Distance to Rosenthal’s Canal for the Slim Modiolar and the Contour Advance Electrode Array

Background

It is widely believed that the placement of a cochlear implant electrode array closer to Rosenthal’s canal leads to lower behavioral and neurophysiological thresholds, as well as to a spatially more confined neural excitation. Recently, the Slim Modiolar electrode was developed to achieve placement close to the hearing nerve, with a thinner and more flexible design compared to the Contour Advance. However, no studies have yet shown any significant differences for the distance to Rosenthal’s canal between these electrodes.

Objective

To compare the distance to Rosenthal’s canal for the Slim Modiolar electrode with that of the Contour Advance electrode.

Methods

The electrode position relative to intracochlear anatomy was obtained from a retrospective analysis of pre- and postoperative cone-beam computed tomography (CBCT). Scans from 16 Contour Advance and 5 Slim Modiolar recipients were investigated. Nonrigid co-registration of a micro-computed tomography atlas yielded the location of Rosenthal’s canal in the CBCTs, which allowed for a determination of the minimal distance between Rosenthal’s canal and each of the intracochlear electrode contacts.

Results

The mean distance across all contacts and subjects was not significantly different between the two electrode arrays (two-tailed t-test, P<0.05). However, when averages were calculated per contact number, the distance is found to be significantly lower at electrodes E16, E17, E18 and E19 for the Slim Modiolar array than for the Contour Advance (two-tailed t-test, P<0.05).

Conclusion

Near the apical end of the cochlea, the Slim Modiolar electrode is on average significantly closer to Rosenthal’s canal than the Contour Advance electrode.