Quantitative analysis of 3D-printed custom ossicular prostheses motion using laser Doppler vibrometry

<b><br>Introduction:</b> In chronic otitis media, the reconstruction of the middle ear's sound conducting system involves repairing the tympanic membrane and filling the space between ossicular chain remnants. The final shape of the prosthesis is usually determined intraoperatively. However, the ossicular chain may be preoperatively measured using computed tomography (CT) scans, and an individualized prosthesis can be designed. Custom 3D printing seems to be an attractive solution for optimal adjustment.</br> <b><br>Aim:</b> Our study aimed to assess the 3D-printed custom prosthesis movability and compare it to the original ossicular chain.</br> <b><br>Material and methods:</b> Five fresh-frozen temporal bone specimens were used. Using Cone-Beam CT scans, the incus model was designed individually and 3D-printed. The ossicular chain was reconstructed inside the cadaveric temporal bone. Acoustic stimuli were applied to the external ear canal one frequency at a time. The laser Doppler vibrometer (LDV) measured the intact and 3D-printed prosthesis reconstructed ossicular chain vibrations.</br> <b><br>Results:</b> At all stimulation frequencies, there was no significant difference in velocity values between the intact and reconstructed ossicular chain at the intensity of 80 dB SPL. The obtained values of the velocity gain were: -7.9 (SD-19) dB, -6.8 (SD8.12) dB, -10,9 (SD-5.3) dB, -7.4 (SD-8.16) dB for 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, respectively. The vibration threshold shift values ranged between -0.57 dB at 500 Hz and 3.81 dB at 2000 Hz.</br> <b><br>Conclusions:</b> This study analyzed the movability of individualized 3D-printed custom ossicular prostheses using LDV. Compared to the intact ossicular chain, the reconstructed ossicular chain movability was characterized by statistically insignificant reduced movability at all tested frequencies. Because the prosthesis's new design conception as custom 3D individualized printing allows for patient-specific ossiculoplasty, it represents a promising new direction for ossicular chain reconstruction. It seems to be an attractive solution for prosthesis optimal adjustment and, hopefully, better hearing results.</br>.

The human middle ear in motion: 3D visualization and quantification using dynamic synchrotron-based X-ray imaging

The characterization of the vibrations of the middle ear ossicles during sound transmission is a focal point in clinical research. However, the small size of the structures, their micrometer-scale movement, and the deep-seated position of the middle ear within the temporal bone make these types of measurements extremely challenging. In this work, dynamic synchrotron-based X-ray phase-contrast microtomography is used on acoustically stimulated intact human ears, allowing for the three-dimensional visualization of entire human eardrums and ossicular chains in motion. A post-gating algorithm is used to temporally resolve the fast micromotions at 128 Hz, coupled with a high-throughput pipeline to process the large tomographic datasets. Seven ex-vivo fresh-frozen human temporal bones in healthy conditions are studied, and the rigid body motions of the ossicles are quantitatively delineated. Clinically relevant regions of the ossicular chain are tracked in 3D, and the amplitudes of their displacement are computed for two acoustic stimuli.

Evaluation of the ear ossicles with photon-counting detector CT

Recently, computed tomography with photon-counting detector (PCD-CT) has been developed to enable high-resolution imaging at a lower radiation dose. PCD-CT employs a photon-counting detector that can measure the number of incident X-ray photons and their energy. The newly released PCD-CT (NAEOTOM Alpha, Siemens Healthineers, Forchheim, Germany) has been in clinical use at our institution since December 2022. The PCD-CT offers several advantages over current state-of-the-art energy-integrating detector CT (EID-CT). The PCD-CT does not require septa to create a detector channel, while EID-CT does. Therefore, downsizing the anode to achieve higher resolution does not affect the dose efficiency of the PCD-CT. CT is an indispensable modality for evaluating ear ossicles. The ear ossicles and joints are clearly depicted by PCD-CT. In particular, the anterior and posterior legs of the stapes, which are sometimes unclear on conventional CT scans, can be clearly visualized. We present cases of congenital anomalies of the ossicular chain, ossicular chain dislocation, tympanosclerosis, and cholesteatoma in which PCD-CT was useful. This short article reports the usefulness of PCD-CT in the 3D visualization of the ear ossicles.

Micro-CT of the human ossicular chain: Statistical shape modeling and implications for otologic surgery

The ossicular chain is a middle ear structure consisting of the small incus, malleus and stapes bones, which transmit tympanic membrane vibrations caused by sound to the inner ear. Despite being shown to be highly variable in shape, there are very few morphological studies of the ossicles. The objective of this study was to use a large sample of cadaveric ossicles to create a set of three-dimensional models and study their statistical variance. Thirty-three cadaveric temporal bone samples were scanned using micro-computed tomography (μCT) and segmented. Statistical shape models (SSMs) were then made for each ossicle to demonstrate the divergence of morphological features. Results revealed that ossicles were most likely to vary in overall size, but that more specific feature variability was found at the manubrium of the malleus, the long process and lenticular process of the incus, and the crura and footplate of the stapes. By analyzing samples as whole ossicular chains, it was revealed that when fixed at the malleus, changes along the chain resulted in a wide variety of final stapes positions. This is the first known study to create high-quality, three-dimensional SSMs of the human ossicles. This information can be used to guide otological surgical training and planning, inform ossicular prosthesis development, and assist with other ossicular studies and applications by improving automated segmentation algorithms. All models have been made publicly available.

Handheld laser-fiber vibrometry probe for assessing auditory ossicles displacement

SIGNIFICANCE

Measurements of auditory ossicles displacement are commonly carried out by means of laser-Doppler vibrometry (LDV), which is considered to be a gold standard. The limitation of the LDV method, especially for in vivo measurements, is the necessity to expose an object in a straight line to a laser beam operating from a distance. An alternative to this approach is the use of a handheld laser-fiber vibrometry probe (HLFVP) with a curved tip.

AIM

We evaluate the feasibility of an HLFVP with a curved tip for measuring sound-induced displacement of the auditory ossicles.

APPROACH

A handheld vibrometer probe guiding the laser beam with a fiber-optic cable was used for displacement measurements of the incus body and the posterior crus of the stapes. Tonal stimuli at frequencies of 0.5, 1, 2, and 4 kHz were presented by means of an insert earphone positioned in the outer ear canal. The probe was fixed at the measurement site using a tripod or hand-held by one of the two surgeons.

