Imaging Anatomy of the Temporal Bone.

Multislice computed tomography (MSCT) is widely used in ear surgery. With the development of cone-beam CT technology it’s become possible to perform CT with comparable precision and facilitate positioning, lower radiation dose and getting primary three-dimensional image. Currently there is no algorithm of three-dimensional tomograms analysis of the temporal bone as part of preoperative preparation in middle ear surgery. A retrospective analysis of 118 temporal bones tomograms made on the cone-beam tomography was performed, from which 58 temporal bones from 32 individuals were selected for study, each of which was related to one of three comparison groups according to the type of pneumatization. Structures of the middle ear were evaluated qualitatively and quantitatively (the depth of the antrum and the sigmoid sinus, antrum size, distance from the antrum to the sigmoid sinus, the presence of lateroposition and prelying sinus, bone wall thickness of the horizontal semicircular canal, facial canal near the aditus ad antrum, and the distance between them). Significant differences were found between anthropometric measurements, depending on the type of pneumatization and the presence of inflammatory changes in the temporal bone. The algorithm of three-dimensional tomograms of temporal bones analysis is proposed, which should be used in preoperative preparation and choosing of surgical access to the structures of middle ear.

What's Your Diagnosis? Symptoms: Middle Ear Mass and Unilateral Hearing Loss

ObjectiveTo evaluate the image quality of low-dose temporal bone computed tomography (CT) in otitis media and mastoiditis patients by using deep learning reconstruction (DLR). Materials and methodsA total of ninety-seven temporal bones from 53 consecutive adult patients who had suspected otitis media and mastoiditis and underwent temporal bone CT were prospectively enrolled. All patients underwent high resolution CT protocol (group A) and an additional low-dose protocol (group B). In group A, high resolution data were reconstructed by filter back projection (FBP). In group B, low-dose data were reconstructed by DLR mild (B1), DLR standard (B2) and DLR strong (B3). The objective image quality was analyzed by measuring the CT value and image noise on the transverse image and calculating the signal-to-noise ratio (SNR) on incudomallear joint, retroauricular muscle, vestibule and subcutaneous fat. Subjective image quality was analyzed by using a five-point scale to evaluate nine anatomical structures of middle and inner ear. The number of temporal bone lesions which involved in five structures of middle ear were assessed in group A, B1, B2 and B3 images. ResultsThere were no significant differences in the CT values of the four reconstruction methods at four structures (all p > 0.05). The DLR group B1, B2 and B3 had significantly less image noise and a significantly higher SNR than group A at four structures (all p < 0.001). The group B1 had comparable subjective image quality as group A in nine structures (all p > 0.05), however, the group B3 had lower subjective image quality than group A in modiolus, spiral osseous lamina and stapes (all p < 0.001), the group B2 had lower subjective image quality than group A in modiolus and spiral osseous lamina (both p < 0.05). The number of temporal bone lesions which involved in five structures for group A, B1 and B2 images were no significant difference (all p > 0.05), however, the number of temporal bone lesions which involved in mastoid for group B3 images were significantly more than group A (p < 0.05). The radiation dose of high resolution CT protocol and low-dose protocol were 0.55 mSv and 0.11 mSv, respectively. ConclusionCompared with high resolution CT protocol, in the low-dose protocol of temporal bone CT, DLR mild and standard could improve the objective image quality, maintain good subjective image quality and satisfy clinical diagnosis of otitis media and mastoiditis patients.

