Design of Scalable Model of Cochlear Scala Tympani / 中国医疗器械杂志

For cochlear implant training and robotic cochlear implant experiments, the design method of scalable scala tympani model was proposed. The mathematical model of the cochlea was used as the central curve of scala tympani channel. Referring to the clinical anatomy data, the contour of the scala tympani cross-section was approximated as an ellipse. The profile was placed along the central curve, and the angle was adjusted to determine the position and orientation of the profile in three dimensions such that the central curve passes through its center. The data was imported into Matlab to generate a three-dimensional mathematical model of scala tympani, which can be expanded by setting different scale factors. The virtual scala tympani model was generated in SolidWorks, and the 2:1 fully transparent scala tympani model were fabricated by 3D printing to replace the specimen for experiment.

A Case of Scala Vestibuli Cochlear Implantation in Tympanogenic Labyrinthitis Ossificans / 대한이비인후과학회지

Labyrinthitis ossificans (LO) is a pathologic formation of fibrosis and new bone within the lumen of the otic capsule. The LO is a challenging issue in cochlear implantation since obliteration and obstruction of the cochlea make electrode insertion through scala tympani (classic route) difficult. Moreover, tympanomastoidectomy for resolution of chronic otitis media is also simultaneously considered for tympanogenic LO with severe to profound hearing loss because ossification could progress in case of staged or delayed implantation after initial tympanomastoidectomy. We report a patient with tympanogenic LO, who received subtotal petrosectomy with simultaneous cochlear implantation via scala vestibuli instead of the scala tympani for hearing rehabilitation.

Neural-Induced Human Mesenchymal Stem Cells Promote Cochlear Cell Regeneration in Deaf Guinea Pigs

OBJECTIVES: In mammals, cochlear hair cell loss is irreversible and may result in a permanent sensorineural hearing loss. Secondary to this hair cell loss, a progressive loss of spiral ganglion neurons (SGNs) is presented. In this study, we have investigated the effects of neural-induced human mesenchymal stem cells (NI-hMSCs) from human bone marrow on sensory neuronal regeneration from neomycin treated deafened guinea pig cochleae. METHODS: HMSCs were isolated from the bone marrow which was obtained from the mastoid process during mastoidectomy for ear surgery. Following neural induction with basic fibroblast growth factor and forskolin, we studied the several neural marker and performed electrophysiological analysis. NI-hMSCs were transplanted into the neomycin treated deafened guinea pig cochlea. Engraftment of NI-hMSCs was evaluated immunohistologically at 8 weeks after transplantation. RESULTS: Following neural differentiation, hMSCs expressed high levels of neural markers, ionic channel markers, which are important in neural function, and tetrodotoxin-sensitive voltage-dependent sodium currents. After transplantation into the scala tympani of damaged cochlea, NI-hMSCs-injected animals exhibited a significant increase in the number of SGNs compared to Hanks balanced salt solution-injected animals. Transplanted NI-hMSCs were found within the perilymphatic space, the organ of Corti, along the cochlear nerve fibers, and in the spiral ganglion. Furthermore, the grafted NI-hMSCs migrated into the spiral ganglion where they expressed the neuron-specific marker, NeuN. CONCLUSION: The results show the potential of NI-hMSCs to give rise to replace the lost cochlear cells in hearing loss mammals.

Isosorbide Concentration in Perilymph of the Guinea Pig After Oral Administration Versus That After Round Window Perfusion

