustic stimulation. The model reproduced the suppression of eCAPs by simultaneously presented acoustic tone bursts for different masker frequencies and probe stimulation electrodes.
CONCLUSION
The proposed model can simulate CAP responses to electric, acoustic, or combined electric-acoustic stimulation. It considers the dependence on stimulation and recording sites in the cochlea, as well as the interaction between electric and acoustic stimulation in the auditory nerve.
SIGNIFICANCE
The model enhances comprehension of CAPs and peripheral electric-acoustic interaction. It can be used in the future to investigate objective methods, such as hearing threshold assessment or estimation of neural health through aCAPs or eCAPs.
PubMed: 38843064
DOI: 10.1109/TBME.2024.3410686 -
Frontiers in Molecular Neuroscience 2024Spiral ganglion neurons (SGNs) transmit auditory information from cochlear hair cells to the brain. SGNs are thus not only important for normal hearing, but also for...
Spiral ganglion neurons (SGNs) transmit auditory information from cochlear hair cells to the brain. SGNs are thus not only important for normal hearing, but also for effective functioning of cochlear implants, which stimulate SGNs when hair cells are missing. SGNs slowly degenerate following aminoglycoside-induced hair cell loss, a process thought to involve an immune response. However, the specific immune response pathways involved remain unknown. We used RNAseq to gain a deeper understanding immune-related and other transcriptomic changes that occur in the rat spiral ganglion after kanamycin-induced deafening. Among the immune and inflammatory genes that were selectively upregulated in deafened spiral ganglia, the complement cascade genes were prominent. We then assessed SGN survival, as well as immune cell numbers and activation, in the spiral ganglia of rats with a CRISPR-Cas9-mediated knockout of complement component 3 (C3). Similar to previous findings in our lab and other deafened rodent models, we observed an increase in macrophage number and increased expression of CD68, a marker of phagocytic activity and cell activation, in macrophages in the deafened ganglia. Moreover, we found an increase in MHCII expression on spiral ganglion macrophages and an increase in lymphocyte number in the deafened ganglia, suggestive of an adaptive immune response. However, C3 knockout did not affect SGN survival or increase in macrophage number/activation, implying that complement activation does not play a role in SGN death after deafening. Together, these data suggest that both innate and adaptive immune responses are activated in the deafened spiral ganglion, with the adaptive response directly contributing to cochlear neurodegeneration.
PubMed: 38840777
DOI: 10.3389/fnmol.2024.1389816 -
Scientific Reports Jun 2024Vestibular schwannomas (VS) are the most common tumor of the skull base with available treatment options that carry a risk of iatrogenic injury to the facial nerve,...
Vestibular schwannomas (VS) are the most common tumor of the skull base with available treatment options that carry a risk of iatrogenic injury to the facial nerve, which can significantly impact patients' quality of life. As facial nerve outcomes remain challenging to prognosticate, we endeavored to utilize machine learning to decipher predictive factors relevant to facial nerve outcomes following microsurgical resection of VS. A database of patient-, tumor- and surgery-specific features was constructed via retrospective chart review of 242 consecutive patients who underwent microsurgical resection of VS over a 7-year study period. This database was then used to train non-linear supervised machine learning classifiers to predict facial nerve preservation, defined as House-Brackmann (HB) I vs. facial nerve injury, defined as HB II-VI, as determined at 6-month outpatient follow-up. A random forest algorithm demonstrated 90.5% accuracy, 90% sensitivity and 90% specificity in facial nerve injury prognostication. A random variable (rv) was generated by randomly sampling a Gaussian distribution and used as a benchmark to compare the predictiveness of other features. This analysis revealed age, body mass index (BMI), case length and the tumor dimension representing tumor growth towards the brainstem as prognosticators of facial nerve injury. When validated via prospective assessment of facial nerve injury risk, this model demonstrated 84% accuracy. Here, we describe the development of a machine learning algorithm to predict the likelihood of facial nerve injury following microsurgical resection of VS. In addition to serving as a clinically applicable tool, this highlights the potential of machine learning to reveal non-linear relationships between variables which may have clinical value in prognostication of outcomes for high-risk surgical procedures.
