OBJECTIVE: To observe the biodegradation of poloxamer 407 gel in acoustic capsule in vitro and in vivo, and to explore the applied perspective in the local drug delayed-release treatment for inner ear disorders. METHOD: Weighing the remained amount of poloxamer 407 gel at 37 degrees C at fixation time interval. The right ears of 15 healthy guinea pigs as experimental group were perfused with 20% poloxamer 407 solution 100 microl in round window niche, the left ears as control group with normal saline. The histology of bullae at 7, 14, 28, 49 days after perfusion was examined by means of serial section after paraffin imbedding. RESULT: The degraded amount were 20% and 25% in two groups respectively. The poloxamer 407 gel at 37 degrees C after 7 weeks was (78.89 +/- 13.10) microg and (75.32 +/- 8.94) microg respectively. The poloxamer gel in bullae was almost biodegraded and discharged 49 days after perfusion, only few gel remained in the middle ear cavity under light microscope. The morphology of the mucosa of middle ear cavity and round window membrane were not significantly damaged after poloxamer 407 perfusion. CONCLUSION Poloxamer 407 biodegraded slowly, but it could be biodegraded in vivo or discharged via eustachian tube, and caused no inflammation and immunologic rejection on the middle ear cavity. Thus, poloxamer 407 gel is suitable for the short-time sustained-release medical treatment in the inner ear diseases.
Animals ; Ear, Inner ; metabolism ; Gels ; pharmacokinetics ; Guinea Pigs ; Poloxamer ; pharmacokinetics ; Round Window, Ear ; metabolism

OBJECTIVE: To evaluate the safety of the circular round window and discus anatomic landmarks of posterior wall of internal auditory canal by investigating the microscopic anatomy of internal auditory canal area of the retrosigmold approach, which can provide the anatomical basis for acoustic neutrinomas surgery. METHOD: Fifteen adult cadaver heads (30 sides) fixed with formalin were used in the study. The retrosigmold approach operations were imitated to dissect the blood vessels and nerves in internal auditory canal area by opening round bony window and removing posterior wall of internal auditory canal. RESULT: Fifteen specimens of 30 sides circular bone window were opened without injury with transverse sinus and sigmoid sinus. The vertical distance between the highest point of bone window margo superior and the lowest point of transverse sinus margo inferior was (4.02 ± 0.32) mm. The vertical distance from the most anterior point of bone window leading edge to the most posterior point of sigmoid sinus trailing edge was (6.31 ± 0.43) mm. The internal auditory canal tubercle located in the anterior superior position of internal auditory canal. The vertical distance from the highest point of internal auditory canal tubercle to the upper margin of internal auditory canal was (2.31 ± 0.32) mm. To expose the whole internal auditory canal, the length and width of the internal auditory canal posterior wall removal was (7.29 ± 0.32) mm, (4.12 ± 0.29) mm. Within this removal range, no case of cochlea, semicircular canal or venous was injured in 30 specimens. CONCLUSION The method of opening round window through retrosigmold approach is simple, practial and convenient. With little variation and easiness of location, the sinternal auditory canal tubercle can be used in the identification of the internal auditory canal. When exposing the whole internal auditory canal, the removal scope of the posterior wall should be paid more attention to, in order to avoid the damage of cochlea, semicircular canal and jugular bulb.
Adult ; Cranial Sinuses ; Ear Canal ; Ear, Inner ; Humans ; Round Window, Ear ; anatomy & histology ; Semicircular Canals ; anatomy & histology ; Temporal Bone

