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Balkan Medical Journal Sep 2017Morphologically congenital sensorineural hearing loss can be investigated under two categories. The majority of congenital hearing loss causes (80%) are membranous...
Morphologically congenital sensorineural hearing loss can be investigated under two categories. The majority of congenital hearing loss causes (80%) are membranous malformations. Here, the pathology involves inner ear hair cells. There is no gross bony abnormality and, therefore, in these cases high-resolution computerized tomography and magnetic resonance imaging of the temporal bone reveal normal findings. The remaining 20% have various malformations involving the bony labyrinth and, therefore, can be radiologically demonstrated by computerized tomography and magnetic resonance imaging. The latter group involves surgical challenges as well as problems in decision-making. Some cases may be managed by a hearing aid, others need cochlear implantation, and some cases are candidates for an auditory brainstem implantation (ABI). During cochlear implantation, there may be facial nerve abnormalities, cerebrospinal fluid leakage, electrode misplacement or difficulty in finding the cochlea itself. During surgery for inner ear malformations, the surgeon must be ready to modify the surgical approach or choose special electrodes for surgery. In the present review article, inner ear malformations are classified according to the differences observed in the cochlea. Hearing and language outcomes after various implantation methods are closely related to the status of the cochlear nerve, and a practical classification of the cochlear nerve deficiency is also provided.
Topics: Classification; Cochlea; Cochlear Nerve; Ear, Inner; Hearing Loss, Sensorineural; Humans; Osteogenesis; Temporal Bone; Tomography, X-Ray Computed
PubMed: 28840850
DOI: 10.4274/balkanmedj.2017.0367 -
JPMA. the Journal of the Pakistan... Sep 2021Evoked Potentials are electrical potentials that occur in a group of neurons in response to stimulation of a sensory organ which can be recorded by surface electrodes.... (Review)
Review
Evoked Potentials are electrical potentials that occur in a group of neurons in response to stimulation of a sensory organ which can be recorded by surface electrodes. Testing evoked potentials is useful in assessing the integrity of neuronal pathways both at sensory and motor levels of neural control. Early auditory evoked potentials include cochlear and brainstem auditory-evoked potentials, popularly known as electrocochleogram, and auditory brainstem response. Evoked potential audiometry is a neurophysiogical test to assess auditory pathway function in response to auditory stimuli. Auditory brainstem response mainly assesses brainstem functions and integrity. These evoked potentials are widely used for assessment of the cochlear functions, auditory nerve and the brainstem. Most common indications for auditory evoked potentials include routine newborn hearing screening for auditory pathway deficits, detecting retrocochlear pathologies, intraoperative and intensive care monitoring, frequency-related measurement of auditory sensitivity and for diagnosing some demyelinating disorders in initial stages. The current narrative review was planned to highlight auditory brainstem response recording's basic principles, uses and methods of interpretation in health and disease phases.
Topics: Brain Stem; Cochlea; Cochlear Nerve; Evoked Potentials, Auditory, Brain Stem
PubMed: 34580520
DOI: 10.47391/JPMA.03-432 -
The Journal of Neuroscience : the... Nov 2009Overexposure to intense sound can cause temporary or permanent hearing loss. Postexposure recovery of threshold sensitivity has been assumed to indicate reversal of...
Overexposure to intense sound can cause temporary or permanent hearing loss. Postexposure recovery of threshold sensitivity has been assumed to indicate reversal of damage to delicate mechano-sensory and neural structures of the inner ear and no persistent or delayed consequences for auditory function. Here, we show, using cochlear functional assays and confocal imaging of the inner ear in mouse, that acoustic overexposures causing moderate, but completely reversible, threshold elevation leave cochlear sensory cells intact, but cause acute loss of afferent nerve terminals and delayed degeneration of the cochlear nerve. Results suggest that noise-induced damage to the ear has progressive consequences that are considerably more widespread than are revealed by conventional threshold testing. This primary neurodegeneration should add to difficulties hearing in noisy environments, and could contribute to tinnitus, hyperacusis, and other perceptual anomalies commonly associated with inner ear damage.
