Measuring the cochlea and cochlear implant electrode depth

Excerpt

The functional benefit of cochlear implants can vary considerably in both children and adults [1, 2]. Outcomes appear to be dependent upon demographic, audiologic, and surgical factors [3]. Given that surgical factors can be optimized and managed, there has been a substantial amount of literature published in recent years with the aim of identifying surgical factors that can be adjusted to improve outcomes. Much of this research has focused on the insertion depth of the cochlear implant electrode arrays. Electrodes that are placed deeply may improve hearing of low-pitched sounds, but also can damage structures and cause loss of residual hearing, cause pitch confusion, and reduce stimulation within the basilar turn [4]. The human cochlea outer wall and first turn lengths can vary by nearly 20% and first turn internal diameters can vary by nearly 80% [5]. Preoperative measurement of the cochlear duct length (CDL) has thus been posited as helpful in projecting electrode insertion depth, which then informs electrode size selection. However, there are multiple proposed methods to measure electrode insertion depth and CDL. …