OBJECTIVES: The aims of this study were to investigate the feasibility of isosorbide delivery into perilymph through the round window membrane (RWM), and to compare the intracochlear isosorbide concentration in perilymph after oral administration (PO) versus that after round window perfusion (RWP). METHODS: Sixteen male guinea pigs (32 ears) were used. Isosorbide, an osmotic diuretic, was administered via RWP or PO. First, to investigate the optimal perfusion time, perilymph sampling of scala tympani from the RWM was performed after RWP for 15, 30, or 60 minutes. Second, to compare the drug concentration after RWP versus that after PO, perilymph was aspirated at 3 and 6 hours after administration. Intracochlear concentration of isosorbide was analyzed by high-performance liquid chromatography coupled to refractive index detection. RESULTS: Isosorbide passed through the RWM into perilymph after RWP. After RWP for 15, 30, and 60 minutes, mean isosorbide concentrations in perilymph were 116.27+/-44.65, 245.48+/-112.84, and 279.78+/-186.32 mM, respectively. The intracochlear concentration after RWP for 30 minutes was higher than that after RWP for 15 minutes (P=0.043). At 3 and 6 hours after PO, isosorbide concentrations in perilymph were 28.88+/-4.69 and 12.67+/-2.28 mM, respectively. In contrast, the corresponding concentrations after RWP were 117.91+/-17.70 and 75.03+/-14.82 mM at 3 and 6 hours, respectively. Isosorbide concentrations in perilymph following RWP were significantly higher than those following PO at both 3 and 6 hours (P=0.025 and P=0.034, respectively). CONCLUSION: Isosorbide can rapidly pass through the RWM after RWP in guinea pigs, and 30 minutes of perfusion is considered to be appropriate. In addition, over a 6-hour period, RWP can deliver higher concentrations of isosorbide into perilymph than those achieved with PO.

Applied anatomy of scala tympani inlet related to cochlear implantation / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the related parameters of the temporal bone structure for determining the position of implanting electrode into the scala tympani in cochlear implantation surgery through the facial recess and epitympanum approach.</p><p><b>METHODS</b>In a surgical simulation experiment, 20 human temporal bones were studied and measured to determine the related parameters of the temporal bone structure.</p><p><b>RESULTS</b>The distance 5.91∓0.29 mm between the short process of the incus and the round window niche, 2.11∓0.18 mm between the stapes and the round window niche, 6.70∓0.19 mm between the facial nerve in the perpendicular paragraph and the round window niche, 2.22∓0.21 mm from the pyramidal eminence to the round window, and 2.16∓0.14 mm between the stapes and the round window. The minimal distance between the implanting electrode and the vestibular window was 2.12∓0.19 mm. The distance between the cochleariform process and the round window niche was 3.79∓0.17 mm. The position of the cochlear electrode array insertion into the second cochlear turn was 2.25∓0.13 mm under the stapes. The location of the cochlear electrode array insertion into the second cochlear turn was 2.28∓0.20 mm inferior to the pyramidal eminence.</p><p><b>CONCLUSION</b>These parameters provide a reference value to determine the different positions of cochlear electrode array insertion into the scale tympani in different patients.</p>

Binaural Electric-Acoustic Interactions Recorded from the Inferior Colliculus of Guinea Pigs: The Effect of Masking Observed in the Central Nucleus of the Inferior Colliculus

OBJECTIVES: To investigate the electric-acoustic interactions within the inferior colliculus of guinea pigs and to observe how central masking appears in invasive neural recordings of the inferior colliculus (IC). METHODS: A platinum-iridium wire was inserted to scala tympani through cochleostomy with a depth no greater than 1 mm for intracochlear stimulation of electric pulse train. A 5 mm 100 microm, single-shank, thin-film, penetrating recording probe was inserted perpendicularly to the surface of the IC in the coronal plane at an angle of 30-40degrees off the parasagittal plane with a depth of 2.0-2.5 mm. The peripheral and central masking effects were compared using electric pulse trains to the left ear and acoustic noise to the left ear (ipsilateral) and to the right ear (contralateral). Binaural acoustic stimuli were presented with different time delays and compared with combined electric and acoustic stimuli. The averaged evoked potentials and total spike numbers were measured using thin-film electrodes inserted into the central nucleus of the IC. RESULTS: Ipsilateral noise had more obvious effects on the electric response than did contralateral noise. Contralateral noise decreased slightly the response amplitude to the electric pulse train stimuli. Immediately after the onset of acoustic noise, the response pattern changed transiently with shorter response intervals. The effects of contralateral noise were evident at the beginning of the continuous noise. The total spike number decreased when the binaural stimuli reached the IC most simultaneously. CONCLUSION: These results suggest that central masking is quite different from peripheral masking and occurs within the binaural auditory system, and this study showed that the effect of masking could be observed in the IC recording. These effects are more evident and consistent with the psychophysical data from spike number analyses than with the previously reported gross potential data.

