Expression of Ca(2+)-activated K(+) channel subunits and splice variants in the rat cochlea.

The recently manifested important role of the Ca(2+)-activated K(+) channels, especially of the Slo gene-coded channels, for the cochlea function of the chicken raised the question of homolog expression in mammalian inner ear tissue. Molecular biological methods were used to demonstrate the expression of Ca(2+)-activated K(+) channel subunits and splice variants of the Slo gene in the rat organ of Corti. RT-PCR experiments for the detection of rat Slo alpha subunit mRNA revealed the presence of several already known splice variants including variants which appeared to be typical for the organ of Corti (+58 aa) and for the brain (+61 aa). To detect the accessory beta subunit we used Southern blot hybridization. Our data support the hypothesis that Ca(2+)-activated K(+) channel subunits (i.e. Slo variants) are also involved in the hearing of mammals in the organ of Corti.

Total implantation of the active hearing implant TICA for middle ear disease: a temporal bone study.

A subpopulation of hearing-impaired patients has conductive hearing loss that cannot be improved by classic tympanoplasty. Other patients have a mixed hearing loss and cannot be helped by present forms of ear surgery or by hearing aids. Possible help for some patients may come from current implantable hearing devices if these are modified for the patient's specific anatomic situation. The TICA LZ 3001 is a hearing implant for total implantation used to treat moderate to severe sensorineural hearing loss. Most patients who use it have a normal ossicular chain that allows coupling of the implant to the incus. The present temporal bone study demonstrates that the TICA can also be used in patients with an interrupted ossicular chain. If the incus long process shows a defect, the TICA may be coupled to the incus body, and connection between the stapes and the long process of the incus can be achieved with a commercially available titanium-angle prosthesis or liquid ionomeric cement. In cases of an absent incus, the coupling axis of the transducer may be coupled to the stapes head via a modified coupling element. With an absent stapes, the coupling axis may be coupled directly to the perilymph by a coupling element similar to a gold stapes prosthesis.

A totally implantable drug delivery system for local therapy of the middle and inner ear.

Local therapy of middle and inner ear diseases is being used, but is restricted to cases of ear drum perforation or to repeated invasive intratympanic drug application by the physician. In accordance with the Medical Device Directive (class III), a bone-anchored, totally implantable drug delivery system (TI-DDS) has been developed. It includes a micropump for subcutaneous, patient-controlled activation, a drug reservoir and a septum port. A thin guide-wired catheter leads from the pump outlet to the point of application in the mastoid or middle ear cavities. Local inner ear therapy with suitable drugs is possible by positioning the catheter's end near the round window membrane. The system requires no battery and will offer a wide range of patient-controlled bolus applications (25 microliters per activation). We first analyzed the three-dimensional implantation geometry of the mastoid cavity. Basic micromechanical problems have been solved in order to create several prototypes. The TI-DDS has already undergone extensive in vitro testing. Recent results of pump rate precision and digital pressure force testing are promising. Local drug treatment for conditions such as lidocaine-sensitive tinnitus, secretory otitis media, Meniere's disease, localized pain and intralesional cancer is under discussion. Furthermore, local application of future biotechnological trophic factors for inner ear treatment is anticipated. The basic engineering is completed and initial animal tests are in preparation.

Preoperative assessment of the implantable middle ear pump system using CT scans and conventional X-rays of the temporal bone.

A completely implantable micropump system for drug delivery has recently been developed. After implantation in the temporal bone, this microdosage system enables application of drugs into the middle ear and round window area. Successful application of this new technology depends upon a suitable fit of the micropump within the patient's temporal bone. To obtain information about the fit before surgery, we analyzed 50 cadaver temporal bone specimens before total mastoidectomy, using conventional X-ray and spiral CT scans for water volume determination. Spiral CT is a feasible method for preoperative planning of the surgical implantation of the implantable middle ear micropump system (TI-DDS). The best parameter for a preoperative judgment is the volume of the mastoid cavity, as determined by CT. Implantation may be recommended when the mastoid volume, as measured by CT, is greater than 6.6 ml. To be certain that the implantable drug delivery system will be implantable, a cut-off value of 9.3 ml seems to be advisable. Spiral CT imaging is of great value as a tool for testing implantation preoperatively. The imaging is accomplished in approximately 30 seconds. Our preliminary results with cadaveric temporal bones are encouraging. Further studies are needed in order to transfer the results to a clinical implantation situation.

