Vestibular Organ and Cochlear Implantation-A Synchrotron and Micro-CT Study

Hao Li; Nadine Schart-Moren; Gunesh Rajan; Jeremy Shaw; Seyed Alireza Rohani; Francesca Atturo; Hanif M Ladak; Helge Rask-Andersen; Sumit Agrawal

doi:10.3389/fneur.2021.663722

Vestibular Organ and Cochlear Implantation-A Synchrotron and Micro-CT Study

Front Neurol. 2021 Apr 7:12:663722. doi: 10.3389/fneur.2021.663722. eCollection 2021.

Authors

Hao Li¹, Nadine Schart-Moren^{1

2}, Gunesh Rajan^{3

4}, Jeremy Shaw⁵, Seyed Alireza Rohani⁶, Francesca Atturo⁷, Hanif M Ladak^{6

8}, Helge Rask-Andersen¹, Sumit Agrawal^{6

8}

Affiliations

¹ Department of Surgical Sciences, Otorhinolaryngology and Head and Neck Surgery, Uppsala University, Uppsala, Sweden.
² Section of Otolaryngology, Head and Neck Surgery, Uppsala University Hospital, Uppsala, Sweden.
³ Department of Otolaryngology, Head & Neck Surgery, Luzerner Kantonsspital, Lucerne, Switzerland.
⁴ Department of Otolaryngology, Head & Neck Surgery, Division of Surgery, Medical School, University of Western Australia, Perth, WA, Australia.
⁵ Centre for Microscopy, Characterization and Analysis, Perth, WA, Australia.
⁶ Department of Otolaryngology-Head and Neck Surgery, Western University, London, ON, Canada.
⁷ Department of Otolaryngology, University of Sapienza, Rome, Italy.
⁸ Department of Medical Biophysics and Department of Electrical and Computer Engineering, Western University, London, ON, Canada.

Abstract

Background: Reports vary on the incidence of vestibular dysfunction and dizziness in patients following cochlear implantation (CI). Disequilibrium may be caused by surgery at the cochlear base, leading to functional disturbances of the vestibular receptors and endolymphatic duct system (EDS) which are located nearby. Here, we analyzed the three-dimensional (3D) anatomy of this region, aiming to optimize surgical approaches to limit damage to the vestibular organ. Material and Methods: A total of 22 fresh-frozen human temporal bones underwent synchrotron radiation phase-contrast imaging (SR-PCI). One temporal bone underwent micro-computed tomography (micro-CT) after fixation and staining with Lugol's iodine solution (I₂KI) to increase tissue contrast. We used volume-rendering software to create 3D reconstructions and tissue segmentation that allowed precise assessment of anatomical relationships and topography. Macerated human ears belonging to the Uppsala collection were also used. Drilling and insertion of CI electrodes was performed with metric analyses of different trajectories. Results and Conclusions: SR-PCI and micro-CT imaging demonstrated the complex 3D anatomy of the basal region of the human cochlea, vestibular apparatus, and EDS. Drilling of a cochleostomy may disturb vestibular organ function by injuring the endolymphatic space and disrupting fluid barriers. The saccule is at particular risk due to its proximity to the surgical area and may explain immediate and long-term post-operative vertigo. Round window insertion may be less traumatic to the inner ear, however it may affect the vestibular receptors.

Keywords: cochlear implant; human; micro-CT; synchrotron; vestibular organ.