MEDICAL NEUROTOLOGYAccess to the Apical Cochlear Modiolus for Possible Stem Cell-based and Gene Therapy of the Auditory NerveWrobel, Christian∗,†; Bevis, Nicholas F.∗; Meyer, Alexander C.∗; Beutner, Dirk∗Author Information ∗Department of Otorhinolaryngology †InnerEarLab, University Medical Center Göttingen, Göttingen, Germany Address correspondence and reprint requests to Dirk Beutner, M.D., Department of Otorhinolaryngology, University Medical Center Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany; E-mail: [email protected]; Alexander C. Meyer, M.D., Department of Otorhinolaryngology, University Medical Center Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany; E-mail: [email protected]. Source of Funding: None. Author contributions: C.W., A.M., and D.B. designed the study. C.W. and A.M. performed preparation of specimen. C.W. and N.B. performed 3D reconstruction and analysis of DICOM-data. All authors prepared the manuscript. The authors disclose no conflicts of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Website (http://journals.lww.com/otology-neurotology). Otology & Neurotology: March 2021 - Volume 42 - Issue 3 - p e371-e377 doi: 10.1097/MAO.0000000000002941 Buy SDC Metrics Abstract Objective: Loss of spiral ganglion neurons (SGN) is permanent and responsible for a substantial number of patients suffering from hearing impairment. It can derive from the degeneration of SGNs due to the death of sensory hair cells as well as from auditory neuropathy. Utilizing stem cells to recover lost SGNs increasingly emerges as a possible therapeutic option, but access to human SGNs is difficult due to their protected location within the bony impacted cochlea. Aim of this study was to establish a reliable and practicable approach to access SGNs in the human temporal bone for possible stem cell and gene therapies. Methods: In seven human temporal bone specimen a transcanal approach was used to carefully drill a cochleostomy in the lateral second turn followed by insertion of a tungsten needle into the apical modiolus to indicate the spot for intramodiolar injections. Subsequent cone beam computed tomography (CBCT) served as evaluation for positioning of the marker and cochleostomy size. Results: The apical modiolus could be exposed in all cases by a cochleostomy (1.6 mm2, standard deviation ±0.23 mm2) in the lateral second turn. 3D reconstructions and analysis of CBCT revealed reliable positioning of the marker in the apical modiolus, deviating on average 0.9 mm (standard deviation ±0.49 mm) from the targeted center of the second cochlear turn. Conclusion: We established a reliable, minimally invasive, transcanal surgical approach to the apical cochlear modiolus in the human temporal bone in foresight to stem cell-based and gene therapy of the auditory nerve. © 2020, Otology & Neurotology, Inc.