Explore the vast range of titles available.

Purpose To compare the calibre of the cochlear (CN), superior vestibular (SVN) and inferior vestibular (IVN) nerves on magnetic resonance imaging (MRI), both between Ménière’s Disease (MD) ears and clinical controls, and between inner ears with and without endolymphatic hydrops (EH) on MRI. Methods A retrospective case–control study evaluated patients undergoing MRI for suspected hydropic ear disease from 9/2017 to 8/2022. The CN, SVN, IVN and facial nerve (FN) diameters and cross-sectional areas (CSA) were measured on T2-weighted sequences whilst EH was evaluated on delayed post-gadolinium MRI. Absolute nerve calibre (and that relative to the FN) in unilateral definite MD ears (2015 Barany criteria) was compared to that in both asymptomatic contralateral ears and clinical control ears. Nerve calibre in ears with severe cochlear and vestibular EH was compared to ears without EH. t tests or Wilcoxon signed-rank test/Mann–Whitney U test were applied ( p  < 0.001). Results 173 patients (mean age 51.3 ± 15.1, 65 men) with 84 MD (62 unilateral) and 62 clinical control ears were studied. Absolute and relative CN dimensions were decreased in both MD ears (CSA and diameter) and the contralateral asymptomatic ears (CSA) when compared to clinical controls ( p  < 0.001). Absolute nerve dimensions were reduced in both severe vestibular EH (CN, IVN and SVN) and severe cochlear EH (CN) ( p  < 0.001), however this was not evident when adjusted according to facial nerve calibre. Conclusion There is decreased absolute CN calibre in both symptomatic and asymptomatic MD ears as well as ears with severe cochlear and vestibular EH on MRI.

The mammalian auditory system comprises a complex network of brain regions. Interpretations and comparisons of experimental results from this system depend on appropriate anatomical identification of auditory structures. The Waxholm Space (WHS) atlas of the Sprague Dawley rat brain (Papp et al., Neuroimage 97:374–86, 2014) is an open access, three-dimensional reference atlas defined in an ex-vivo magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) volume. Version 2.0 of the atlas (Kjonigsen et al., Neuroimage 108:441–9, 2015) includes detailed delineations of the hippocampus and several major subcortical regions, but only few auditory structures. To amend this, we have delineated the complete ascending auditory system from the cochlea to the cerebral cortex. 40 new brain structure delineations have been added, and the delineations of 10 regions have been revised based on the interpretation of image features in the WHS rat brain MRI/DTI volumes. We here describe and validate the new delineations in relation to corresponding cell- and myelin-stained histological sections and previous literature. We found it possible to delineate all main regions and the majority of subregions and fibre tracts of the ascending auditory pathway, apart from the auditory cortex, for which delineations were extrapolated from a conventional two-dimensional atlas. By contrast, only parts of the descending pathways were discernible in the template. Version 3.0 of the atlas, with altogether 118 anatomical delineations, is shared via the NeuroImaging Tools and Resources Collaboratory (www.nitrc.org). [Display omitted] •Waxholm Space atlas (v3) of the rat brain.•Volumetric atlas of the rat auditory system.•MRI-and DTI-based boundary criteria.•3D visualization of the rat auditory system.

Traditional approaches to the human cochlear nerve have been impeded by its bony encasement deep inside the skull base. We present an innovative, minimally invasive, therapeutic pathway for direct access to the nerve to deliver novel regenerative therapies. Neuroanatomical studies on 10 cadaveric human temporal bones were undertaken to identify a potentially safe therapeutic pathway to the cochlear nerve. Simulations based on three-dimensional delineation of anatomical structures obtained from synchrotron phase-contrast imaging were analyzed. This enabled the identification of an approach to the nerve in the fundus of the internal auditory meatus by trephining the medial modiolar wall of the cochlea via the round window for a median depth of 1.48 mm (range 1.21–1.91 mm). The anatomical access was validated on 9 additional human temporal bones using radio-opaque markers and contrast injection with micro-computed tomography surveillance. We thus created an effective conduit for the delivery of therapeutic agents to the cochlear nerve.

Hidden hearing refers to the functional deficits in hearing without deterioration in hearing sensitivity. This concept is proposed based upon recent finding of massive noise-induced damage on ribbon synapse between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) in the cochlea without significant permanent threshold shifts (PTS). Presumably, such damage may cause coding deficits in auditory nerve fibers (ANFs). However, such deficits had not been detailed except that a selective loss of ANFs with low spontaneous rate (SR) was reported. In the present study, we investigated the dynamic changes of ribbon synapses and the coding function of ANF single units in one month after a brief noise exposure that caused a massive damage of ribbon synapses but no PTS. The synapse count and functional response measures indicates a large portion of the disrupted synapses were re-connected. This is consistent with the fact that the change of SR distribution due to the initial loss of low SR units is recovered quickly. However, ANF coding deficits were developed later with the re-establishment of the synapses. The deficits were found in both intensity and temporal processing, revealing the nature of synaptopathy in hidden hearing loss.