OBJECTIVE: To study the dexamethasone pharmacokinetics of human inner ear perilymph under different drug administration using computer simulations. METHOD: The dexamethasone pharmacokinetics in guinea pigs inner ear perilymph under an intratympanic application with high-performance liquid chromatography. Dexamethasone pharmacokinetics in the guinea pigs cochlear fluid were simulated with a computer model, the Washington University Cochlear Fluids Simulator, version 1.6 and the best Simulations parameters to the experimental data could be obtain. With best Simulations parameters based on the experimental data, seven kinds application protocols were designed for human inner ear perilymph. RESULT: After an intratympanic application dose of 0.5% dexamethasone 150 ml in guinea pigs, the T(1/2K) was (2.918 +/- 0.089) h, and Cmax was (231.25 +/- 6.89) microg/L. The best Simulations parameters were that concentration of the dexamethasone 21-Phosphate disodium salt was 0.5% and the formula weight was 516, as well as drug diffusion coefficient was 0.6939 x 10(-5) cm2/s and round window permeability was 2.2 x 10(-11) cm/s while drug clearance half time was 175 minutes and scala tympaniscala vestibuli communication was 45 minutes. After an intratympanic application dose of 0.5% dexamethasone 500 mL, which the applied drug stayed in contact with the round window membrane for 15, 30, 60 and 120 minutes, the Cmax was 32.8, 64.3, 122.6 and 203.3 microg/L and the AUC was 116.5, 229.1, 423.6 and 759.2 microg/(h x L), respectively. After an intratympanic application dose of 0.5%, 1%, 2% and 4% dexamethasone 500 ml, which the applied drug stayed in contact with the round window membrane for 30 minutes respectively, the Cmax was 64.3, 127.3, 255.4 and 575.6 microg/L respectively and the AUC was 229.1, 462.8, 920.59 and 1525.2 microg/(h x L), respectively. CONCLUSION The dexamethasone pharmacokinetics in human inner ear perilymph by computer simulations was reported. As the time contact with the round window membrane increased, the inner ear perilymph concentration of dexamethasone increased. As the concentration of dexamethasone increased, the inner ear perilymph concentration of drug increased.
Animals ; Computer Simulation ; Dexamethasone ; pharmacokinetics ; Ear, Inner ; metabolism ; Guinea Pigs ; Humans ; Perilymph ; metabolism ; Round Window, Ear ; metabolism

OBJECTIVE: To investigate the feasibility of the round window stimulation electrical evoked auditory brainstem response (EABR) test, and optimize the parameters of recording and stimulation electrodes positions. METHOD: Ten healthy Hartley guinea pigs (20 ears) were used for the EABR test. The positive stimulation electrodes were placed into the round window niche, the animals were divided into three group according to the negative electrodes position, group A: the electric field was parallel with the projection of cochlear modiolus on the tympanic membrane, group B: the electric field was perpendicular to modiolus projection toward to the mastoid, group C: the electric field was perpendicular to modiolus projection toward to the zygomatic process. A series of optimized recording and stimulation parameters were uesed to reduce the electrical artifact. RESULT: All the 20 ears were normal in the ABR testing, and EABR waves were stable and well-differentiated in the EABR tests out of cochlea. But EABR waves of group A were more stable and differentiated than those of group B and C. In group A, the threshold of EABR was (0.54 ± 0.11) mA, and latency of wave III was (1.71 ± 0.05) ms when the stimulus intensity was 0.8 mA. In group B, the threshold of EABR was (0.62 ± 0.12) mA, and latency of wave III was (1.77 ± 0.03) ms. In group C, the threshold of EABR was (0.70 ± 0.14) mA, and latency of wave III was (1.86 ± 0.04)ms. The threshold of EABR and latency of wave III were significantly different among the three groups by statistic analysis. CONCLUSION EABR waves were stable and well-differentiated in the EABR tests out of cochlea. The EABR waves were recorded more stably and differentiated when the stimulating electrode and recording electrode were paralleled with the projection of modiolus on the tympanic membrane.
Animals ; Cochlea ; physiology ; Electric Stimulation ; Electrodes ; Evoked Potentials, Auditory, Brain Stem ; Guinea Pigs ; Round Window, Ear ; Tympanic Membrane

