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Physics in Medicine and Biology Jun 2024Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is...
OBJECTIVE
Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation.
APPROACH
Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar, and partial tripolar modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve.
MAIN RESULTS
The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities.
SIGNIFICANCE
Full head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.
PubMed: 38925131
DOI: 10.1088/1361-6560/ad5c38 -
Journal of Biomedical Materials... Jul 2024Sensorineural hearing loss (SNHL) is mainly caused by injury or loss of hair cells (HCs) and associated spiral ganglion neurons (SGNs) in the inner ear. At present,...
Sensorineural hearing loss (SNHL) is mainly caused by injury or loss of hair cells (HCs) and associated spiral ganglion neurons (SGNs) in the inner ear. At present, there is still no effective treatment for SNHL in clinic. Recently, advances in organoid bring a promising prospect for research and treatment of SNHL. Meanwhile, three-dimensional (3D) printing provides a tremendous opportunity to construct versatile organoids for tissue engineering and regenerative medicine. In this study, gelatin (Gel), sodium alginate (SA), and polyvinyl alcohol (PVA) were used to fabricate biomimetic scaffold through 3D printing. The organ of Corti derived from neonatal mice inner ear was seeded on the PVA/Gel/SA scaffold to construct organ of Corti organoid. Then, the organ of Corti organoid was used to study the potential protective effects of berberine sulfate on neomycin-juried auditory HCs and SGNs. The results showed that the PVA/Gel/SA biomimetic 3D scaffolds had good cytocompatibilities and mechanical properties. The constructed organoid could maintain organ of Corti activity well in vitro. In addition, the injury intervention results showed that berberine sulfate could significantly inhibit neomycin-induced HC and SGN damage. This study suggests that the fabricated organoid is highly biomimetic to the organ of Corti, which may provide an effective model for drug development, cell and gene therapy for SNHL.
Topics: Animals; Organ of Corti; Mice; Berberine; Tissue Scaffolds; Organoids; Printing, Three-Dimensional; Alginates; Gelatin; Hair Cells, Auditory; Tissue Engineering; Polyvinyl Alcohol; Hearing Loss, Sensorineural; Spiral Ganglion
PubMed: 38923766
DOI: 10.1002/jbm.b.35439 -
Methods and Protocols May 2024Auditory impairment stands as a pervasive global issue, exerting significant effects on individuals' daily functioning and interpersonal engagements. Cochlear implants... (Review)
Review
Auditory impairment stands as a pervasive global issue, exerting significant effects on individuals' daily functioning and interpersonal engagements. Cochlear implants (CIs) have risen as a cutting-edge solution for severe to profound hearing loss, directly stimulating the auditory nerve with electrical signals. The success of CI procedures hinges on precise pre-operative planning and post-operative evaluation, highlighting the significance of advanced three-dimensional (3D) inner ear reconstruction software. Accurate pre-operative imaging is vital for identifying anatomical landmarks and assessing cochlear deformities. Tools like 3D Slicer, Amira and OTOPLAN provide detailed depictions of cochlear anatomy, aiding surgeons in simulating implantation scenarios and refining surgical approaches. Post-operative scans play a crucial role in detecting complications and ensuring CI longevity. Despite technological advancements, challenges such as standardization and optimization persist. This review explores the role of 3D inner ear reconstruction software in patient selection, surgical planning, and post-operative assessment, tracing its evolution and emphasizing features like image segmentation and virtual simulation. It addresses software limitations and proposes solutions, advocating for their integration into clinical practice. Ultimately, this review underscores the impact of 3D inner ear reconstruction software on cochlear implantation, connecting innovation with precision medicine.
PubMed: 38921825
DOI: 10.3390/mps7030046 -
Scientific Reports Jun 2024Variations in the biomechanical stiffness of brain tumors can not only influence the difficulty of surgical resection but also impact postoperative outcomes. In a...
