Evaluating cochlear insertion trauma and hearing preservation after cochlear implantation (CIPRES): a study protocol for a randomized single-blind controlled trial

Background

In order to preserve residual hearing in patients with sensorineural hearing loss (SNHL) who receive a cochlear implant (CI), insertion trauma to the delicate structures of the cochlea needs to be minimized. The surgical approach comprises the conventional mastoidectomy-posterior tympanotomy (MPT) to arrive at the middle ear, followed by either a cochleostomy (CO) or the round window (RW) approach. Both techniques have their benefits and disadvantages. Another important aspect in structure preservation is the design of the electrode array. Two different designs are used: a “straight” lateral wall lying electrode array (LW) or a “pre-curved” perimodiolar lying electrode array (PM). Interestingly, until now, the best surgical approach and design of the implant is uncertain. Our hypothesis is that there is a difference in hearing preservation outcomes between the four possible treatment options.

Methods

We designed a monocenter, multi-arm, randomized controlled trial to compare insertion trauma between four groups of patients, with each group having a unique combination of an electrode array type (LW or PM) and surgical approach (RW or CO). In total, 48 patients will be randomized into one of these four intervention groups. Our primary objective is the comparison of postoperative hearing preservation between these four groups. Secondly, we aim to assess structure preservation (i.e., scalar translocation, with basilar membrane disruption or tip fold-over of array) for each group. Thirdly, we will compare objective outcomes of hearing and structure preservation by way of electrocochleography (ECochG).

Discussion

Cochlear implantation by way of a cochleostomy or round window approach, using different electrode array types, is the standard medical care for patients with severe to profound bilateral sensorineural hearing loss, as it is a relatively simple and low-risk procedure that greatly benefits patients. However, loss of residual hearing remains a problem. This trial is the first randomized controlled trial that evaluates the effect of cochlear insertion trauma of several CI treatment options on hearing preservation.

Trial registration

Netherlands Trial Register (NTR) NL8586. Registered on 4 May 2020. Retrospectively registered; 3/48 participants were included before registration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05878-2.

Fusion of Preoperative MRI and Postoperative FD-CT for Direct Evaluation of Cochlear Implants : An Analysis at 1.5 T and 3 T

AIM

This study was carried out to evaluate the diagnostic value of merging preoperative magnetic resonance imaging (MRI) with postoperative flat-panel computed tomography (FD-CT) and compare it to standard postoperative FD-CT for assessment of cochlear implant (CI) insertion.

METHODS

The T2-weighted (T2w) constructive interference in steady state (CISS) data sets of preoperative 1.5 T and 3 T MRI scans of CI patients with both regular and adverse implant spiralization were co-registered with the corresponding postoperative FD-CT data sets using defined anatomic landmarks. These merged FD-CT/MRI volumes (CMV) were compared to the corresponding postoperative FD-CT MPRs in consensus reading with respect to qualitative, i.e. scala tympani spiralization, scala vestibuli spiralization, scalar translocation and quantitative, i.e. distance of the last electrode to the lateral cochlea wall (D1) distance of the 2nd/5th electrode to the basal cochlear wall (D2) and the transition point (TP) of the scalar translocation, parameters.

RESULTS

In total 30 patients (n 1.5T MRI = 18 patients; n 3T MRI = 12 patients) were included in the analysis. In all cases both CMVs and FD-CT MPRs were generated. Qualitative analysis of intracochlear CI position with CMVs (both 1.5 T and 3 T) and FD-CT was equivalent: In 20 patients the CI showed a regular implant spiralization, in 10 cases a scalar translocation was identified with both CMVs and FD-CT. Quantitative analysis showed a high level of congruency between CMVs (both 1.5 T and 3T) and FD-CT for fusion accuracy (D1: mean FD-CT D1 = 1.30 ± 0.7 mm; mean CMV D1 = 1.27 ± 0.77 mm, correlation r = 0.94, p < 0.0001; D2: mean FD-CT D2 = 1.17 ± 0.34 mm; mean CMV D2 = 1.10 ± 0.31 mm, correlation r = 0.89, p < 0.0001) and TP of the scalar translocation (mean FD-CT = 126.0 ± 59.25°, mean CMV = 117.0 ± 52.82°, correlation r = 0.95, p < 0.0001).

CONCLUSION

The co-registration of preoperative 1.5 and 3 T MRI with postoperative FD-CT enables a direct evaluation of the position of a CI equivalent to the current standard FD-CT. Despite the fact that CMV provided no additional diagnostic value in this series, regardless whether preoperative 1.5 or 3 T MRI was used for co-registration, it might help to simplify postoperative CI diagnostics.