Kontrolle der intracochleären Lage der Elektrodenträger nach Cochlea-Implantation mittels digitaler Volumentomographie

Cochlear implant surgery is a well established and accepted procedure to reconstitute congenital or acquired deafness. Over the past years the indications for cochlear implantation have expanded and now include patients with leftover hearing and children. To improve the quality of speech understanding, an insertion into the scala tympani with minimized intracochlear trauma is desired. Consequently, an exact imaging and assessment of the postoperative situation of cochlea implants is an important element for the quality control. Against this background the aim of this dissertation was to question the clinical practicability of the DVT to determine the postoperative electrode position.Previous studies presented a high rate of scala vestibuli insertions and dislocations from scala tympani to scala vestibuli. A scala tympani insertion is highly influenced by a precise and adequate choice for the cochleostomy. Because of that the operation reports have been analysed with special regard to the arranged cochleostomy site. A total of 49 patients between 11 and 85 years have been analysed from October 2002 to December 2009. The mean age was 49. 26 patients were female, 23 male. Three patients received a bilateral sequentially implantation. In total 52 electrodes have been evaluated. 37 patients received a Cochlear Nucleus System, 8 an Advanced Bionics electrode array and 7 a MED-EL electrode array. An intracochlear positioning with full insertion of the electrode could be demonstrated in all cases. 46/52 electrodes (88.5 %) could be evaluated relative to their exact intracochlear localisation with a differentiation between scala tympani, scala vestibuli or a change of scalae. 6/52 electrodes (21.5 %) had to be excluded because of motion artefacts, metal artefacts and deficient picture quality. 29/46 electrodes (63 %) were placed in the scala tympani and 10/46 electrodes (21.7 %) in the scala vestibuli. 7/46 electrodes (15.2 %) showed a dislocation from one scala to another. It was possible to show the single electrodes and their relation to the modiolus. The operation reports showed a great variability of the choice for cochleostomy site. If the cochleostomy has been arranged more inferior or anterior-inferior to the round window membrane scala tympani insertions increased.The presented dissertation underlines, that digital volume tomography is a qualified imaging procedure for the postoperative evaluation of cochlear implants. High resolution combined with minimized metal artefacts and a suitable post processing allows an exact localisation of the implant with a determination of the exact scala. This detailed postoperative imaging is a desirable possibility to analyse the individual techniques of the surgeon. Consequently digital volume tomography is an excellent instrument for clinical quality control after cochlear implantation. Further development in soft tissue imaging for an improved evaluation of intracochlear trauma as well as intraoperative examination is desirable for the future.