RESULTS

The measurements were carried out on six fresh temporal bones. Multivariate analysis of variance showed statistically significant differences for stimulus frequency (F3,143  =  29.37, p  <  0.001, and η2  =  0.35), bone (F5,143  =  4.61, p  =  0.001, and η2  =  0.01), and measurement site (F1,143  =  4.74, p  =  0.03, and η2  =  0.02) in the absence of statistically significant differences for the probe fixation method (F2,143  =  0.15, p  =  0.862, and η2  =  0.001). Standard deviations of the means were 6.9, 2.6, 1.9, and 0.6  nm  /  Pa for frequency, bone, site, and fixation, respectively. Ear transfer functions were found to be consistent with literature data.

CONCLUSIONS

The feasibility of applying HLFVP to measure the displacement of auditory ossicles has been confirmed. HLFVP offers the possibility of carrying out measurements at various angles; however, this needs to be standardized taking into account anatomical limitations and surgical convenience.

Traumatic dislocation of middle ear ossicles: A new computed tomography classification predicting hearing outcome

Objectives

To assess the feasibility of radiologic measurements and find out whether hearing outcome could be predicted based on computer tomography (CT) scan evaluation in patients with temporal bone fractures and suspected ossicular joint dislocation.

Methods

We assessed 4002 temporal bone CT scans and identified 34 patients with reported ossicular joint dislocation due to trauma. We excluded those with no proven traumatic ossicular dislocation in CT scan and patients with bilateral temporal bone fractures. We measured four parameters such as malleus-incus axis distance, malleus-incus angle at midpoints, malleus- incus axis angle and ossicular joint space. The contralateral healthy side served as its own control. Hearing outcome 1–3 months after the index visit was analyzed. We assessed diagnostic accuracy and performed a logistic regression using radiologic measurement parameters for outcome prediction of conductive hearing loss (defined as >20dB air-bone gap).

Results

We found excellent inter-rater agreement on the measurement of axis deviation between incus and malleus in CT scans (interclass correlation coefficient 0.81). The larger the deviation of incus and malleus axis, the higher probability of poor hearing outcome (odds ratio (OR) 2.67 per 0.1mm, p = .006). A cut-off value for the axis deviation of 0.25mm showed a sensitivity of 0.778 and a specificity of 0.94 (p < .001) for discrimination between poor and good hearing outcome in terms of conductive hearing loss.

Conclusion

Adequate assessment of high resolution CT scans of temporal bone in which ossicular chain dislocation had occurred after trauma was feasible. Axis deviations of the incus and the malleus were strongly predictive for poor hearing outcome in terms of air conduction 1–3 months after trauma. We propose a 3-level classification system for hearing outcome prediction based on radiologic measures.

Precision Medicine in Ossiculoplasty

INTRODUCTION

Long term results of ossiculoplasty surgery are considered poor with displacement and extrusion amongst the common reasons for failure. Application of 3Dimensional (3D) printing may help overcome some of these barriers, however digital methods to attain accurate 3D morphological studies of ossicular anatomy are lacking, exacerbated by the limitation of resolution of clinical imaging.

METHODS

20 human cadaveric temporal bones were assessed using micro computed tomography (CT) imaging to demonstrate the lowest resolution required for accurate 3D reconstruction. The bones were then scanned using conebeam CT (125 μm) and helical CT (0.6 mm). 3D reconstruction using clinical imaging techniques with microCT imaging (40 μm resolution) as a reference was assessed. The incus was chosen as the focus of study. Two different methods of 3D printing techniques were assessed.

RESULTS

A minimum resolution of 100 μm was needed for adequate 3D reconstruction of the ossicular chain. Conebeam CT gave the most accurate data on 3D analysis, producing the smallest mean variation in surface topography data relative to microCT (mean difference 0.037 mm, p < 0.001). Though the incus varied in shape in between people, paired matches were identical. Thus, the contralateral side can be used for 3D printing source data if the ipsilateral incus is missing. Laser based 3D printing was superior to extrusion based printing to achieve the resolution demands for 3D printed ossicles.

CONCLUSION

Resolution of modern imaging allows 3D reconstructions and 3D printing of human ossicles with good accuracy, though it is important to pay attention to thresholding during this process.

Optical coherence tomographic measurements of the sound-induced motion of the ossicular chain in chinchillas: Additional modes of ossicular motion enhance the mechanical response of the chinchilla middle ear at higher frequencies

Wavelength-swept optical coherence tomography (OCT) was used to scan the structure of cadaveric chinchilla ears in three dimensions with high spatial resolution and measure the sound-induced displacements of the entire OCT-visible lateral surfaces of the ossicles in the lateral-to-medial direction. The simultaneous measurement of structure and displacement allowed a precise match between the observed motion and its structural origin. The structure and measured displacements are consistent with previously published data. The coincident detailed structural and motion measurements demonstrate the presence of several frequency-dependent modes of ossicular motion, including: (i) rotation about an anteriorly-to-posteriorly directed axis positioned near the commonly defined anatomical axis of rotation that dominates at frequencies below 8 kHz, (ii) a lateral-to-medial translational component that is visible at frequencies from 2 to greater than 10 kHz, and (iii) a newly described rotational mode around an inferiorly-to-superiorly directed axis that parallels the manubrium of the malleus and dominates ossicular motion between 10 and 16 kHz. This new axis of rotation is located near the posterior edge of the manubrium. The onset of the second rotational mode leads to a boost in the magnitude of sound-induced stapes displacement near 14 kHz, and adds a half-cycle to the accumulating phase in middle-ear sound transmission. Similar measurements in one ear after interruption of the incudostapedial joint suggest the load of the cochlea and stapes annular ligament is important to the presence of the second rotational mode, and acts to limit simple ossicular translation.

Conductive hearing loss with a "dry middle ear cleft"-A comprehensive pictorial review with CT

Conductive hearing loss (CHL) commonly results from middle ear fluid and inflammation (otitis media). Less commonly in patients with CHL, the middle ear cleft is well aerated or 'dry' with absence of soft tissue or fluid clinically and on imaging. There are numerous causes for this but they can be clinically challenging to diagnose. This pictorial review aims to illustrate and discuss the CT features of both common and less common causes of CHL in patients with a "dry middle ear cavity".

Atlas-Based Segmentation of Temporal Bone Anatomy

PURPOSE

To develop a time-efficient automated segmentation approach that could identify critical structures in the temporal bone for visual enhancement and use in surgical simulation software.