[Variable length titanium prostheses for type III tympanoplasty. Intraoperative length adjustment and fixation of the cartilage overlay]. / Längenvariable Titanprothesen bei Typ-III-Tympanoplastik. Intraoperative Längeneinstellung und Fixation der Knorpelauflage.

INTRODUCTION: For type III tympanoplasty by partial ossicular replacement prosthesis (PORP) or total ossicular replacement prosthesis (TORP), the length of the prosthesis must match the individual intraoperative anatomical and physiological characteristics. MATERIALS AND METHODS: Databanks were used to determine the necessary sizer length of the sizer disc. The measurement template for the size of the cartilage to overlay the prosthesis headplate was derived from the headplates of the Tübinger titanium prostheses (TTP) and the Dresdener titanium prostheses. Finally all functions were integrated into a synthetic plate. RESULTS: The result was a simple and reasonably priced disposable multifunctional instrument (Tübinger sizer disc TSD) which allowed an exact measurement for every prosthesis in TORP and PORP. For the TTP-Variac, the TSD enabled the simple intraoperative production of prostheses with the length desired by the surgeon. For PORP the TSD enabled an adaptation of the diameter of the prosthesis foot for TTP, TTP-Vario and TTP-Variac and provided a template for the size determination of the cartilage overlay of the titanium prosthesis head. The sizers and the resulting prostheses were used for initial tympanoplastic operations. Audiometric investigations carried out 6 weeks postoperatively gave results corresponding to those previously obtained in a study with TTP and TTP-Vario using the old instrumentation. CONCLUSIONS: The new instrumentation leads to an improvement of the intraoperative practicability and a simplification. The audiological results remain the same.

[Laser-based quality assurance for robot-assisted milling at the base of the skull]. / Laserbasierte Qualitätssicherung für die robotergestützte Fräsabtragung an der Schädelbasis.

BACKGROUND: Implanting active hearing devices in the lateral base of the skull requires high-precision, secure fixation of the electromagnetic transducer and long-life anchorage using osteosynthetic fixation plates referred to as mountain brackets. Nonlinear distortion in the acoustic signal path and consecutive implant loosening can only be avoided by exact osseous milling to create the necessary cavity bed while avoiding excessive milling. Robot technology is ideal for high-precision milling. However, safety measures are necessary in order to prevent errors from occurring during the reduction process. Ideally, a robot should be guided by a navigation system. However, robotic systems so far available do not yet have an integrated global navigation system. MATERIALS AND METHODS: We used an animal model under laboratory conditions to examine the extent to which the semiautomatic ROBIN assistant system developed could be expected to increase osseous milling accuracy before implanting active electronic hearing devices into the recipient tissue in the cranium. An existing prototype system for robot-assisted skull base surgery was equipped with laser sensors for geometric measurement of the operation site. The three-dimensional measurement data was compared with CT simulation data before, during, and after the robot-assisted operation. The experiments were conducted on test objects as well as on animal models. RESULTS: Under ideal conditions, the operation site could be measured at a spatial resolution of better than 0.02 mm in each dimension. However, reflections and impurities in the operation site from bleeding and rinsing fluids did have a considerable effect on data collection, necessitating specialised registering procedures. Using an error-tolerant procedure specifically developed, the effective registering error could be kept under 0.3 mm. After milling, the resulting shape matched the intended form at an accuracy level of 0.8 mm. CONCLUSION: The results show that robot systems can reach the accuracy required for reliable microsurgery on the cranial base. High-resolution laser-based geometric measurement of the operation site enables head registration without additional artificial landmarks. During the navigated operation, the procedure can be used to ensure that the resulting cavity matches the intended shape as determined in the preoperative planning phase. This will enable quantitative analysis of, and improvement in the quality of robot-assisted surgery in the future.

[Quality of life in patients with oropharyngeal carcinoma. Gender influences the subjective evaluation]. / Lebensqualität bei Patienten mit Oropharynxkarzinom. Das Geschlecht beeinflusst die subjektive Bewertung.

