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Variational anatomy of the human cochlea: implications for cochlear implantation
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.
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.
2009 (English)In: Otology and Neurotology, ISSN 1531-7129, E-ISSN 1537-4505, Vol. 30, no 1, 14-22 p.Article in journal (Refereed) Published
Abstract [en]

HYPOTHESIS: To study variations in human cochlea anatomy with potential implications for cochlear implantation surgery. BACKGROUND: A comprehension of the anatomic variations of the human cochlea is essential for understanding the degree of surgical trauma induced by inserting various electrode arrays in cochlear implantation surgery. Variations in anatomy may also limit the potential for performing hearing preservation. METHODS: We studied 73 archival, nonselected, adult, corrosion casts of human inner ears. Anatomic reference points were constructed from photographic reproductions taken at different angles, and various dimensions were assessed using planimetry. Anatomic variants with particular clinical/surgical interests were pinpointed. RESULTS: Results showed that the human cochlea is individually shaped, varying greatly in dimensions ("fingerprint"). The outer cochlear wall length ranged from 38.6 to 45.6 mm with a mean length of 42.0 mm. The first turn represented 53% of the total length and ranged from 20.3 to 24.3 mm. The number of quadrants varied from slightly more than 8 to 12. The facial nerve canal ran in close proximity to the upper first turn explaining facial nerve excitement during stimulation of electrodes in this region in some instances. The internal diameter (height) of the cochlear tube in the first turn varied broadly (1.6-2.6 mm), occasionally with limited space for conventional implants. CONCLUSION: The human cochlea exhibits extensive anatomic variations. These variations will influence the location of cochlear implant arrays and affect the potential of hearing preservation surgery. Our results may explain the surgeon's difficulties sometimes to insert electrode arrays even in so-called "normal" cochleae.

Place, publisher, year, edition, pages
2009. Vol. 30, no 1, 14-22 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-113210DOI: 10.1097/MAO.0b013e31818a08e8ISI: 000276925300003PubMedID: 18833017OAI: oai:DiVA.org:uu-113210DiVA: diva2:290135
Available from: 2010-01-26 Created: 2010-01-26 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Hearing Preservation CI Surgery and Hybrid Hearing: From Anatomical Aspects to Patient Satisfaction
Open this publication in new window or tab >>Hearing Preservation CI Surgery and Hybrid Hearing: From Anatomical Aspects to Patient Satisfaction
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A common cause of profound deafness is hair cell dysfunction in the cochlea. Cochlear implants (CI) bypass the hair cells via an electrode and stimulate the cochlear nerve directly. Nowadays, it is possible to preserve residual hair cell function and hearing through flexible electrodes and a-traumatic CI surgery techniques; called hearing preservation CI surgery. This may suit partially deaf patients who can use natural low frequency hearing in combination with electric high frequency hearing; so-called hybrid hearing. The aim of this thesis was to elucidate the effectiveness of hearing preservation CI surgery. The thesis demonstrates human cochlear anatomy in relation to CI and evaluates hearing and patient satisfaction after hearing preservation CI surgery.

Analyses of human cochlear moulds belonging to the Uppsala collection showed large variations in dimensions and coiling characteristics of the cochlea. Each cochlea was individually shaped. The size and shape of the cochlea influences the position of the electrode. The diameter of the basal cochlear turn could predict insertion depth of the electrode, which is crucial for hearing preservation. The first 21 patients operated with hearing preservation CI surgery in Uppsala, showed preserved hearing.

Nine-teen partially deaf patients receiving implants intended for hybrid hearing, were evaluated concerning pure tone audiometry, monosyllables (MS) and hearing in noise test (HINT). They also responded to a questionnaire, consisting of the IOI-HA, EQ-5D VAS and nine questions about residual hearing. The questionnaire results indicated a high degree of patient satisfaction with improved speech perception in silence and noise. This was also reflected by improved results in MS and HINT. Hearing was preserved in all patients, but there was an on-going deterioration of the residual hearing in the operated ear which surpassed the contralateral ear. There were no correlations between the amount of residual hearing and patient satisfaction or speech perception results. Electric stimulation provides a major contribution to speech comprehension in partially deaf patients. All the patients showed a high degree of satisfaction with their CI, regardless of varying hearing preservation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 997
Keyword
anatomic variations, human cochlea, cochlear implantation, EAS, electro-acoustic stimulation, residual hearing, partial deafness, IOI-HA, EQ-5D
National Category
Otorhinolaryngology
Research subject
Oto-Rhino-Laryngology
Identifiers
urn:nbn:se:uu:diva-221536 (URN)978-91-554-8949-6 (ISBN)
Public defence
2014-06-05, Skoogsalen, ingång 78/79, Akademiska sjukhuset, Uppsala, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2014-05-14 Created: 2014-04-01 Last updated: 2014-06-30

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