METHODS

An atlas-based segmentation approach was developed to segment the cochlea, ossicles, semicircular canals (SCCs), and facial nerve in normal temporal bone CT images. This approach was tested in images of 26 cadaver bones (13 left, 13 right). The results of the automated segmentation were compared to manual segmentation visually and using DICE metric, average Hausdorff distance, and volume similarity.

RESULTS

The DICE metrics were greater than 0.8 for the cochlea, malleus, incus, and the SCCs combined. It was slightly lower for the facial nerve. The average Hausdorff distance was less than one voxel for all structures, and the volume similarity was 0.86 or greater for all structures except the stapes.

CONCLUSIONS

The atlas-based approach with rigid body registration of the otic capsule was successful in segmenting critical structures of temporal bone anatomy for use in surgical simulation software.

Traumatic ossicular disruption with isolated fracture of the stapes suprastructure: comparison with incudostapedial joint dislocation

CONCLUSION

More severe high frequency hearing loss, especially at 8 kHz, occurs with fracture of the stapes suprastructure (SSF) compared with isolated incudostapedial joint dislocation (ISD). Successful hearing gain can be achieved in the speech range with appropriate ossicular reconstruction.

OBJECTIVES

Traumatic SSF is a rare consequence of head trauma. This study aimed to demonstrate the characteristic features of SSF compared with traumatic ISD.

METHODS

Eighteen patients who suffered from conductive hearing loss after head trauma and were operated from 2000 to 2012 were enrolled. Eight and 10 patients were confirmed to have a traumatic SSF (SSF group) and ISD (ISD group), respectively. The etiology of ossicular disruption, preoperative CT scan of the temporal bone, and intraoperative findings were retrospectively reviewed. Pre- and postoperative hearing was analyzed by both pure tone averages and thresholds at each frequency (0.5-8 kHz).

RESULTS

The most common etiologies in the SSF group were fall (n = 3) and direct ear trauma (n = 3), and for those in the ISD group, the most common etiology was traffic accident (n = 6). CT scan showed no evidence of fracture in the SSF group, whereas findings of ossicular dislocation were found in 70% of patients in the ISD group. Hearing outcomes according to the frequencies demonstrated that pre- and postoperative hearing loss at 8 kHz was more severe in the SSF group than in the ISD group. In a comparison of hearing outcomes at each frequency, the postoperative hearing threshold at 8 kHz was higher than for other frequencies. Postoperatively, 63% of the SSF group and 70% of the ISD group obtained an air-bone gap of within 15 dB.

[On the clinical application of spiral CT three-dimensional reconstruction of middle ear ossicles]

OBJECTIVE

To investigate the CT virtual endoscopy (CTVE) shows the display method of the normal structure of the middle ear, and evaluation of middle ear disease, particularly in the value and significance of the connection status of the ossicular chain, established display ossicular chain and middle ear structure methods.

METHOD

Volume scanning with a spiral CT unit was performed in forty normal cases and thirty patients with suspected lesions of middle ear. Respectively, with Germany's Siemens (Siemens SOMATOM Sensation 16) spiral CT the Inner Ear scanner patients with axial scanning, reconstruction of the original image, the software selected Fly-through A, B, C the point approach CTVE imaging studies. Focus ossicular chain connection status, and chronic otitis media shown the results of surgery in exploratory image control.

RESULT

Normal group CTVE in the hammer bone, incus promontory, facial nerve, the lateral semicircular canal display rate was 100%; stapes, the two arch of the display rate in three display levels, respectively, to 57.5%, 70.0%, 97.5%; round window, oval window was 90.0%, 93.0%, 97.5%. Ossicular injury, displacement, interruption, deletion, deformity in cases of otitis media, trauma, temporal bone malformations.

CONCLUSION

CTVE link relations between the three ossicles (such as interrupt, etc.) have a certain advantage. By choosing the appropriate approach, CTVE has a considerable advantage in the ossicles and their connections, relations as well as pathological state. By comparing CTVE in three different display levels,the technique of CTVE is considered to be an advantageous supplement of tomography.

Restoring hearing using total ossicular replacement prostheses--analysis of 3D finite element model

CONCLUSIONS

During total ossicular replacement surgery, a better auditory functional recovery is obtained when the stapes footplate is retained. Also, the best hearing restoration is obtained when the total ossicular replacement prosthesis (TORP) is placed onto the center of the stapes footplate during operation.

OBJECTIVES

The effects of TORPs connecting to different positions of the stapes footplate or oval window membrane on hearing restoration were investigated.

METHODS

A healthy volunteer's right ear was scanned to obtain the CT data, which were digitalized using a self-compiling program and imported into PATRAN software to establish a 3D finite element model, and a harmonic response analysis was carried out using NASTRAN software. Then the effect of TORPs connecting to different positions on the stapes footplate or oval window membrane was studied.

RESULTS

The displacement curve of the stapes footplate was in good agreement with that of the normal ear when the TORP was connected onto the center of the stapes footplate. The best hearing restoration was obtained when the TORP was placed onto the center of the stapes footplate. The displacement curve of the stapes footplate was basically equivalent to that of the normal ear when the TORP was connected onto the anterior site, while the displacement curve of the stapes footplate differed from that of the normal ear when the TORP was connected onto the posterior site. In addition, when the TORP was connected onto the oval window membrane, the displacement curve of the stapes footplate was different from that of the normal ear.

Controlling the position and the dislocation of the middle ear transducer with high-resolution computed tomography and digital volume tomography: implications for the transducers' design

A minimal tip dislocation of the middle ear transducer (MET(®), Otologics Ltd) may result in poor hearing performance. Our objective was to examine if a defined MET dislocation can be diagnosed by high-resolution computed tomography (HRCT) or digital volume tomography (DVT). A human cadaver head was sequentially implanted with different MET tips (incus application) including a ceramic tip (T 1c), a titanium tip (T 1t), a new, thinner titanium tip (T 2), and a spherical titanium tip (Ts). HRCT and DVT studies were performed. Afterward, the tips were pulled back 0.5 mm, so that they were not attached to the incus. HRCT and DVT scans were repeated to identify the dislocation. Using the best plain in HRCT images, the dislocation of the transducer could be measured reliably and reproducibly in half of the cases. In particular, the precise positioning and the dislocation could be identified when T 1t and Ts were implanted, with the Ts showing the best visibility. DVT failed in recognizing the dislocation in all cases. The identification of MET tip's dislocation with HRCT depends on the shape, size, and material of the tip. This knowledge is useful for the design of the implants, as determination of the right position of the middle ear transducer may be proven important for the hearing outcome. In some cases, however, surgical exploration may still be required. Although DVT represents a promising imaging method for the otologists, it can barely help when MET dislocation is suspected.