BACKGROUND: The purpose of this study was to evaluate the impact of patient characteristics and surgical interventions on quality of life (QoL) after primary surgery and postoperative irradiation in patients with oropharyngeal carcinoma. PATIENTS AND METHODS: Between January 1997 and February 2002, 169 patients with carcinoma of the oropharynx were treated with curative intent. In September 2002, a total of 88 disease-free survivors were identified and included in this study. A retrospective chart review was performed and patient responses to the SF-36 Health Survey, EORTC QLQ-C30 and EORTC QLQ-H&N35 questionnaires were evaluated. The questionnaires were completed by 34 patients (39% response rate). RESULTS: All patients were treated with primary surgery followed by postoperative irradiation. The median follow-up was 2.3 years (range 0.5-4.9 years). Using Bonferroni-Holm adjustment for alpha, gender was found to be an important factor in QoL. Females scored significantly worse than males in all three questionnaires. We could not identify other factors influencing QoL. CONCLUSION: The impact of gender on QoL must be considered as very significant.

Tympanoplasty type II with ionomeric cement and titanium-gold-angle prostheses.

OBJECTIVE: The pronounced isolated erosion of the long incus process is a challenging situation during tympanoplasty. Here, we report two methods for reconstruction of the ossicular chain as tympanoplasty type II with the incus remaining in situ. (1) lonomeric cement is used, resulting in two characteristics: a direct link between stapes head and the long incus process is achieved. At the stapes head the link possesses a joint allowing physiological movements between incus and stapes. (2) Titanium-gold-angle prosthesis according to Plester were crimped to the long process of the incus and positioned onto the head of the stapes forming an articulation. STUDY DESIGN: Forty-five patients with missing long incus process underwent ossiculoplasty among which 41 patients were operated within a randomized, prospective clinical trial. For myringoplasty, the underlay technique with tragus perichondrium was used in all patients. SETTING: We investigated hospitalized patients. INTERVENTION: In 26 patients ossiculoplasty was performed as tympanoplasty type II, in 19 patients with incus interposition. MAIN OUTCOME MEASURE: The essential criterion was the postoperative air-bone-gap (dB). RESULTS: Incus interposition achieved less satisfactory results with an average remaining air-bone gap of 10-20 dB. By contrast, the two tympanoplasty type II procedures yielded average postoperative air-bone-gaps of 0-10 dB (p=0.0003 at 1 kHz; p=0.0028 at 4 kHz), thus reaching the "gold standard" of stapedotomy. The two type II procedures, however, were not equal. The angle prosthesis was restricted to cases with a sufficiently long incus process, whereas the cement-technique is also applicable, when only a short part of the long incus process remained. CONCLUSION: In the present study we show that in the case of a missing crus longum of the incus, a tympanoplasty type II achieved a statistically significant better hearing gain than an autograft interposition.

[Jaffé-Lichtenstein fibrous dysplasia as a cause of progressive protrusio bulbi and temporary vision loss]. / Fibröse Dysplasie Jaffé-Lichtenstein als Ursache von progredienter Protrusio bulbi und temporärem Visusverlust.

We report the rare clinical and morphological features found in a patient with fibrous dysplasia of the paranasal sinuses. In general, diagnosis of tumor sinuses can be made without difficulty and can be made on the basis of three criteria: clinical examination, radiographic findings and histologic examination of a biopsy. Nevertheless, if rare morphological findings occur, obtaining the correct diagnosis can be complicated. Therefore, we report our experiences in managing a 22 year old woman with fibrous dysplasia located in the paranasal sinuses that resulted in proptosis and temporary blindness. The diagnostic and therapeutic implications are elucidated.

[Recovery of hearing: results of delayed medical treatment in patients with idiopathic sudden hearing loss]. / Erholung der Hörschwelle bei verzögert einsetzender Therapie des Hörsturzes.

For the treatment of idiopathic sudden sensorineural hearing loss (ISSNHL), a variety of studies about intravenous drug administration with the beginning of treatment in the early period of less then one week after the onset of hearing loss have been performed. In contrast, very little information is available about the efficacy of intravenous drug therapy for ISSNHL with the beginning of treatment later than four weeks after the onset of hearing loss. In a retrospective chart review we studied the treatment results of 57 patients with ISSNHL with beginning of treatment later than four weeks after the onset of hearing loss with no spontaneous recovery of hearing. Patients received a treatment with intravenous administration of Dextran (concentration 40 g/l with NaCl 0.9%) and Procain-HCl (a derivative of the local anaesthetic lidocaine,400-800 mg in a 500 ml rheologic infusion of Dextran 40). 25% of the patients showed a significant improvement of 10 dB or more in hearing threshold at 1000 Hz measured in bone-conducted pure tone audiometry. In a subjective evaluation 53% of the patients noticed a subjective improvement of their individual hearing thresholds.

