Surgical anatomy of the ear of the fat sand rat.

OBJECTIVE: This study was conducted to investigate and describe the anatomical details of the ear of the fat sand rat (Psammomys obesus). METHODS: Thirty ears (15 in dry skull and 15 in live animals) were dissected with the aid of an operating microscope and microsurgical techniques. Photographs were taken through an operating microscope. RESULTS: The temporal bone of the fat sand rat consists mainly of an unusually large bulla. Three distinct auditory ossicles were visualized and the manubrium of the malleus is relatively long in relation to the size of the ear. Most parts of the inner ear bulge into the bulla cavity and are easily accessible. The cochlea consists of 3.25 turns. The tympanic membrane, facial nerve, stapedial artery, and eustachian tube are described in detail. The large size of the bulla is probably related to the high sensitivity, particularly at low frequencies of the animals ear. CONCLUSION: The fat sand rat was found to be an excellent experimental animal for the investigation of middle and inner ear physiology.     

Improved inner ear diagnosis by controlled use of computerized tomography

Problems in the examination of the inner ear using conventional CT are described. Intraoperative findings often differ from CT findings. A new development HR-CT is introduced. Findings of middle and inner ear malformations and otosclerosis are demonstrated. It is shown that HR-CT imaging using a new 1024 matrix, enables better spatial resolution. This new CT technique improves inner ear examination, especially in the preparation for cochlear implantation.     

Autoimmune mouse antibodies recognize multiple antigens proposed in human immune-mediated hearing loss.

HYPOTHESIS: Autoimmune diseased mice with hearing loss will have autoantibodies against the various cochlear antigens proposed in clinical autoimmune inner ear disease. BACKGROUND: Serum antibodies of patients with hearing loss recognize several proteins that are proposed as possible antigenic targets in the ear. This often leads to a clinical diagnosis of autoimmune inner ear disease, although it is not clear how these antibodies cause inner ear disease. Therefore, to better understand the relationship of autoantibodies and ear disease, an examination was made of serum autoantibodies in the MRL/MpJ-Fas(lpr) autoimmune mouse with hearing loss. Similar antibody patterns in the mouse would provide an animal model in which to investigate potential autoimmune mechanisms of this clinical ear disorder. METHODS: Sera from MRL/MpJ-Fas(lpr) autoimmune mice and normal C3H mice were tested by the enzyme-linked immunosorbent assay technique for reactivity against various reported cochlear antigens: heat shock protein 70 (bovine, human, bacterial), laminin, heparan sulfate proteoglycan, cardiolipin, and collagen types II and IV. RESULTS: The autoimmune mouse sera showed significantly greater antibody reactivity against all of the antigens when compared with normal mouse sera. CONCLUSIONS: Serum antibodies from autoimmune mice recognized several putative autoantigens reported for patients with hearing loss, suggesting that comparable antigen-antibody mechanisms might be operating. However, the recognition of multiple antigens did not identify any one as being the specific target in autoimmune hearing loss. The correlation of antibodies in the MRL/MpJ-Fas(lpr) autoimmune mouse and human studies indicates this animal model should aid further investigations into potential cochlear antigens in autoimmune hearing loss.     

Optimizing immunofluorescence for the testing of autoantibodies in inner ear disorders

A method is described for the immunofluorescent testing of autoantibodies in the sera of patients with vestibulo-cochlear disorders, using fixed decalcified inner ear tissue preparations from guinea pigs. Fixation in cold ethanol and decalcification in EDTa at 4 degrees C preserved the immunological reactivity of the inner ear tissue in use and allowed excellent delineation of its structural details. Counterstaining of the sections with Evans-blue dye aided in a better identification of the inner ear anatomical structures and in a more precise location of the antibodies present. By mounting the sections in p-phenylenediamine-PBS-glycerin solution, the rapid extinction of the fluorescence seen during photomicroscopy was retarded and the intensity of the immunofluorescence was enhanced. Preservation of the slides for documentation was improved by fixing the intermediate layer of the antigen and the labeled antibody in cold ethanol. The inner ear tissue preparations retained their fluorescent staining up to 6 months. Our method is convenient for screening patients with inner ear disorders for autoantibodies against the different cellular elements and for testing the possible presence of antibodies against the inner ear tissue. So far, we believe that the antibodies detected are not tissue (inner ear) specific.     

