Anatomic verification of a novel method for precise intrascalar localization of cochlear implant electrodes in adult...

We have previously described a novel, automated, nonrigid, model-based method for determining the intrascalar position of cochlear implant (CI) electrode arrays within human temporal bones using clinically available, flat-panel volume computed tomography (fpVCT). We sought to validate this method by correlating results with anatomic microdissection of CI arrays in cadaveric bones.

Basic science.

Seven adult cadaveric temporal bones were imaged using fpVCT before and after electrode insertion. Using a statistical model of intracochlear anatomy, an active shape model optimization approach was employed to identify the scalae tympani and vestibuli on the preintervention fpVCT. The array position was estimated by identifying its midline on the postintervention scan and superimposing it onto the preintervention images using rigid registration. Specimens were then microdissected to demonstrate the actual array position.

Using microdissection as the standard for ascertaining electrode position, automatic identification of the basilar membrane coupled with postintervention fpVCT for electrode position identification accurately depicted the array location in all seven bones. In four specimens, the array remained within the scala tympani; in three, the basilar membrane was breached.

We have anatomically validated this automated method for predicting the intrascalar location of CI arrays using CT. Using this algorithm and pre- and postintervention CT, rapid feedback regarding implant location and expected audiologic outcomes could be obtained in clinical settings.