[Pharyngeal reconstruction after salvage pharyngolaryngectomy in recurrent tumors]. / Pharynxrekonstruktion nach Rettungspharyngolaryngektomie bei Rezidivtumoren.

BACKGROUND: Total pharyngeal reconstruction after salvage pharyngolarynectomy in recurrent tumors after primary surgery or radiation therapy may be performed by ENT surgeons in the oncologic field. PATIENTS: We report on six patients that underwent salvage pharyngolaryngectomy and total pharyngeal reconstruction. METHODS: In three cases pharyngeal reconstruction was performed as a two-stage procedure with deltopectoral flaps. One of these patients died before the completion of reconstruction. In three other patients the reconstruction was performed with a tubed pectoralis major myocutaneous flap including one patient after a failed reconstruction with a jejunum segment. or fistula prevention we applied silicon stents in three patients and self-expanding Nitinol stents in three other patients. RESULTS: Of five successfully reconstructed patients two fed orally, one fed combined orally and via PEG and two fed via PEG. CONCLUSIONS: Summarizing our experiences the use of silicon tubes and nitinol stents has proved its worth. Experiences with a larger number of patients must be collected in the future.

Cognitive and psychomotor function during hypoglycemia: a comparison between porcine and human insulin.

After an overnight euglycemic clamp, blood glucose levels were precisely lowered on two nonconsecutive mornings via a glucose-controlled insulin infusion system (GCIIS, Biostator) using either purified porcine insulin (PPI) or human insulin (HI). Two cognitive and psychomotor tests were significantly different in 8 type-I diabetic subjects and 8 healthy volunteers at four timepoints, when mean blood glucose concentrations (BGCs) were 100, 65, 50, and 40 mg/dl. Also, a significant difference (p = 0.005) could be found between the mean of all reaction time testing (RTT) values under HI as compared with the mean of all RTT values under PPI. Lowering the BGC resulted in a significant increase in the reaction time (p = 0.012). These effects were not dependent on the type of insulin being used nor were they typical of a particular study group.

Computer-aided surgical planning for implantation of hearing aids based on CT data in a VR environment.

A study was undertaken to assess the feasibility of a preoperative fitting test for an implantable hearing aid in a virtual reality (VR) environment. High-resolution spiral computed tomography (CT) of the mastoid bone was performed, and the results of a mastoidectomy were simulated with manual segmentation on a standard medical workstation. CT was also performed on a temporal bone specimen obtained at real mastoidectomy, and the bone margins were segmented automatically with threshold-based techniques. A triangulated surface representation of the bone structures including the mastoid cavity was generated. These data as well as the computer-aided design (CAD) files of the medical devices were transferred into a VR environment. The CAD components of the hearing aid were manipulated to simulate the surgical implantation procedure. Merging CAD data of an implantable hearing aid with CT data of the temporal bone in a VR environment was shown to be a feasible method of providing three-dimensional information for the presurgical determination of fit and mountability. Advances in hardware and software are expected to improve the usability of this method. Although clinical studies are needed, these results may serve as an impetus for exploring the use of low-cost, widely available VR computer equipment in a potentially broad field of clinical applications.

[Cold deformation elements for attaching an implantable hearing aid transducer to ear ossicles or perilymph]. / Kaltfliessende Elemente zur Ankopplung eines implantierbaren Hörgerätewandlers an Gehörknöchelchen oder Perilymphe.

Development and short-term implantation results of the Tübingen implantable hearing aid (TI = Tübingen implant) have been presented. The TI is designed for patients with sensorineural hearing loss due to a malfunction of the cochlear amplifier. This can be identified by the presence of positive recruitment and the absence of TEOAE (transitory evoked otoacoustic emissions). The Tübingen implant functions in two ways: it allows electronic amplification of the auditory signal and electromechanical signal transduction into a micromechanical vibratory stimulus. There are two paths by which vibratory stimulus reaches the cochlea: (1) directly through a perforation in the stapes foot plate into the perilymph or (2) via the ossicular chain. Made of pure titanium, the casing of the helium-tight welded transducer includes the piezoelectric actuator. An implantable manipulator device is designed for transducer positioning and anchoring in the mastoid cavity. Usually, the transducer probe tip is directly coupled to the body of the incus. This functions without a special coupling device by utilization of an Erbium-YAG laser. Special anatomical situations or the loss of incus and/or stapes suprastructure, however, requires coupling of the vibratory signal to other points of the ossicular chain or to the perilymph. A major problem, however, was an intraoperative, irreversible link between the titanium probe tip and coupling elements. To overcome this problem, the coupling elements were made of gold. A crimp technique was developed, allowing the surgeon to induce cold deformation of the gold. The cold deformation technique (crimp) results in an irreversible coupling between the titanium probe tip and the golden coupling element.

