The internal part of the cochlear implant

The electrode array of the HiRes90K® implant was called the HiFocus1j and consisted of 16 planar contacts arranged along the medial surface of the electrode array for stimulation of discrete segments of the cochlea. The electrode array was pre-curved and contacts were oriented toward the modiolus wall. This focused stimulation towards the nerve fibers and helped reduce neural spread of excitation around contacts. It was designed to be inserted approximately 25 mm into a normally patent cochlea, the distance over which the electrode contacts lay over being about 17 mm. The spacing between active contacts (distance from midpoint of one contact to another) was 1.1 mm. The electrode array diameter was about 0.4 mm at its tip (distal part) and 0.8 mm at its base (proximal part). Figure 1 shows a drawing of the HiFocus1j electrode.

Figure 1. The HiFocus electrode consists of a fantail, electrode lead and electrode array on which the electrode contacts are numbered 1 to 16 from apex to base.