Evaluation of a new mid-scala cochlear implant electrode using microcomputed tomography

Area of Science:

• Otolaryngology
• Neurosurgery
• Biomedical Engineering

Background:

• Cochlear implantation requires precise electrode placement within the cochlea for optimal hearing restoration.
• Understanding electrode array behavior during insertion is crucial for minimizing intracochlear trauma.

Purpose of the Study:

• To evaluate the electrode position, insertion depth, and contact of a mid-scala electrode array.
• To compare outcomes between round window (RW) and cochleostomy insertion approaches.

Main Methods:

• Eight fresh-frozen cadaveric cochleae were implanted with a styleted mid-scala electrode array.
• Half were implanted via the RW approach, and half via an anteroinferior cochleostomy.
• Microcomputed tomography and Image J software were used to analyze electrode position and depth.

Main Results:

• All electrodes were inserted without significant resistance, achieving proximal perimodiolar and basal turn lateral wall positions.
• Distal electrodes were mostly in the mid-scala (78%), but one cochleostomy array fractured into the scala vestibuli.
• Cochleostomy insertion showed a 2.7 times higher likelihood of abutting critical structures or fracturing (P=.032).

Conclusions:

• The mid-scala electrode design generally achieves desired proximal and basal turn positioning.
• Cochleostomy insertion increases the risk of interscalar partition excursion and contact with intracochlear structures.
• Round window insertion may offer a safer trajectory for mid-scala electrode placement.