Abstract Otology 2000 C12-1

Arvind Kumar MD, Mahmood Mafee MD

Department of Otolaryngology University of Illinois at Chicago USA-Chicago IL

In most patients, the exact cause of acquired unilateral sensori-neural hearing loss (SNHL), even after extensive investigations, remains unkown. In 1984 Hassard (1) found a tumor within the endolymphatic sac during the course of endolymphatic sac surgery for management of Meniere's disease. Sensori-neural hearing loss was a prominent symptom in this patient. Eventually this tumor was characterized as a papillary adenocarcinoma since its histologic characteristics were similar to those of other endolymphatic sac tumors studied by Heffner (2). Hearing loss, of varying degrees, presumably sensori-neural, was noted in 17 of the 20 cases he reported. The radiographic center of all these tumors appeared to be the area between the sigmoid sinus and the internal auditory canal and Heffner (2) proposed that papillary adenocarcinomas of the temporal bone arise from the endolymphatic sac. This concept received strong support from Batsakis and El-Naggar (3) and others, and today it is established dogma that papillary adenocarcinomas arise from the endolymphatic sac. Pollak et al. (4) were the first to challenge this concept based on a careful longitudinal study of a patient in whom, though the histological features were characteristic, the origin of the tumor, judged from bone destruction noted by high resolution CT scans, was the top of the jugular bulb. At surgery the lumen of the endolymphatic sac was found to be free of tumor. The purpose of this paper is to report a case of a patient with unilateral SNHL who had a small papillary adenocarcinoma arising from the area adjacent to the endolymphatic sac but not from it. This was confirmed radiologically, surgically and histologically. We therefore feel that not all papillary adenocarcinomas of the temporal bone arise from the endolymphatic sac. REFERENCES 1. Hassard AD, Boundreau SF, Cron CC. Adenoma of the endolymphatic sac. J Otolaryngol 1984; 13:213-6. 2. Heffner DK. Low-grade adenocarcinoma of probable endolymphatic sac origin. Cancer 1989;64:2292-302. 3. Batsakis JG, El-Naggar AK. Papillary neoplasms (Hefner's tumors) of the endolymphatic sac. Ann Otol Rhinol Laryngol 1993; 102:648-51. 4. Pollak A, et al. Are papillary adenomas endolymphatic sac tumors? Ann Otol Rhinol Laryngol 1995; 104:613-9.

Abstract Otology 2000 C12-2

Hiroaki Miyashita MD, Michio Isono MD, Kiyotaka Murata MD, Kazuko Nakayama MD, Kei Saito MD, Masahiro Ishikawa MD

ENT Department Kinki University School of Medicine J-Osaka

The deafness associated with the inner ear anomaly ranges extensively in its degree from complete deafness and advanced hearing disorder to asymptomatic one. For this reason, it is rather difficult, at present, to establish definite diagnosis through the functional examination such as pure tone hearing test alone, in the clinical diagnosis of inner ear anomaly. Since earlier, pathohistology has been playing a major role in the diagnosis of inner ear anomaly, and the recent advent of high resolution CT(computer tomography) for the temporal area has allowed to acquire detailed information on the inner ear anomaly in the living state. We have a lot of experience with high resolution temporal CT for cases of inner ear anomaly, and the use of 3D-CT has made it possible to look into more detailed anatomy of inner ear. The present report concerns a case of bilateral inner ear anomaly of Mondini type (complete deafness for the left ear, and 40 dB HL hearing in the conversation range for the right ear), suffering from repeated meningitis caused by leakage of cerebrospinal fluid out of vestibular window. The patient's inner ear was examined by use of 3D-MRI which allowed to visualize the stereoscopic structures of the temporal area in more detail than the examination by use of two-dimensional imaging with 2D-CT or 2D-MRI.

Abstract Otology 2000 C12-3

Euan Murugasu MD

California Ear Institute atStanford Dr. Joseph Roberson USA-Palo Alto, CA

An integral component of the pre-operative assessment for cochlear implantation is radiological imaging of the cochlea to assess patency of the cochlear duct for the insertion of the intracochlear electrode array. Such information can be obtained by using high resolution computed tomography (HRCT) or magnetic resonance imaging (MRI) using a surface coil. In this paper presentation, we report on the use of three-dimensional (3D) rendering of T2-weighted magnetic resonance (MR) images into 3D models of the inner ear. Using this technique, we illustrate a range of normal and abnormal 3D models in ten adult and paediatric subjects. These 3D models provide the implanting surgeon with precise, detailed and yet easily interpretable information about the cochlea which help either to guide surgical implantation, or in certain cases, to decide against attempting surgery in the presence of unfavourable anatomical factors.

Abstract Otology 2000 C12-4

Bernhard Schick MD (11), Dominik Brors MD (1), Oliver Koch (1), Gabriele Kahle MD (2)

(11) Department of ENT-Diseases, Head, Neck and Facial Plastic Surgery Academic Teaching Hospital D-Fulda