Variations in the biomechanical stiffness of brain tumors can not only influence the difficulty of surgical resection but also impact postoperative outcomes. In a prospective, single-blinded study, we utilize pre-operative magnetic resonance elastography (MRE) to predict the stiffness of intracranial tumors intraoperatively and assess the impact of increased tumor stiffness on clinical outcomes following microsurgical resection of vestibular schwannomas (VS) and meningiomas. MRE measurements significantly correlated with intraoperative tumor stiffness and baseline hearing status of VS patients. Additionally, MRE stiffness was elevated in patients that underwent sub-total tumor resection compared to gross total resection and those with worse postoperative facial nerve function. Furthermore, we identify tumor microenvironment biomarkers of increased stiffness, including αSMA + myogenic fibroblasts, CD163 + macrophages, and HABP (hyaluronic acid binding protein). In a human VS cell line, a dose-dependent upregulation of HAS1-3, enzymes responsible for hyaluronan synthesis, was observed following stimulation with TNFα, a proinflammatory cytokine present in VS. Taken together, MRE is an accurate, non-invasive predictor of tumor stiffness in VS and meningiomas. VS with increased stiffness portends worse preoperative hearing and poorer postoperative outcomes. Moreover, inflammation-mediated hyaluronan deposition may lead to increased stiffness.
Topics: Humans; Meningioma; Neuroma, Acoustic; Elasticity Imaging Techniques; Female; Male; Middle Aged; Biomarkers, Tumor; Aged; Prospective Studies; Adult; Meningeal Neoplasms; Treatment Outcome; Tumor Microenvironment; Magnetic Resonance Imaging
PubMed: 38914647
DOI: 10.1038/s41598-024-64597-1 -
Academic Radiology Jun 2024To determine if super-resolution deep learning reconstruction (SR-DLR) improves the depiction of cranial nerves and interobserver agreement when assessing neurovascular...
Super-resolution Deep Learning Reconstruction for 3D Brain MR Imaging: Improvement of Cranial Nerve Depiction and Interobserver Agreement in Evaluations of Neurovascular Conflict.
RATIONALE AND OBJECTIVES
To determine if super-resolution deep learning reconstruction (SR-DLR) improves the depiction of cranial nerves and interobserver agreement when assessing neurovascular conflict in 3D fast asymmetric spin echo (3D FASE) brain MR images, as compared to deep learning reconstruction (DLR).
MATERIALS AND METHODS
This retrospective study involved reconstructing 3D FASE MR images of the brain for 37 patients using SR-DLR and DLR. Three blinded readers conducted qualitative image analyses, evaluating the degree of neurovascular conflict, structure depiction, sharpness, noise, and diagnostic acceptability. Quantitative analyses included measuring edge rise distance (ERD), edge rise slope (ERS), and full width at half maximum (FWHM) using the signal intensity profile along a linear region of interest across the center of the basilar artery.
RESULTS
Interobserver agreement on the degree of neurovascular conflict of the facial nerve was generally higher with SR-DLR (0.429-0.923) compared to DLR (0.175-0.689). SR-DLR exhibited increased subjective image noise compared to DLR (p ≥ 0.008). However, all three readers found SR-DLR significantly superior in terms of sharpness (p < 0.001); cranial nerve depiction, particularly of facial and acoustic nerves, as well as the osseous spiral lamina (p < 0.001); and diagnostic acceptability (p ≤ 0.002). The FWHM (mm)/ERD (mm)/ERS (mm) for SR-DLR and DLR was 3.1-4.3/0.9-1.1/8795.5-10,703.5 and 3.3-4.8/1.4-2.1/5157.9-7705.8, respectively, with SR-DLR's image sharpness being significantly superior (p ≤ 0.001).
CONCLUSION
SR-DLR enhances image sharpness, leading to improved cranial nerve depiction and a tendency for greater interobserver agreement regarding facial nerve neurovascular conflict.
PubMed: 38897913
DOI: 10.1016/j.acra.2024.06.010 -
Cerebral Cortex (New York, N.Y. : 1991) Jun 2024Network connectivity, as mapped by the whole brain connectome, plays a crucial role in regulating auditory function. Auditory deprivation such as unilateral hearing loss...
