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Anatomical Characteristics of Facial Nerve and Cochlea Interaction
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Otolaryngology and Head and Neck Surgery.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Orthopaedics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Otolaryngology and Head and Neck Surgery.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Otolaryngology and Head and Neck Surgery.
2017 (English)In: Audiology & neuro-otology, ISSN 1420-3030, E-ISSN 1421-9700, Vol. 22, no 1, p. 41-49Article in journal (Refereed) Published
Abstract [en]

Objective: The aim was to study the relationship between the labyrinthine portion (LP) of the facial canal and the cochlea in human inner ear molds and temporal bones using micro-CT and 3D rendering. A reduced cochlea-facial distance may spread electric currents from the cochlear implant to the LP and cause facial nerve stimulation. Influencing factors may be the topographic anatomy and otic capsule properties.

Methods: An archival collection of human temporal bones underwent micro-CT and 3D reconstruction. In addition, cochlea-facial distance was assessed in silicone and polyester resin molds, and the association between the LP and upper basal turn of the cochlea was analyzed.

Results: Local thinning of the otic capsule and local anatomy may explain the development of cochlea-facial dehiscence, which was found in 1.4%. A reduced cochlea-facial distance was noted in 1 bone with a superior semicircular canal dehiscence but not in bones with superior semicircular canal "blue line." The otic capsule often impinged upon the LP and caused narrowing.

Conclusion: Micro-CT with 3D rendering offers new possibilities to study the topographic anatomy of the human temporal bone. The varied shape of the cross-section of the LP could often be explained by an "intruding" cochlea.

Place, publisher, year, edition, pages
KARGER , 2017. Vol. 22, no 1, p. 41-49
Keywords [en]
Human temporal bones, Cochlea, Facial canal, Micro-CT
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-333425DOI: 10.1159/000475876ISI: 000406762600006PubMedID: 28628917OAI: oai:DiVA.org:uu-333425DiVA, id: diva2:1156511
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2019-01-27Bibliographically approved
In thesis
1. The Human Cochlea and Cochlear Implantation: Morphological Characteristics and Clinical Correlations
Open this publication in new window or tab >>The Human Cochlea and Cochlear Implantation: Morphological Characteristics and Clinical Correlations
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The most common sensory deficit in the world is sensorineural hearing loss. Cochlear implantation (CI) can majorly contribute to restore hearing, not only in patients with severe to profound hearing loss, but also in hearing-impaired patients with residual low-frequency hearing. The overall aims of the present thesis were to study human cochlear anatomy in order to improve structural preservation during CI surgery. An archival collection of temporal bones underwent micro-computer tomography and synchrotron radiation phase-contrast imaging (SR-PCI) with 3D reconstructions, new techniques to digitally image and reproduce the human inner ear. Studying the anatomy of the facial nerve and its interaction with the cochlea revealed that a fusion of the two was found in 1.4 % of the specimens (cochlear-facial dehiscence). This may cause facial nerve excitation after CI. CT-scans and intraoperative electrically auditory brainstem response (e-ABR) measurements were analyzed in patients with cochlear-facial dehiscence. A large evoked late myogenic potential at low stimulation levels during intraoperative e-ABR measurements, can foresee excitation at CI activation. The 3D anatomy of the fundus of the inner acoustic canal was also studied, helping to interpret preoperative imaging of the VIIIth nerve before CI. In a subsequent study, SR-PCI reproduced the soft tissue anatomy at the round window region. Results indicated a high risk for trauma at cochleostomy. For optimal preservation, the round window approach was recommended. In a long-term follow-up the first 21 consecutively operated patients in Uppsala, that underwent hearing preservation CI-surgery, data could be retrieved in 15 patients. Pure tone audiometry was assessed preoperatively and at one, three and >5 years following surgery. Insertion angle, number of electrodes inside the cochlea, user-time of the processor, and stimulation strategies were documented. Results showed that long-term preservation of hearing is possible in most cases. There was a high correlation between insertion depth and preservation of residual hearing. Also, patients with complete hearing loss experienced good performance in speech discrimination and user time.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 45
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1537
Keywords
cochlear implantation, micro-CT, synchrotron, facial nerve stimulation, hearing preservation, round window
National Category
Otorhinolaryngology
Identifiers
urn:nbn:se:uu:diva-373643 (URN)978-91-513-0566-0 (ISBN)
Public defence
2019-03-15, Enghoffsalen, Akademiska sjukhuset, ingång 50, Uppsala, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2019-02-19 Created: 2019-01-27 Last updated: 2019-03-18

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Schart-Moren, NadineLarsson, SuneRask-Andersen, HelgeLi, Hao

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