Facial nerve lying lateral to ossicles in one case of congenital aural atresia

An abnormal facial nerve (FN) course can be found in a significant number of patients with congenital aural atresia. However, the literature does not include any cases in which the tympanic portion of the FN was displaced lateral to ossicles. We report a unique case of unilateral congenital aural atresia with this rare FN displacement. A review of the existing literature and a discussion are also provided.

Middle ear osteoma: a rare cause of conductive hearing loss with normal tympanic membrane

Osteomas of the temporal bone are benign osseous tumors usually located to the external auditory canal. Osteomas involving the middle ear are very rare. We report the case of a patient presenting with a progressive hearing loss caused by a middle ear osteoma involving the incus and contiguous to the tympanic segment of the facial nerve. This report highlights the value of CT scan in the work-up of conductive or mixed hearing loss with normal tympanic membrane. The management of middle ear osteoma is discussed.

[Functional multispiral computed tomography of sound-transmitting structures in the middle ear]

The objective of this work was to estimate the potential of functional multispiral computed tomography (fMSCT) for the choice and planning of the treatment strategy and the extent of surgical intervention in the patients presenting with fibroosseous diseases of the middle ear associated with the pathologically altered mobility of the auditory ossicles. Studies with the use of MSCT and fMSCT for the examination of temporal bones in 21 patients (25 observations) provided information about normal CT anatomy of the middle ear and a basis for the development of the fMSCT protocol; moreover they allowed the range of mobility of the auditory ossicles to be determined in healthy subjects and patients with middle ear disorders. It is concluded that fMSCT of temporal bones may be recommended to patients suffering otosclerosis, tympanosclerosis, and adhesive otitis media. The use of this technique improves the accuracy of diagnosis and facilitates the choice and planning of the treatment strategy and the extent of surgical intervention in the patients presenting with middle ear diseases.

A preliminary investigation of four-dimensional ultrasound for evaluation of middle ear ossicles: an in vitro study

OBJECTIVE

Temporal bone imaging in children has several inherent limitations. Computed tomography has the disadvantage of ionizing radiation, possible sedation, cost and accessibility. Magnetic resonance imaging has most of these disadvantages, with the exception of radiation, and provides bone images of limited resolution. Recent advances in ultrasound have led to its increased application in numerous medical fields. The purpose of this study was to investigate the ability of four-dimensional ultrasound (4DUS) to image middle ear ossicles in vitro and determine if this technology should be adapted for future clinical use.

METHODS

Thirty cadaveric ossicles (10 malleus, 10 incus, and 10 stapes) were randomized and measured by two evaluators under a microscope. The ossicles were then immersed in a cold water bath and imaged, randomized, and measured using four-dimensional ultrasound by the same two evaluators. A separate cadaveric temporal bone, modified to allow the ultrasound probe to rest on the tympanic membrane, was imaged to visualize the ossicles in situ and evaluate whether or not the tympanic membrane and malleus would impede visualization of more medial structures.

RESULTS

Microscopic measurements were: malleus (h=8.0 mm+/-0.32, w=2.7 mm+/-0.20), incus (h=6.8 mm+/-0.41, w=5.3 mm+/-0.46), stapes (h=3.5 mm+/-0.34, w=2.4 mm+/-0.17). Inter-rater reliability was 0.8. Measurements were in agreement with previously published values. Ultrasound measurements were: malleus (h=8.0 mm+/-0.51, w=2.9 mm+/-0.27), incus (h=6.8 mm+/-0.49, w=5.5 mm+/-0.42), stapes (h=3.6 mm+/-0.41, w=2.5 mm+/-0.19). Inter-rater reliability was 0.7. Mean intra-class correlation coefficient for microscopic and ultrasound measurements was 0.7. Images of the ossicular chain in continuity in the temporal bone specimen were not as clear as images of individual ossicles that were disarticulated and imaged under water.

CONCLUSIONS

4DUS provides reasonable images of ossicles disarticulated and mounted in underwater medium. However, images of the intact ossicular chain in a modified cadaveric temporal bone were not as clear, making interpretation difficult. Further investigation into the development of a thinner ultrasound probe that can pass through the external auditory canal and into overcoming limitations of air in the middle ear cleft are warranted. This could allow for a clinically relevant, faster, lower cost and lower risk alternative to current imaging techniques.

Roles of an anti-tuberculosis medication and surgery in patients with tuberculous otitis media

CONCLUSION

The standard treatment for tuberculous otitis media (TOM) without complications consists of anti-tuberculosis (anti-TB) medication, with which we experienced good treatment outcomes. However, surgery is required for recovery of anatomy and hearing function.

OBJECTIVE

To determine the clinical characteristics of TOM that might optimize diagnosis and to evaluate the differences in clinical courses between patients treated with and without surgery.

METHODS

We analyzed 14 patients (16 ears) who had been diagnosed and treated for TOM. Radiologic findings, laboratory data, and audiometry results were also evaluated. Patients were divided into a chemotherapy group and a surgery group according to treatment modality.

RESULTS

Temporal bone CT (TBCT) showed total occupation of the tympanic cavity by soft tissue and little evidence of ossicular erosion. In the chemotherapy group, dry ears were obtained in all but one patient (14 ears) after treatment. Normalized tympanic membrane (TM) was found in 50% in the chemotherapy group and in 75% in the surgery group. The air-bone gap (ABG) changed from 40.3 +/- 2.5 dB to 47.0 +/- 19.2 dB in the chemotherapy group and from 35.2 +/- 7.6 dB to 30.2 +/- 11.4 dB in the surgery group. After treatment, ABG improved by > 10 dB in one ear in the chemotherapy group and in four ears in the surgery group.

High-frequency ex vivo ultrasound imaging of the auditory system

A 50MHz array-based imaging system was used to obtain high-resolution images of the ear and auditory system. This previously described custom built imaging system (Brown et al. 2004a, 2004b; Brown and Lockwood 2005) is capable of 50 microm axial resolution, and lateral resolution varying from 80 microm to 130 microm over a 5.12 mm scan depth. The imaging system is based on a 2mm diameter, seven-element equal-area annular array, and a digital beamformer that uses high-speed field programmable gate arrays (FPGAs). The images produced by this system have shown far superior depth of field compared with commercially available single-element systems. Ex vivo, three-dimensional (3-D) images were obtained of human cadaveric tissues including the ossicles (stapes, incus, malleus) and the tympanic membrane. In addition, two-dimensional (2-D) images were obtained of an intact cochlea by imaging through the round window membrane. The basilar membrane inside the cochlea could clearly be visualized. These images demonstrate that high-frequency ultrasound imaging of the middle and inner ear can provide valuable diagnostic information using minimally invasive techniques that could potentially be implemented in vivo.