Network connectivity, as mapped by the whole brain connectome, plays a crucial role in regulating auditory function. Auditory deprivation such as unilateral hearing loss might alter structural network connectivity; however, these potential alterations are poorly understood. Thirty-seven acoustic neuroma patients with unilateral hearing loss (19 left-sided and 18 right-sided) and 19 healthy controls underwent diffusion-weighted and T1-weighted imaging to assess edge strength, node strength, and global efficiency of the structural connectome. Edge strength was estimated by pair-wise normalized streamline density from tractography and connectomics. Node strength and global efficiency were calculated through graph theory analysis of the connectome. Pure-tone audiometry and word recognition scores were used to correlate the degree and duration of unilateral hearing loss with node strength and global efficiency. We demonstrate significantly stronger edge strength and node strength through the visual network, weaker edge strength and node strength in the somatomotor network, and stronger global efficiency in the unilateral hearing loss patients. No discernible correlations were observed between the degree and duration of unilateral hearing loss and the measures of node strength or global efficiency. These findings contribute to our understanding of the role of structural connectivity in hearing by facilitating visual network upregulation and somatomotor network downregulation after unilateral hearing loss.
Topics: Humans; Female; Male; Hearing Loss, Unilateral; Middle Aged; Adult; Connectome; Brain; Neuroma, Acoustic; Neural Pathways; Magnetic Resonance Imaging; Aged; Diffusion Tensor Imaging; Functional Laterality; Nerve Net
PubMed: 38896551
DOI: 10.1093/cercor/bhae220 -
Sensors (Basel, Switzerland) Jun 2024Ultrasound imaging is an essential tool in anesthesiology, particularly for ultrasound-guided peripheral nerve blocks (US-PNBs). However, challenges such as speckle...
Ultrasound imaging is an essential tool in anesthesiology, particularly for ultrasound-guided peripheral nerve blocks (US-PNBs). However, challenges such as speckle noise, acoustic shadows, and variability in nerve appearance complicate the accurate localization of nerve tissues. To address this issue, this study introduces a deep convolutional neural network (DCNN), specifically Scaled-YOLOv4, and investigates an appropriate network model and input image scaling for nerve detection on ultrasound images. Utilizing two datasets, a public dataset and an original dataset, we evaluated the effects of model scale and input image size on detection performance. Our findings reveal that smaller input images and larger model scales significantly improve detection accuracy. The optimal configuration of model size and input image size not only achieved high detection accuracy but also demonstrated real-time processing capabilities.
Topics: Nerve Block; Neural Networks, Computer; Humans; Ultrasonography; Image Processing, Computer-Assisted; Peripheral Nerves; Ultrasonography, Interventional
PubMed: 38894486
DOI: 10.3390/s24113696 -
Journal of Clinical Medicine May 2024Progressive auditory dysfunction is common in patients with generalized neurodegenerative conditions, but clinicians currently lack the diagnostic tools to determine the...
BACKGROUND
Progressive auditory dysfunction is common in patients with generalized neurodegenerative conditions, but clinicians currently lack the diagnostic tools to determine the location/degree of the pathology and, hence, to provide appropriate intervention. In this study, we present the white-matter microstructure measurements derived from a novel diffusion-weighted magnetic resonance imaging (dMRI) technique in a patient with axonal auditory neuropathy and consider the findings in relation to the auditory intervention outcomes.
METHODS
We tracked the hearing changes in an adolescent with Riboflavin Transporter Deficiency (Type 2), evaluating the sound detection/discrimination, auditory evoked potentials, and both structural- and diffusion-weighted MRI findings over a 3-year period. In addition, we explored the effect of bilateral cochlear implantation in this individual.
RESULTS
Between the ages of 15 years and 18 years, the patient showed a complete loss of functional hearing ability. The auditory brainstem response testing indicated an auditory neuropathy with evidence of normal cochlear function but disrupted auditory neural activity. While three structural MRI assessments across this period showed a clinically normal cochleovestibular anatomy, the dMRI evaluation revealed a significant loss of fiber density consistent with axonopathy. The subsequent cochlear implant function was affected with the high levels of current required to elicit auditory sensations and concomitant vestibular and facial nerve stimulation issues.
