Auswertung radiologischer und biophysikalischer Parameter bei Patienten mit Skalendislokation nach Cochleaimplantation

Biophysical measurements in form of impedances and t-NRT values are being established together with radiological images as a quality criterion for evaluating the implant function and the neural auditory structures. In postoperative diagnostics, radiological procedure by DVT (digital volume tomography) is a reliable method to check the position of electrode after implantation and to detect scale dislocations. Biophysical parameters can be measured intraoperatively without any considerable effort. Up to now, they have been indispensable for the initial setting of the language processor and the hearing rehabilitation. Furthermore, they are used for quality control in order to test functionality of every electrode immediately after implantation. The analysis of these measurements has been subject of many studies, since better and more exact telemetry procedures had been developed. Concerning this matter, another aim of intraoperative diagnostics is to make a statement regarding electrode position. In this dissertation, a total of 56 cochlear implant patients with 60 DVT images from the ENT-department of the University Hospital Marburg were examined. The objective was to look for a correlation between imaging and biophysics of the cochlear implant. Main goal was the ability to differentiate intraoperatively between dislocated and non- dislocated electrodes. 22 patients showed a radiologically secure scale dislocation, 34 patients a normal position of the electrode in the tympanic scale. The radiological images were analyzed and the biophysical parameters (t-NRT, impedances) were statistically evaluated. The results show, as radiologically expected, that - with regard to the electrode situation - a significantly different course could be proved. In the evaluation of biophysical measurements, it also showed significant differences between the patients with and without scale dislocation. The present dissertation proves that it is possible to differentiate between radiological imaging and intraoperative measured biophysical parameters for patients with and without scale dislocation. This means the intracochlear electrode position can be already estimated before making a radiological image. This knowledge allows the surgeon to make corrections after measuring the parameters. Thus the chance to gain a better hearing success is given. Furthermore, the postoperative position control with DVT would neither be longer necessary. The patient would have an advantage, because he would not be at risk of more radiation exposure. In addition, with the analysis of the biophysical parameters it is now possible to estimate the audiological outcomes. The recommended insertion of the electrodes in the scale tympani promises a better hearing success regarding speech comprehension, than electrodes inserted in scala vestibuli or with dislocated electrodes. The guidelines of the "Deutsche Gesellschaft für HNO" recommend a radiological imaging for the postoperative control. By further analyses and prospective studies about biophysical measurements with regard to position control, telemetry could be an alternative for radiological imaging in reference to the determination of the intracochlear electrode position.