Applied anatomic study on lamina spiralis below promontory for cochlear implantation / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To provide anatomic data for cochlear implantation, and to find the method of locating lamina spiralis (LS) on the surface of promontory.@*METHOD@#Microanatomical study was carried out on 30 sides of human temporal bones by observing and measuring lamina spiralis below promontory, including its location, course and adjacent structures.@*RESULT@#(1) The basal turn of lamina spiralis below promontory can be divided into three segments: the hook segment (1.52 +/- 0.16) mm, the anteroinferior round window segment (3.83 +/- 0.37) mm and the forwarding segment (2.70 +/- 0.36) mm by two hinge points of which one was located at anterior of the junction of superior margin and anterior border of RW, and the other was located at anteroinferior of the round window; (2) The plane of round window anteroinferior segment of LS lay (51.00 +/- 5.97) degrees anteroinferior to horizontal segment of the facial nerve and comparative permanently meet posterior margin of'stapes head. Made posterior margin of stapes head as a fixation point and draw a line on promontory lay (51.00 +/- 45.97) degrees anteroinferior to horizontal segment of the facial nerve. This line can be thought as the projection of anteroinferior round window segment of LS on promontory; (3) The width of scala tympani at cochleostomy site on promontory: width of scala tympani at midpoint of superior margin of round window was (0.36 +/- 0.06) mm; width of scala tympani at midpoint of anterior border of round window was (0.97 +/- 0.14) mm; width of scala tympani at 3 mm point of anteroinferior round window segment was (1.24 +/- 0.21) mm.@*CONCLUSION@#(1) The basal turn lamina spiralis below promontory can be divided into three segments (the hook segment, the anteroinferior round window segment and the forwarding segment) by two hinge points; (2) The projection of anteroinferior round window segment of LS and the features exhibited in its course provide reference for locating the basal turn scala tympani and offer reliable anatomical basis for minimal invasive intervention during cochlear implantation.

Impedance between modiolus and different walls of scala tympani / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To compare the impedance between the modiolus and the inner wall of scala tympani with that between the modiolus and the outer wall of scala tympani.@*METHOD@#The impedances between the modiolus and the inner wall of scala tympani and the impedance between the modiolus and the outer wall of scala tympani were measured, calculated and compared under different stimulating rates 0.1, 1.0, 10.0 kHz.@*RESULT@#The impedance between the modiolus and the inner wall of scala tympani is less than that between the modiolus and the outer wall of scala tympani (P < 0.05).@*CONCLUSION@#To effectively stimulate the residual neurons in the spiral ganglion, the electrodes should be kept close to the inner wall of scale tympani.

A Temporal Bone Study of Insertion Trauma and Intracochlear Position of Straight Type Electrode for Cochlear Implant / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The goal of this study was to examine insertion depth, intracochlear position and insertion trauma with the stimulation electrode of the Nurobiosys cochlear implant. SUBJECTS AND METHOD: Four electrodes were implanted in fresh temporal bones of the human cadavers using realistic surgical procedures. Plain film X-ray images were taken from the electrode inserted in the specimens to estimate the insertion depth. After the electrode implantation, all human temporal bones were trimmed to extract the cochleae. The extracted cochleae from the temporal bone were immersed in acrylic resin to fix the position of electrode placed in the scala tympani. The resin treated cochleae were cut in radial section and polished. All crosssections were imaged with a microscope to assess the trauma by the electrode implantation. RESULTS: The mean insertion depth was about 300degrees with the cochlea angle. The insertion trauma was observed in one section of a temporal bone. The mean distance from electrode to modiolus was about 0.75 millimeter. CONCLUSION: The incidence, severity of trauma and insertion depth of the studied electrode showed similar results with that of other straight type electrode in literature.

