Abstract Otology 2000 A11-1

Albert Mudry MD

ENT Department University Hospital CHUV CH-Lausanne

Purpose of study: To study the historical development of the binocular microscope and to understand the resulting revolution in auricular surgery. Method: Compilation of the texts of the era, books dealing with auricular surgery and a revue of the international litterature on the subject. Results: The first descriptions of the microscope date back to the 17th century, but it was not until 1921 that it was really used for the first time in auricular surgery by a Swedish otologist: Olaf Nylen. This monocular microscope was rapidly replaced by a binocular microscope developed in 1922 by Gunnar Holmgren. Due to a limited field of vision, a very short focal distance, bad light quality, and an unstable fixation this microscope was used very little to start with. Despite many differing models being developed, it was only in 1953 that a new model appeared, perfected by Littmann and the company Zeiss. It was this model which was to progressively replace all other models, thanks to its easy use and the possibility of changing the magnification without modifying its focal distance. It allowed for the development of new techniques in tympanoplasties and interposition. The microscope continued to be improved, notably by the addition of a zoom system and the possibility of connecting a photographic camera. Conclusion: Auricular surgery would not really have been conceived if it had not been for the binocular microscope. Without it, auricular surgery would not be what it is today.

Abstract Otology 2000 A11-2

Hartmut Meister MD, A. Mickenhagen MD, M. Walger PhD, Hasso Von Wedel Prof.Dr., Eberhardt Stennert Prof.Dr.

ENT-Department University of Cologne D-Köln

Several methods to evaluate the sound transmission properties of middle ear implants are established. On the one hand, mathematical simulations based on finite element methods or circuit models can be used to estimate acoustical parameters. Computer-based models allow accurate approximations, but a large number of parameters is required, all of which have to be determined first. On the other hand, measurements with temporal bone preparations can be performed. Those experiments consider various anatomical properties but a large number of parameters influence the outcome of measurements. Additionally, a marked interindividual variability can occur. To facilitate standardized measurements we developed a mechanical middle ear model which can be used to evaluate the transfer function of middle ear implants on defined conditions, comparable to coupler measurements with conventional hearing aids. A number of experiments was carried out which focused on the fundamental sound transmission properties. Several commercially available prostheses were examined. They differed mainly in the high-frequency range corresponding to their mass. The outcome of the measurements has been confirmed by a simple theoretical model. The mass of the prosthesis had the strongest influence on sound conduction. Middle ear implants should be as light as possible to allow optimum high-frequency-transmission which is important for consonant discrimination and speech perception in noise.

Abstract Otology 2000 A11-3

Frank Böhnke PhD, Wolfgang Arnold MD

HNO-Klinik Univ.-Klinik Rechts der Isar D-München 80

The success of stapedectomy/stapedotomy surgery depends on the surgeons expertise and on the type of prosthesis used. In order to develop the most ideal prosthesis a three-dimensional numerical simulation of the transition mechanics between the stapes footplate and the cochlea is done, which leads to a certain geometry regarding the boundary surface between prosthesis and the connecting perilymph. The perilymph is idealized as a compressible and inviscous fluid. The modulus of elasticity of the annular ligament is chosen as 650 kPA which is the value for elastin. The results show that an increase in the surface size of the stapes footplate from 3 mm2 to 3.9 mm2 ( 30 % ) can produce an increase in perilymphatic pressure of about 6.8 dB ( F = 2.18 ), i.e. more than twice as much. The increase is limited to frequencies up to 2 kHz which is in agreement with experimental results. Since the result is accompanied by an increase in the maximal basilar membrane displacement and provided that certain boundary conditions discussed are fulfilled, we predict an improvement in the hearing threshold of patients on whom a stapedectomy was performed using the appropriately improved prosthesis. Examples how the ideal prosthesis should look like are given.

Abstract Otology 2000 A11-4

Sugata Takahashi MD (1), Shigehisa Hashimoto MD (2), Yutaka Yamamoto MD (3), Hitoshi Satoh MD (3)

(1) Department of Otolaryngology Niigata University School of Medicine J-Niigata
(2) Department of Otolaryngology Niigata Univ. School of Medicine J-Niigata
(3) Department of Otolaryngology Niigata University School of Medicine J-Niigata