[Functional long-term results after open cholesteatoma surgery and ossiculoplasty with allogenic ossicles in adulthood]. / Funktionelle Langzeitresultate nach offener Cholesteatomchirurgie und Ossikuloplastik mit allogenen Ossikeln im Erwachsenenalter.

BACKGROUND: Characteristic features of cholesteatoma of the middle ear are destruction of the bone and a high tendency for recurrent disease. The choice of surgical procedure is determined by audiological results and the rate of recurrent cholesteatoma. PATIENTS: One hundred fifty patients who underwent primary cholesteatoma surgery were investigated 3-5 years postoperatively. Preoperative and postoperative audiological results and rate of revision surgery were compared for the respective surgical procedures. All cholesteatomas were treated with an open surgical technique. The lateral attic walls and cholesteatomas were removed. RESULTS: Cholesteotoma recurred in 15 patients (10%). Primary reconstruction of the ossicular chain with a tympanoplasty (type III) was performed in 98 patients in the first operation. Approximately 80% of patients treated with a type III tympanoplasty had a maximum postoperative air-bone gap of 20 dB in the main speech range, depending on the frequency. In about 50% of patients, this value was 10 dB or less. Comparison of preoperative and postoperative conductive hearing loss between 250 Hz and 8000 Hz revealed an improvement (p < 0.05) of 10 dB (500 Hz, 3000 Hz, 4000 Hz) and 15 dB (250 Hz, 1500 Hz, 2000 Hz, 8000 Hz). CONCLUSIONS: In our opinion, a second look operation should be performed in cases where a large cholesteatoma cannot be removed with sufficient reliability. This applies especially to a cholesteatoma in the oval window. Here, we suggest second-look surgery after one year.

[Ossicular coupling of an implantable hearing aid transducer using an Er:YAG laser]. / Ossikelankopplung eines implantierbaren Hörgertewandlers mittels eines Er:YAG-Lasers.

Special coupling devices made of pure gold or titanium have been developed to connect a new implantable hearing aid transducer (Tübingen implant) to the ossicular chain. They allow piezotransducer probe-tip connection to the long process of the incus or the stapedial head. Similar to the design of conventional PORPs (partial ossicular replacement prostheses), the coupling devices can be fixed at the ossicular chain, e.g., with the eye loop of stapedial piston prostheses or the bell element of golden wire PORPs. A crimp technique allows connection between coupling device and transducer probe tip [5]. The main disadvantage in connecting the long process of the incus or the stapes having is to drill a dorsal tympanotomy in the posterior wall of the ear canal during surgery. The short distance between tympanotomy and N. facialis contains serious surgical risks. To avoid the risk of facial paralysis, Fredrickson's alternative coupling technique for the body of the incus is investigated in this paper [2]. In this case, the transducer probe tip will be positioned to the incus body and placed on its surface with controlled elastic displacement of the ossicular chain. The simple direct attachment of the probe-tip end on the surface of the incus, however, will not guarantee a stable long-term connection. Thus, by creating a conical, 0.5-to 0.7-mm-deep hole in the incus, the probe tip will be fitted much better. With a novel surgical Erbium-YAG laser this can be done in a contactless procedure. In this paper, first results of microsurgical laser applications with human temporal bones will be shown.

[An implantable hearing aid for inner ear hearing loss. Short-term implantation of microphone and transducer]. / Ein implantierbares Hörgerät für Innenohrschwerhörigkeiten. Kurzzeitimplantation von Mikrophon und Wandler.