The Role of Inflammatory Mediators in the Pathogenesis of Otitis Media and Sequelae

This review deals with the characteristics of various inflammatory mediators identified in the middle ear during otitis media and in cholesteatoma. The role of each inflammatory mediator in the pathogenesis of otitis media and cholesteatoma has been discussed. Further, the relation of each inflammatory mediator to the pathophysiology of the middle and inner ear along with its mechanisms of pathological change has been described. The mechanisms of hearing loss including sensorineural hearing loss (SNHL) as a sequela of otitis media are also discussed. The passage of inflammatory mediators through the round window membrane into the scala tympani is indicated. In an experimental animal model, an application of cytokines and lipopolysaccharide (LPS), a bacterial toxin, on the round window membrane induced sensorineural hearing loss as identified through auditory brainstem response threshold shifts. An increase in permeability of the blood-labyrinth barrier (BLB) was observed following application of these inflammatory mediators and LPS. The leakage of the blood components into the lateral wall of the cochlea through an increase in BLB permeability appears to be related to the sensorineural hearing loss by hindering K+ recycling through the lateral wall disrupting the ion homeostasis of the endolymph. Further studies on the roles of various inflammatory mediators and bacterial toxins in inducing the sensorineumral hearing loss in otitis media should be pursued.

Therapeutic effect of insulin-like growth factor-1 injection into the inner ears through scala tympani fenestration on gentamicin-induced hearing loss in guinea pigs / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the therapeutic effect of insulin-like growth factor-1 (IGF-1) injection into the inner ears through a scala tympani fenestration on sensorineural deafness in a guinea pig model of gentamicin-induced hearing loss.</p><p><b>METHODS</b>Twenty guinea pigs with gentamicin-induced hearing loss were randomized equally into IGF-1 group and control group. In both groups, scala tympani fenestration was performed for injection of IGF-1 (10 microl) or artificial perilymphatic fluid (10 microl). Auditory brainstem responses (ABR) test was performed before and 7 and 14 days after surgery, respectively, and the cochlea was removed by decollation of 3 guinea pigs from each group after ABR test for observing the changes in the hair cells using scanning electron microscope.</p><p><b>RESULTS</b>Significant reduction in the ABR response threshold (RT) occurred in IGF-1 group 7 and 14 days after the surgery, and on day 14, ABR RT showed significant difference between IGF-1 group and the control group. Scanning electron microscopy revealed severer damages of the hair cells in the control group, and in the IGF-1 group, finger-like microvilli was detected on the surface of the damaged hair cells.</p><p><b>CONCLUSION</b>IGF-1 injection in the inner ear through the scala tympani fenestration may ameliorate the damages of the auditory function and relieve sustained toxicity of gentamicin in guinea pigs possibly by protection and partial repair of the damaged cochlea hair cells as well as protection of the afferent nerves.</p>

Application of Intra-operative Neural Response Telemetry in Cochlear Implant / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Neural response telemetry (NRT) has been used as one of the most useful tools to measure neural responses ranging from spiral ganglion cells to electrical stimulation via the Nucleus 24 cochlear implant. The purpose of this study was to assess and analyze the result of NRT measured intraopertively and apply the result in postoperative mapping. SUBJECTS AND METHOD: The NRT test was administered to 72 patients (49 children and 23 adults) with the Nucleus 24 cochlear implant. After inserting of the electrode array into the scala tympani, an impedance test was administered to check the integrity of each inserted electrode. In cases of partial insertion, the electrodes outside the cochlear were excluded along with those proven to be short circuited. The electrically evoked action potential (EAP) was recorded using version 3.0 of NRT software. One intra-cochlear electrode (electrode 2, 4, 6, 8, 10, 12, 14, 16) with MP1 as reference was chosen for the stimulating pair. The recording electrode was located 3 electrodes away apically from the stimulating intracochlear electrode and referenced to MP2. The amplifier gain and sampling delay were optimized for each subject using electrode 4 and these same parameters were used throughout the test. RESULTS: Out of 72 implantees, 56 patients (78%) were observed to produce reliable responses: 16 (70%) of 23 adults and 40 (82%) of 49 children responded. The patients who failed to produce NRT response had higher T levels than patients who had NRT response. CONCLUSION: Eighty percent of the implantees without any inner ear anomaly showed reliable response to intraopertive NRT measurement. The intra-operarative NRT data may be used to predict electrical stimulation levels in programming.

