scholarly journals Potential implications of slim modiolar electrodes for severely malformed cochlea: A comparison with the straight array with circumferential electrodes

2021 ◽  
Author(s):  
Sang-Yeon Lee ◽  
Byung Yoon Choi
Keyword(s):  
Spiral Ganglion ◽  
Compound Action Potential ◽  
Lateral Wall ◽  
Electrode Position ◽  
Type I ◽  
Evoked Compound Action Potential ◽  
Incomplete Partition ◽  
Auditory Performance ◽  
Ganglion Neurons ◽  
Selection Of

Objectives: Malformations of the inner ear account for approximately 20% of congenital deafness. In current practice, the straight arrays with circumferential electrodes (i.e., full-banded electrodes) are widely used in severely malformed cochlea. However, the unpredictability of the location of residual spiral ganglion neurons in such malformations argues against obligatorily pursuing the full-banded electrode in all cases. Here, we present an experience of electrically evoked compound action potential (ECAP) and radiography-based selection of an appropriate electrode for severely malformed cochlea. Methods: Three patients with the severely malformed cochlea, showing cochlear hypoplasia type II (CH-II), incomplete partition type I (IP-I), and cochlear aplasia with a dilated vestibule (CADV), were included, and the cochlear nerve deficiency (CND) was evaluated. Full-banded electrode (CI24RE(ST)) and slim modiolar electrode (CI632) were alternately inserted to compare ECAP responses and electrode position. Results: In patient 1 (CH-II with CND) who had initially undergone cochlear implantation (CI) using the lateral wall electrode (CI422), a revision CI was performed due to incomplete insertion of CI422 and resultant unsatisfactory performance, thus explanting the CI422 and re-inserting the CI24RE(ST) and CI632 sequentially. Although both electrodes elicited reliable ECAP responses with correct positioning, CI24RE(ST) showed overall lower ECAP thresholds compared to CI632; thus, CI24RE(ST) was selected. In patient 2 (IP-I with CND), CI632 elicited superior ECAP responses relative to CI24RE(ST), with correct positioning of the electrode; CI632 was chosen. In patient 3 (CADV), CI632 did not elicit an ECAP response while meaningful ECAP responses were obtained with the CI24RE(ST) array once correct positioning was achieved. All patients markedly improved auditory performance postoperatively. Conclusion: ECAP and radiography-based strategy for an appropriate electrode may be useful for severely malformed cochlea, leading to enhanced functional outcomes. Additionally, the practice of sticking to the full-banded straight electrode may not always be the best for IP-I and CH-II.

scholarly journals Pou4f1 Defines a Subgroup of Type I Spiral Ganglion Neurons and Is Necessary for Normal Inner Hair Cell Presynaptic Ca2+ Signaling

2019 ◽  
Vol 39 (27) ◽  
pp. 5284-5298 ◽  
Author(s):  
Hanna E. Sherrill ◽  
Philippe Jean ◽  
Elizabeth C. Driver ◽  
Tessa R. Sanders ◽  
Tracy S. Fitzgerald ◽  
...  
Keyword(s):  
Hair Cell ◽  
Spiral Ganglion ◽  
Spiral Ganglion Neurons ◽  
Type I ◽  
Inner Hair Cell ◽  
Ganglion Neurons

Dynamic firing properties of type I spiral ganglion neurons

2015 ◽  
Vol 361 (1) ◽  
pp. 115-127 ◽  
Author(s):  
Robin L. Davis ◽  
Robert A. Crozier
Keyword(s):  
Spiral Ganglion ◽  
Spiral Ganglion Neurons ◽  
Type I ◽  
Firing Properties ◽  
Ganglion Neurons

Analog Transmission of Action Potential Fine Structure in Spiral Ganglion Axons

2021 ◽  
Author(s):  
Wenke Liu ◽  
Qing Liu ◽  
Robert A. Crozier ◽  
Robin L. Davis
Keyword(s):  
Fine Structure ◽  
Action Potential ◽  
Action Potentials ◽  
Spiral Ganglion ◽  
Type I ◽  
Sensory Afferents ◽  
Conduction Pathway ◽  
Highly Correlated ◽  
Voltage Gated Ion Channels ◽  
Ganglion Neurons