Optimizing immunofluorescence for the testing of autoantibodies in inner ear disorders

Summary A method is described for the immunofluorescent testing of autoantibodies in the sera of patients with vestibulo-cochlear disorders, using fixed decalcified inner ear tissue preparations from guinea pigs. Fixation in cold ethanol and decalcification in EDTa at 4°C preserved the immunological reactivity of the inner ear tissue in use and allowed excellent delineation of its structural details. Counterstaining of the sections with Evans-blue dye aided in a better identification of the inner ear anatomical structures and in a more precise location of the antibodies present. By mounting the sections in p-phenylenediamine-PBS-glycerin solution, the rapid extinction of the fluorescence seen during photomicroscopy was retarded and the intensity of the immunofluorescence was enhanced. Preservation of the slides for documentation was improved by fixing the intermediate layer of the antigen and the labeled antibdoy in cold ethanol. The inner ear tissue preparations retained their fluorescent staining up to 6 months. Our method is convenient for screening patients with inner ear disorders for autoantibodies against the different cellular elements and for testing the possible presence of antibodies against the inner ear tissue. So far, we believe that the antibodies detected are not tissue (inner ear) specific.     

Three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging investigation of inner ear disturbances in cases of middle ear cholesteatoma with labyrinthine fistula.

OBJECTIVE: To investigate the cause of inner ear disturbances in cases of middle ear cholesteatoma with labyrinthine fistula. SETTING: University hospital. STUDY DESIGN: Prospective case study. PATIENTS: Eight patients who were scheduled to undergo surgery for middle ear cholesteatoma with labyrinthine fistula were included in this study. INTERVENTION: Imaging analysis was performed using a 3-dimensional fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging sequence. MAIN OUTCOME MEASURES: Three-dimensional FLAIR findings were compared with clinical symptoms associated with inner ear disturbance and surgical observations of the fistula. RESULTS: Three-dimensional FLAIR in 6 patients revealed areas of high signal intensity in the inner ears on the affected sides and areas with increased signal after the administration of gadolinium, especially in cases accompanied by acute sensorineural hearing loss. These images were considered to be indicative of breakdown of the blood-labyrinth barrier due to middle ear cholesteatoma. This finding was also present in a patient with no clinical symptoms of inner ear disturbances. CONCLUSION: Three-dimensional FLAIR images of the inner ear are valuable in evaluating labyrinthine fistula in patients with cholesteatoma. Future studies are needed to better understand the role of 3-dimensional FLAIR in predicting the severity of inner ear disturbance.     

Autoimmunity in otology

Experimental and clinical studies over the past ten years have confirmed that immune-mediated disease can involve the external, middle, and/or inner ear. Autoimmune inner ear dysfunction can result from systemic or localized disease. The pathogenesis of autoimmunity and the responsible antigen(s) of the inner ear is not known at present. The clinical course, laboratory test results, and treatment response often follow a consistent pattern but in some cases may be highly variable. Empirical treatment of autoimmune inner ear disease has produced encouraging preliminary results, and further research should provide better understanding of these otoimmune disorders.     

Evaluation of the inner ear fluorescence

Searching for the methods, which may improve the visualisation of the membranous labyrinth, authors decided to evaluate autofluorescence of the membranous structures of the inner ear. The analysis of the inner ear autofluorescence parameters was performed. We assessed, whether the detected differences in autofluorescence between the bony elements and the membranous structures, allows the practical apply, owning to increased contrast in the operating microscope. The optimal wave length inducing autofluorescence of membranous labyrinth amounts to 465 nm. Obtained in these circumstances contrast of the membranous structures don't cause a significant improvement in their visualisation, comparing with the picture received in the traditional optical microscope.     

Optical coherence tomography as an orientation guide in cochlear implant surgery?

