Our goal was to determine the optimal orientation of insertion of the Slim Modiolar electrode and develop an easy-to-use method to aid implantation surgery. In some instances, the electrode arrays cannot be inserted in their full length. This can lead to buckling, interscalar dislocation or tip fold-over. In our opinion, one of the possible reasons of tip fold-over is unfavourable orientation of the electrode array. Our goal was to determine the optimal orientation of the Slim Modiolar electrode array relative to clear surgical landmarks and present our method in one specified case. For the measurement, we used the preoperative CT scan of one of our cochlear implant patients. These images were processed by an open source and free image visualization software: 3D Slicer. In the first step we marked the tip of the incus short process and then created the cochlear view. On this view we drew two straight lines: the first line represented the insertion guide of the cochlear implant and the second line was the orientation marker (winglet). We determined the angle enclosed by winglet and the line between the tip of the incus short process and the cross-section of previously created two lines. For the calculation we used a self-made python code. The result of our algorithm for the angle was 46.6055°. To validate this result, we segmented, from the CT scan, the auditory ossicles and the membranaceous labyrinth. From this segmentation we generated a 3D reconstruction. On the 3D view, we can see the position of the previous lines relative to the anatomical structures. After this we rotated the 3D model together with the lines so that the insertion guide forms a dot. In this view, the angle was measured with ImageJ and the result was 46.599°. We found that our method is easy, fast, and time-efficient. The surgery can be planned individually for each patient, based on their routine preoperative CT scan of the temporal bone, and the implantation procedure can be made safer. In the future we plan to use this method for all cochlear implantation surgeries, where the Slim Modiolar electrode is used.

Background - Several cochlear implant recipients experience functionality loss due to electrode array mal-positioning. The application of delicate perimodiolar electrodes has many electrophysiological advantages, however, these profiles may be more susceptible to tip fold-over. Purpose - The prompt realization of such complication following electrode insertion would be auspicious, thus the electrode could be possibly repositioned during the same surgical procedure. Methods - The authors present three tip fold-over cases, experienced throughout their work with Slim Modiolar Electrode implants. Implantations were performed through the round window approach, by a skilled surgeon. Standard intraoperative measurements (electric integrity, neural response telemetry, and electrical stapedial reflex threshold tests) were successfully completed. The electrode position was controlled by conventional radiography on the first postoperative day. Results - Tip fold-over was not tactilely sensated by the surgeon. Our subjects revealed normal intraoperative telemetry measurements, only the postoperative imaging showed the tip fold-over. Due to the emerging adverse perception of constant beeping noise, the device was replaced by a CI512 implant after 6 months in one case. In the two remaining cases, the electrode array was reloaded into a back-up sheath, and reinserted into the scala tympani successfully through an extended round window approach. Discussion - Future additional studies using the spread of excitation or electric field imaging may improve test reliability. As all of these measurements are still carried out following electrode insertion, real-time identification, unfortunately, remains questionable. Conclusion - Tip fold-over could be reliably identified by conventional X-ray imaging. By contrast, intraoperative electrophysiology was not sufficiently sensitive to reveal it.

Although vertigo is one of the most common complaints, intracranial malignant tumors rarely cause sudden asymmetry between the tone of the vestibular peripheries masquerading as a peripheral-like disorder. Here we report a case of simultaneous temporal bone infiltrating macro-metastasis and disseminated multi-organ micro-metastases presenting as acute unilateral vestibular syndrome, due to the reawakening of a primary gastric signet ring cell carcinoma. Purpose – Our objective was to identify those pathophysiological steps that may explain the complex process of tumor reawakening, dissemination. The possible causes of vestibular asymmetry were also traced. A 56-year-old male patient’s interdisciplinary medical data had been retrospectively analyzed. Original clinical and pathological results have been collected and thoroughly reevaluated, then new histological staining and immunohistochemistry methods have been added to the diagnostic pool. During the autopsy the cerebrum and cerebellum was edematous. The apex of the left petrous bone was infiltrated and destructed by a tumor mass of 2x2 cm in size. Histological reexamination of the original gastric resection specimen slides revealed focal submucosal tumorous infiltration with a vascular invasion. By immunohistochemistry mainly single infiltrating tumor cells were observed with Cytokeratin 7 and Vimentin positivity and partial loss of E-cadherin staining. The subsequent histological examination of necropsy tissue specimens confirmed the disseminated, multi-organ microscopic tumorous invasion. Discussion – It has been recently reported that the expression of Vimentin and the loss of E-cadherin is significantly associated with advanced stage, lymph node metastasis, vascular and neural invasion and undifferentiated type with p<0.05 significance. As our patient was middle aged and had no immune-deficiency, the promoting factor of the reawakening of the primary GC malignant disease after a 9-year-long period of dormancy remained undiscovered. The organ-specific tropism explained by the “seed and soil” theory was unexpected, due to rare occurrence of gastric cancer to metastasize in the meninges given that only a minority of these cells would be capable of crossing the blood brain barrier. Patients with past malignancies and new onset of neurological symptoms should alert the physician to central nervous system involvement, and the appropriate, targeted diagnostic and therapeutic work-up should be established immediately. Targeted staining with specific antibodies is recommended. Recent studies on cell lines indicate that metformin strongly inhibits epithelial-mesenchymal transition of gastric cancer cells. Therefore, further studies need to be performed on cases positive for epithelial-mesenchymal transition.