CT-scanning of the cochlea in Pendred's syndrome

The inner ears of 5 adult patients with Pendred's syndrome were investigated using a Siemens SOMATOM DRG. Five normal hearing adults participated in the investigation as a control group. The CT-scanning comprised 10-15 consecutive scans of the cochlea. The CT evaluation was performed using both a special bone setting and a soft tissue setting. The cochlear content was quantitatively evaluated by drawing an irregular region of interest on the bone pictures. The region of interest was then transferred to the soft tissue pictures by means of the standard program of the CT-scanner. The resulting mean values of attenuation expressed in Hounsfield Units were significantly lower in the Pendred cochleas than in the normal cochleas. At the same time a typical Mondini malformed cochlea was demonstrated in all patients with Pendred's syndrome. The lower values of attenuation of the cochlea in Pendred's syndrome reflect the rudimentarily developed infra-cochlear osseous structures in this disease. We conclude that CT-scanning of the cochlea using this procedure is reliable enough to replace the conventional axial-pyramidal tomography when a Mondini cochlea is suspected.     

Advances in oto-immunology: new trends in functional pathology of the temporal bone

By using monoclonal and polyclonal antibodies against cell-membrane receptors and cytoskeletal proteins, the cellular and tissue composition of any organ can be far better determined. This is illustrated in the tympanic membrane, middle ear mucosa, and cholesteatoma. Immunotechnology applied to the temporal bone is shown with an animal-ototoxicity model. Antibodies to keratin and vimentin (i.e., to proteins of the fibrillar components that make up the cytoskeleton) stain specific tissue compartments. Langerhans' cell and T-lymphocyte subsets predominate in a cholesteatoma. The normal human tympanic membrane is devoid of these cells. Gentamicin can be traced with a polyvalent anti-gentamicin antiserum in serial sections of the cochlea and kidney. The drug accumulates in the outer hair cells and proximal tubular cells, respectively. A new technique of CT-scanning, microslicing, plastic embedding, and semithin sectioning of undecalcified human temporal bone is described. Perspectives in applying immunotechnology to this method of human temporal bone processing are discussed.     

Densitometry of the cochlear capsule and correlation between bone density loss and bone conduction hearing loss in otosclerosis

Radiodensity of the bony cochlear capsule was investigated by CT-scanning in 134 ears with otosclerosis and 35 normal control ears. A technique of densitometry of the cochlea was developed comprising the measurement of maximum and minimum density together with mapping of the cochlea and measurement of the density at six predefined points in the cochlear capsule. Bone density in the normal cochlea showed very little interindividual variation. In the otosclerosis patients, minimum density was decreased in 58% of the ears, indicating the presence of a focus. At visual examination, foci were only detectable when density loss exceeded 200 Hounsfield. A positive correlation was found between bone density loss and bone conduction hearing loss with a maximum at 2,000 Hz and the medioventral point of the cochlear wall. The method appears to be useful for the follow-up during fluoride treatment, as is demonstrated by a case report.     

Extraskeletal Ewing's Sarcoma of parapharyngeal space

Extraskeletal Ewing's Sarcoma (EES) of head and neck region, is a rare soft tissue tumour morphologically similar to the commoner Ewing's Sarcoma arising from bone. We report a case of EES in parapharyngeal space in a 6-year-old male; who presented with stridor. CT scan of neck showed soft tissue mass in right parapharyngeal space with intraorbital and intracranial extention. Histopathological examination showed round cell tumour and immunohistochemistry was positive for CD99 and Vimentin. The patient responded very well to Concurrent Chemoradiation. An extensive review of English literature, to the best of our knowledge, did not reveal any previous case of EES in parapharyngeal space in children; although one similar case in a 53-year male is reported.     