Ceramic ossicular prostheses available in Japan include aluminum oxide ceramics [Al2O3, CORP] and hydroxyapatite ceramics [Ca10(PO4)6(OH)2, Apaceram]. Tympanoplasty with these ceramic prostheses was performed in91 ears of 83 patients at the Niigata University Hospital. CORP was utilized in 67 ears and Apaceram in 24 ears. The mean follow-up period was 6 years and 3 months. Extrusion of the prosthesis to the external auditory canal was recognized in 15 cases (16%), 14 cases of CORP and 1 of Apaceram. The overall mean period of extrusion was 2 years and 6 months (range from 1 month to 7 years and 8 months). Diseases of the ceramic extrusion consisted of 8 of 55 cases of cholesteatoma, 4 of 27 cases of chronic otitis media, 3 of 4 cases of adhesive otitis media and 0 of 4 cases of ossicular malformations and 1 case of one traumatic ossicular disruption. Prosthetic dislocation in the middle ear cleft was recognized in 20 cases (22%), 18 cases of CORP and 2 of Apaceram. An air bone gap closure, less than 20 dB of the pure tone average, was achieved in 14 ears (21%) of the CORP and 13 ears (54%) of Apaceram.

Abstract Otology 2000 A11-5

Hidemitsu Sato MD (1), Kiyofumi Gyo MD (1), Goran Bredberg MD (2)

(1) Department of Otolaryngology Head and Neck Surgery Ehime Univ. School of Medicine J-Onsen-Gun Ehime
(2) Audiology Department Karolinska Institute Stockholm Soder Hospital S-Stockholm

Partially implantable hearing aid (PIHA) has been implanted in the patients with conductive or mixed deafness. Generally, hearing afforded by PIHA is highly affected by mobility of the stapes. Therefore, implantation of the PIHA in patients with stapes fixation has been the problem. In this paper we studied a new surgical technique for PIHA implantation by using animals with experimental stapes fixation. Eight rabbits with normal hearing were used in this study. Tympanic membrane and ossicles except stapes were removed to set the vibrator of the PIHA. Cochleostomy was performed on the basal turn of the cochlea by 0.5 mm width with preserving membranous labyrinth. Stapes fixation was made by cementing the stapes with glass cement. The stapes and the opening of cochlea were stimulated by the vibrator and hearing thresholds were measured respectively. This study showed no hearing loss by cochleostomy and good sensitivity of the vibrator in stimulating the opening of cochlea even in stapes fixation. We concluded that cochleostomy was a possible procedure for implantation of the PIHA in patients with stapes fixation.

Abstract Otology 2000 A11-6

Elena Dimeska MD, Ilija Filipche MD, PhD, Marina Chakar MD, PhD, Aleksandrova Merzuha MD

ENT Department University Hospital MAZ-Skopje

This paper reports on the reconstruction of the sound-conducting system in the middle ear in those ears in which the incus and the stapes suprastructure are either absent or inadequate as after prior otitis media or tympanoplasty/stapedectomy. In these situations, the Teflon malleus attachment piston in 38 operations over an 6-year period. The hearing results show that a closure of the pure-tone average air bone gap to within 10db was possible in 73.6% (28/38) and to within 20db in 84.2% (32/38). A residual air bone gap of 30 db was seen in two cases. Sensoneural hearing loss of 10db not occur and there was no decline in speech discrimination. We believe that the malleus attachmet piston has a big part and role in the reconstruction of the conducting mechanism of the middle ear in cases of absent or damage incus, congenital malformation and epitympanic fixation of the incus and malleus.

Abstract Otology 2000 A11-7

Matthew W. Yung PhD, FRCS, DLO

Consultant ENT Surgeon The Ipswich Hospital NHS Trust GB-Ipswich Suffolk

It has long been recognised that a technically successful hearing restorative procedure may not always produce a grateful patient. Numerous methods have been proposed to predict the patient benefit following ear surgery, such as the Belfast rule of thumb and the Glasgow benefit plot. Most reports on surgical outcome following tympanoplasty is based on audiometry. At the Ipswich Hospital, the social hearing handicap index has also been used to measure the patient benefit following tympanoplasty since 1995. It is a set of questionnaires originally designed for hearing aid users to test their ability to hear conversation in quiet and noisy environments. The response to the questionnaires can be developed into a score (handicap score), this enables the pre-operative and post-operative hearing ability to be compared. 110 patients with tympanoplasty were studied. All the patients had a pure tone audiogram and the handicap score recorded before the operation and also 12 months after the operation. The relationship between the improvement in hearing threshold and the handicap score was studied in the following situations: 1. Bilateral hearing loss with the operation on the better hearing ear. 2. Bilateral hearing loss with the operation on the worse hearing ear. 3. Symmetrical hearing loss; operation on one ear only. 4. Normal hearing in one ear with operation on the opposite hearing impaired ear. The result showed that operation on patients with unilateral hearing loss yield as much hearing benefit as operation on patients with bilateral hearing loss.