Topics: Acoustic Stimulation; Animals; Cell Death; Cochlear Nerve; Ear, Inner; Ganglia, Sensory; Hearing Loss, Noise-Induced; Male; Mice; Mice, Inbred CBA; Nerve Degeneration; Neurons; Neurons, Afferent; Noise; Otoacoustic Emissions, Spontaneous; Synapses; Vestibulocochlear Nerve Diseases
PubMed: 19906956
DOI: 10.1523/JNEUROSCI.2845-09.2009 -
Audiology & Neuro-otology 2022The rates of cochlear nerve abnormalities and cochlear malformations in pediatric unilateral hearing loss (UHL) are conflicting in the literature, with important...
INTRODUCTION
The rates of cochlear nerve abnormalities and cochlear malformations in pediatric unilateral hearing loss (UHL) are conflicting in the literature, with important implications on management. The aim of this study was to investigate the incidence of cochlear nerve deficiency (CND) in pediatric subjects with UHL or asymmetric hearing loss (AHL).
METHODS
A retrospective chart review of pediatric subjects <18 years of age evaluated for UHL or AHL with fine-cut heavily T2-weighted magnetic resonance imaging (MRI) between January 2014 and October 2019 (n = 291) at a tertiary referral center was conducted. MRI brain and computed tomography temporal bone were reviewed for the presence of inner ear malformations and/or CND. Status of the ipsilateral cochlear nerve and inner ear was evaluated. Pure tone average (PTA) at 500, 1,000 and 2,000 Hz was assessed.
RESULTS
204 subjects with UHL and 87 subjects with AHL were included. CND (aplasia or hypoplasia) was demonstrated in 61 pediatric subjects with UHL (29.9%) and 10 with AHL (11.5%). Ipsilateral cochlear malformations were noted in 25 subjects with UHL (12.3%) and 11 with AHL (12.6%), and ipsilateral vestibular malformations in 23 (11.3%) and 12 (13.8%) ears, respectively. Median PTA was statistically significantly higher in ears with CND (98.33) than ears with normal nerves (90.84).
DISCUSSION/CONCLUSION
Imaging demonstrated a high incidence of inner ear malformations, particularly CND, in pediatric subjects with UHL. Auditory findings indicated CND cannot be ruled out by thresholds alone as some CND ears did demonstrate measurable hearing. Radiologic evaluation by MRI should be performed in all patients within this population to guide counseling and management of hearing loss based on etiology, with implications on candidacy for cochlear implantation.
Topics: Child; Cochlear Implantation; Cochlear Nerve; Hearing; Hearing Loss, Sensorineural; Hearing Loss, Unilateral; Humans; Magnetic Resonance Imaging; Retrospective Studies
PubMed: 35344959
DOI: 10.1159/000522566 -
RoFo : Fortschritte Auf Dem Gebiete Der... Oct 2022Detection of cochlear nerve deficiency (CND) is usually straightforward using magnetic resonance imaging (MRI). In patients in whom MRI cannot be performed or imaging...
PURPOSE
Detection of cochlear nerve deficiency (CND) is usually straightforward using magnetic resonance imaging (MRI). In patients in whom MRI cannot be performed or imaging provides equivocal findings, computed tomography (CT) of the temporal bone might offer indirect evidence of CND. Our study aimed to derive a cut-off value for the diameter of the cochlear nerve canal (CNC) and internal auditory canal (IAC) in temporal bone CT to predict CND.
MATERIALS AND METHODS
This retrospective study included 70 children with sensorineural hearing loss (32 with CND and 38 control patients). The height, width, and cross-sectional area of the IAC and diameter of the CNCs were determined using temporal bone CT. Receiver operating characteristic (ROC) and Student's t-tests were performed for each parameter.
RESULTS
The mean diameter of the CNCs was significantly smaller in children with CND than in the control group (1.2 mm versus 2.4 mm, p < .001). The optimal threshold for CNC for separation of the two groups was 1.9 mm, resulting in a sensitivity of 98.7 % and specificity of 89.2 %. The IAC dimensions could not distinguish between children with CND and controls.
CONCLUSION
A CNC diameter of less than 1.9 mm is a reliable predictor of CND in children with sensorineural hearing loss.