CONCLUSION: With optical coherence tomography (OCT) it is basically possible to reveal parts of the cochlear morphology without opening its enveloping membranes. Thus, it may serve as a helpful guide for the surgeon to localize the scala tympani precisely before opening the fluid-filled inner ear to insert the electrode array. OBJECTIVE: To improve anatomical orientation in cochlear implant surgery before definitively opening the fluid-filled inner ear. The question was whether a new imaging technique, OCT, might provide information about the site of the underlying inner ear structures (scala tympani, scala vestibuli) and could, consequently, guide the surgeon towards the scala tympani. MATERIALS AND METHODS: In a preliminary study, OCT was carried out on human temporal bone preparations, in which a cochleostomy ('fenestration') was performed leaving the endosteum and the fluid-filled inner ear intact. OCT was applied via a prototype of a specially equipped operating microscope. The mode of OCT used in this context was spectral-domain (SD)-OCT. RESULTS: On scans, which can be read analogous to B-mode sonography, OCT provides information about structures on the inner surface of the partly exposed but still intact membranous cochlear lining - such as scala tympani or scala vestibuli.     

Middle ear physiology

The middle ear forms part of the sound transformer mechanism, together with the outer ear and the conducting system of the inner ear. An intermediate sensory organ, sensitive to acoustic vibration, and linked to the inner ear, the middle ear made its appearance during the period of adaptation of marine creatures to a terrestrial habitat; its presence is therefore a phylogenetic requirement. It is classical to ascribe three functions to the middle ear: the transmission of acoustic vibrations from the tympanic membrane to the cochlea, impedance matching between the air in the external auditary meatus and the labyrinthine fluids, and protection of the inner ear by means of the acoustic reflex. If the classical mechanical explanation has been able to explain its function, the conceptualization of its physiology in terms of energy allows an even better understanding, as well as providing and explanation for the paradoxes which arise in clinical practice when the classical model is used.     

Three-dimensional imaging of the inner ear by volume-rendered reconstructions of magnetic resonance data

OBJECTIVE: To evaluate 3-dimensional inner ear visualization by volume rendering of high-resolution magnetic resonance data in patients with clinically suspected inner ear abnormality. DESIGN: Prospective comparative study of different postprocessing techniques, based on blinded film readings. SETTING: Tertiary referral hospital. SUBJECTS: Fifty patients (17 females and 33 males) aged 1 to 77 years (average age, 42 years) with sensorineural hearing loss, vertigo, and/or tinnitus. INTERVENTION: Postprocessing of magnetic resonance data to inner ear reconstructions by the use of volume rendering as well as maximum-intensity projection; caloric testing by electronystagmography. MAIN OUTCOME MEASURES: Film was read blindly by 4 radiologists using a 5-point parameter scale for image quality and diagnostic value. The assessibility of inner ear subsegments was evaluated. The specificity of volume-rendered reconstructions for detecting semicircular canal obliterations was assessed in a subgroup of 9 patients by caloric testing. The time required for data postprocessing as well as film reading was recorded by means of a stopwatch. RESULTS: Volume-rendered inner ear reconstructions were superior in image quality (P<.001), diagnostic value (P<.001), subsegment inner ear assessment (P<.01 to P<.001), and film reading time (P<.001) compared with maximum-intensity projections. The data postprocessing time was comparable for both techniques. Caloric weakness was noted in all patients assessed by electronystagmography. CONCLUSION: Volume rendering is the postprocessing technique of choice for 3-dimensional inner ear visualization, performing better than maximum-intensity projections with respect to various parameters.     

How to perform 3D reconstruction of skull base tumours

The surgical management of skull base lesions is difficult due to the complex anatomy of the region and the intimate relations between the lesion and adjacent nerves and vessels. Minimally invasive approaches are increasingly used in skull base surgery to ensure an optimal functional prognosis. Three-dimensional (3D) computed tomography (CT) reconstruction facilitates surgical planning by visualizing the anatomical relations of the lesions in all planes (arteries, veins, nerves, inner ear) and simulation of the surgical approach in the operating position. Helical CT angiography is performed with optimal timing of the injection in terms of tumour and vessel contrast enhancement. 3D definition of each structure is based on colour coding by automatic thresholding (bone, vessels) or manual segmentation on each slice (tumour, nerves, inner ear). Imaging is generally presented in 3 dimensions (superior, coronal, sagittal) with simulation of the surgical procedure (5 to 6 reconstructions in the operating position at different depths).     

