Cochlea size in children measured in high-resolution MRI
23 April 2019 (online)
The individual cochlea size is very important for the preoperative planning of an atraumatic cochlear implantation. In infants and children MRI is used as preoperative imaging. As age dependent normal values for cochlea size are rare we aimed to establish reference values for children.
Two independent physicians retrospectively examined high resolution T2w MRI (CISS or T2 SPACE) of petrous bones performed in children aged 6 months to 17 years. The measure included cochlear height, diameter and – in a curved multiplanar reconstruction – the length of the cochlear canal both along the outer and inner walls.
50 patients (100 petrous bones) were evaluated. Median length of cochlear canal along the outer wall was 32.1 mm (+/- SD 2.23), along inner wall 15.42 mm (+/- SD 1.71). Interobserver agreement: mean differences (95% confidence interval) for length of canal along the outer wall 0.36 mm (0.09 – 0.81), along inner wall 0.52 (0.06 – 0.98). No correlation to patient age or sex.
Cochlea size was independent of patient age or sex with good interobserver agreement. However, measurements in our study differed considerably (by 17 mm) if measured along the outer or inner wall of the cochlear canal. This difference should be considered in preoperative planning of electrode length and position.