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Hearing Preservation CI Surgery and Hybrid Hearing: From Anatomical Aspects to Patient Satisfaction
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Otolaryngology and Head and Neck Surgery.
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.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 997
Keyword [en]
anatomic variations, human cochlea, cochlear implantation, EAS, electro-acoustic stimulation, residual hearing, partial deafness, IOI-HA, EQ-5D
National Category
Research subject
URN: urn:nbn:se:uu:diva-221536ISBN: 978-91-554-8949-6OAI: diva2:711365
Public defence
2014-06-05, Skoogsalen, ingång 78/79, Akademiska sjukhuset, Uppsala, 09:00 (Swedish)
Available from: 2014-05-14 Created: 2014-04-01 Last updated: 2014-06-30
List of papers
1. Variational anatomy of the human cochlea: implications for cochlear implantation
Open this publication in new window or tab >>Variational anatomy of the human cochlea: implications for cochlear implantation
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.

National Category
Medical and Health Sciences
urn:nbn:se:uu:diva-113210 (URN)10.1097/MAO.0b013e31818a08e8 (DOI)000276925300003 ()18833017 (PubMedID)
Available from: 2010-01-26 Created: 2010-01-26 Last updated: 2014-06-30Bibliographically approved
2. How to predict cochlear length before cochlear implantation surgery
Open this publication in new window or tab >>How to predict cochlear length before cochlear implantation surgery
2013 (English)In: Acta Oto-Laryngologica, ISSN 0001-6489, Vol. 133, no 12, 1258-1265 p.Article in journal (Refereed) Published
Abstract [en]

Conclusions: The basal turn diameter of the human cochlea predicts the outer wall length of the basal and two first turns relatively well but there was less correlation for the total cochlear length. The linear regression graph defines the length of the basal turn within an error of +/- 1 mm and could be used clinically to distinguish small and large cochleae. Objective: The human cochlea varies in size. The preoperative assessment of cochlear length can be crucial for non-traumatic electrode insertion and hearing preservation. In this study, we estimated the external cochlear wall length by assessing the basal turn diameter. Methods: A total of 51 non-selected, human inner ear moulds were analysed. A line was drawn from the midpoint of the round window through the cochlear mid-portion to the opposite side (A) and correlated to the cochlear turn lengths. Linear regression analyses were carried out. Results: Mean diameter A was 9.3 mm. The mean basal turn length was 22.8 mm, the two first turns were 35.1 mm and the total length was 41.2 mm. Linear regression analyses indicated a coefficient of determination (R-2) of 0.74 for diameter A and the basal turn length, R-2 = 0.70 for the two-turn length and R-2 = 0.39 for the total length.

Human cochlea, electro-acoustic-stimulation, EAS, partial deafness, cochlear implant, hearing preservation
National Category
Medical and Health Sciences
urn:nbn:se:uu:diva-213453 (URN)10.3109/00016489.2013.831475 (DOI)000327419700004 ()
Available from: 2013-12-30 Created: 2013-12-23 Last updated: 2014-06-30Bibliographically approved
3. Cochlear implantation and hearing preservation: results in 21 consecutively operated patients using the round window approach
Open this publication in new window or tab >>Cochlear implantation and hearing preservation: results in 21 consecutively operated patients using the round window approach
2012 (English)In: Acta Oto-Laryngologica, ISSN 0001-6489, Vol. 132, no 9, 923-931 p.Article in journal (Refereed) Published
Abstract [en]


Prevalent hearing conservation may be achieved after round window (RW) cochlear implantation using soft and flexible electrode arrays if variations of RW anatomy, topography, and facial nerve position are considered. The most favorable electrode insertion depth remains to be established.


We assessed the incidence of cochlear function after cochlear implant (CI) electrode insertion through the RW in our first 21 consecutively operated patients aimed at hearing conservation.


Eleven patients had a preoperative low frequency hearing suitable for electro-acoustic stimulation. Hearing was preserved in an additional nine patients at their request with the intention to use full frequency CI stimulation. Anatomic variations of the RW were carefully considered using our temporal bone collection of micro-dissected ears. Electrode extension was assessed on X-ray by measuring the insertion angle of the first electrode and intra-cochlear length and correlated with audiometric data.


There was no incidence of total loss of residual hearing in any of the patients. A slight deterioration of low frequency thresholds occurred in some patients. Mean hearing loss at 125-500 Hz was 14.4 dB at 1 month following surgery and 15.6 dB after 1 year. Insertion angle (300-540°) and depth (17.5-28.5 mm) were not statistically correlated to hearing loss.

National Category
Medical and Health Sciences
urn:nbn:se:uu:diva-181696 (URN)10.3109/00016489.2012.680198 (DOI)000307995600003 ()22667762 (PubMedID)
Available from: 2012-09-27 Created: 2012-09-27 Last updated: 2014-06-30Bibliographically approved
4. Hearing and patient satisfaction in 19 patients receiving implants intended for hybrid hearing: A two-year follow-up
Open this publication in new window or tab >>Hearing and patient satisfaction in 19 patients receiving implants intended for hybrid hearing: A two-year follow-up
(English)In: International Journal of Audiology, ISSN 1499-2027, E-ISSN 1708-8186Article in journal (Refereed) Accepted
National Category
Medical and Health Sciences
urn:nbn:se:uu:diva-221532 (URN)
Available from: 2014-04-01 Created: 2014-04-01 Last updated: 2014-09-17Bibliographically approved

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