In Vivo Estimates of the Position of Advanced Bionics Electrode Arrays in the Human Cochlea

Abstract

Objectives: A new technique for determining the position of each electrode in the cochlea is described and applied to spiral computed tomography data from 15 patients implanted with Advanced Bionics HiFocus I, lj, or Helix arrays. Methods: ANALYZE imaging software was used to register 3-dimensional image volumes from patients' preoperative and postoperative scans and from a single body donor whose unimplanted ears were scanned clinically, with micro computed tomography and with orthogonal-plane fluorescence optical sectioning (OPFOS) microscopy. By use of this registration, we compared the atlas of OPFOS images of soft tissue within the body donor's cochlea with the bone and fluid/ tissue boundary available in patient scan data to choose the midmodiolar axis position and judge the electrode position in the scala tympani or scala vestibuli, including the distance to the medial and lateral scalar walls. The angular rotation 0 0 start point is a line joining the midmodiolar axis and the middle of the cochlear canal entry from the vestibule. Results: The group mean array insertion depth was 477 0 (range, 286 0 to 655 0). The word scores were negatively correlated (r =-0.59; P = .028) with the number of electrodes in the scala vestibuli. Conclusions: Although the individual variability in all measures was large, repeated patterns of suboptimal electrode placement were observed across subjects, underscoring the applicability of this technique.

Insertionsergebnisse von Contour™- und Contour-Advance™-Elektroden

“…Darüber hinaus haben Qualitätskontrollstudien bei erwachsenen CI-Trägern zeigen können, dass die Elektrodenposition (Scala tympani, Scala vestibuli oder Dislokation von einer Scala in die andere) ein prognostischer Faktor für die Rehabilitationsergebnisse ist. Dabei ist die Anzahl der Elektrodenkontakte in der Scala tympani positiv korreliert mit den Ergebnissen der Rehabilitation [3,13,24].…”

“…Der Vorteil der Scala-tympani-Insertion in Bezug auf die Rehabilitationsergebnisse konnte durch eigene Untersuchungen [3] sowie durch die Untersuchungen von Skinner et al [24] und Finley et al [13] bestätigt werden. Gleichzeitig liegen jedoch Berichte über ausgezeichnete Ergebnisse in Einzelfällen auch nach einer Scala-vestibuli-Insertion vor [7,17,25].…”

Assessing the Electrode-Neuron Interface with the Electrically Evoked Compound Action Potential, Electrode Position, and Behavioral Thresholds

“…Some insight into the electrode-neuron interface can be obtained via postoperative computerized tomography (CT) imaging, which provides information about electrode placement, such as electrodemodiolus distance, scalar location, insertion depth, and wrapping factor (Holden et al 2013;Skinner et al 2007;Teymouri et al 2011;Verbist et al 2005). A portion of the variability in speech scores can be explained by electrode insertion depth and scalar location (Finley et al 2008;Holden et al 2013;Skinner et al 2007), with deeper insertion and a greater number of electrodes in the SV correlated with poorer speech perception.…”

Effect of frequency mismatch and band partitioning on vocal tract length perception in vocoder simulations of cochlear implant processing

“…The information in each channel is usually delivered to a separate electrode in the stimulating array, which determines the resolution (number of electrode channels) dedicated to the specified frequency range. To minimize trauma while maintaining sufficient stimulation of surviving auditory nerve fibres, electrode arrays are seldom inserted more than 2.6 rounds into the cochlea (Skinner et al, 2007). This means that the frequency corresponding to the location of the most apical electrode falls between about 250 Hz and 870 Hz, depending on the cochlear dimensions, electrode array length, and insertion depth (Franke-Trieger and M€ urbe, 2015;Skinner et al, 2007).…”

“…To minimize trauma while maintaining sufficient stimulation of surviving auditory nerve fibres, electrode arrays are seldom inserted more than 2.6 rounds into the cochlea (Skinner et al, 2007). This means that the frequency corresponding to the location of the most apical electrode falls between about 250 Hz and 870 Hz, depending on the cochlear dimensions, electrode array length, and insertion depth (Franke-Trieger and M€ urbe, 2015;Skinner et al, 2007). Consequently, if the frequency partitioning map fully matches the frequencies corresponding to electrode locations, low-frequency information important for speech intelligibility would be lost (Başkent and Shannon, 2004), especially for cases in which the most apical electrode location corresponds to around 800 Hz.…”