Histologic and morphologic evaluation of explanted bone anchors from bone-anchored hearing aids

Bone-anchored hearing aids are a standard option in rehabilitation of patients with conductive or mixed hearing loss, and also CROS fitting. However, the skin-penetrating bone anchor repeatedly gives reason for discussion about the risk of infection of surrounding tissues as a major cause of malfunction. In the present study, explanted bone anchors with surrounding bone and soft tissue were examined and compared with the morphology of lost implants. The anchors originated from five patients. Two needed explantation due to deafness with the need of cochlea implantation. A third patient underwent explantation due to meningeal irritation by the bone anchor. Another patient lost the implant due to mechanical stress shortly after implantation. The last implant was lost in a child without apparent reason. All implants were clinically free of infection and had been stable for a median implantation period of 12 months. During the explantation procedure, the fixtures were recovered together with the attached soft tissue and bone. The specimens were examined by light microscopy or scanning electron microscopy (SEM). Sectioning for light microscopy was performed with a diamond-coated saw microtome. Histopathologic examination of the surrounding skin and subcutaneous soft tissue showed slight inflammation in one case only. The bone was regularly vital, presenting no signs of inflammation. The threads of the fixtures were filled with bone, with particularly strong attachment to the flank of traction. The SEM investigation exposed the ultrastructural interaction of bone with the implant surface. Filiform- and podocyte-like processes of osteocytes attach to the implant; lost implants did not reflect these features. Implant integration involves both osseointegration as well as soft tissue integration. Titanium oxide as the active implant surface promotes this integration even in unstable implants. The morphologic analysis exposed structural areas of the implant with weak bone-to-metal contact. Optimized implant design with modified surface and threads may additionally improve osseointegration of hearing aid bone anchors.     

Bilateral fitting of BAHAs and BAHA® fitted in unilateral deaf persons: Acoustical aspects Adaptación bilateral de BAHA y adaptación de BAHA en sorderas unilaterales: Aspectos acústicos

The benefit of a bone-anchored hearing aid (BAHA) to a patient fitted bilaterally; and the benefit of a BAHA®to a unilaterally deaf person was estimated by four acoustical measurements: directional sensitivity of a BAHA® placed at the skull, vibration transmission in the skull, gain, and estimated transcranial attenuation of bone conducted sound. Provided a patient has a similar bone conduction hearing ability at both cochlea, it was found that a patient should, theoretically, benefit from bilateral fitting of BAHAs in terms of better hearing thresholds from the front, and better overall hearing ability from the surround. The data indicates further, that bilateral fitting facilitates extraction of interaural cues, which should lead to greater ability to determine the direction of a sound source, as well as better hearing in noise. However, due to the cross-hearing of bone conducted sound, the binaural processing for the patient fitted bilaterally with BAHAs is less than for normal binaural air conduction hearing. Finally, the data showed that the benefit of fitting a BAHA® in a unilaterally deaf person, depends on that person's transcranial attenuation.     

Submillimeter Magnetic Resonance Imaging of the Temporal Bone in Meniere's Disease

The pathoetiology of Meniere's disease remains elusive. Histopathologic and imaging studies have implicated congenital or developmental abnormality of the endolymphatic duct as a likely predisposing factor to the development of endolymphatic hydrops and clinical Meniere's disease. Recently, improved high-resolution magnetic resonance imaging (MRI) protocols have allowed better demonstration of the soft tissues of the endolymphatic duct and sac. This study is a prospective evaluation of the ability of submillimeter MRI to detect the endolymphatic duct in Meniere's disease patients and control subjects. In addition, the development of the temporal bone in the region of the endolymphatic sac and duct is evaluated by measurements of the distance from the posterior semicircular canal to the subarachnoid space and the distance from the vestibule to the subarachnoid space. Visualization of the endolymphatic duct was found to be significantly less frequent in the Meniere's disease patients (29%) than in the control subjects(91%). Temporal bone measurements in the region of the endolymphatic duct showed patients with Meniere's disease to have smaller dimensions than control subjects.     

Investigation of lateral pharyngeal walls in OSAS

The aim of this study is to investigate the relationship between the site of obstruction detected on Müller’s maneuver and the polysomnography findings in patients with obstructive sleep apnea syndrome. This study is a prospective cohort study in a setting of Tertiary referral center. The study was performed on 87 patients (59 males and 28 females) with a mean age of 50 ± 10.34 years (range 20–83 years) who presented with the complaints of snoring, apnea, witnessed apnea and daytime sleepiness. The height and body weight of the enrolled patients were measured and the body mass indexes were calculated. The obstruction degrees of the soft palate and lateral pharyngeal walls at the level of the soft palate and the obstruction degrees of the tongue base and lateral pharyngeal walls at the level of the tongue base were determined using the Müller’s maneuver. All patients underwent whole-night polysomnography at our hospital’s Sleep Center. The apnea–hypopnea index values of the patients increased as their ages and body mass index values increased. There was a highly statistically significant correlation between apnea–hypopnea index and the obstruction degree of the lateral pharyngeal walls at the level of the tongue base on Müller’s maneuver (p < 0.01). We found that the apnea–hypopnea index increased as the obstruction degree of the lateral pharyngeal walls increased on Müller’s maneuver. In patients with obstructive sleep apnea syndrome, a high apnea–hypopnea index can be predicted if the obstruction degree of the lateral pharyngeal walls is high at the level of the tongue base on Müller’s maneuver.     

