Martin Leinung

A true minimally invasive approach for cochlear implantation: high accuracy in cranial base navigation through flat-panel-based volume computed tomography.

Objective: High-precision intraoperative navigation using high-resolution flat-panel volume computed tomography makes feasible the possibility of minimally invasive cochlear implant surgery, including cochleostomy. Conventional cochlear implant surgery is typically performed via mastoidectomy with facial recess to identify and avoid damage to vital anatomic landmarks. To accomplish this procedure via a minimally invasive approach-without performing mastoidectomy-in a precise fashion, image-guided technology is necessary. With such an approach, surgical time and expertise may be reduced, and hearing preservation may be improved. Interventions: Flat-panel volume computed tomography was used to scan 4 human temporal bones. A drilling channel was planned preoperatively from the mastoid surface to the round window niche, providing a margin of safety to all functional important structures (e.g., facial nerve, chorda tympani, incus). Main Outcome Measures: Postoperatively, computed tomographic imaging and conventional surgical exploration of the drilled route to the cochlea were performed. Results: All 4 specimens showed a cochleostomy located at the scala tympani anterior inferior to the round window. The chorda tympani was damaged in 1 specimen-this was preoperatively planned as a narrow facial recess was encountered. Conclusion: Using flat-panel volume computed tomography for image-guided surgical navigation, we were able to perform minimally invasive cochlear implant surgery defined as a narrow, single-channel mastoidotomy with cochleostomy. Although this finding is preliminary, it is technologically achievable.

Placement of Intraventricular Catheters Using Flexible Electromagnetic Navigation and a Dynamic Reference Frame: A New Technique

Background: Catheterization of narrow ventricles may prove difficult resulting in misplacement or inefficient trials with potential damage to brain tissue. Material and Methods: The application of a new module for navigated ventricular catheterization using flexible electromagnetic navigation and a dynamic reference frame is presented. Results: Navigated catheter placement was successful and accurate in a pilot study. Electromagnetic interferences had to be taken into consideration. Conclusion: Flexible electromagnetic navigation with a dynamic reference frame is a useful tool for catheter placement as it reduces the risk of misplacement or repeated catheterization trials.

Contact endoscopy for the evaluation of the pharyngeal and laryngeal mucosa

Contact endoscopy is a noninvasive tool that allows in vivo and in situ examination of superficial mucosa. Its use for early diagnosis of cancerous lesions of the oropharynx and larynx has not been evaluated. The aim of the study was to validate contact endoscopy for the examination of pharyngeal and laryngeal mucosa.

Conception and design of an automated insertion tool for cochlear implants

Cochlear implants (CI) are electronic devices incorporating an electrode inserted into the human cochlea for direct electric stimulation of the auditory nerve. The implantation has become the standard treatment for patients with severe-to-profound sensorineural loss not aidable with conventional hearing aids. The state of the art operative technique is a facial recess approach to the middle ear, following the opening of the scala tympani (cochleostomy) and insertion of the electrode array. The facial recess approach is applicable only by experienced surgeons and optimal CI results primarily depend on optimal electrode placement and minimal traumatic insertion. This also requires a certain amount of experience. Additionally several groups work on minimally-invasive approaches to the cochlea, resulting in the necessity to insert the implant via a keyhole access, which is not applicable with current techniques. This paper presents a mechatronic device for an automated insertion of the electrode array of a cochlear implant system. Being designed especially for minimally-invasive approaches, the tool is also applicable for regular facial recess approaches. Moreover the device allows reliable and repeatable insertion studies at synthetic models or cadaver specimen. The functionality of the tool is proofed with first experiments on a synthetic model.