Action potential waveforms generated at the axon initial segment (AIS) are specialized between and within neuronal classes. But is the fine structure of each electrical event retained when transmitted along myelinated axons or is it rapidly and uniformly transmitted to be modified again at the axon terminal? To address this issue action potential axonal transmission was evaluated in a class of primary sensory afferents that possess numerous types of voltage-gated ion channels underlying a complex repertoire of endogenous firing patterns. In addition to their signature intrinsic electrophysiological heterogeneity, spiral ganglion neurons are uniquely designed. The bipolar, myelinated somata of type I neurons are located within the conduction pathway, requiring that action potentials generated at the first heminode must be conducted through their electrically excitable membrane. We utilized this unusual axonal-like morphology to serve as a window into action potential transmission to compare locally-evoked action potential profiles to those generated peripherally at their glutamatergic synaptic connections with hair cell receptors. These comparisons showed that the distinctively-shaped somatic action potentials were highly correlated with the nodally-generated, invading ones for each neuron. This result indicates that the fine structure of the action potential waveform is maintained axonally, thus supporting the concept that analog signaling is incorporated into each digitally-transmitted action potential in the specialized primary auditory afferents.

scholarly journals Ultrastructural localization of Na,K-ATPase in the gerbil cochlea.

1995 ◽  
Vol 43 (10) ◽  
pp. 981-991 ◽  
Author(s):  
K Nakazawa ◽  
S S Spicer ◽  
B A Schulte
Keyword(s):  
Cell Membrane ◽  
Spiral Ganglion ◽  
Ultrastructural Localization ◽  
Cell Types ◽  
Spiral Ligament ◽  
Type I ◽  
Electron Microscopic ◽  
Enzyme Cytochemistry ◽  
Efferent Nerve ◽  
Ganglion Neurons

The transport enzyme Na,K-ATPase has been localized to several different cell types within the inner ear by enzyme cytochemistry, immunohistochemistry, and in situ hybridization. Although these histochemical procedures have provided a fairly consistent pattern of the enzyme's distribution, the precise location of Na,K-ATPase in the cell membrane of some polarized and non-polarized cell types remains uncertain. We addressed this problem in the gerbil cochlea using electron microscopic immunogold cytochemistry. The results confirmed prior ultrastructural localization of Na,K-ATPase along the basolateral plasma membrane of strial marginal and outer sulcus epithelial cells but differed from a previous report in failing to detect the enzyme at the surface of strial intermediate cells. The findings also concurred with and extended previous work in showing immunogold labeling along the entire cell membrane of non-polarized Type II fibrocytes in the inferior portion of the spiral ligament and of subpopulations of fibrocytes in the suprastrial and supralimbal regions. Our observations agreed further with light microscopic immunostaining in displaying uniform gold labeling for Na,K-ATPase in the neurilemma of Type I spiral ganglion neurons, even though these cells are completely ensheathed by myelin. Surprisingly, the enzyme was detectable in the neurilemma of afferent but not that of efferent nerve processes beneath hair cells.

Radiological measurement of cochlear dimensions in cochlear hypoplasia and its effect on cochlear implant selection

2021 ◽  
pp. 1-7
Author(s):  
G Pamuk ◽  
A E Pamuk ◽  
A Akgöz ◽  
M D Bajin ◽  
B Özgen ◽  
...  
Keyword(s):  
Cochlear Implant ◽  
Lateral Wall ◽  
Control Group ◽  
Type I ◽  
Basal Turn ◽  
Radiological Measurement ◽  
Computed Tomography Images ◽  
Implant Selection ◽  
Incomplete Partition ◽  
Electrode Selection

Abstract Objective To determine the effect of cochlear dimensions on cochlear implant selection in cochlear hypoplasia patients. Methods Temporal bone computed tomography images of 36 patients diagnosed with cochlear hypoplasia between 2010 and 2016 were retrospectively reviewed and compared with those of 40 controls without sensorineural hearing loss. Results Basal turn length and mid-modiolar height were significantly lower in the cochlear hypoplasia patients with subtypes I, II and III than in the control group (p < 0.001). Mid-scalar length was significantly shorter in subtype I–III patients as compared with the control group (p < 0.001). In addition, cochlear canal length (measured along the lateral wall) was significantly shorter in subtype I–IV patients than in the control group (subtypes I–III, p < 0.001; subtype IV, p = 0.002) Conclusion Cochlear hypoplasia should be considered if basal turn length is less than 7.5 mm and mid-modiolar height is less than 3.42 mm. The cochlear implant should be selected according to cochlear hypoplasia subgroup. It is critically important to differentiate subtype II from incomplete partition type I and subtype III from a normal cochlea, to ensure the most appropriate implant electrode selection so as to optimise cochlear implantation outcomes.

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