Optical coherence tomography of the cochlea in the porcine model

Objectives/Hypothesis: To demonstrate the feasibility of optical coherence tomography in microstructural imaging of the porcine cochlea. Study Design: Ex vivo, porcine model. Methods: Optical coherence tomographic images of the porcine cochlea were obtained by thinning the bone from the basal turn of the cochlea leaving the endosteum intact. The images were compared with the corresponding histological sections. Results: In the areas of thinned bone, images were obtained of the stria vascularis, Reissner's membrane, basilar membrane, tectorial membrane, scala media, scala tympani, and scala vestibuli. The bone was too thick for adequate light penetration in the areas where it was not thinned. Good histological correlation was obtained. Conclusions: Cochlear and vestibular microanatomic structures of the pig cochlea were clearly identified with histological confirmation, suggesting the potential application of this noninvasive imaging modality for in vivo imaging of the human cochlea.     

Intracochlear tPA infusion may reduce fibrosis caused by cochlear implantation surgery

Background: Experiments show that the extent of ongoing fibrotic change within the cochlea can be determined by the volume and pattern of bleeding within the first 24?h following cochlear implantation. Tissue-type plasminogen activator (tPA) is effective at reducing thrombus volume when administered both within and external to the systemic circulation.

Aims/Objectives: To determine if tPA delivered into the scala tympani immediately following implantation will reduce thrombus volume within the lower basal turn of the cochlea.

Materials and Methods: Guinea pigs were implanted with either ‘soft’ or ‘hard’ arrays and administered tPA or saline via an intra-cochlear infusion immediately after implantation. Hearing was checked prior to, and 2 weeks after implantation. Cochleae were then harvested and imaged.

Results: Animals implanted with ‘soft’ arrays had 4.2% less tissue response compared with animals implanted with ‘hard’ arrays. In animals receiving ‘soft’ arrays, tPA reduced the volume of tissue response (measured by the percentage of the lower basal turn of the scala tympani occupied by tissue response) compared with saline.

Conclusions and Significance: tPA may be effective in reducing the overall volume of tissue response in routine ‘soft’ cochlear implantation and may have a greater effect in the event of significant surgical trauma.     

Research software in cochlear duct length estimation,Greenwood frequency mapping and CI electrode array length simulation

Background and objectiveThe size of the cochlea varies a lot among the human population bringing the necessity for electrode arrays to be available in various lengths irrespective of the cochlear implant (CI) brand. This research software helps in the estimation of the patient''s cochlear duct length (CDL) which is then used for the simulation of the correct length electrode array matching the patient''s cochlear size and as well in getting the patient specific cochlear frequency map.MethodsVisual Studio Express 2012 for Windows Desktop is used in the architecture of this research software. The basal turn diameter of the cochlea (“A” value) needs to be measured from the pre-operative computed tomography (CT) image of the patient''s temporal bone. This “A” will be taken as the input for the CDL equations proposed by Alexiades et al for estimating the CDL along the basilar membrane for various insertion depths. Greenwood''s equation is then used in combination with the CDL for the full length of the cochlea in getting the patient specific frequency map.ResultsThe research software with the help of the “A” value as input, with few button clicks, gives the patient specific CDL for various insertion depths and the Greenwood''s frequency map. The users have the choice to select any electrode array of their choice and place it under the frequency map to see how good it fits to that particular patient''s cochlea. Also, given the possibility to drag and move the electrode array picture to mimic the post-operative actual electrode insertion depth.ConclusionsThis research software simplifies the overall process of CDL estimation and in getting the patient specific cochlear frequency map. The clinicians get the chance to simulate placing the various electrode array lengths in patient cochlea in identifying the best fit electrode. This could help in pushing the CI field into the concept of individualized CI electrode array solution that ultimately benefits the patients.     