A microphone constructed for implantation in the posterior wall of the auditory canal and a piezoelectric transducer serving as the main components of an implantable hearing aid were temporally implanted in five patients during middle ear surgery under local anesthesia. The microphone was positioned beneath the skin of the auditory canal such that it completely covered the microphone membrane. The vibratory element of the transducer was coupled to the malleus in four patients with normal ossicular chains and directly to the stapes in one patient with missing incus. The microphone and transducer were electrically connected with an external battery-driven signal amplifier. Speech material and music were presented in the operation room at a sound level of 65 dB SPL under free-field conditions. The patients had to estimate the quality of speech, music, and their own voice as well as the effects of bone-conducting noises. All patients were able to hear with the system. An intraoperative talk without vision contact was possible without any problems, as was understanding of numerals ("Freiburger Zahlentest"). Perception of music was judged as "clear and undistorted with all broadband component." The estimation was also valid for one patient with a sensorineural hearing loss. One patient declared the music to be "a little of unnatural." Bone-conducted sound was estimated as normal in two patients, better than without an implant in one patient with sensorineural hearing loss, and "somewhat metallic" in another patient. Hearing the own voice was considered "normal" in two cases "monotonous" in one case, and "a little bit roaring" in another case. An amplification factor that can be technically realized in an implantable hearing aid was necessary for one of the patients with sensorineural hearing loss to perceive music at a pleasant volume. On the basis of this study, essential requirements for the construction of a fully implantable hearing aid are fulfilled.

[An osseointegrated micromanipulator as anchor for implantable hearing aid transducers. 1: Fitting to the surgical anatomy of the temporal bone and surgical technical properties]. / Ein osseointegrierter Mikromanipulator als Halterung für implantierbare Hörgerätewandler. Teil 1: Anpassung an die chirurgische Anatomie des Felsenbeins und operationstechnische Eigenschaften.

The first electronic implantable hearing aids for patients with hearing loss are coupled to the ossicular chain or perilymph during implantation and are now available. Our new Tübingen implant designed for sensorineural hearing loss (SNHL) is the combination of an implantable microphone and piezotransducer. To avoid hearing losses during implantation, the Tübingen piezotransducer will be (1) fixed to the mastoid cavity and (2) positioned to one of the ossicular target points. This can be done with a micromanipulator which will be implanted together with transducer and microphone in the mastoid cavity. The manipulator weights 0.7 g. With four degrees of freedom, it allows highly secure and safe positioning of the transducer's probe tip to the ossicular chain under close to stereotactic conditions. The main advantages of the present micromanipulator are (1) easy handling during surgery, (2) the transducer's precise positioning to the ossicular target point with sufficient degrees of freedom, and (3) the transducer's stable fixation in the mastoid cavity in the final position. Following integrated safety as the leading principle, ossicular or inner ear injuries caused, e.g., by the patient's head movement or unintentional manual contact by the surgeon, are minimized. The micromanipulator is, as it were, the surgeon's vibration-free "artificial hand". The manipulator's development and its optimization to the mastoid cavity by test implantation in 50 human temporal bones are shown in detail. While coupling the transducer to the body of the incus, transducer, microphone, and micromanipulator can be implanted into 76% of all mastoid cavities without protrusion. In the case of transducers coupling to the long process of the incus, the protrusion-free implantation rate of the above-mentioned three implant modules is 78%.

[Value of Schüller conventional roentgen diagnosis and computerized tomography of the temporal bone in preoperative diagnosis of the Tübingen implantable cochlear amplifier]. / Der Stellenwert der konventionellen Röntgendiagnostik nach Schüller sowie der Computer-tomographie des Felsenbeins bei der präoperativen Diagnostik des Tübinger implantierbaren Kochleaverstärkers.

Recently, the transducer and microphone of a cochlea amplifier implant (CAI) for the treatment of sensorineural cochlear hearing loss have been developed further for implantation into the mastoid cavity. At present, the University of Tuebingen implantable cochlea amplifier consists of an implantable microphone and an implantable piezoelectric transducer. It has been implanted into the first patients. Successful future application of this new implant depends on the suitable fit of the CAI within a patient's mastoid cavity. Using conventional X-ray and CT scans, we analyzed 50 cadaver specimens of the temporal bone before total mastoidectomy. After total mastoidectomy, the volume of the mastoid cavity was measured using CT scans and water volume determination. Finally, the CAI was implanted into those temporal bones that were large enough to house it. Our results demonstrate that the degree of pneumatization in the conventional Schüller X-ray is already a good parameter for preoperative evaluation.