Topics: Humans; Neuroma, Acoustic; Male; Female; Middle Aged; Microsurgery; Machine Learning; Prognosis; Facial Nerve Injuries; Retrospective Studies; Adult; Aged; Algorithms
PubMed: 38839778
DOI: 10.1038/s41598-024-63161-1 -
The Laryngoscope Jun 2024Syndromic patients can have severely anomalous anatomy significantly challenging conventional cochlear implant (CI) surgery. This case report describes a 20-year-old...
Syndromic patients can have severely anomalous anatomy significantly challenging conventional cochlear implant (CI) surgery. This case report describes a 20-year-old with brachio-oto-renal syndrome with a severely anomalous facial nerve completely covering the round window and preventing a traditional posterior tympanotomy CI. This is the first report to illustrate the performance of an endoscopic trans-canal bony cochleostomy with insertion of the CI performed via a "microfacial recess." We describe the performance of an endoscopic trans-canal bony cochleostomy and a modification of the conventional wide posterior tympanotomy usually performed into a 1 mm "microfacial recess," which allowed a full insertion to take place. Laryngoscope, 2024.
PubMed: 38837783
DOI: 10.1002/lary.31562 -
Muscle & Nerve Jun 2024Many people living with amyotrophic lateral sclerosis (PALS) report restrictions in their day-to-day communication (communicative participation). However, little is...
INTRODUCTION/AIMS
Many people living with amyotrophic lateral sclerosis (PALS) report restrictions in their day-to-day communication (communicative participation). However, little is known about which speech features contribute to these restrictions. This study evaluated the effects of common speech symptoms in PALS (reduced overall speaking rate, slowed articulation rate, and increased pausing) on communicative participation restrictions.
METHODS
Participants completed surveys (the Communicative Participation Item Bank-short form; the self-entry version of the ALS Functional Rating Scale-Revised) and recorded themselves reading the Bamboo Passage aloud using a smartphone app. Rate and pause measures were extracted from the recordings. The association of various demographic, clinical, self-reported, and acoustic speech features with communicative participation was evaluated with bivariate correlations. The contribution of salient rate and pause measures to communicative participation was assessed using multiple linear regression.
RESULTS
Fifty seven people living with ALS participated in the study (mean age = 61.1 years). Acoustic and self-report measures of speech and bulbar function were moderately to highly associated with communicative participation (Spearman rho coefficients ranged from r = 0.48 to r = 0.77). A regression model including participant age, sex, articulation rate, and percent pause time accounted for 57% of the variance of communicative participation ratings.
DISCUSSION
Even though PALS with slowed articulation rate and increased pausing may convey their message clearly, these speech features predict communicative participation restrictions. The identification of quantitative speech features, such as articulation rate and percent pause time, is critical to facilitating early and targeted intervention and for monitoring bulbar decline in ALS.
PubMed: 38837773
DOI: 10.1002/mus.28170 -
Journal of Perioperative Practice Jun 2024Throughout history, many innovations have contributed to the development of modern otolaryngological surgery, improving patient outcomes and expanding the range of...
Throughout history, many innovations have contributed to the development of modern otolaryngological surgery, improving patient outcomes and expanding the range of treatment options available to patients. This article explores five key historical innovations that have shaped modern otolaryngological surgery: Operative Microscope, Hopkins Rigid Endoscope, Laryngeal Nerve monitoring, Cochlear implants and Laser surgery. The selection of innovations for inclusion in this article was meticulously determined through expert consensus and an extensive literature review. We will review the development, impact and significance of each innovation, highlighting their contributions to the field of otolaryngological surgery and their ongoing relevance in contemporary and perioperative practice.
PubMed: 38828977
DOI: 10.1177/17504589241244996 -
Journal of Clinical Neuroscience :... May 2024Facial nerve hemangiomas (FNHs) are rare tumors that primarily occur near the geniculate ganglion in the temporal bone. Despite their rarity, they can cause significant... (Review)
Review
BACKGROUND
Facial nerve hemangiomas (FNHs) are rare tumors that primarily occur near the geniculate ganglion in the temporal bone. Despite their rarity, they can cause significant facial nerve dysfunction. The optimal management approach for FNHs remains uncertain, with surgery being the mainstay but subject to debate regarding the extent of resection and preservation of the facial nerve.