OBJECTIVES: It is not unusual for a cochlear implantation (CI) candidate to have some type of ear malformation, in particular an abnormal course of the facial nerve (FN). In this study, we attempted to reconstruct a three-dimensional (3D) image of temporal bone structures with malformation using computed tomography (CT) imaging and examined its usefulness in the surgical planning of CI in a malformed ear. METHODS: We prepared 3D images for 6 separate CI cases before surgery. First, we manually colored preoperative CT images using Photoshop CS Extended. We then converted the colored CT images to 3D images using Delta Viewer, free-ware for Macintosh. Before surgery, we discussed any problems anticipated based on the 3D images and plans for surgery with those who would be performing the CI. RESULTS: Case 1: The subject was a 3-year-old boy with malformed ossicles, semicircular canal (SC) hypoplasia, internal auditory canal stenosis, and an abnormal course of the FN. 3D image indicated that the stapes were absent, and the FN was more anteriorly displaced, so that it was difficult to perform cochleostomy. The surgical findings were similar to those depicted on the 3D image, so we could insert an electrode based on the preoperative image simulation without complications. Case 2: The subject was a 7-year-old boy with malformed stapes, atresia of the round window, cochlear and SC aplasia, and an abnormal course of the FN with bifurcation. CI was performed with no problems, in the same manner as in Case 1. CONCLUSION: We were able to successfully depict the structures of the inner ear, ossicles, and FN as 3D images, which are very easy to understand visually and intuitively. These 3D images of the malformed ear are useful in preoperative image simulation and in surgical planning for those performing a CI procedure.
Child ; Cochlear Implantation ; Cochlear Implants ; Constriction, Pathologic ; Ear ; Ear, Inner ; Electrodes ; Facial Nerve ; Humans ; Imaging, Three-Dimensional ; Preschool Child ; Round Window, Ear ; Semicircular Canals ; Stapes ; Temporal Bone

Stimulation of the round window (RW) for coupling an implantable hearing system to the cochlea has gained increasing clinical importance. To compare the vibration transfer to the cochlear fluids and partition in response to normal acoustic stimulation and to mechanical stimulation of the RW, we carried out an acoustic-structure coupled finite element analysis using a recently developed finite element (FE) model in our laboratory, which consisted of external ear canal, middle ear and cochlea. Intracochlear pressures were derived during normal forward sound stimulation as well as reverse RW stimulation. A model was utilized to calculate the force required of an actuator at the RW to produce a differential intracochlear pressure that is equivalent to a stimulus produced in normal ear by a given external ear-canal pressure. The current results provided further information to support the optimization of the actuators and adapt existing prostheses for RW stimulation in order to insure sufficient acoustic output.
Acoustic Stimulation ; Cochlea ; physiology ; Cochlear Microphonic Potentials ; physiology ; Ear Canal ; physiology ; Finite Element Analysis ; Hearing Aids ; Humans ; Ossicular Prosthesis ; Pressure ; Round Window, Ear ; physiology ; Vibration