Objectives: An extensive test battery is used in patients with audiovestibular symptoms to consider the wide field of differential diagnosis including labyrinthine and retrolabyrinthine diseases. Although the value of magnetic resonance imaging (MRI) of labyrinth in patients with audiovestibular symptoms is discussed controversial, MRI presents the diagnostic tool of choice to depict small acoustic neuromas. The study highlights on labyrinthine, internal auditory meatus, cerebellopontine angle and cerebral MRI findings in patients with acute symptoms of hearing loss, tinnitus and/or vertigo of unknown etiology. Methods: Retrospective analysis of MRI findings in 294 patients (148 male, 146 female; aged 8-85 years with an median age of 47 years) with acute hearing loss, tinnitus and/or vertigo treated at a tertiary care facility. Evaluation was performed with the statistic program SPSS 8,0. Results: Pathological findings in MRI were found in 87 (29,6%) out of 294 patients with acute audiovestibular symptoms of unknown etiology. MRI depicted in these cases 1 perilymph fistula, 1 enhancement of the cochlea, 2 labyrinthine hemorrhages, 5 acoustic neuromas, 5 inflammatory lesions and 5 loopings of the AICA in the internal auditory meatus, 45 cerebral microangiopathies, 22 cerebral gliosis, which indicated in one case multiple sclerosis, 2 meningiomas, and 1 cerebral mucoepidermoid metastasis. Cerebral hypoplasia (5), pineal cysts (4), vascular anomalies (3) and pachymeningiosis (1) were additionally found. Conclusion: Even MRI is still an expansive investigation this retrospective analysis indicates a more accurate diagnosis by MRI in patients with audiovestibular symptoms. The radiological investigation should not be limited to the internal auditory meatus and the cerebellopontine angle for acoustic neuroma detection. Additional MRI analysis of the labyrinth and brain is desirable for complete neurootologic evaluation.

Abstract Otology 2000 C12-5

Uwe Vogel PhD, Gert Hofman PhD, Thomas Zahnert MD, Karl-Bernd Hüttenbrink MD

Fraunhofer Institute for Microelectronic Circuits &Systems D-Dresden

Imaging of the temporal bone is heading towards increased spatial, temporal and functional resolution. Depending on the imaging motivation and environment (diagnostics/therapy, modeling, education) different levels of spatial resolution may be reached so far. Here a new approach to 3D imaging and derived structure differentiation of internal temporal bone components by microtomography is presented, which was focused on geometry modeling and general visualization tasks. This allows resolution in the 10 micron range and below. The related procedure is basically noninvasive and thus preserves the original morphology and position of the investigated region. By that approach the external ear canal, ossicles, tympanic cavity, and liquid-filled caves of the osseous labyrinth have been visualized clearly. Even soft tissue components (e.g., tympanic membrane, ligaments, vessels, nerves) have been detected, but with less quality and accuracy due to the radiation energy in contrast to the ordinal numbers of the chemical compartments of those tissues. The results were processed for presentation as pseudo three-dimensional images and animations, on autostereoscopic displays, or as enlarged scalable solid models from rapid prototyping respectively. Very detailed views incorporating multiple perspectives of middle and inner ear complex, ossicles including their internal structure, bony labyrinth, cochlea, or saccus endolymphaticus will be shown. The results indicate the high performance of microtomographic approaches for imaging temporal bone morphology at spatial resolution currently in the 10 micron range and capabilities for future enhancements down to the submicron level. This allowed the semi-automated derivation of individual data-based geometry models of various components relevant for the mechanics of hearing. These models have been successfully fed into FEM analysis for simulating the sound transfer through the middle ear. The upcoming introduction of new physical tomographic imaging principles promises the additional accurate detection of soft tissue components too. Alternative work is directed on in vivo applications for diagnostics.

Abstract Otology 2000 C12-6

Marco D. Caversaccio MD, Daniel Zulliger MD, Richard Bächler , Rudolf Häusler MD

Imperial College of Medicine Leukocyte biology section Biomedical sciences division GB-London

Objective: Optimal registration on the lateral skull base with different anatomical landmarks and surface matching with the frameless opto-electronic navigation surgery system developed in Berne and distributed by Medivision (Stratec Medical, CH-4436 Oberdorf) in a theoretical/practical trial and during operation. Materials and Methods: On a skull we performed an axial CT with a layer thickness of 1.5mm and a scan space of 1.5mm. Different anatomical landmarks are then taken on the skull and evaluated with our navigation system for paired-point matching with or without surface matching (2 regions). This assay was compared with the clinic. Results: The optimal matching points are presented and discussed. We found a maximal theoretical/practical inaccuracy error from the target of 1.24mm (minimum 0.56) and with surface matching a maximal error of 1.17mm (minimum 0.54). During operation we have other conditions:eg the anatomical landmarks of the bone can`t be reached with a high exactness and therefore an optimal surface matching is necessary. We found a clinical inaccuracy between 0.5-2mm. Conclusion: Optimal restricted surface matching with our system gives a good accuracy in theoretical/practical and clinical trial not only on the surface of the lateral skull base but also at the apex of the petrous bone.

Abstract Otology 2000 C12-7

Wolfgang Freysinger PhD, A.R. Gunkel MD, W.F. Thumfart MD

ENT Clinic University of Innsbruck A-Innsbruck

Even a surgeon who is highly experienced in microsurgery of the petrous bone may encounter difficult situations, especially when performing minimally invasive microscopic procedures, during which he could need additional positional and orientational information. This is provided by contemporary navigational technology. By using our armamentarium of navigational systems (Zeiss MKM and STN, ISG/ELEKTA Viewing Wand, ARTMA Virtual Patient) we have demonstrated for the first time that "almost diagnostic" CT scans of the petrous bone can be used for intraoperative 3D navigation. Depending on the patient, pathology, access route and the surgeon´s preferences the navigation system is selected. We have been able to achieve sufficient intraoperative accuracy to provide valuable position information, i.e. in the millimetric, even sub-millimetric, regime. We are now able to provide an almoust routine application of 3D navigation for microsurgery of the petrous bone. So far, we have performed 15 navigated procedures including transtemporal cholesteatoma removal, posttraumatic petrous bone revision surgery, one Cochlea implantation, one acoustic neuroma. We discuss technological issues, surgical practicability, problems and further necessary developments to create an integrated navigated microsurgical approach to the petrous bone: navigable instruments, display and tracking technologies.