Among patients attending to ENT OPD, chronic suppurative otitis media (CSOM) is one of the common conditions. Mastoid, middle ear surgeries are difficult at times because, the CSOM can be associated with complications; the temporal bone accommodates vital structures (internal carotid artery, facial nerve, jugular bulb etc.) and its anatomical variations. In this study, we planned to investigate the use of preoperative HRCT scan to assess the pathology, extent of the disease, middle ear structures, and presence of cholesteatoma and also to compare with intra operative findings. Materials and Methods: The HRCT findings of 40 patients with CSOM with cholesteatoma were compared with operative findings. CT scan was performed with Seimens Somatom emotion 6 scanner. With the help of HRCT status of the middle ear structures (ossicles, scutum, facial nerve canal and tegmen tympani), semicircular canals and sigmoid plate were assessed and compared with operative findings. Correlation between radiological and intra-operative findings was calculated. Results: A good radio surgical correlation is seen in CSOM with cholesteatoma for status of most middle and inner ear structures except for the integrity of the facial canal. A poor radiosurgical correlation was observed for differentiating cholesteatoma from chronic mucosal thickening as the underlying pathology in cases with CSOM. HRCT was found to be sensitive in detecting erosions of incus(85%), stapes(82.3%), scutum(91.67%), sigmoid plate(100%) and mastoid cortex(100%) whereas less sensitive in erosions of malleus (68.75%), tegmen(32.6%), semicircular canal(71.4%) and facial canal(53.3%). 100% specificity was obtained for erosions of malleus, incus, scutum, sinus plate and mastoid cortex whereas it is relatively less specific for erosions of facial canal(84%) and tegmen(81%). Interpretation and Conclusion: HRCT of temporal bone has a definitive role in pre-operative assessment of CSOM with cholesteatoma as it helps in assessing the extent of the disease and integrity of most of the middle ear structures. Keywords: CSOM, HRCT, Cholesteatoma, Radiosurgical correlation, Temporal bone

Objective: This study emphasizes the role of preoperative high-resolution computed tomography (HRCT) temporal bone in evaluating the variation in cochlear orientation and proposes a grading system to determine the level of intraoperative difficulties encountered. Methods: Preoperative correlation of middle ear and inner ear structures along with the basal turn angle (BTA) was done to assess the orientation. Patients were divided into three groups depending on BTA and radiology findings. Results: Group A (BTA = 55°-60°) had statistically significant (p < 0.05) correlation between middle ear to inner ear structures on HRCT, whereas group B (BTA >60°) and C (BTA <55°) had variations in the alignment of middle ear structures to their corresponding inner ear structures. Conclusion: The association of BTA to the correlation between middle ear and inner ear structures can determine the orientation of the cochlea. This evaluation makes the surgeon aware of intraoperative challenges and helps in surgical planning.

The purpose of this study was to establish guidelines that help radiation oncologists contour the inner and middle ear on treatment planning scans. The radiotherapy computed tomography (CT) scans of 15 previously treated patients were reviewed for the ability to identify 3 separate auditory structures. The middle ear, the cochlea, and the vestibular apparatus were identified and contoured on each scan using anatomic landmarks. The volume and maximum axial dimension of each contour were calculated. The middle ear, cochlea, and vestibular apparatus were identified on all scans. The middle ear was defined by the tympanic membrane laterally and by the interface between air and the temporal bone in all other directions. The plane of the internal auditory canal through the temporal bone was the landmark distinguishing the vestibular apparatus from the cochlea. The mean volume of the middle ear, vestibular apparatus, and cochlea were 0.58 cm3, 0.44 cm3, and 0.14 cm3, respectively. The maximum axial dimension across the contour averaged 1.57 cm for the middle ear, 1.10 cm for the vestibular apparatus, and 0.69 cm for the cochlea. A reference atlas was constructed that shows the contour of each structure on 5 consecutive CT images. Accurate identification of the middle ear and inner ear structures on radiotherapy planning scans is possible and is necessary if critical auditory organs are to be spared during radiotherapy of targets that are located near the base of the skull. The information generated in this study will help radiation oncologists contour auditory structures accurately.