Imaging of Cochlear Structures by Optical Coherence Tomography (OCT). Temporal bone experiments for an OCT-guided cochleostomy technique

BACKGROUND: Optical Coherence Tomography (OCT) is a relatively new imaging technique, which provides scans similar to sonography on an optical base. We questioned whether OCT may be helpful in optimizing anatomical orientation in cochlear implant (CI) surgery. In a study on temporal bone specimens we tested, whether OCT provides information about the cochlear topography, particularly in situations, when for cochleostomy the bony otic capsule is already opened but the membranous endosteal layer is still intact. MATERIAL AND METHODS: OCT was performed on five human temporal bone preparations, in which the cochleostomy was carried out still leaving the endosteum covering the fluid-filled inner ear intact. A prototype of operating microscope was used, in which a spectral-domain OCT (SD-OCT) with a central wavelength of 840 nm was integrated. RESULTS: On all scans, OCT supplies information about inner ear structures, such as the lateral attachment of the basilar membrane dividing the scalae. Even delicate structures like the Reissner's membrane could be identified in one case. CONCLUSIONS: This pilot study clearly documents the possibility to identify inner ear structures, especially the site of the scala tympani while its enveloping membranes are still intact. These findings may have an impact on cochlear implant surgery, especially as an orientation guide to localize the scala tympani precisely before opening the fluid-filled inner ear.     

Optical coherence tomography as an orientation guide in cochlear implant surgery?

Conclusion: With optical coherence tomography (OCT) it is basically possible to reveal parts of the cochlear morphology without opening its enveloping membranes. Thus, it may serve as a helpful guide for the surgeon to localize the scala tympani precisely before opening the fluid-filled inner ear to insert the electrode array. Objective: To improve anatomical orientation in cochlear implant surgery before definitively opening the fluid-filled inner ear. The question was whether a new imaging technique, OCT, might provide information about the site of the underlying inner ear structures (scala tympani, scala vestibuli) and could, consequently, guide the surgeon towards the scala tympani. Materials and methods: In a preliminary study, OCT was carried out on human temporal bone preparations, in which a cochleostomy (‘fenestration’) was performed leaving the endosteum and the fluid-filled inner ear intact. OCT was applied via a prototype of a specially equipped operating microscope. The mode of OCT used in this context was spectral-domain (SD)-OCT. Results: On scans, which can be read analogous to B-mode sonography, OCT provides information about structures on the inner surface of the partly exposed but still intact membranous cochlear lining – such as scala tympani or scala vestibuli.     

小儿正常耳蜗与内耳畸形人工耳蜗植入术后电极阻抗及NRT值对比研究

目的：探讨小儿正常耳蜗与内耳畸形人工耳蜗植入手术后,植人体电极阻抗值及神经反应遥测（NRT）值的变化特点及规律。方法：将88例澳大利亚CochlearNucleus24型人工耳蜗植人手术患儿分为正常耳蜗组与内耳畸形耳蜗组,测试手术中及手术后1年阻抗值及NRT值,并分析对比。结果：两组患者阻抗值差异有统计学意义（P〉0．05）,其阻抗变化趋势相同。开机3个月内阻抗值变化明显,其后趋于稳定。两组患者NRT值差异有统计学意义（P〈0．05）,其NRT值变化趋势相同。总的趋势是低频值较低,高频值较高,术中至术后1年NRT值逐渐增高。结论：电极阻抗值及NRT值开机3个月内变化明显,故需多次调机,以使患者语言感知达到最佳状态。     

Sudden hearing loss due to diving and its prevention with heparin.

Vascular embolic and thrombotic problems postulated to be the cause of inner ear sudden deafness have been reported with decompression sickness also. Decompression sickness has been found to lead to cochlear potential loss in the guinea pig, and these losses are minimized by the prophylactic administration of heparin. Preliminary results show that inner ear hemorrhage may be associated with diving deafness, but plasma protein leakage into the perilymph of the ear may precede the hemorrhage. Inner ear hemorrhage in diving deafness seems to be restricted to the microcirculation. Until we gain a better understanding of the pathophysiology of diving induced deafness, it would be premature to consider agents such as heparin for the treatment of the problem in man.     

