[Surgical technique in cochlear implantation]

The growth of the mastoid volume in children with a cochlear implant

The aim of this study was to understand the mastoid volume development in children who undergo cochlear implantation surgery. Cochlear implant (CI) database of our clinic (Kuopio University Hospital) was reviewed for computed tomography (CT) images of CI patients (age under 12 years at the time of implantation) with a minimum time interval of twelve months between their pre- and postoperative CT. Eight patients (nine ears) were found eligible for inclusion. Three linear measurements were taken by using picture archiving and communication systems (PACS) software and the volume of the MACS was measured with Seg 3D software. The mastoid volume increased on average 817.5 mm3 between the pre- and the postoperative imaging time point. The linear distances measured between anatomical points like the round window (RW)- bony ear canal (BEC), the RW-sigmoid sinus (SS), the BEC-SS, and the mastoid tip (MT)-superior semicircular canal (SSC) increased significantly with the age of the patient at both the pre-op and post-op time points. The linear measurements between key anatomical points and mastoid volume showed a positive linear correlation. The correlation between linear measurement and volume were significant between the MT-SSC (r = 0.706, p = 0.002), RW-SS (r = 0.646, p = 0.005) and RW-BEC (r = 0.646, p = 0.005). Based on our findings from the CI implanted patients and comparing it with the previous literature findings from non-CI implanted patients, we could say that the CI surgery seem to have no effect on the development of mastoid volume in children.

Suitable Electrode Choice for Robotic-Assisted Cochlear Implant Surgery: A Systematic Literature Review of Manual Electrode Insertion Adverse Events

Background and Objective

The cochlear implant (CI) electrode insertion process is a key step in CI surgery. One of the aims of advances in robotic-assisted CI surgery (RACIS) is to realize better cochlear structure preservation and to precisely control insertion. The aim of this literature review is to gain insight into electrode selection for RACIS by acquiring a thorough knowledge of electrode insertion and related complications from classic CI surgery involving a manual electrode insertion process.

Methods

A systematic electronic search of the literature was carried out using PubMed, Scopus, Cochrane, and Web of Science to find relevant literature on electrode tip fold over (ETFO), electrode scalar deviation (ESD), and electrode migration (EM) from both pre-shaped and straight electrode types.

Results

A total of 82 studies that include 8,603 ears implanted with a CI, i.e., pre-shaped (4,869) and straight electrodes (3,734), were evaluated. The rate of ETFO (25 studies, 2,335 ears), ESD (39 studies, 3,073 ears), and EM (18 studies, 3,195 ears) was determined. An incidence rate (±95% CI) of 5.38% (4.4-6.6%) of ETFO, 28.6% (26.6-30.6%) of ESD, and 0.53% (0.2-1.1%) of EM is associated with pre-shaped electrodes, whereas with straight electrodes it was 0.51% (0.1-1.3%), 11% (9.2-13.0%), and 3.2% (2.5-3.95%), respectively. The differences between the pre-shaped and straight electrode types are highly significant (p < 0.001). Laboratory experiments show evidence that robotic insertions of electrodes are less traumatic than manual insertions. The influence of round window (RW) vs. cochleostomy (Coch) was not assessed.

Conclusion

Considering the current electrode designs available and the reported incidence of insertion complications, the use of straight electrodes in RACIS and conventional CI surgery (and manual insertion) appears to be less traumatic to intracochlear structures compared with pre-shaped electrodes. However, EM of straight electrodes should be anticipated. RACIS has the potential to reduce these complications.

Comparison of 128-section single-shot technique with conventional spiral multisection CT for imaging of the temporal bone

BACKGROUND AND PURPOSE

Computed tomography is an essential modality for imaging of the temporal bone. Newest generation scanners allow the coverage of large examination volumes with a single gantry rotation. The objective of this study was to compare a 128-section SST (1 single rotation of the x-ray tube) with conventional spiral MSCT (ultra-high-resolution mode) for imaging of the temporal bone.

MATERIALS AND METHODS

Fifty-four temporal bones in 27 patients were scanned with both a conventional MSCT and 128-section SST. After blinding and randomization of both examinations, 2 observers assessed the visualization of 38 anatomic structures (eg, various segments of the facial nerve canal, mallear ligaments) by using multiplanar reconstructions in the axial and coronal planes. The differences in evaluation scores obtained for the 2 techniques were analyzed by using a Wilcoxon signed rank test, with a P value of < .05 considered significant. For both methods, imaging time and radiation exposure were noted.

RESULTS

Overall visualization of anatomic structures did not differ significantly between the 2 techniques (P > .05). When we compared the anatomic structures separately, there was better visualization of the lateral mallear ligament with MSCT, whereas the cochlear septa were ranked higher with SST (P < .05). Imaging time and average DLP for MSCT were 12.3 seconds and 306 mGy cm, respectively; for SST, values they were 1 second and 64 mGy cm, respectively (ie, a dose reduction of 79%).

CONCLUSIONS

For imaging of the temporal bone with adequate diagnostic quality, 128-section SST can be used. The main advantages over MSCT are the dramatic reductions of imaging time and radiation exposure, which are particularly important when scanning uncooperative patients or children.

The MED-EL SONATATI 100 cochlear implant: an evaluation of its safety in adults and children

CONCLUSIONS

Data from 50 patients suggest that the SONATATI(100) cochlear implant (CI) is a safe and effective device.

OBJECTIVE

MED-EL has developed and tested a CI with titanium housing (the SONATATI(100)), which has the same internal components as the PULSARCI(100). Implant surgery should be less traumatic, as with these CIs smaller incisions and less drilling are involved. The study aimed to assess surgical issues pertaining to the implantation of the device, patient compatibility with the titanium of the implant housing, and other patient-related issues.

METHODS

Fifty patients were recruited into this multicenter study. In phase 1, 30 adults and in phase 2, 20 children received a SONATATI(100) cochlear implant. An intraoperative survey was completed by the surgeons for all patients. A postoperative survey was completed by the audiologists/fitting engineers at first fitting and 3 and 6 months after the first fitting to evaluate the safety and the efficacy of the device.

RESULTS

The device was proven to be effective in that it was stable in the implant bed and that minimally invasive surgery could be carried out. The device was proven to be safe after medium-term use and no unexpected adverse events were reported.

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

PURPOSE

Accurate 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.

METHODS

The curling characteristic of a commercially available state-of-the-art preformed electrode array (Cochlear Ltd. Contour Advance(TM) 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).

RESULTS

All 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.

CONCLUSION

These 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.