THE INCIDENCE of trauma to the temporal bone is increasing because of the rising number of automobile accidents. Blows to the head can produce damage within the temporal bone which is difficult to visualize on the conventional radiographic examination of the skull. Using thin-section tomography, however, one can visualize the structures within the temporal bone to identify ossicular dislocation, fractures across the facial nerve canal, and stenosis of the external auditory canal. It is important to identify and localize the damage, since many of these injuries can be corrected surgically. Tomography Technic and Normal Anatomy Thin-section tomography is necessary for the radiological diagnosis of fractures within the temporal bone and dislocation of the auditory ossicles. The pluri-directional tomograph (Philip's Universal Polytome) allows sections 1 mm in thickness. The hypocycloidal movement of the tube results in more efficient blurring of superimposed objects, with resultant finer details of the layer in focus. The frontal and lateral projections are best suited for the middle and inner ear structures, including the malleus and incus. The stapes is seen only in the 20° oblique frontal projection (9). Pathology Two types of fractures occur in the temporal bone: longitudinal and transverse. The longitudinal fracture shown in Fig. 1 is four times more common than the transverse and results from force applied either to the temporoparietal region or to the mandibular condyle. This fracture extends medially along the bony external canal, and at the middle ear turns either anteriorly to end in the region of the carotid canal or posteriorly to end in the mastoid region. The clinical symptoms of a longitudinal fracture are a ruptured drum and bleeding into the middle ear and external canal. If the dura overlying the tegmen is lacerated, cerebrospinal fluid will drain into the external canal. Facial nerve paralysis occurs in 10 to 40 per cent of these patients, but 75 per cent recover spontaneously. They often have a conductive hearing loss; a sensorineural loss may result from labyrinthine concussion. A transverse fracture crosses perpendicularly to the long axis of the petrous pyramid. This fracture is the result of a force applied to either the occipital or the occipitomastoid region. The fracture proceeds through the labyrinthine capsule and may cross the facial nerve canal. Clinically, facial nerve palsy occurs in 30 to 50 per cent of the patients. Total nerve deafness and vertigo are common. Blood or cerebrospinal fluid can leak through the fracture into the middle ear cavity but may go undetected because of an intact ear drum. Rarely, the longitudinal and transverse fractures may be combined.

Recent developments in 3D reconstructions can enhance the quality and diagnostic value of axial 2D image data sets with direct benefits for clinical practice. To show the possible advantages of a hybrid rendering method [color-coded 3D shaded-surface display (SSD)- and volume rendering method] with the possibility of virtual endoscopy we have specifically highlighted the use in relation to the middle and inner ear structures. We examined 12 patients with both normal findings and postoperative changes, using image data sets from high-resolution spiral computed tomography (HRSCT). The middle and inner ear was segmented using an interactive threshold interval density volume-growing method and visualized with a color-coded SSD rendering method. The temporal bone was visualized using a transparent volume rendering method. The 3D- and virtual reconstructions were compared with the axial 2D source images. The evaluated middle and inner ear structures could be seen in their complete form and correct topographical relationship, and the 3D- and virtual reconstructions indicated an improved representation and spatial orientation of these structures. A hybrid and virtual endoscopic method could add information and improve the value of imaging in the diagnosis and management of patients with middle or inner ear diseases making the understanding and interpretation of axial 2D CT image data sets easier. The introduction of an improved rendering algorithm aids radiological diagnostics, medical education, surgical planning, surgical training, and postoperative assessment.

Background and Objective: Noninvasive middle and inner ear imaging using optical coherence tomography (OCT) presents some unique challenges for real-time, clinical use in animals and humans. The goal of this study was to investigate whether OCT provides information about the middle and inner ear microstructures by examining extratympanic structures. Materials and Methods: Five mice and rats were included in the experiment, and the swept-source OCT system was tested to identify the middle and inner ear microstructures and to measure the length or thickness of various structures. Results: It was possible to see middle ear structures through the tympanic membrane with the OCT instrument located extratympanically in both rats and mice. We could also obtain the inner ear images through the otic capsule in the mice, but the bulla needed to be removed to visualize the inner ear structures in the rats. The whole apical, middle and basals of the cochlea and the thickness of the otic capsule covering the cochlea could be visualized simultaneously. Conclusions: OCT is a promising technology to assess middle ear and inner ear microanatomy noninvasively in both mice and rats. OCT imaging could provide additional diagnostic information about the diseases of the middle and inner ear.