KEY POINTS
· A small cochlear nerve canal predicts cochlear nerve deficiency (CND). · The size of the internal auditory canal cannot predict CND. · Whenever MRI is impossible or ambigous, CT can rule out CND.
CITATION FORMAT
· Sorge M, Sorge I, Pirlich M et al. Diameter of the Cochlear Nerve Canal predicts Cochlear Nerve Deficiency in Children with Sensorineural Hearing Loss. Fortschr Röntgenstr 2022; 194: 1132 - 1139.
Topics: Child; Cochlear Nerve; Hearing Loss, Sensorineural; Humans; Infant; Magnetic Resonance Imaging; Retrospective Studies; Tomography, X-Ray Computed
PubMed: 35915911
DOI: 10.1055/a-1826-0641 -
ENeuro 2018Modeling is a useful tool for investigating various biophysical characteristics of neurons. Recent simulation studies of propagating action potentials (spike conduction)...
Modeling is a useful tool for investigating various biophysical characteristics of neurons. Recent simulation studies of propagating action potentials (spike conduction) along axons include the investigation of neuronal activity evoked by electrical stimulation from implantable prosthetic devices. In contrast to point-neuron simulations, where a large variety of models are readily available, Hodgkin-Huxley-type conductance-based models have been almost the only option for simulating axonal spike conduction, as simpler models cannot faithfully replicate the waveforms of propagating spikes. Since the amount of available physiological data, especially in humans, is usually limited, calibration, and justification of the large number of parameters of a complex model is generally difficult. In addition, not all simulation studies of axons require detailed descriptions of nonlinear ionic dynamics. In this study, we construct a simple model of spike generation and conduction based on the exponential integrate-and-fire model, which can simulate the rapid growth of the membrane potential at spike initiation. In terms of the number of parameters and equations, this model is much more compact than conventional models, but can still reliably simulate spike conduction along myelinated and unmyelinated axons that are stimulated intracellularly or extracellularly. Our simulations of auditory nerve fibers with this new model suggest that, because of the difference in intrinsic membrane properties, the axonal spike conduction of high-frequency nerve fibers is faster than that of low-frequency fibers. The simple model developed in this study can serve as a computationally efficient alternative to more complex models for future studies, including simulations of neuroprosthetic devices.
Topics: Action Potentials; Animals; Axons; Cochlear Nerve; Humans; Models, Neurological; Neural Conduction
PubMed: 30225348
DOI: 10.1523/ENEURO.0112-18.2018 -
Prilozi (Makedonska Akademija Na... Mar 2023: The presence of a functional cochlear nerve is a key issue in the preoperative evaluation of pediatric candidates for cochlear implants. Correlations between cochlear...
: 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. : 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. : 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. : 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.
Topics: Child; Humans; Infant; Retrospective Studies; Constriction, Pathologic; Tomography, X-Ray Computed; Cochlear Nerve; Hearing Loss, Sensorineural; Magnetic Resonance Imaging
PubMed: 36987763
DOI: 10.2478/prilozi-2023-0017 -
ELife Sep 2023Profound congenital sensorineural hearing loss (SNHL) prevents children from developing spoken language. Cochlear implantation and auditory brainstem implantation can...
Profound congenital sensorineural hearing loss (SNHL) prevents children from developing spoken language. Cochlear implantation and auditory brainstem implantation can provide partial hearing sensation, but language development outcomes can vary, particularly for patients with inner ear malformations and/or cochlear nerve deficiency (IEM&CND). Currently, the peripheral auditory structure is evaluated through visual inspection of clinical imaging, but this method is insufficient for surgical planning and prognosis. The central auditory pathway is also challenging to examine in vivo due to its delicate subcortical structures. Previous attempts to locate subcortical auditory nuclei using fMRI responses to sounds are not applicable to patients with profound hearing loss as no auditory brainstem responses can be detected in these individuals, making it impossible to capture corresponding blood oxygen signals in fMRI. In this study, we developed a new pipeline for mapping the auditory pathway using structural and diffusional MRI. We used a fixel-based approach to investigate the structural development of the auditory-language network for profound SNHL children with normal peripheral structure and those with IEM&CND under 6 years old. Our findings indicate that the language pathway is more sensitive to peripheral auditory condition than the central auditory pathway, highlighting the importance of early intervention for profound SNHL children to provide timely speech inputs. We also propose a comprehensive pre-surgical evaluation extending from the cochlea to the auditory-language network, showing significant correlations between age, gender, Cn.VIII median contrast value, and the language network with post-implant qualitative outcomes.