METHODS
Systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We queried the PubMed/Medline (accessed on 5 March 2024) electronic database using combinations of the following search terms and words text: "geniculate ganglion hemangioma", "ganglional hemangioma", "hemangioma of the facial nerve", "facial hemangioma", and "intratemporal hemangioma".
RESULTS
We identified a total of 30 literatures (321 patients). The most common site involved for the facial nerve hemangioma was the geniculate ganglion area followed by internal auditory canal, tympanic segment, labyrinthine segment and mastoid involvement. All patients were treated with conservative management or surgery. We report a 48-year-old female patient with HB grade 2 facial palsy and hemifacial spasm underwent SRS using Cyberknife technology. The treatment targeted the FNH in the left internal acoustic canal near the geniculate ganglion. Six months post-treatment, clinical improvement was evident, and lesion control was confirmed in a follow-up brain MRI.
CONCLUSION
The rarity of FNHs contributes to the lack of consensus on optimal management. This illustrative case demonstrates the feasibility of SRS as a standalone treatment for FNHs.
PubMed: 38823231
DOI: 10.1016/j.jocn.2024.05.023 -
Frontiers in Neurology 2024Despite its location near infection-prone areas, the human inner ear demonstrates remarkable resilience. This suggests that there are inherent instruments deterring the...
BACKGROUND
Despite its location near infection-prone areas, the human inner ear demonstrates remarkable resilience. This suggests that there are inherent instruments deterring the invasion and spread of pathogens into the inner ear. Here, we combined high-resolution light microscopy, super-resolution immunohistochemistry (SR-SIM) and synchrotron phase contrast imaging (SR-PCI) to identify the protection and barrier systems in the various parts of the human inner ear, focusing on the lateral wall, spiral ganglion, and endolymphatic sac.
MATERIALS AND METHODS
Light microscopy was conducted on mid-modiolar, semi-thin sections, after direct glutaraldehyde/osmium tetroxide fixation. The tonotopic locations were estimated using SR-PCI and 3D reconstruction in cadaveric specimens. The sections were analyzed for leucocyte and macrophage activity, and the results were correlated with immunohistochemistry using confocal microscopy and SR-SIM.
RESULTS
Light microscopy revealed unprecedented preservation of cell anatomy and several macrophage-like cells that were localized in the cochlea. Immunohistochemistry demonstrated IBA1 cells frequently co-expressing MHC II in the spiral ganglion, nerve fibers, lateral wall, spiral limbus, and tympanic covering layer at all cochlear turns as well as in the endolymphatic sac. RNAscope assays revealed extensive expression of fractalkine gene transcripts in type I spiral ganglion cells. CD4 and CD8 cells occasionally surrounded blood vessels in the modiolus and lateral wall. TMEM119 and P2Y12 were not expressed, indicating that the cells labeled with IBA1 were not microglia. The round window niche, compact basilar membrane, and secondary spiral lamina may form protective shields in the cochlear base.
DISCUSSION
The results suggest that the human cochlea is surveilled by dwelling and circulating immune cells. Resident and blood-borne macrophages may initiate protective immune responses via chemokine signaling in the lateral wall, spiral lamina, and spiral ganglion at different frequency locations. Synchrotron imaging revealed intriguing protective barriers in the base of the cochlea. The role of the endolymphatic sac in human inner ear innate and adaptive immunity is discussed.
PubMed: 38817543
DOI: 10.3389/fneur.2024.1355785 -
Ear and Hearing May 2024Electrocochleography (ECochG) appears to offer the most accurate prediction of post-cochlear implant hearing outcomes. This may be related to its capacity to interrogate...