Electrically evoked compound action potentials are different depending on the site of cochlear stimulation

One of the many parameters that can affect cochlear implant (CI) users’ performance is the site of presentation of electrical stimulation, from the CI, to the auditory nerve. Evoked compound action potential (ECAP) measurements are commonly used to verify nerve function by stimulating one electrode contact in the cochlea and recording the resulting action potentials on the other contacts of the electrode array.

The present study aimed to determine if the ECAP amplitude differs between the apical, middle, and basal region of the cochlea, if double peak potentials were more likely in the apex than the basal region of the cochlea, and if there were differences in the ECAP threshold and recovery function across the cochlea.

ECAP measurements were performed in the apical, middle, and basal region of the cochlea at fixed sites of stimulation with varying recording electrodes. One hundred and forty one adult subjects with severe to profound sensorineural hearing loss fitted with a Standard or FLEX^SOFT electrode were included in this study. ECAP responses were captured using MAESTRO System Software (MED-EL). The ECAP amplitude, threshold, and slope were determined using amplitude growth sequences. The 50% recovery rate was assessed using independent single sequences that have two stimulation pulses (a masker and a probe pulse) separated by a variable inter-pulse interval. For all recordings, ECAP peaks were annotated semi-automatically.

ECAP amplitudes were greater upon stimulation of the apical region compared to the basal region of the cochlea. ECAP slopes were steeper in the apical region compared to the basal region of the cochlea and ECAP thresholds were lower in the middle region compared to the basal region of the cochlea. The incidence of double peaks was greater upon stimulation of the apical region compared to the basal region of the cochlea.

This data indicates that the site and intensity of cochlear stimulation affect ECAP properties.     

Laser light transmission and laser Doppler blood flow measurements on human,rat and guinea pig cochlea

Summary In order to test the applicability of laser-Doppler flowmetry in monitoring cochlear blood flow clinically, the thickness and the helium-neon laser light transmission of specimens of human, rat and guinea pig promontory bone and human skin were determined. Furthermore, comparative laser-Doppler measurements were taken from the promontory in patients, rats and guinea pigs. Due to the different thicknesses of the promontory bone in different species, the light transmission was found to be considerably higher for the animal cochlea (rat, 15%; guinea pig, 6.6%) than the human cochlea (1.7%). However, a clearly higher laser-Doppler signal was recorded from both the human and the rat cochleas as compared with the guinea pig. The relative laser light attenuation by the human skin specimens corresponded to that of the human promontory bone. The findings are discussed with regard to the suitability of the laser-Doppler method for blood flow measurements in the human cochlea.Presented at the 25th Workshop on Inner Ear Biology in London, England, 4–7 September 1988     

上气道CT软组织测量值与阻塞性睡眠呼吸暂停低通气综合征病情程度的关系

目的 探讨上气道形态学指标尤其是气道壁软组织体积与阻塞性睡眠呼吸暂停低通气综合征(OSAHS)患者病情严重程度的关系.方法 经多道睡眠图监测确诊的82例OSAHS患者行平静呼吸时的上气道CT扫描,并行三维重建,测量上气道不同部位的左右径、截面积,尤其是气道腔内容积、气道壁软组织体积等指标,并进行各测量值与呼吸暂停低通气指数(AHI)、最低动脉血氧饱和度(lowest arterial oxygen saturation,LSaO2)的相关性分析.结果 各研究平面的左右径、面积与AHI的大小均呈负相关,与LSaO2呈正相关,尤其是AHI与整个气道的最小左右径相关性更明显(r=-0.558,P<0.01).AHI与鼻腔骨性容积、鼻咽腔内容积、腭咽气道腔内容积、腭咽气道腔内容积占腭咽骨性框架包绕容积的比值、整个气道腔内容积占整个气道骨性框架包绕容积的比值均呈不同程度的负相关(P值<0.05或<0.01),同时与腭咽气道壁软组织体积、腭咽气道壁软组织体积占腭咽骨性框架内包绕容积的比值、整个气道壁软组织体积占整个气道骨性框架包绕容积的比值,腭咽气道壁软组织体积与腭咽腔内容积的比值、整个气道壁软组织体积与整个气道腔内容积的比值均呈正相关(P值<0.05或<0.01).结论 OSAHS患者上气道CT测量二维指标与三维指标均可对OSAHS病情严重程度的预测提供一定的参考信息.气道的左右径、面积及气道腔内容积、气道壁软组织体积,尤其是腭咽区气道腔内容积及气道壁软组织体积,对病情的判别均有意义.     