Topics: Humans; Child; Hearing Loss, Sensorineural; Language; Hearing; Cochlea; Cochlear Nerve
PubMed: 37697742
DOI: 10.7554/eLife.85983 -
Hearing Research Nov 2015In early tetrapods, it is assumed that the tympana were acoustically coupled through the pharynx and therefore inherently directional, acting as pressure difference... (Review)
Review
In early tetrapods, it is assumed that the tympana were acoustically coupled through the pharynx and therefore inherently directional, acting as pressure difference receivers. The later closure of the middle ear cavity in turtles, archosaurs, and mammals is a derived condition, and would have changed the ear by decoupling the tympana. Isolation of the middle ears would then have led to selection for structural and neural strategies to compute sound source localization in both archosaurs and mammalian ancestors. In the archosaurs (birds and crocodilians) the presence of air spaces in the skull provided connections between the ears that have been exploited to improve directional hearing, while neural circuits mediating sound localization are well developed. In this review, we will focus primarily on directional hearing in crocodilians, where vocalization and sound localization are thought to be ecologically important, and indicate important issues still awaiting resolution.
Topics: Alligators and Crocodiles; Animals; Behavior, Animal; Biological Evolution; Biophysical Phenomena; Birds; Cochlear Nerve; Ear; Evoked Potentials, Auditory, Brain Stem; Mammals; Reptiles; Sound Localization
PubMed: 26048335
DOI: 10.1016/j.heares.2015.05.009 -
Ear and HearingIn this study, we aimed to (1) review the long-term outcomes of cochlear implantation in children with cochlear nerve aplasia and (2) compare the development of their...
OBJECTIVES
In this study, we aimed to (1) review the long-term outcomes of cochlear implantation in children with cochlear nerve aplasia and (2) compare the development of their auditory and speech abilities to children with normal-sized cochlear nerves.
DESIGN
This is a retrospective case-control study. Patients who underwent unilateral cochlear implant (CI) surgery in a tertiary referral center from September 2012 to December 2018 were reviewed. The study group included 55 children with cochlear nerve aplasia diagnosed using preoperative images. The control group included 35 children with normal-sized cochlear nerves. The control group did not differ from the study group in terms of age at implantation, pre-implantation auditory and speech abilities, or the electrode array type. Cochlear implantation outcomes were assessed using a test battery, including the Categories of Auditory Performance (CAP) score, the Speech Intelligibility Rating (SIR) score, behavioral audiometry, and closed- or open-set speech recognition tests. The development of auditory and speech abilities was compared between the two groups using Generalized Linear Mixed-effect Models.
RESULTS
The mean duration of CI usage was 4.5 years (SD = 1.5, range = 2.0 to 9.5) in the study group. The CAP scores, SIR scores, and aided hearing thresholds improved significantly post-implantation in the study group, but were significantly poorer than those in the control group. Generalized Linear Mixed-effect Models showed that the development of CAP and SIR scores was significantly slower in the study group than in the control group. Overall, 27 (49%) children with cochlear nerve aplasia had some degree of open-set speech perception skills, but the monosyllabic and bisyllabic word recognition rates were significantly lower than those in the control group.
CONCLUSION
For children with cochlear nerve aplasia, auditory perception and speech intelligibility continued to improve in the long-term follow-up, but this progress was significantly slower than in children with normal-sized cochlear nerves. Most children with cochlear nerve aplasia could obtain the ability of common phrase perception and understanding simple spoken language with consistent CI usage and auditory rehabilitation.
Topics: Child; Humans; Infant; Cochlear Implantation; Retrospective Studies; Case-Control Studies; Hearing Tests; Cochlear Implants; Speech Perception; Speech Intelligibility; Cochlear Nerve; Treatment Outcome; Deafness
PubMed: 36476611
DOI: 10.1097/AUD.0000000000001299