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

OBJECTIVE: To provide the anatomic data for the correlated otologic microsurgery by the microdissection of temporal bone through facial recess approach. METHOD: Sixteen human temporal bones of eight adult cadaveric heads were dissected under surgical microscope through facial recess approach, and the relative anatomic structures were observed and measured, such as the bony entrance of facial recess approach, facial nerve, stapes, round window, round window niche, pyramidal eminence, cochleariform process, etc. The data were analyzed statistically. RESULT: The width of the bony entrance of facial recess approach was (2.94 +/- 0.32) mm, the height was (8.83 +/- 0.84) mm, the depth was (3.51 +/- 0.17) mm. The distances from stapes to tympanic segment of facial nerve, mastoid segment of facial nerve, round window, cochleariform process and anterior ligament of malleus were (1.38 +/- 0.21) mm, (6.94 +/- 0.47) mm, (3.60 +/- 0.55)mm, (2.23 +/- 0.33)mm, (4.93 +/- 0.61) mm, respectively. The distances from pyramidal eminence to tympanic segment of facial nerve, mastoid segment of facial nerve, round window, round window niche and cochleariform process were (1.05 +/- 0.09) mm, (5.63 +/- 0.41) mm, (3.01 +/- 0.34) mm, (3.29 +/- 0.44) mm, (4.13 +/- 0.51) mm, respectively. The distances from round window to cochleariform process and tympanic segment of facial nerve were (5.11 +/- 0.61) mm and (3.97 +/- 0.61) mm. The distances from round window niche to tympanic segment of facial nerve and mastoid segment of facial nerve were (4.13 +/- 0.38) mm and (7.28 +/- 0.29) mm. CONCLUSION The facial recess approach played an important role in modern otologic microsurgery. The position of anatomical structure was constant relatively, including short crus of incus, stapes, pyramidal eminence and cochleariform process, etc. These could be used as reference marks for otologic microsurgery.
Adult ; Ear, Middle ; anatomy & histology ; surgery ; Facial Nerve ; anatomy & histology ; surgery ; Humans ; Microsurgery ; Round Window, Ear ; anatomy & histology ; surgery ; Stapes ; anatomy & histology ; Temporal Bone ; anatomy & histology ; surgery

In order to study the influence of tympanic membrane lesion and ossicular erosion caused by otitis media on the hearing compensation performance of round-window stimulation, a human ear finite element model including cochlear asymmetric structure was established by computed tomography (CT) technique and reverse engineering technique. The reliability of the model was verified by comparing with the published experimental data. Based on this model, the tympanic membrane lesion and ossicular erosion caused by otitis media were simulated by changing the corresponding tissue structure. Besides, these simulated diseases' effects on the round-window stimulation were studied by comparing the corresponding basilar-membrane's displacement at the frequency-dependent characteristic position. The results show that the thickening and the hardening of the tympanic membrane mainly deteriorated the hearing compensation performance of round-window stimulation in the low frequency; tympanic membrane perforation and the minor erosion of ossicle with ossicular chain connected slightly effected the hearing compensation performance of round-window stimulation. Whereas, different from the influence of the aforementioned lesions, the ossicular erosion involving the ossicular chain detachment increased its influence on performance of round-window stimulation at the low frequency. Therefore, the effect of otitis media on the hearing compensation performance of round-window stimulation should be considered comprehensively when designing its actuator, especially the low-frequency deterioration caused by the thickening and the hardening of the tympanic membrane; the actuator's low-frequency output should be enhanced accordingly to ensure its postoperative hearing compensation performance.
Acoustic Stimulation ; Ear Ossicles ; pathology ; Finite Element Analysis ; Hearing ; Humans ; Otitis Media ; physiopathology ; Reproducibility of Results ; Round Window, Ear ; physiology ; Tomography, X-Ray Computed ; Tympanic Membrane Perforation

OBJECTIVE: To study a new surgical approach for cochlear implantation. METHOD: We operated on 8 cadaver heads (16 side) use Suprameatal approach for cochlear implantation, describe related anatomic mark. RESULT: The electrode is passed through the suprameatal tunnel, the EAC groove, the space underneath the chorda tympani between the malleal and the long process of the incus, and the cochleostomy. Angle between tunnel and temporal imaginary line is 28.0 degrees +/- 1.3 degrees in adult, 29.0 degrees +/- 1.7 degrees in children, the location of inserting electrode into cochleostomy is (1.31 +/- 0.13) mm to round window in adult, (1.19 +/- 0.12) mm in child. CONCLUSION The SMA approach is a safe technique, maintaining a safe distance to facial nerve and chorda tympani. So We should make right decision in clinic.
Adult ; Child ; Chorda Tympani Nerve ; anatomy & histology ; Cochlear Implantation ; methods ; Ear Canal ; anatomy & histology ; surgery ; Facial Nerve ; anatomy & histology ; Humans ; Round Window, Ear ; anatomy & histology