Dataset Information

Patient specific selection of lateral wall cochlear implant electrodes based on anatomical indication ranges.

ABSTRACT:

Objectives

The aim of this study was to identify anatomical indication ranges for different lateral wall cochlear implant electrodes to support surgeons in the preoperative preparation.

Methods

272 patients who were implanted with a FLEX20, FLEX24, FLEX28, or a custom-made device (CMD) were included in this study. The cochlear duct length (CDL) and basal cochlear diameter (length A) were measured within preoperative imaging data. The parameter A was then employed to additionally compute CDL estimates using literature approaches. Moreover, the inserted electrode length (IEL) and insertion angle (IA) were measured in postoperative CT data. By combining the preoperative measurements with the IA data, the covered cochlea length (CCL) and relative cochlear coverage (CC) were determined for each cochlea.

Results

The measurements of the CDL show comparable results to previous studies. While CDL measurements and estimations cover similar ranges overall, severe deviations occur in individual cases. The electrode specific IEL and CCL are fairly consistent and increase with longer electrodes, but relatively wide ranges of electrode specific CC values were found due to the additional dependence on the respective CDL. Using the correlation of IEL and CCL across electrode arrays, CDL ranges for selected arrays were developed (FLEX24: 31.3-34.4, FLEX28: 36.2-40.1, FLEXSoft: 40.6-44.9).

Conclusions

Our analysis shows that electrode specific CC varies due to the CDL variation. Preoperative measurement of the CDL allows for an individualized implant length selection yielding optimized stimulation and a reduced risk of intraoperative trauma. The CDL, as derived from preoperative CT imaging studies, can help the implant surgeon select the appropriate electrode array to maximize the patient's outcomes.

SUBMITTER: Timm ME

PROVIDER: S-EPMC6203394 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:HypothesisInsertion forces can be reduced by magnetically guiding the tip of lateral-wall cochlear-implant electrode arrays during insertion via both cochleostomy and the round window.BackgroundSteerable electrode arrays have the potential to minimize intracochlear trauma by reducing the severity of contact between the electrode-array tip and the cochlear wall. However, steerable electrode arrays typically have increased stiffness associated with the steering mechanism. In addition, steerable electrode arrays are typically designed to curve in the direction of the basal turn, which is not ideal for round-window insertions, as the cochlear hook's curvature is in the opposite direction. Lateral-wall electrode arrays can be modified to include magnets at their tips, augmenting their superior flexibility with a steering mechanism. By applying magnetic torque to the tip, an electrode array can be navigated through the cochlear hook and the basal turn.MethodsAutomated insertions of candidate electrode arrays are conducted into a scala-tympani phantom with either a cochleostomy or round-window opening. The phantom is mounted on a multi-degree-of-freedom force sensor. An external magnet applies the necessary magnetic bending torque to the magnetic tip of a modified clinical electrode array, coordinated with the insertion, with the goal of directing the tip down the lumen. Steering of the electrode array is verified through a camera.ResultsStatistical t-test results indicate that magnetic guidance does reduce insertion forces by as much as 50% with certain electrode-array models. Direct tip contact with the medial wall through the cochlear hook and the lateral wall of the basal turn is completely eliminated. The magnetic field required to accomplish these insertions varied from 77 to 225 mT based on the volume of the magnet at the tip of the electrode array. Alteration of the tip to accommodate a tiny magnet is minimal and does not change the insertion characteristic of the electrode array unless the tip shape is altered.ConclusionMagnetic guidance can eliminate direct tip contact with the medial walls through the cochlear hook and the lateral walls of the basal turn. Insertion-force reduction will vary based on the electrode-array model, but is statistically significant for all models tested. Successful steering of lateral-wall electrode arrays is accomplished while maintaining its superior flexibility.