OBJECTIVES
Electrocochleography (ECochG) appears to offer the most accurate prediction of post-cochlear implant hearing outcomes. This may be related to its capacity to interrogate the health of underlying cochlear tissue. The four major components of ECochG (cochlear microphonic [CM], summating potential [SP], compound action potential [CAP], and auditory nerve neurophonic [ANN]) are generated by different cochlear tissue components. Analyzing characteristics of these components can reveal the state of hair and neural cell in a cochlea. There is limited evidence on the characteristics of intracochlear (IC) ECochG recordings measured across the array postinsertion but compared with extracochlear recordings has better signal to noise ratio and spatial specificity. The present study aimed to examine the relationship between ECochG components recorded from an IC approach and postoperative speech perception or audiometric thresholds.
DESIGN
In 113 human subjects, responses to 500 Hz tone bursts were recorded at 11 IC electrodes across a 22-electrode cochlear implant array immediately following insertion. Responses to condensation and rarefaction stimuli were then subtracted from one another to emphasize the CM and added to one another to emphasize the SP, ANN, and CAP. Maximum amplitudes and extracochlear electrode locations were recorded for each of these ECochG components. These were added stepwise to a multi-factor generalized additive model to develop a best-fit model predictive model for pure-tone audiometric thresholds (PTA) and speech perception scores (speech recognition threshold [SRT] and consonant-vowel-consonant phoneme [CVC-P]) at 3- and 12-month postoperative timepoints. This best-fit model was tested against a generalized additive model using clinical factors alone (preoperative score, age, and gender) as a null model proxy.
RESULTS
ECochG-factor models were superior to clinical factor models in predicting postoperative PTA, CVC-P, and SRT outcomes at both timepoints. Clinical factor models explained a moderate amount of PTA variance ( r2 = 45.9% at 3-month, 31.8% at 12-month, both p < 0.001) and smaller variances of CVC-P and SRT ( r2 range = 6 to 13.7%, p = 0.008 to 0.113). Age was not a significant predictive factor. ECochG models explained more variance at the 12-month timepoint ( r2 for PTA = 52.9%, CVC-P = 39.6%, SRT = 36.4%) compared with the 3-month one timepoint ( r2 for PTA = 49.4%, CVC-P = 26.5%, SRT = 22.3%). The ECochG model was based on three factors: maximum SP deflection amplitude, and electrode position of CM and SP peaks. Adding neural (ANN and/or CAP) factors to the model did not improve variance explanation. Large negative SP deflection was associated with poorer outcomes and a large positive SP deflection with better postoperative outcomes. Mid-array peaks of SP and CM were both associated with poorer outcomes.
CONCLUSIONS
Postinsertion IC-ECochG recordings across the array can explain a moderate amount of postoperative speech perception and audiometric thresholds. Maximum SP deflection and its location across the array appear to have a significant predictive value which may reflect the underlying state of cochlear health.
PubMed: 38816899
DOI: 10.1097/AUD.0000000000001506 -
APL Bioengineering Jun 2024The realm of implantable bioelectronics represents a frontier in medical science, merging technology, biology, and medicine to innovate treatments that enhance, restore,...
The realm of implantable bioelectronics represents a frontier in medical science, merging technology, biology, and medicine to innovate treatments that enhance, restore, or monitor physiological functions. This field has yielded devices like cochlear implants, cardiac pacemakers, deep brain stimulators, and vagus nerve stimulators, each designed to address a specific health condition, ranging from sensorineural hearing loss to chronic pain, neurological disorders, and heart rhythm irregularities. Such devices underscore the potential of bioelectronics to significantly improve patient outcomes and quality of life. Recent technological breakthroughs in materials science, nanotechnology, and microfabrication have enabled the development of more sophisticated, smaller, and biocompatible bioelectronic devices. However, the field also encounters challenges, particularly in extending the capabilities of devices such as retinal prostheses, which aim to restore vision but currently offer limited visual acuity. Research in implantable bioelectronics is highly timely, driven by an aging global population with a growing prevalence of chronic diseases that could benefit from these technologies. The convergence of societal health needs, advancing technological capabilities, and a supportive ecosystem for innovation marks this era as pivotal for bioelectronic research.
PubMed: 38812757
DOI: 10.1063/5.0209537