[Treating traumatic ossicular chain disruption with epitympanum approach following tympanotomy]

OBJECTIVE

To evaluate the therapeutic effects of epitympanum approach tympanotomy in treating traumatic ossicular chain disruption.

METHOD

Ten patients with temporal bone fracture and trauma of ear, whose CT scan of temporal bone showed that Malleoincudal joint irregular shape in the axial view and incudostapedial joint dislocation in the coronal view, were included in this study, Virtual endoscopy showed Malleoincudal joint separation, incudostapedial joint dislocation and interruption, ossicular chain disruption in all patients. The surgical approach was opening the atticus via temporal line, remaining the intact posterior and superior wall of external acoustic meatus, exposing the atticus and posterior tympanic cavity sufficiently, and treating the lesions of ossicular chain.

RESULT

One patient with the long process of the incus fracture, adopted the fitted incus prosthesis between the handle of the malleus and the head of the stapes. Six patients with Malleoincudal joint separation or incudostapedial joint dislocation, 3 patients with incus body dislocation completely, adopted incus positioning two articulation decis. The air-conducting hearing levels had an enhancement of 25-50dB in average after surgery.

CONCLUSION

The effect of intact canal wall epitympanum approach ossicular reposition in treating traumatic ossicular chain disruption is satisfying.

[Evaluation of the virtual endoscopy on traumatic ossicular chain disruption pre- and post-operation]

OBJECTIVE

To evaluate the clinical use of virtual endoscopy in the traumatic ossicular chain disruption with intact tympanum pre- and post-operation.

METHODS

The series consisted of 17 cases with temporal bone fracture and 4 cases with tympanum contusion. All were examinated with a high resolution spiral CT by axial and oblique coronal planes of the temporal bone. Three-dimensional reconstruction was processed using the virtual endoscopy software. Ten cases of traumatic ossicular chain disruption were performed with intact canal wall epitympanum approach Ossicular reposition. Eleven patients with facial paralysis were performed ossiculoplasty and facial nerve decompression. Nine cases re-examinated virtual endoscopy after operation.

RESULTS

Seventeen cases with temporal bone fractures and traumatic ossicular chain disruption, including 3 cases with the long process of the incus fracture, 9 cases with incus bone dislocation, and 5 cases with incus shedding. In the 4 cases of tympanum contusion, 2 cases with incus bone dislocation, 2 cases with incus bone shedding. The axial plane of temporal bone CT could only showed the fracture line and the hammer and incus bone irregular shape. Perioperatively virtual endoscopy showed hammer incus joint separation, incus stirrup dislocation and joint deformation. Surgery confirmed that the incus body was torn off below the hammer following bone displacement, soft tissue wrapped articular surface, incus and stapes just connected with soft tissue. During the tympanum contusion operation could see incus bone-shedding was valgus. Three to six months after surgery, re-examinated virtual endoscopy showed incus bone dislocation ossicular chain was restored to normal, temporal bone shedding ossicular chain connecting almost intact Hearing increased significantly to the level of practical hearing. The coincidence of traumatic disruption of the ossicular chain by virtual endoscopy and surgery was 100%.

CONCLUSION

Virtual endoscopy was valuable for providing accurate assessment and individual program for treating and following-up the traumatic ossicular chain disruption.

[Os odontoideum: clinical and radiological aspects]

Few reports of os odontoideum have been made. We report two cases where this affection was revealed by cervical pain and hemiparesis in one case and acute tetraparesis in the other. Patients with os odontoideum usually present with neurological signs, but some have only cervical pain and some others remain asymptomatic. Radiological exams, including radiograms, cervical scanner and MRI lead to the diagnosis. Different surgical treatment can be proposed to symptomatic patients. Prophylactic surgical treatment is not indicated.

Bilateral duplication of the internal auditory canal

Duplication of the internal auditory canal is an extremely rare temporal bone anomaly that is believed to result from aplasia or hypoplasia of the vestibulocochlear nerve. We report bilateral duplication of the internal auditory canal in a 28-month-old boy with developmental delay and sensorineural hearing loss.

[Virtual endoscopy view of ossicular chain in the congenital aural atresia]

OBJECTIVE

To investigate the function of virtual endoscopy in assessing ossicular chain deformity in the congenital ear malformation.

METHOD

In 23 cases 28 ears with congenital atresia of external auditory meatus. A high resolution spiral CT is used to display the temporal bone by axial and direct coronal planes. Perspective virtual endoscopy was processed using the virtual endoscopy software. To compare the views of the operative exploration and the virtual endoscopy then draw the responding conclusions.

RESULT

Twenty-eight ears with congenital microtia were showed ossicular deformity in 25 ears, while flache pauke in 3 ears. Twenty-four ears treated by canaloplasty of external auditory meatus and tympanoplasty, hammer and incus hypoplasia in 19 ears, stapes abnormity were demonstrated in 11 ears, ossicles absence in 3 ears, vestibular window clausura in 1 ears. The coincidence between Virtual endoscopy and operating view were 100% in cases with congenital ear deformity.

CONCLUSION

Virtual endoscopy can provide reliable information on the ossicles pathological conditions in congenital congenital aural atresia.

CT scans and 3D reconstructions of Florida manatee (Trichechus manatus latirostris) heads and ear bones

The auditory anatomy of the Florida manatee (Trichechus manatus latirostris) was investigated using computerized tomography (CT), three-dimensional reconstructions, and traditional dissection of heads removed during necropsy. The densities (kg/m3) of the soft tissues of the head were measured directly using the displacement method and those of the soft tissues and bone were calculated from CT measurements (Hounsfield units). The manatee's fatty tissue was significantly less dense than the other soft tissues within the head (p<0.05). The squamosal bone was significantly less dense than the other bones of the head (p<0.05). Measurements of the ear bones (tympanic, periotic, malleus, incus, and stapes) collected during dissection revealed that the ossicular chain was overly massive for the mass of the tympanoperiotic complex.