Objective To optimize high-resolution 7 T MRI of the cochlea and measure normal cochlea and the cochlear nerve morphometry in vivo. Materials and methods Eight volunteers with normal hearing were scanned at 7 T using an optimized protocol. Two neuroradiologists independently scored image quality. The basal turn lumen diameter (BTLD), height, width, length and volume of the cochlear, long (LD) and short (SD) diameter the calculated cross-sectional area (CSA) of the cochlear nerve were measured. Intra and inter-observer reliability was assessed using intraclass correlation (ICC). Results 3D T2W DRIVE combined with dielectric pads, allowed acquisition of high-resolution images showing detailed structures, such as the crista ampullaris in the semicircular canals. The overall grading scores from neuroradiologists were excellent. In the left ear, averaging over all subjects gave BTLD of 2.6 ± 0.05 mm, height of 4.9 ± 0.1 mm, width of 4.4 ± 0.2 mm, length of 36.5 ± 0.4 mm, volume of 0.16 ± 0.02 ml, LD of 1.31 ± 0.1 mm, SD of 1.06 ± 0.1 mm, and CSA of 1.1 ± 0.1 mm 2 . The right ear gave BTLD of 2.6 ± 0.04 mm, height of 4.9 ± 0.1 mm, width of 4.4 ± 0.3 mm, length of 35.5 ± 0.4 mm, volume of 0.16 ± 0.02 ml, LD of 1.29 ± 0.1 mm, SD of 1.07 ± 0.1 mm, and CSA of 1.10 ± 0.2 mm 2 . No statistically significant difference was found between the sides of the head ( p -value > 0.05). The intra-observer reliability was high (0.77–0.94), while the inter-observer reliability varied from moderate to high (0.55–0.81). Conclusion 7 T MRI can provide excellent visualization of the internal structure of the cochlear and of the vestibulocochlear nerve in vivo.

Background Axonal neuropathies are disorders that impair neural transmission, leading to substantial sensory deficits. In the auditory system, axonal degeneration can disrupt auditory processing, causing significant hearing difficulties. Understanding the extent of axonal degeneration and its impact on auditory function is crucial for improving diagnosis and management. This study aims to quantify axonal degeneration in the VIIIth nerve using diffusion‐weighted MRI and to correlate these findings with auditory function. Methods Fifty‐two children and adults participated. A total of, 27 with normal hearing, 7 with cochlear hearing loss and 18 with auditory neuropathy (AN). Hearing thresholds and dMRI data was collected for all participants and the VIIIth nerve was evaluated using the fixel‐based analysis metric of Apparent Fibre Density (AFD). Results AFD was significantly lower in participants with AN compared to participants with normal hearing and cochlear hearing loss (p < 0.05). 9/18 participants with AN exhibited AFD values ≥ 2 standard deviations below the normal range. Additionally, AFD was strongly correlated with hearing thresholds in participants with no evidence of cochlear dysfunction (r = −0.776, p < 0.001), suggesting reduced auditory nerve fibre density is associated with impaired sound detection. Conclusions dMRI‐derived AFD is a sensitive marker for axonal degeneration in the VIIIth nerve. This study provides the first in vivo evidence linking VIIIth nerve microstructure with hearing thresholds, highlighting the potential of dMRI in diagnosing and monitoring AN. The findings suggest that dMRI could be a valuable tool in clinical settings for assessing auditory nerve health and guiding treatment strategies for individuals with AN.

The bony cochlear nerve canal is the space between the fundus of the internal auditory canal and the base of the cochlear modiolus that carries cochlear nerve fibres. This study aimed to determine the distribution of bony labyrinth anomalies and cochlear nerve anomalies in patients with bony cochlear nerve canal and internal auditory canal atresia and stenosis, and then to compare the diameter of the bony cochlear nerve canal and internal auditory canal with cochlear nerve status. The study included 38 sensorineural hearing loss patients (59 ears) in whom the bony cochlear nerve canal diameter at the mid-modiolus was 1.5 mm or less. Atretic and stenotic bony cochlear nerve canals were examined separately, and internal auditory canals with a mid-point diameter of less than 2 mm were considered stenotic. Temporal bone computed tomography and magnetic resonance imaging scans were reviewed to determine cochlear nerve status. Cochlear hypoplasia was noted in 44 out of 59 ears (75 per cent) with a bony cochlear nerve canal diameter at the mid-modiolus of 1.5 mm or less. Approximately 33 per cent of ears with bony cochlear nerve canal stenosis also had a stenotic internal auditory canal and 84 per cent had a hypoplastic or aplastic cochlear nerve. All patients with bony cochlear nerve canal atresia had cochlear nerve deficiency. The cochlear nerve was hypoplastic or aplastic when the diameter of the bony cochlear nerve canal was less than 1.5 mm and the diameter of the internal auditory canal was less than 2 mm. The cochlear nerve may be aplastic or hypoplastic even if temporal bone computed tomography findings indicate a normal cochlea. If possible, patients scheduled to receive a cochlear implant should undergo both computed tomography and magnetic resonance imaging of the temporal bone. The bony cochlear nerve canal and internal auditory canal are complementary structures, and both should be assessed to determine cochlear nerve status.

