Biomedical Engineering Reference
In-Depth Information
FIGURE 6-28
Cumulative number
of cochlear implants
over time.
FIGURE 6-29
Cochlear
implant—overview.
Electrodes are introduced into the tympanic canal, one of the three fluid-filled cham-
bers along the length of the cochlea. A cutaway drawing shown in Figure 6-30 shows the
partial insertion of an array of electrodes into the cochlea. The array is generally inserted
through a drilled opening made by the surgeon into the bony shell of the cochlea overly-
ing the tympanic canal and close to the base of the cochlea. Alternatively, the electrode
array can be introduced through the round window. The depth of insertion is limited by
the decreased diameter of the tympanic canal, the curvature of the cochlear spiral, and
irregularities in the structure that snag the electrode tip.
The total length of the human cochlea is about 35 mm, and no array has ever been
inserted more than 30 mm, with typical insertions much less than that (18 to 26 mm).