Improvement of spatial resolution in the longitudinal direction for isotropic imaging in helical CT

Experiments were conducted to confirm the isotropic spatial resolution of multislice CT with a 0.5 mm slice thickness. Isotropic spatial resolution means that the spatial resolution in the transaxial plane (X-Y plane) and that in the longitudinal direction (Z direction) are equivalent. To obtain point spread function (PSF) values in the X-Y-Z directions, three-dimensional voxel data were obtained by helical scanning of a bead phantom. The modulation transfer function (MTF) values were then obtained by three-dimensional Fourier transform of the PSF. Evaluation of the spatial resolution in the X-Y-Z directions by the MTF values showed that the spatial resolution in the Z direction does not depend on the reconstruction kernel used. It was also found that the spatial resolution in the Z direction, as compared with that in the X-Y plane, is superior with the standard kernel for the abdomen and is inferior with the high-definition kernel for the ears/bones. By performing sharpening filter processing in the Z direction with a high-definition kernel, comparable spatial resolution could be obtained in the X-Y-Z directions. It was confirmed that adjusting the spatial resolution in the Z direction with the reconstruction kernel used is an effective method for isotropic imaging.

[Useful imaging of the ear]

Good anatomical knowledge is necessary to make an effective diagnosis in ear pathology. The purpose of this article is to summarize the main landmarks of the ear. Anatomic definitions of the external ear, middle ear, and bony labyrinth are described on routine spiral CT, and the anatomic definition of the membranous labyrinth and the cochleovestibular nerve on MRI is reviewed.

Ossicular density in golden moles (Chrysochloridae)

The densities of middle ear ossicles of golden moles (family Chrysochloridae, order Afrosoricida) were measured using the buoyancy method. The internal structure of the malleus was examined by high-resolution computed tomography, and solid-state NMR was used to determine relative phosphorus content. The malleus density of the desert golden mole Eremitalpa granti (2.44 g/cm3) was found to be higher than that reported in the literature for any other terrestrial mammal, whereas the ossicles of other golden mole species are not unusually dense. The increased density in Eremitalpa mallei is apparently related both to a relative paucity of internal vascularization and to a high level of mineralization. This high density is expected to augment inertial bone conduction, used for the detection of seismic vibrations, while limiting the skull modifications needed to accommodate the disproportionately large malleus. The mallei of the two subspecies of E. granti, E. g. granti and E. g. namibensis, were found to differ considerably from one another in both size and shape.

[The clinical application of spiral CT virtual endoscopy of middle ear]

OBJECTIVE

To explore the clinical application of CT virtual endoscopy (CTVE) of ossicular chain in middle ear, and to establish the accurate method of observing ossicular chain and middle ear anatomy.

METHOD

Volume scanning with spiral CT unit was performed in forty normal cases without illness of ear. Endoscopic 3D processing was carried out on a separate workstation equipped with a flying through program. From three isolated points(A, B and C), ear drum and ossicles were observed with CTVE method. The status of auditory ossicles connection were focused.

RESULT

In CTVE via A, B and C points, the indication rates of the malleus, the indus, the drum cape, the canalis facialis horizontal section, and the prominence of horizontal semicircular canals were prosperously 100%. The indication rates of round window and the fenestra ovalis were 90%, 93%, 98% via A, B and C points respectively. And the indication rates of complete demonstration of ear ossicles were 100%, 95%, 93%, respectively.

CONCLUSION

With appropriate approach, CTVE has advantage of showing ear ossicles and their connections, which is a good supplement of routine CT.

Resorption of auditory ossicles and hearing loss in mice lacking osteoprotegerin

Bones conduct sound in the middle ear. The three ossicles-the malleus, incus, and stapes-form a chain that transmits vibrations from the tympanic membrane to the oval window of the inner ear. Little is known about bone remodeling events in these ossicles and about potential effects of osteoporosis on hearing loss. Osteoclastic bone resorption is enhanced in Opg(-/-) mice lacking osteoprotegerin, which is a soluble decoy receptor for the osteoclastogenic cytokine RANKL. We asked whether auditory ossicles are resorbed in Opg(-/-) mice, and whether these mice suffer from impaired auditory function. All three ossicles in Opg(-/-) mice showed thinning, especially at the malleal manubrium and incus body. Most notably, unlike in the case in wild-type mice, the junction between the stapes and the otic capsule was fixed in Opg(-/-) mice, and the stapedial footplate was thinner and broader. Radiological analyses revealed that malleal cortical thickness was positively correlated with tibial bone mineral density in Opg(-/-) and control littermate mice. Furthermore, progressive hearing loss was detected in Opg(-/-) mice starting at 6 to 15 weeks of age. These data suggest that osteoprotegerin plays a crucial role in hearing by protecting the auditory ossicles and otic capsule from osteoclastic bone resorption.

[Evaluation of maximum intensity projection in HRCT in the diagnosis of the destruction of ossicular chain in chronic otitis media]

OBJECTIVE

To observe the ossicular chain structure with maximum intensity projection (MIP) and to evaluate the diagnostic value of it in the destruction of ossicular chain in chronic otitis media (COM).

METHOD

Sixty-eight patients (136 ears) were scanned with HRCT. The original data was processed with MIP reconstruction technique. The images of the ossicular chain structure in normal ears were observed, while the images in suffering ears were compared with the findings in operation.

RESULT

In normal ears, the ossicular chain structure was shown clearly by MIP, which can also display three-dimensional images of the ossicular chain. In the suffering ears of chronic otitis media of cholesteatoma type, granuloma type and simple type, MIP displayed the destruction of ossicular chain in 39 ears, 5 ears and 0 ear respectively, which was observed in 39 ears, 6 ears and 0 ears respectively in operation.

CONCLUSION

MIP technique in HRCT can display the ossicular chain spatial structure clearly, which is very helpful to evaluate the destruction of ossicular chain in chronic otitis media (COM) and to make accurate operation plan.

Multidetector row CT demonstration of inner and middle ear structures

The aim of this study is to evaluate the anatomical details of the inner ear and middle ear, using multidetector row CT. Temporal bone CT scans were obtained using 16-detector row CT scanner (Lightspeed 16, General Electric Medical Systems, Milwaukee, WI) in 30 patients with dizziness, vertigo, or hearing loss. The three-dimensional (3D) images were reconstructed with volume rendering techniques. The 3D images were reviewed by two radiologists and scored by using a three-point quality rating for qualitative assessment of the 23 representative structures of the middle and inner ear. The malleus, incus, and facial nerve canal were identified in all patients. The incudomalleolar joint appeared fused in all patients. The stapes were seen clearly in 27 (90%) of 30 patients except in three patients. Among the three remaining patients, there was one who had effusions in the middle ear cavity. Another patient had left cholesteatoma. The third patient had normal middle ear cavity. The cochlea and the three semicircular canals (anterior, posterior, and lateral) were well demonstrated in 29 (97%) of 30 patients except for one old woman with osteoporosis. Sixteen-detector row CT imaging of temporal bone with advanced 3D reformation yields state-of-the-art anatomical details of the temporal region useful to address anatomical localization issues and ease conceptual structural learning.