What's Your Diagnosis? Symptoms: Ear Pain and Chronic Ear Drainage

Finite element modeling of energy absorbance in normal and disordered human ears

Anatomic definition of the middle ear and bony labyrinth in the clinical setting remains limited despite significant technological advances in computed tomography (CT). Recent developments in ultra-high resolution imaging for use in the research laboratory on small animals and pathologic specimens have given rise to the field of imaging microscopy. We have taken advantage of this technique to image a human temporal bone cadaver specimen to delineate middle ear and labyrinthine structures, only seen previously using standard light microscopy. This approach to the study of the inner ear avoids tissue destruction inherent in histological preparations. We present high-resolution MicroCT images of the middle ear and bony labyrinth to highlight the utility of this technique in teaching radiologists and otolaryngologists clinically relevant temporal bone anatomy. This study is not meant to function as a complete anatomic atlas of the temporal bone. We have selected several structures that are routinely delineated on clinical scanners to highlight the utility of imaging microscopy in displaying critical anatomic relationships in three orthogonal planes. These anatomic relationships can be further enhanced using 3D volume rendering.

A cooperative study between the Department of Otorhinolaryngology and the Highway Safety Research institute of the University of Michigan was designed to study temporal bone fracture produced in cadavers subjected to realistic automotive impact situations. Utilizing sled and piston impact configurations frontal and parietal impacts were noted to produce ipsilateral and contralateral fractures of nine temporal bones in seven cadavers. The impact velocities varied between 18.1 and 25.0 mph. Using standard otologic microsurgical techniques, the temporal bones were dissected and numerous gross and microscopic injuries to middle and inner ear structures were found. The authors conclude that extensive comminuted fracture of the human temporal bone is seen with realistic crash situations of low velocity, and that lateral impact which produces a longitudinal fracture with a posterior fossa comminution is associated with disruption of the cochlea and facial nerve, as well as of middle ear structures. The classical transverse fracture of extensive skull trauma lies medial to these structures and does not involve the otologic contents of the human temporal bone. Associated brain and skull injuries are also described.

The study of cross sectional anatomy of the normal human temporal bones was performed by macrosections, Softex radiographs and tomographs.The temporal bones, taken at autopsy, were sectioned tomographically in planes similar to those employed in clinical examination, then they were decalcified, and macrosections in the desired planes were made by cutting 2mm. thick with a commercial meat slicer. Then Softex radiographs of the macrosections were taken with a low intensity x-ray machine.Their comparative study demonstrated that macrosections of the normal middle and inner ear structures were useful for analysis of tomograms, and that Softex radiographs of the macrosections with 2mm of depth could elucidate details of the tomographic sections of the temporal bones.

This thesis proposes the use of human cadaver non-ossicle temporal homograft bone as middle ear reconstructive material. Bone obtained from the otic capsule histologically resembles that of the ossicles more so than any other bone in the body. The otic capsule, due to its proximity to the middle ear, can be harvested with the middle ear structures when bone cores are obtained, making it easily accessible. These prostheses are cost effective because multiple prostheses can be sculptured from one temporal bone core. This paper further proposes the use and introduction of non-ossicle homografts in primary stapedectomy, as well as in selected cases to bypass the incus and the superstructure of the stapes. Audiological data is provided. Some of the grafts have been in the middle ear for up to 5 years. There have been no extrusions and no complications. The method of harvesting, preservation, and sterilization is presented, as well as a pictorial illustration of the finished product and its relation to the natural ossicles. One histological specimen is presented. On the basis of the audiologic results, as well as the fact that no ossicles have extruded and none have been resorbed, it is proposed that non-ossicle temporal bone homografts have a place in transplantation surgery.