Auditory Effects of Microperfused Lidocaine on Guinea Pig Cochlea / 대한이비인후과학회지

OBJECTIVES: Lidocaine is one of the therapeutic trials to treat tinnitus. However, the exact mechanism of the effect of lidocaine remains unclear. The aim of this study was to elucidate the action site of lidocaine in the cochlea by measuring compound action potential (CAP) and transient evoked otoacoustic emission (TEOAE) amplitude in guinea pigs. METHOD: Artificial perilymph was perfused into the scala tympani of the guinea pig cochlea in the control group, and lidocaine diluted with artificial perilymph was perfused into the scala tympani of the experimental groups. Electrocochleogram (ECoG) and TEOAE were measured in each groups both before and after lidocaine perfusion. RESULTS: Artificial perilymph perfused to the scala tympani of the guinea pig cochleae did not affect either the CAP threshold or the TEOAE response. But, lidocaine perfused into the scala tympani of the guinea pig cochleae produced a dose-dependent increase in CAP threshold, but did not affect TEOAE response. CONCLUSION: This study revealed that lidocaine perfused into the scala tympani of the guinea pig cochlea affects the CAPthreshold but not the TEOAE amplitude and reproducibility. It means that the locally perfused lidocaine affects the cochlear nerve greater than the outer hair cells.

Expression of Tonicity-Responsive Enhancer Binding Protein (TonEBP) in the Rat Cochlea: An Immunohistochemical Study / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The inner ear is an organ used for hearing and balance. For its normal function, the inner ear fluid homeostasis is required. There has been controversy over the regulatory mechanisms of maintaining inner ear fluid balance, and they have not yet been clearly defined. TonEBP is the protein that binds tonicity-responsive enhancer elements in the osmoprotective gene, which elevates the compatible osmolytes, which in turn induces cell survival in hypertonic condition. The aim of this study was to elucidate if there is an osmoregulatory mechanism in cochlea. Material and Method: The localization of TonEBP in the cochlea of male Sprague-Dawley rats was studied by immunohistochemistry with an anti rabbit polyclonal anti-rat TonEBP antibody. RESULTS: TonEBP was expressed at outer hair cells, Deiter cells, spiral ligaments, sprial limbus connective tissues, and epithelial lining of basilar membrane facing scala tympani. CONCLUSION: TonEBP in cochlea is one of the proteins involved in elucidating cell survival in changed tonicity during inner ear homeostasis.

Intraotic drug delivery following gentamicin Infusion using the an osmotic pump in chinchilla / 대한이비인후과학회지

BACKGROUNDS AND OBJECTIVES: We developed a method of intraotic treatment using gentamicin (GM) in chinchillas. MATERIALS AND METHOD: An osmotic pump, connected near the round window by a Teflon tube (0.13mm ID X 0.18mm OD) through an opening in the scala tympani, continuously perfused 12microliter of GM per day for a week. In the three experimental groups (n=12), each animal was treated with a total dose of 0.1mg of GM for a week. Animals in the control group (n=4) were immediately sacrificed after perfusion with saline for a week. RESULTS: In the control group, there was no damage in any of the hair cells. In the treatment group, the hair cells were more severely damaged at 4 weeks than at 1 week. The outer hair cells were more sensitive to GM than the inner hair cells. Among the outer hair cells, the first rows were damaged first. The basal part of cochlea was damaged earlier than the apical. The ototoxic effect continued even after perfusion had ceased. CONCLUSIONS: This pump system limits drug distribution to the target tissue, minimizing systemic side effects while permitting precise control of delivery rate, volume, concentration and duration.