Value of digital volume tomography in patients with conductive hearing loss

Digital volume tomography (DVT) is an extension of panoramic tomography. With this diagnostic technique, characterized by high resolution, a narrow section width (0.125 mm) and three-dimensional display, small pathological processes can be well visualized. Twenty-five patients with the history of a progressive hearing loss were examined with DVT (Accu-I-tomo, Morita, Japan). The results were compared with pre- and intraoperative findings to evaluate the diagnostic value of DVT in cases of erosion of the ossicular chain. With high resolution and artifact-free demonstration of the middle ear and the ossicular chain, it was possible to define its continuity preoperatively by DVT in all 25 cases. An intact ossicular chain was found by DVT in 13 cases and was later confirmed by surgery. The predicted erosion of the ossicles was verified in 12 patients, and a tympanoplasty type III was performed. Digital volume tomography is an excellent technique to examine the middle ear cleft and inner ear, and expands the application of diagnostic possibilities in the lateral skull base. Therefore, improvement in preoperative diagnosis is achieved along with more accurate planning of the surgical procedure. Digital volume tomography delivers a small radiation dose with a high resolution and a low purchase price for the equipment.

CT findings of head and neck anomalies in lacrimo-auriculo-dento-digital (LADD) syndrome

We present computed tomography (CT) findings of a boy with lacrimo-auriculo-dento-digital (LADD) syndrome. Bilateral lacrimal glands were not detected and CT imaging of this abnormality in LADD syndrome has not been reported before. Despite suggestions from previous reports of multiple temporal bone abnormalities resulting in hearing losses in these patients, only minor temporal bone abnormalities were seen in our deaf-mute patient. Dysplasia of salivary glands was noted. CT findings of head and neck abnormalities in LADD syndrome are discussed.

[Virtual otoscopy of middle ear structure and pathology]

OBJECTIVE

To assess the value of high-resolution CT data of the temporal bone for the virtual endoscopic (VE) visualization of the ossicular chain and the temporal bone.

METHODS

Fifty patients with suspected lesions of middle ear underwent a high-resolution CT of the temporal bone with VE, seventeen patients were subsequently operated. CT examinations of the temporal bone were carried out using spiral equipment and endoscopic 3D processing was carried out on a separate workstation equipped with a flying through program.

RESULTS

VE is valuable for the evaluation of ossicular dislocation, disruption and ossicular lysis, morphological anomalies of the malleus, incus, and stapes, as well as for evaluation of normal middle ear structures with high detail. The VE assessment in detecting ossicular disruption of chronic otitis media match the operation exploration perfectly (10 in 11 ears), whereas only 3 in 6 ears of cholesteatoma match the operation exploration.

CONCLUSIONS

This image processing method can be used pre-operatively for the individual planning, simulation, and post-operatively for assessment of the position of implants.

Middle ear cholesteatoma: characteristic CT findings in 64 patients

BACKGROUND

High resolution computerized tomography (HRCT) is valuable for detection of early erosive changes suggestive of cholesteatoma. The aim of our study was to determine characteristic CT findings in patients with middle ear cholesteatoma.

METHODS

We conducted a retrospective review of CT scans and surgical and histopathological reports in 64 patients with middle ear cholesteatoma (35 male, 29 female; age range, 7-80 years, median age, 22 years). CT scans were evaluated for the presence of intra-tympanic non-dependent soft tissue density, the extent of middle ear involvement, bone expansion and thinning, and bone erosions involving the ossicles and adjacent structures.

RESULTS

Middle ear cholesteatoma was more common in male patients and in patients aged 20-35 years. All patients had soft tissue density in the middle ear. Fifty-nine (92%) had expansion of the aditus and mastoid antrum, 59 (92%) had erosions of the ossicles, with involvement of the long process of the incus in 48 (75%), 55 (86%) had an eroded scutum, 55 (86%) an eroded facial nerve canal, 57 (89%) an eroded Koerner's septum, which was totally destroyed in 19 (27%), 48 (75%) had tegmen erosion, and 63 (98%) had erosions of the antral walls. The correlation of pre-operative CT with surgical and histopathological findings was 97%.

CONCLUSION

Middle ear cholesteatoma is a distinct clinical entity with characteristic findings that may be suggested by CT imaging. These findings should alert the clinician to the possibility of cholesteatoma, which will guide in the surgical approach and treatment plan.

Pathology of the ossicular chain: comparison between virtual endoscopy and 2D spiral CT-data

OBJECTIVE

The purpose of this study was to assess the value of virtual endoscopy (VE) in the diagnosis of lesions of the ossicular chain and to compare virtual endoscopy and two-dimensional (2D) spiral computed tomography (CT) data.

STUDY DESIGN

Retrospective study.

SETTING

A university hospital.

PATIENTS

Fifty-eight patients with suspected ossicular chain lesions underwent a high-resolution CT of the temporal bone with both 2D data and VE before surgery.

MAIN OUTCOME MEASURES

Two views were chosen for VE. The CT data obtained (2D, VE, and both 2D and VE) were compared with the lesions noted during surgery.

RESULTS

In the diagnosis of dislocation of the ossicles or prostheses, VE seemed to be a better technique than 2D CT. Views chosen for the VE proved to be ineffective for diagnosing epitympanic fixations. VE was not adapted to the study of otosclerosis. We found it necessary to use the data provided by the addition to 2D CT data in the diagnosis of ossicular lysis and minor aplasia. Radiologic analysis of the lesions of the long process of the incus and the incudostapedial joint was improved by performing both 2D CT and VE. VE reconstruction of the stapes proved to be difficult, especially in cases of inflammation of the middle ear.

CONCLUSION

This study demonstrates the value of VE in the diagnosis of dislocation of the ossicles and ossicular prostheses. VE was less effective in diagnosing other pathologies of the ossicular chain.

Experimental flat-panel high-spatial-resolution volume CT of the temporal bone

BACKGROUND AND PURPOSE

A CT scanner employing a digital flat-panel detector is capable of very high spatial resolution as compared with a multi-section CT (MSCT) scanner. Our purpose was to determine how well a prototypical volume CT (VCT) scanner with a flat-panel detector system defines fine structures in temporal bone.