Increase of Accuracy in Intraoperative Navigation Through High-resolution Flat-panel Volume Computed Tomography: Experimental Comparison With Multislice Computed Tomography-based Navigation

Hypothesis: High-resolution imaging, as provided by flat-panel-based volume computed tomography (fpVCT), could increase navigation accuracy and could therefore improve image-guided procedures or make novel navigated surgery concepts possible. Background: Intraoperative navigation is an accepted tool in head and neck surgery. However, its use is limited in the lateral cranial base because of its low surgical accuracy. Surgical accuracy is substantially influenced by the resolution of the underlying data set. The fpVCT offers a resolution of nearly two times higher than multislice computed tomography (MSCT). Target registration error (TRE), as a measurement for surgical navigation accuracy, should decrease when navigation is based on fpVCT data sets. Methods: An acrylic glass phantom with 37 fiducial points was scanned in a current MSCT and in an experimental fpVCT. Both data sets were imported in an optical navigation system. Five fiducial points were used for registration, and seven points were used for measuring TRE. The distance between the indicated pointer tip and the corresponding fiducial point in data set was measured as TRE. Registration and TRE measurement were repeated five times for each computed tomographic data set. Average TREs were calculated, and results were compared using t-test. Results: The average TRE using MSCT (0.82 mm [standard deviation, 0.35 mm]) was significantly higher than that using fpVCT (0.46 mm [standard deviation, 0.22 mm]) (p < 0.01). Conclusion: Submillimeter surgical navigation accuracy is possible using high-resolution fpVCT. This could be highly beneficial in cranial base surgery navigation.

Navigated, robot assisted drilling of a minimally invasive cochlear access

Due to ever increasing requirements of high precision surgery, robotic assistance is becoming an emerging and highly demanded technology. Especially in the field of minimally invasive surgery, missing anatomic landmarks and restricted visibility limit the surgeons control and thus restrict surgical interventions. In particular cochlear implant (CI) surgery is an example of a procedure, characterized by a high degree of complexity and required accuracy. Using mechatronical devices, solutions are provided for the surgeon to cope with these challenges. This paper presents a minimally-invasive approach to cochlea implantation, using an image guided surgery system (IGS) and a robotic manipulator equipped with a surgical drill. This includes computer assisted 3D-planning of the drill coordinates to ensure a maximum safety margin of the drill canal to the vital parts, such as the facial nerve. In order to determine the systems accuracy, preliminary measurements were done using a laser pointer and a camera based appraisal of laser pointer movements. Finally, the drilling was successfully performed on five cadaveric specimens of the human temporal bone. This contribution presents hardware and software components of this approach as well as the results of the robotic assisted drilling experiments.

Hearing preservation and improved speech perception with a flexible 28-mm electrode.

Objective The present study aimed to determine the extent of hearing preservation retrospectively after atraumatic cochlear implant (CI) surgery using a specialized surgical technique and specially designed flexible electrode to minimize cochlear trauma. Study Design Retrospective study. Setting Academic tertiary care center. Patients A consecutive series of 34 patients who had some preoperative residual hearing were included in this study. Intervention Patients underwent CI surgery with a flexible 28-mm electrode using a round window insertion technique. Main Outcome Measures All patients had at least 6 months of postoperative follow-up including audiometric testing and speech perception determined using the Freiburg monosyllable word test and the Oldenburger Sentence Test in noise. Audiometric testing served as a proxy for the evaluation of cochlear trauma and hearing preservation. Results Hearing was preserved to within 20 dB of preoperative low-frequency pure-tone audiometry (PTA) in 40.7% of patients. Hearing was preserved to within 20 dB of preoperative high-frequency PTA in 35.7% of patients. Overall, a deterioration in hearing thresholds was observed between preoperative assessment and first fitting. Speech perception improved significantly over time after surgery. Conclusion Using appropriate surgical techniques, and electrodes specially designed to minimize cochlear trauma, hearing preservation can be achieved.

