SUMMARYCommon techniques to evaluate intracochlear electrode position include ionised radiation by multi-slice computer tomography, digital volume tomography (MSCT, DVT) and flat panel tomography (FPT). Recent advances in the knowledge about handling MRI artefacts and the pain-free performance of MRI scans in cochlear implantees showed that estimation of the intracochlear electrode position is possible at 1.5 T with perimodiolar or midmodiolar arrays. The aim of the present study is to evaluate the assessment of the ipsilateral scalar position of a cochlear implant lateral wall electrode by MRI sequences at 3T. In a prospective study we evaluated 10 patients implanted with a diametrically bipolar implant magnet system with a lateral wall electrode in the intrascalar electrode position in an axial and coronal position and a T2 weighted sequence at 3T and a resolution of 0.8 mm. We compared the intracochlear position with routine postoperative DVT scan. In all cases, the MRT-estimated scalar position corresponded with that estimated by DVT scan. In all cases, a scala tympani position was present. While the position in the basal turn is reliably localisable, the first-turn visual assessment is difficult. Estimation of the intracochlear position of lateral wall cochlear implant electrodes by 3T MRI is possible for the basal turn. Electrode design plays a major role in visual assessment.

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Background: The insertion of the stapes piston into the vestibule provides the physical basis for a successful stapedotomy. In routine clinical practice, two different ways to handle prosthesis length are performed: (1) an individualized measurement of the stapes prosthesis length or (2) a standard prosthesis length for all cases. Objective: The objective of this study was to compare both ways of handling prosthesis length and the effect of these methods on insertional prosthesis depth. Material and Method: We retrospectively evaluated 39 patients after performing a stapedotomy for radiologically estimated vestibular stapes prosthesis insertion depth. The individual measured length data were hypothetically changed to a standard length of 4.75, 5, 5.25, and 5.5 mm, and the insertion depths were compared. Results: The individually measured prosthesis lengths led to an insertion depth between 0.2 and 1.6 mm (mean 0.74 mm). The ratio of insertion depth/vestibular depth was between 8 and 59.1% (mean 26.6%). The different assumed standard lengths led to different rates of the vestibulum positions and possible bony contacts at the vestibulum floor. Conclusion: The individual measurement led to a zero rate of the vestibulum positions of stapes prosthesis pistons with a low insertion depth/vestibular depth ratio.

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