Testing a Cochlear Implant Electrode Insertion Training System for Optimal Electrode Array Placement in Different Inner Ear Anatomies

We wanna do is we wanna mimic and train an impression of the three-dimensional shape of the cochlea, which this model shows us, and we want to introduce the electrode as deep as we can into the cochlea, mimicking nature, and for that, they will test the tool. We cannot only test the normal anatomy, but we have also cochlear models from all malformations that I've seen throughout my whole life. Existing training opportunities lack the exposure to inner ear malformations.

This protocol uses interchangeable transparent models enabling a realistic, repeatable, and anatomy-specific insertion training. To begin, set up the electrode insertion training system. Prepare the electrode and required instruments before insertion.

Using the manufacturers provided angled soft-grip forceps, hold the electrode and position the electrode lead within the straight segment of the angled tip. Then, lock the electrode directly behind the array stopper. Confirm stable fixation of the electrode before approaching the cochleostomy or round window.

Now align the forceps before advancing the electrode. Maintain a superior-inferior insertion angle during advancement. Guide the electrode toward the lateral wall of the cochlea while avoiding an inferior-superior angle and the medial wall.

Stop advancing the electrode immediately if resistance occurs and withdraw the electrode by a few millimeters. Re-advance the electrode slowly while maintaining the lateral wall trajectory and preventing extracochlear buckling. For incomplete partition type 1 anatomy, identify a complete cystic cochlear portion on the imaging software.

Select an electrode length appropriate for limited angular insertion. Insert the electrode at a superior-inferior angle strictly along the lateral wall. Limit insertion depth to a maximum of 360 degrees and prevent overlap of apical contacts.

For incomplete partition type 2 anatomy, identify a normal basal turn with a cystic apex. Insert the electrode through the normally formed basal scala and maintain the lateral wall trajectory. Advance it up to 450 degrees and stop before entering the cystic apex to avoid overlap.

For incomplete partition type 3 anatomy, identify a widened internal auditory canal. Insert the electrode at a superior-inferior angle and continuously guide along the lateral wall, confirming the electrode remains within the cochlea. For the common cavity, identify a single undivided cavity.

Prebend the electrode array gently, and introduce the curved segment first. Allow the electrode to form a loop within the cavity. Stabilize the configuration while preventing the electrode's entry into the internal auditory canal.

For cochlear hypoplasia, measure cochlear length before insertion. Select a matching electrode length and advance only until the lumen is fully covered without over insertion beyond the basal turn. For an enlarged vestibular aqueduct, identify normal basal turns with a mildly cystic apex.

Insert the electrode along the lateral wall at a superior-inferior angle and advance up to 540 degrees. Stop insertion before the cystic apex and avoid apical overlap. For normal anatomy of different sizes, measure the A-value preoperatively.

Select the electrode length based on cochlear size and insert it fully along the lateral wall. Expect deeper angular insertion in smaller cochleae and reduced angular insertion in larger cochleae. Different grasping techniques using soft-grip forceps resulted in variable control of the electrode lead with correct engagement of the straight portion of the angled tip at the array stopper, ensuring reliable control during insertion.

A superior-inferior alignment guided the electrode along the lateral cochlear wall, while an inferior-superior orientation increased the likelihood of medial wall deviation. In incomplete partition type 1, selecting an electrode length matching the cystic cochlea enabled appropriate angular coverage. Insertion beyond 360 degrees of angular depth led to electrode overlap.

In incomplete partition type 2, stable positioning was achieved when insertion was limited to the formed cochlear turns. In incomplete partition type 3, a lateral wall-directed insertion approach reduced unintended entry into the internal auditory canal and supported retention within the cochlear lumen. In common cavity malformations, introducing the curved segment first promoted a looped configuration within the cavity and facilitated stable positioning.

In cochlear hypoplasia, reduced cochlear dimensions limited achievable insertion depth and required careful electrode length selection. In enlarged vestibular aqueduct anatomy, limiting insertion depth reduced the risk of electrode overlap and potential interchannel interference. Smaller cochlear dimensions resulted in greater angular coverage for electrodes of identical length compared with larger cochleae.

Anatomical identification and proper electrode selection are crucial for reproducible and valuable postoperative results. Post procedure analysis include assessing insertion accuracy, trajectory, angular depth, and comparing different techniques for different anatomies to optimize the results. Future studies can test different electrode designs, including multi-manufacturer systems and correlate training performance with real surgical outcome.