Determination of the curling behavior of a preformed cochlear implant electrode array

PurposeAccurate insertion of a cochlear implant electrode array into the cochlea’s helical shape is a crucial step for residual hearing preservation. In image-guided surgery, especially using an automated insertion tool, the overall accuracy of the operative procedure can be improved by adapting the electrode array’s intracochlear movement to the individual cochlear shape.MethodsThe curling characteristic of a commercially available state-of-the-art preformed electrode array (Cochlear Ltd. Contour AdvanceTM Electrode Array) was determined using an image-processing algorithm to detect its shape in series of images. An automatic image-processing procedure was developed using Matlab and the Image Processing Toolbox (MathWorks, Natick, Massachusetts, USA) to determine the complete curvature of the electrode array by identifying the 22 platinum contacts of the electrode. A logarithmic spiral was used for a comprehensive mathematical description of the shape of the electrode array. A fitting algorithm for nonlinear least-squares problems was used to provide a complete mathematical description of the electrode array. The system was tested for curling behavior as a function of stylet extraction using nine Contour Advance Research Electrodes (RE) and additionally for nine Contour Advance Practice Electrodes (PE).ResultsAll arrays show a typical pattern of curling with adequate predictability after the first 2 or 3 millimeters of stylet extraction. Although non-negligible variations in the overall curling behavior were detected, the electrode arrays show a characteristic movement due to the stylet extraction and only vary minimally after this initial phase.ConclusionThese results indicate that the risk of intracochlear trauma can be reduced if the specific curling behavior of the electrode carrier is incorporated into the insertion algorithm. Furthermore, the determination of the curling behavior is an essential step in computer-aided cochlear implant electrode development. Experimental data are required for accurate evaluation of the simulation model.

Management of Cochlear Implant Electrode Migration.

Objective: The present study reviewed a cochlear implant (CI) patient population after surgery, which received a free-fitting electrode carrier designed for hearing preservation. The aim was to determine the rate of electrode migration of the CI electrodes and present clinical and surgical implications. Study Design: Retrospective patient review. Setting: Tertiary referral university hospital. Patients: Two hundred seventy-eight patients implanted uni- or bilaterally with lateral wall electrodes designed for hearing preservation (358 implants). The control group was 323 patients implanted uni- or bilaterally with preformed perimodiolar electrodes (468 implants). Interventions: Determination of CI electrode migration was conducted according to a clinical test protocol. Revision surgery was offered in confirmed patients of electrode migration. A bone groove was considered to improve the fixation of the electrode. Main Outcome Measures: Audiological testing including speech audiometry, subjective sound quality rating, and bilateral pitch comparison in bilateral patients, as well as radiological examinations, were conducted. Results: Electrode migration was observed solely in patients implanted with lateral wall electrodes; 10 of 358 patients with free-fitting electrodes (2.8%) had electrode migration, which was successfully confirmed by the proposed clinical test protocol. Nine of the 10 confirmed patients underwent reinsertion surgery. Mean perception score decreased from 75.0% to 62.1% after electrode migration and recovered completely after reinsertion surgery. A flowchart to detect electrode migration was designed for clinical practice. Conclusion: Although electrode migration is a rare complication in CI surgery, long-term follow-up diagnostics should include a test protocol to detect electrode shifts of lateral wall electrode arrays. A reinsertion surgery should be conducted in confirmed patients to recover speech perception.

Die Bonebridge – das erste aktive Knochenleitungsimplantat

Knochenleitungshorgerate regen das Innenohr uber Korperschall an, der auf unterschiedliche Arten auf den Schadelknochen ubertragen werden kann. Die beste Ankopplung erhalt man, wenn das Horsystem fest mit dem Knochen verbunden wird. In der Praxis bedeutete dies bislang, dass die Patienten dauerhaft eine die Haut penetrierende und somit standig sichtbare Titanschraube hinter dem Ohr trugen. Hierdurch besteht das Risiko einer Infektion, die schlimmstenfalls zum Verlust des Implantats fuhren konnte. Seit letztem Jahr ist nun erstmalig ein teilimplantierbares Knochenleitungsgerat verfugbar, das diese Nachteile umgeht.