Intraoperative use of cone-beam computed tomography in a cadaveric ossified cochlea model

Abstract

Objectives: To describe a cadaveric temporal bone model of labyrinthitis ossificans and investigate the utility of intraoperative cone-beam computed tomography (CBCT) in the facilitating cochlear implantation.

Design: Cadaveric temporal bone study.

Methods: Five cadaveric heads had cement introduced into the 10 cochleas. CBCT and a conventional CT scan were compared to assess the extent of cochlear obliteration. The cement was drilled-out (under CBCT guidance, if required) and cochlear implant electrode arrays (from 3 different manufacturers) inserted.

Results: CBCT images demonstrated temporal bone anatomy and the extent of cochlear obliteration as clearly as conventional CT in all cases. Intraoperative CBCT guided drilling and facilitated electrode placement in two of five heads (3 of 10 ears). Streak-artifact from the electrodes of two devices partially obscured image clarity.

Conclusions: The obliterated cochlear model reproduced a disease-ossified cochlear both radiographically and surgically. CBCT is useful for intraoperative imaging to facilitate electrode array placement in the obliterated or congenitally abnormal cochlea.

Figure 1

Illustration of the experimental set-up.

Figure 2

Illustration of an ossified cochlea as seen in (a) diagnostic CT and (b) intraoperative CBCT (c) clinical diagnostic CT of ossified cochlea (post meningitis).

Figure 3

Photographs illustrating the cement-ossified cochlea (A) posterior tympanotomy (left ear) showing Simplex B cement filling the cochleostomy (arrow). (B) right cochleostomy after drill out of cement-ossification. A rim of residual cement is still present (arrow).

Figure 4

CBCT of an implanted cochlea to demonstrate metal streak artifact. (A) Implant # (Nucleus Contour, Cochlea); (B) Implant #2 (Maestro, MED-EL) and (C) Implant #3 (HiFocus 1j, Advanced Bionics).

Figure 5

Reconstructed CBCT of Implant #3 (HiFocus 1j, Advanced Bionics) to demonstrate surface rendering in the context of CBCT cut-planes, illustrating the full electrode length.