CONCLUSIONS
The case study demonstrates the ability of dMRI technologies to identify the subtle white-matter microstructure changes in the auditory pathway, which may disrupt the neural function in patients with auditory axonopathy.
PubMed: 38892782
DOI: 10.3390/jcm13113072 -
Journal of Clinical Medicine May 2024: Vestibular schwannoma (VS) is a benign tumor of the eighth cranial nerve formed from neoplastic Schwann cells. Although VS can cause a variety of symptoms, tinnitus is... (Review)
Review
: Vestibular schwannoma (VS) is a benign tumor of the eighth cranial nerve formed from neoplastic Schwann cells. Although VS can cause a variety of symptoms, tinnitus is one of the most distressing symptoms for patients and can greatly impact quality of life. The objective of this systematic review is to comprehensively examine and compare the outcomes related to tinnitus in patients undergoing treatment for VS. Specifically, it evaluates patient experiences with tinnitus following the removal of VS using the various surgical approaches of traditional surgical resection and gamma knife radiosurgery (GKS). By delving into various aspects such as the severity of tinnitus post-treatment, the duration of symptom relief, patient quality of life, new onset of tinnitus after VS treatment, and any potential complications or side effects, this review aims to provide a detailed analysis of VS treatment on tinnitus outcomes. : Following PRISMA guidelines, articles were included from PubMed, Science Direct, Scopus, and EMBASE. Quality assessment and risk of bias analysis were performed using a ROBINS-I tool. : Although VS-associated tinnitus is variable in its intensity and persistence post-resection, there was a trend towards a decreased tinnitus burden in patients. Irrespective of the surgical approach or the treatment with GKS, there were cases of persistent or worsened tinnitus within the studied cohorts. : The findings of this systematic review highlight the complex relationship between VS resection and tinnitus outcomes. These findings underscore the need for individualized patient counseling and tailored treatment approaches in managing VS-associated tinnitus. The findings of this systematic review may help in guiding clinicians towards making more informed and personalized healthcare decisions. Further studies must be completed to fill gaps in the current literature.
PubMed: 38892775
DOI: 10.3390/jcm13113065 -
Operative Neurosurgery (Hagerstown, Md.) Jun 2024The extended translabyrinthine approach to acoustic neuroma (AN) was created to allow improved visualization and access to larger tumors.1,2 The dural opening, however,...
The extended translabyrinthine approach to acoustic neuroma (AN) was created to allow improved visualization and access to larger tumors.1,2 The dural opening, however, remained confined to the presigmoid space. Other authors have introduced modifications to increase the dura exposure around the internal auditory canal (IAC).3-5 The extra-extended translabyrinthine approach was conceptualized by the senior author (CC) to maximize AN exposure and early cranial nerve identification. The tentorial peeling was added to allow extradural mobilization of the temporal lobe.6 This allows further safe bone removal around the IAC and petrous apex and consistent opening of the facial canal at IAC fundus. This modification creates 280-to-360-degree dura exposure at the IAC. The dural opening extends to the petrous apex superiorly and the prepontine arachnoid cistern inferiorly and includes resection of a tentorium dural flap created by the tentorial peeling.6 This exposure allows for near circumferential exposure of the tumor and early identification of the glossopharyngeal nerve in the cochlear aqueduct area, the trigeminal nerve at the porus trigeminal, and the facial nerve (FN) at IAC fundus. In addition, this ample exposure permits identification of the FN trajectory in the tumor capsule before any tumor dissection. We present a detailed video of extra-extended translabyrinthine approach technique in a patient with a large left AN (Hannover classification T4B).7 This video does not involve any human research projects not requiring Institutional Review Board/ethic committee approval. The patient consented to the procedure and to the publication of his image. Complete resection was obtained. The FN function was House-Brackman I/VI.
PubMed: 38888316
DOI: 10.1227/ons.0000000000001223