The secondary spiral lamina and its relevance in cochlear implant surgery

Sumit Agrawal; Nadine Schart-Morén; Wei Liu; Hanif M Ladak; Helge Rask-Andersen; Hao Li

doi:10.1080/03009734.2018.1443983

The secondary spiral lamina and its relevance in cochlear implant surgery

Ups J Med Sci. 2018 Mar;123(1):9-18. doi: 10.1080/03009734.2018.1443983. Epub 2018 Mar 14.

Authors

Sumit Agrawal¹, Nadine Schart-Morén², Wei Liu², Hanif M Ladak^{1

3}, Helge Rask-Andersen², Hao Li²

Affiliations

¹ a Department of Otolaryngology-Head and Neck Surgery , Western University , London , ON , Canada.
² b Department of Surgical Sciences, Section of Otolaryngology, Department of Otolaryngology , Uppsala University Hospital , Uppsala , Sweden.
³ c Department of Medical Biophysics and Department of Electrical and Computer Engineering , Western University , London , ON , Canada.

Abstract

Objective: We used synchrotron radiation phase contrast imaging (SR-PCI) to study the 3D microanatomy of the basilar membrane (BM) and its attachment to the spiral ligament (SL) (with a conceivable secondary spiral lamina [SSL] or secondary spiral plate) at the round window membrane (RWM) in the human cochlea. The conception of this complex anatomy may be essential for accomplishing structural preservation at cochlear implant surgery.

Material and methods: Sixteen freshly fixed human temporal bones were used to reproduce the BM, SL, primary and secondary osseous spiral laminae (OSL), and RWM using volume-rendering software. Confocal microscopy immunohistochemistry (IHC) was performed to analyze the molecular constituents.

Results: SR-PCI reproduced the soft tissues including the RWM, Reissner's membrane (RM), and the BM attachment to the lateral wall (LW) in three dimensions. A variable SR-PCI contrast enhancement was recognized in the caudal part of the SL facing the scala tympani (ST). It seemed to represent a SSL allied to the basilar crest (BC). The SSL extended along the postero-superior margin of the round window (RW) and immunohistochemically expressed type II collagen.

Conclusions: Unlike in several mammalian species, the human SSL is restricted to the most basal portion of the cochlea around the RW. It anchors the BM and may influence its hydro-mechanical properties. It could also help to shield the BM from the RW. The microanatomy should be considered at cochlear implant surgery.

Keywords: Basilar membrane; cochlea; human; secondary spiral lamina; synchrotron-phase contrast imaging.

MeSH terms

Basilar Membrane / anatomy & histology
Basilar Membrane / diagnostic imaging
Cochlear Implantation / methods*
Humans
Immunohistochemistry
Round Window, Ear / anatomy & histology
Round Window, Ear / diagnostic imaging
Spiral Lamina / anatomy & histology
Spiral Lamina / diagnostic imaging*

Grants and funding

This study was supported by Swedish Research Council [2017-03801], ALF grants from the Uppsala University Hospital, Tysta Skolan Foundation, Swedish Hearing Research Foundation, by The Ingrid Löwenström Foundation, and by generous private funds from Börje Runögård and David Giertz of Sweden. Part of the research described in this paper was performed at the BMIT facility at the Canadian Light Source, which is funded by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, the National Research Council Canada, the Canadian Institutes of Health Research, the Government of Saskatchewan, Western Economic Diversification Canada, and the University of Saskatchewan.