Autoimmune inner ear disease: a review of basic mechanisms and clinical correlates

Otolaryngologists have long sought to identify causes of sensorineural hearing loss that might be reversed by medical treatment. One such entity has become known as autoimmune inner ear disease. The potential improvement in auditory function in these patients subsequent to immunosuppressive therapy has created a desire in clinicians to better understand this disease. This paper begins by reviewing the basic concepts of autoimmunity. The experimental and clinical data concerning autoimmune inner ear disease are then described and analyzed. Finally, conclusions are drawn concerning our current state of understanding of this disease process.     

Transtympanic management of tinnitus

Transtympanic therapy is becoming and important treatment modality for many inner ear disorders. The current therapies aimed at Meniere's disease, sudden sensorineural hearing loss, noise-induced hearing loss, and the tinnitus associated with these disorders and idiopathic tinnitus, however, represents simply an evolutionary step in this treatment modality and must be validated by further scientific study. A number of promising developments including newer more targeted neuroactive medicines, a better understanding of medicine delivery, and the knowledge of the site, origin, and pathophysiology of the symptoms complex will make this therapy more effective. In the future it is possible that many inner ear disorders will be amenable to inner ear medical therapy. Ideally in the future with knowledge of the disease and its etiology the physician will simply pick the established medicine, the established dose, and the established route of administration and achieve a relatively predictable result.     

Comparison of vulnerability between avian and mammalian inner ears--electrophysiological and morphological studies]

In order to assess the vulnerability of the inner ear, auditory function and morphology of the inner ear were compared between adult budgerigars and adult guinea pigs. Budgerigars have been considered to have an excellent auditory-vocal system. Two experimental conditions were produced in each species; one by acoustic hyperstimulation (1500 Hz, 120 dBSPL) for 96 hours, the other by administration of kanamycin (200 mg/kg) for 7 weeks. Measurement of auditory evoked potentials (AEP) and observation of hair cells by electron microscopy were performed both immediately and 14 days after exposure. In the acoustic hyperstimulation experiment, AEPs of budgerigars showed less damage and better recovery than those of guinea pigs, probably because of morphological differences between the two species in hair and supporting cells. Electron microscopic observation on the budgerigars showed that a small part of the hair cell area was damaged and that regeneration of hair cells had occurred in this area 14 days after exposure. Such observations in guinea pigs revealed that outer hair cells had been damaged and replaced by supporting cells 14 days after exposure. In the kanamycin administration experiment, AEPs showed the same degree of damage and recovery in both species. This suggests that blood supply and drug transport to the inner ear are almost the same although the structure of the inner ear differs markedly between the two species. Electron microscopic observation did not show an apparent regeneration of hair cells 14 days after administration in the budgerigars. Guinea pigs had a tendency to show progressive damage of both auditory function and inner ear morphology even after the cessation of administration. Regeneration of hair cells in the budgerigar differed under both experimental conditions, suggesting that there is a difference in the mode of auditory disturbance between acoustic hyperstimulation and administration of kanamycin. In conclusion, resistance to acoustic hyperstimulation is higher in the avian inner ear than in the mammalian inner ear, while resistance to administration of kanamycin does not differ significantly between the two species.     

Embolic inner ear decompression illness: correlation with a right-to-left shunt

OBJECTIVES/HYPOTHESIS: Inner ear decompression illness is thought to be a rare phenomenon in recreational divers, isolated signs and symptoms of inner ear dysfunction usually being attributed to inner ear barotrauma. STUDY DESIGN: We present 11 cases of inner ear dysfunction in nine divers with inner ear decompression illness. RESULTS: All nine divers had significant right-to-left shunt as diagnosed by transcranial Doppler sonography. CONCLUSIONS: The authors thought that mechanism of causation in these cases may have been intravascular bubble emboli and that inner ear decompression illness may be more common among recreational divers than currently recognized. Failure to treat inner ear decompression illness with recompression therapy can result in permanent disability. Because the differential diagnosis between inner ear barotrauma and inner ear decompression illness can be impossible, the authors suggested that divers who present with inner ear symptoms following a dive should have recompression immediately after having undergone bilateral paracentesis.