What is Piezosurgery? Two-years experience in craniomaxillofacial surgery

INTRODUCTION: Piezosurgery is a new surgical technique used in dentistry to section hard tissues without damaging adjacent soft tissues. We hypothesized that such a device could also be useful in craniofacial and orthognathic surgery. MATERIAL AND METHOD: An ultrasonic device (Mectron) was employed in different craniofacial surgical procedures: a) to perform 144 Le Fort I osteotomies, 140 palatal expansions after Le Fort I osteotomies, and 134 bilateral sagittal osteotomies; b) to perform a Le Fort III osteotomy for treatment of Crouzon syndrome in 2 patients; c) to perform 5 segmental osteotomies and 3 osteotomies of the inferior edge of the mandible for facial asymmetry; d) to perform 12 cases of unicortical calvarial bone grafting; e) to remove the superior orbital roof in 20 cases of craniofaciostenosis and the frontal bone in 5 cases; f) to remove the external wall of the orbit or the anterior and posterior wall of the frontal sinuses in 10 cases of orbital cavity tumors; g) to approach the skull base through the frontal sinuses in 4 cases. Integrity of soft tissues and surgical time were evaluated. RESULTS: Analysis of the results showed that Piezosurgery: a) allows very precise cutting; b) avoids bone cutting using an osteotome; c) spares soft tissue such as brain, dura-mater, palatal mucosa, and the inferior alveolar nerve; d) increases the time of bone cutting but not the overall operative time because of the absence of soft tissue protection. DISCUSSION: Piezosurgery is a new technical procedure, which can be advantageous for bone cutting in many situations, sparing adjacent soft tissues such as brain, palatal mucosa, and the inferior alveolar nerve from any damage. The device's lack of power appears to be a minor problem compared with the advantages.     

Fixation of soft tissue surrounded by bone with microwave irradiation: electron microscopic observation of guinea pig inner ear

When electron microscopy is performed on organs such as the inner ear that cannot be removed immediately after decapitation of animals, it is necessary to fix the target organ or tissue by systemic or regional perfusion fixation. However, such methods of fixation can increase vascular pressure or perilymphatic pressure, making it difficult to perform precise morphological observation of the vascular endothelial cells and membranous labyrinth. We recently attempted fixation of the cochlea by microwave irradiation. Guinea pigs were decapitated. The bullas were then removed from each animal and fixed in a mixture of 2% paraformaldehyde and 0.5% glutaraldehyde. Microwave (300 W) irradiation was then applied to the specimen for 1 minute. The fixative was immediately replaced with new fixative (4 degrees C). This sequence of manipulations was repeated 10 times, for a cumulative microwave irradiation time of 10 minutes. During the microwave irradiation period, the fixative temperature was kept at about 30 degrees C. After the last round of irradiation, the specimens were kept immersed in the fixative for 1 hour. After a small slit was created in the bone on the lateral wall of the cochlea, the specimens were post-fixed in osmic acid and embedded in Epon 812. Each specimen was cut into halves along the plane containing the modiolus of the cochlea. After the bone on the lateral wall of the cochlea was cut off under a stereoscopic microscope, ultrathin sections were prepared for observation under a transmission electron microscope. With this technique, the stria vascularis and the organ of Corti were fixed to a degree comparable to or better than that achieved with the conventional method of fixation. Fixation with microwave irradiation is relatively simple and can solve the problems associated with perfusion fixation, and thus provides an excellent means of fixation. This technique appears to be particularly promising for fixation for soft tissue surrounded by bone.     

Interactions in the cochlea between air conduction and osseous and non-osseous bone conduction stimulation

Since air-conducted (AC) and clinical (mastoid) bone-conducted (BC) sounds interact in the cochlea (e.g. pitch, cancellation, masking, beats), it has been thought that both AC and BC stimulations lead to a mechanical wave in the cochlea. However, there are also “non-osseous” forms of BC, i.e. auditory sensation produced when the clinical bone vibrator is applied to “non-osseous” soft tissue sites. In the present study, such “non-osseous” sites were identified (e.g. eye, cheek, neck) and they interacted with AC and osseous BC (pitch matching, beats, masking), indicating that all of these forms of auditory stimulation converge in the cochlea, producing the same pattern of mechanical activity, leading to their interactions.