Purpose The purpose of this retrospective study is to compare the results of electrically evoked compound action potential (ECAP) measurements using automatic auditory response telemetry (AutoART) with those obtained by ART in adults. The study also aimed to evaluate the predictive value of intraoperative ART and AutoART ECAPs for speech intelligibility (SI) and hearing success (HS), and to determine if cochlear nerve (CN) cross-sectional area (CSA) obtained preoperatively by magnetic resonance imaging (MRI) scans could predict ART and AutoART ECAPs and SI and HS outcome. Methods The study analyzed and correlated ART and AutoART ECAP thresholds at electrodes E2, E6, and E10, as well as averaged ECAP thresholds over electrodes E1–E12, using data from 32 implants. Correlations were also examined for ART and AutoART ECAP slopes. In addition, averaged ART and AutoART ECAP thresholds and slopes over all 12 electrodes for each participant were correlated with CN CSA measured from MRI sequences. SI of the monosyllabic Freiburg Speech Test at 65 dB sound pressure level was examined along with averaged ART and AutoART thresholds and slopes over all 12 electrodes. A parallel analysis was performed for HS, derived from the difference between baseline and 6-month SI. Finally, correlations between CN CSA and SI, as well as CN CSA and HS were examined. Results The results of the study showed a significant positive correlation between ART and AutoART ECAP thresholds and as well as slopes for E2, E6, E10 and averaged thresholds and slopes of E1–E12. However, no significant correlation was observed between ART and AutoART averaged ECAP thresholds and slopes and either SI and HS or CN CSA. Furthermore, no significant correlation was found between CN CSA and SI and HS. Conclusion While AutoART is a reliable and safe program for measuring ECAPs in adults, the study found no preoperative prognostic information on intraoperative ECAP results using parameters extracted from current MRI sequences or pre-/intraoperative information on subsequent hearing outcome using ECAP and CN CSA.

Objectives: The presence of a functional cochlear nerve is a key issue in the preoperative evaluation of pediatric candidates for cochlear implants. Correlations between cochlear nerve deficiency (CND) and bony abnormalities of the labyrinth or bony canal of the cochlear nerve are not yet well understood. The aim of this study was to determine whether the width of the bony cochlear canal (BCNC) can serve as a reliable predictive factor for the existence of a CND.Materials and methods: A total of 11 children with a confirmed diagnosis of prelingual, severe sensorineural hearing loss were included in this study. In all patients, indication for CI was confirmed and according to the preoperative protocol, high-resolution CT and MR were performed. Reconstructions at a distance of 0.6 mm of the axial plane and images from the HRCT of temporal bones were used for measuring the width of the BCNC. The cochlear nerves were evaluated on axial and sagittal – oblique T2 – MRI images and classified as normal, hypoplastic or aplastic. Two factors were reviewed retrospectively: the presence of inner ear anomalies and the relationship between BCNC stenosis and the existence of CND.Results: From a total of 22 temporal bones analyzed (22 ears in 11 patients), inner ear malformations were detected in 6 ears from 3 patients (27.27%). All three children had a bilateral malformation, in one it was Michel deformity and in two it was IP2 (incomplete partition 2). The BCNC diameter ranged from 0.1mm to 2.33mm with a mean value of 1.46±0.6mm. CND was recorded in 4 of 22 ears and all were associated with stenosis of the BCNC. In a total of three ears with a stenotic canal, we obtained a normal finding for the cochlear nerve on MR.Conclusion: Children with BCNC stenosis have a high incidence of CND. A narrowed BCNC on CT can be an indicator for the selection of children with sensorineural hearing loss who will need to be additionally referred for MRI in order to definitively assess the status of the cochlear nerve.

MRI provides excellent images of the cisternal and intracanal segments of the facial nerve and the three divisions of the vestibulocochlear nerve: the superior vestibular, inferior vestibular and cochlear nerves.2 Facial nerve anomalies have been associated with hearing loss. Aplasia or stenosis of the IAC affects the intracanal portion of the facial nerve that accompanies the vestibulocochlear nerve.3 In our case, IAC has symmetrical dimensions and hearing loss is explained by cochlear nerve absence. 3 Hamizan AW, Yean KT, Abdullah A. Congenital bilateral facial nerve hypoplasia with sensorineural hearing loss: a case report.