Anatomic considerations of cochlear morphology and its implications for insertion trauma in cochlear implant surgery.
OBJECTIVE
The goal of this study is to analyze the 3-dimensional anatomy of the cochlear spiral and to investigate the consequences of its course to insertion trauma during cochlear implantation.


BACKGROUND
Insertion trauma in cochlear implant surgery is a feared surgical risk, potentially causing neural degeneration and altered performance of the implant. In literature, insertion trauma is reported to occur at specific locations. This has been ascribed to surgical technique and electrode design in relation to the size of the scala tympani. This study investigates whether there is an underlying anatomic substrate serving as a potential source for insertion trauma at these specific locations.


METHODS
The 3-dimensional path of the cochlear spiral of 8 human temporal bones was determined by segmentation, skeletonization, distance mapping, and wave propagation technique applied on microcomputer tomography images. Potential pressure points along this path were estimated with linear regression.


RESULTS
The cochlear lumen shows a noncontinuous spiraling path leading to potential pressure points during cochlear implantation at the basilar membrane in the region of 180 to 225 (12-14 mm) and 725 degrees (22-26 mm) and at the floor of the scala tympani around 0 to 90, 225 to 270, and 405 to 450 degrees.


CONCLUSIONS
Our data favor the idea that the intrinsic 3-dimensional cochlear morphology contributes to the risk for insertion trauma during cochlear implantation at specific locations.
Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands. b.m.verbist@lumc.nl
Berit M
BM
Verbist
Luca
L
Ferrarini
Jeroen J
JJ
Briaire
Andrzej
A
Zarowski
Faiza
F
Admiraal-Behloul
Hans
H
Olofsen
Johan H C
JH
Reiber
Johan H M
JH
Frijns
D003051:Cochlea / Q000033:anatomy & histology / Q000293:injuries / Q000601:surgery; D019929:Cochlear Implantation / Q000009:adverse effects* / Q000379:methods; D003054:Cochlear Implants / Q000009:adverse effects; D006801:Humans; D021621:Imaging, Three-Dimensional; D009410:Nerve Degeneration / Q000209:etiology; D011183:Postoperative Complications; D012307:Risk Factors; D012533:Scala Tympani / Q000033:anatomy & histology / Q000601:surgery; D015898:Tomography Scanners, X-Ray Computed