METHODS

Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel detector system at an isometric resolution of 150 microm at the isocenter. These specimens were also depicted by state-of-the-art multisection CT (MSCT). Forty-two structures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT.

RESULTS

Qualitative assessment of anatomic structures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT (P < .001). Structures near the spatial-resolution limit of MSCT (e.g., bony covering of the tympanic segment of the facial canal, the incudo-stapedial joint, the proximal vestibular aqueduct, the interscalar septum, and the modiolus) had higher contrast and less partial-volume effect with VCT.

CONCLUSION

The flat-panel prototype provides better definition of fine osseous structures of temporal bone than that of currently available MSCT scanners. This study provides impetus for further research in increasing spatial resolution beyond that offered by the current state-of-the-art scanners.

The otodystrophies: Diagnosis and differential diagnosis

The imaging evaluation of hearing loss is usually focused on inflammatory entities, especially chronic otitis/ cholesteatoma and cerebellopontine angles lesions, particularly acoustic tumors. This discussion concerns several developmental and acquired entities. The developmental entities referred to as the otodystrophies include otosclerosis, Paget's disease, fibrous dysplasia, and osteogenisis imperfecta. Otosyphilis and postradiation temporal bone changes are also included because of the overlapping imaging appearances.

3D-Darstellung des Mittelohres mittels computergestützter Nachverarbeitung helikaler Mehrschicht-CT-Daten

Post-processing of CT-data allows non-invasive 3D-Visualisation of the middle ear for diagnosis and surgical planning. In this study different post-processing techniques and the clinical application of a 3D-postprocessing algorithm in a large number of patients are presented. 20 normal patients, 6 dissected temporal bones and 213 patients with suspected middle ear pathology were examined using a low-dosage Multi-Slice CT protocol. Virtual endoscopic views of the middle ear and 3D-images of the ossicles were generated using a standardised algorithm. Evaluation of the image quality was performed. The virtual views of the dissected temporal bones were compared to real views. In 32 patients high-quality 3D-models of the individual anatomical structures were generated and displayed using different visualisation techniques. The standardised and evaluated method enabled visualisation of the normal middle ear anatomy. Assessment of different pathologies, especially malformation, trauma, implants and postoperative alterations, was facilitated. The high-quality 3D-models allowed precise imaging of the anatomical structures. 3D-Visualisation of the middle ear using CT-data is beneficial for radiological diagnosis and surgical planning in cases of complex middle ear pathology as a complementary examination technique.

3D micro-CT images of ossicles destroyed by middle ear cholesteatoma

OBJECTIVES

To reconstruct the 3D structures of normal ossicles and ossicles destroyed by different cholesteatomas, and to compare the volume fractions of the two types of ossicles.

MATERIALS AND METHOD

Thirteen pathological ossicles from four kinds of middle ear cholesteatoma obtained during surgery were used. Normal ossicles harvested from cadaveric temporal bone specimens were used as controls. The structures of the ossicles were analyzed using micro-CT by filming 2D cross-sectional images perpendicular to the long axis, from which 3D images were reconstructed. The volume fraction was measured using a CT-Analyzer and Ant.

RESULTS

The volume fraction, indicating the relative strength of normal ossicles, was lower in the portion close to the articular surface. As the four types of cholesteatoma were found to express their patterns of destruction at various sites in the ossicles, they revealed a different volume fraction in each ossicle.

CONCLUSION

Our preliminary data on ossicular structure obtained using micro-CT will be helpful for elucidating the normal and pathological structure of ossicles and for the further development of artificial prostheses.

[Computed tomography (CT) of the temporal bone in diagnosis of acquired cholesteatoma of the middle ear]

The analysis of 51 CTs of the temporal bone in patients aged from 2 to 74 years with otitis media purulenta chronica, cholesteatoma has established that cholesteatoma of different location and severity has specific CT-symptoms. A reliable diagnostic key to CT-diagnosis of cholesteatoma is attic deformation due to destruction of the lateral wall by a soft tissue lesion, extension of the aditus to the antrum, the presence of the cavity with sclerotic walls in the antromastoid area, carious changes in the auditory ossicles, medial or lateral shift of the ossicles. CT registers carious alterations in the middle ear cavity walls including the roof and labyrinthine wall of the tympanic cavity. This allows diagnosis of a labyrinthine fistula and intracranial complications of cholesteatoma. CT well visualizes spread of cholesteatoma on the top of the pyramid. Age-related features of cholesteatoma are studied.

[Advantage of virtual endoscopy in the evaluation of the ossicular chain]

PURPOSE

Our study consists of a comparison of traditional computed tomography (CT) data sets with 2 views of virtual endoscopy in the preoperative evaluation of various diseases of the middle ear.

MATERIALS AND METHODS

We studied 59 patients, all sent for conductive hearing loss with normal eardrum who underwent a complete CT examination: axial helical acquisition and coronal incremental acquisition: virtual endoscopy with selection of two reproducible views: an external one of the auditory canal and a lower one of the hypotympanum. Reading was performed by 2 independent radiologists. All patients were subsequently operated by the same surgeon. Results were compared with surgical reports.

RESULT

Virtual endoscopy is valuable for the evaluation of ossicular and prosthesis dislocations, morphological anomalies of the malleus, incus, and stapes superstructure. Nevertheless, standard axial and coronal CT images remain necessary as confirmed by the poor results of virtual endoscopy in cases of attic obstruction, cholesteatomas and otospongiosis.

CONCLUSION

Virtual endoscopy is a valuable technique of the evaluation of some ossicular chain pathologies but it cannot be used alone.

Imaging of congenital middle ear deafness

INTRODUCTION

Conductive hearing loss, in the presence of a normal external ear, is usually due to an interference with the normal transmission of sound from the tympanic membrane across the ossicular chain to the oval window. If conductive hearing loss occurs in a young child, congenital middle ear pathology is the most likely cause.

MATERIALS AND METHODS

High resolution computed tomography of the middle ear is the diagnostic modality of choice. Details of the imaging technique are outlined in this article. Eight cases of congenital middle ear deafness imaged in the radiological departments of Changi General Hospital and Tan Tock Seng Hospital in Singapore are illustrated.

RESULTS

Congenital middle ear deafness may be classified into ossicular chain abnormalities, congenital ossicular fixation, congenital oval window atresia and congenital round window atresia. The imaging features for each category are described.

CONCLUSION

With proper imaging technique and a systemic analysis of the images, the abnormalities that result in congenital middle ear deafness can usually be demonstrated on most occasions.