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.
Cochlea/surgery* ; Cochlear Implantation ; Cochlear Implants ; Robotics ; Scala Tympani/surgery*

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.
Cochlea ; Cochlear Implantation* ; Cochlear Implants* ; Ear, Inner* ; Electrodes ; Fibrosis ; Hearing ; Hearing Loss ; Humans ; Labyrinthitis* ; Otitis Media ; Rehabilitation ; Scala Tympani ; Scala Vestibuli*

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.
Animals ; Bone Marrow ; Cell Differentiation ; Cochlea ; Cochlear Nerve ; Colforsin ; Ear ; Fibroblast Growth Factor 2 ; Guinea Pigs* ; Hair ; Hearing Loss ; Hearing Loss, Sensorineural ; Humans ; Ion Channels ; Mammals ; Mastoid ; Mesenchymal Stromal Cells* ; Neomycin ; Neurons ; Organ of Corti ; Regeneration* ; Scala Tympani ; Sensory Receptor Cells ; Sodium ; Spiral Ganglion ; Transplantation ; Transplants

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.
Administration, Oral* ; Animals ; Chromatography, Liquid ; Diuretics, Osmotic ; Guinea Pigs* ; Humans ; Isosorbide* ; Male ; Membranes ; Meniere Disease ; Perfusion* ; Perilymph* ; Refractometry ; Scala Tympani

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.
Acoustics ; Animals ; Ear ; Electrodes ; Evoked Potentials ; Guinea ; Guinea Pigs ; Inferior Colliculi ; Masks ; Noise ; Scala Tympani

OBJECTIVETo 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.

METHODSIn a surgical simulation experiment, 20 human temporal bones were studied and measured to determine the related parameters of the temporal bone structure.

RESULTSThe 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.

CONCLUSIONThese parameters provide a reference value to determine the different positions of cochlear electrode array insertion into the scale tympani in different patients.

Adult ; Cochlea ; anatomy & histology ; surgery ; Cochlear Implantation ; Cochlear Implants ; Ear, Middle ; anatomy & histology ; surgery ; Female ; Humans ; Male ; Round Window, Ear ; anatomy & histology ; surgery ; Scala Tympani ; anatomy & histology ; surgery

OBJECTIVETo 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.

METHODSTwenty 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.

RESULTSSignificant 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.

CONCLUSIONIGF-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.

Animals ; Ear, Inner ; drug effects ; physiopathology ; Gentamicins ; Guinea Pigs ; Hair Cells, Auditory ; ultrastructure ; Hearing Loss ; chemically induced ; drug therapy ; Insulin-Like Growth Factor I ; pharmacology ; Microscopy, Electron, Scanning ; Scala Tympani

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.
Bacterial Toxins ; Chemokines ; Cholesteatoma ; Cochlea ; Cytokines ; Ear, Inner ; Ear, Middle ; Endolymph ; Evoked Potentials, Auditory, Brain Stem ; Hearing Loss ; Hearing Loss, Sensorineural ; Homeostasis ; Membranes ; Models, Animal ; Otitis ; Otitis Media ; Permeability ; Recycling ; Scala Tympani

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.
Cadaver ; Cochlea ; Cochlear Implants ; Electrodes ; Humans ; Incidence ; Scala Tympani ; Temporal Bone

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.
Adult ; Cochlea ; physiology ; Cochlear Implants ; Electric Impedance ; Electrodes ; Humans ; Scala Tympani ; physiology ; Spiral Ganglion ; Temporal Bone ; physiology