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The Chorda Tympani Nerve: Role in Taste Impairment in Middle Ear Disease and after Ear Surgery
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The chorda tympani nerve, also known as the taste nerve, runs uncovered through the middle ear cavity, a localization that exposes the nerve to pathological processes and surgical trauma in the middle ear. People operated on for otosclerosis tend to complain more about postoperative taste disturbances than those operated on for chronic otitis media. It has been suggested that this difference may be explained by gradual deterioration of chorda tympani nerve function caused by chronic otitis media infection and that further impairment caused by surgery is less noticeable in these patients.

This thesis aimed to evaluate the function of the chorda tympani nerve, the effects of middle ear disease on taste and complications resulting from ear surgery for chronic otitis media or otosclerosis. This information will help to improve the ear surgeon’s ability to predict the prognosis of iatrogenic taste disturbances in patients with middle ear disease and after ear surgery.

Taste was assessed using electrogustometry and the filter paper disc method before and after surgery for chronic otitis media or otosclerosis. Patients also completed questionnaires about symptoms and quality of life. The status of the chorda tympani nerve upon surgical opening of the ear and grading of the trauma to the nerve during the surgery were recorded. The ultrastructure of the chorda tympani nerve from healthy ears and from ears with chronic otitis media was examined. Electrogustometry and the filter paper disc method were evaluated.

The results of electrogustometry and the filter paper disc method were highly reproducible, although their correlation was moderate. Patients with chronic otitis media, patients with a more traumatized nerve, female patients and younger patients were more likely to report postoperative taste disturbances. Most of the patients recovered their taste after 1 year. The quality of life study showed only minor changes after surgery. Electron microscopic observations of nerves from ears with chronic otitis media showed signs of structural degeneration, although signs of regeneration, such as sprouting were also observed. This results may explain the recovery of taste postoperatively and indicate that the nerve should be carefully handled during surgery.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. , 54 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1306
Keyword [en]
Chorda tympani nerve, ear surgery, taste, chronic suppurative otitis media, otosclerosis, electrogustometry, filter paper disc method, quality of life, transmission electron microscopy, degeneration, sprouting
National Category
Medical and Health Sciences
Research subject
Surgery
Identifiers
URN: urn:nbn:se:uu:diva-316591ISBN: 978-91-554-9837-5 (print)OAI: oai:DiVA.org:uu-316591DiVA: diva2:1078890
Public defence
2017-04-27, Vårdskolans Aula, Ing 21, Västmanlands sjukhus Västerås, Västerås, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2017-04-05 Created: 2017-03-07 Last updated: 2017-04-18
List of papers
1. Evaluation of electrogustometry and the filter paper disc method for taste assessment
Open this publication in new window or tab >>Evaluation of electrogustometry and the filter paper disc method for taste assessment
2011 (English)In: Acta Oto-Laryngologica, ISSN 0001-6489, Vol. 131, no 5, 488-493 p.Article in journal (Refereed) Published
Abstract [en]

Conclusion:

The results indicate that electrogustometry and the filter paper disc method are reliable methods to measure taste with a high degree of reproducibility.

Objectives:

To thoroughly evaluate the reliability of electrogustometry and the filter paper disc method for taste assessments.

Methods:

Thirty-nine healthy test persons without any history of chronic middle ear disease, aged between 27 and 62 years, were recruited. In all, 772 electrogustometry and 30 filter paper disc assessments were made. A nerve decay test was performed, with measures taken before and after eating sweet, sour, bitter, salt, a mild or spicy meal, after smoking, and after taking Swedish tobacco snuff ('snus'), as well as before and after local anesthesia of the tongue. Measurements were performed on 5 consecutive days and repeatedly during 1 day. The correlation between electrogustometry and the filter paper disc method was also studied.

Results:

The results indicate that electrogustometry and the filter paper disc method are reliable methods to measure taste with a high degree of reproducibility. The only actions causing significant changes in the electrogustometry readings were eating bitter a substance and having local anesthesia of the tongue. The correlation between the methods was statistically significant except for the bitter flavor, where the correlation was just below the level of significance.

Keyword
Chorda tympani, ear disease, ear surgery
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-152942 (URN)10.3109/00016489.2010.535850 (DOI)000289562600005 ()21391775 (PubMedID)
Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2017-03-07Bibliographically approved
2. The chorda tympani degenerates during chronic otitis media: an electron microscopy study
Open this publication in new window or tab >>The chorda tympani degenerates during chronic otitis media: an electron microscopy study
Show others...
2015 (English)In: Acta Oto-Laryngologica, ISSN 0001-6489, Vol. 135, no 6, 542-548 p.Article in journal (Refereed) Published
Abstract [en]

Conclusion: Chorda tympani nerve specimens from ears with chronic inflammatory middle ear disease exhibit structural signs of degeneration. These correlate well with taste disturbance. Simultaneously, they exhibit signs of regeneration, which may explain the ability for taste recovery. Objectives: The chorda tympani, the major taste nerve, runs uncovered through the middle ear cavity. This situation exposes it to various forms of middle ear pathology. A difference has been noticed regarding taste symptoms pre- and postoperatively between inflammatory and non-inflammatory diseases. The present study aimed to investigate ultrastructural changes of chorda tympani in different forms of inflammatory middle ear disease, such as chronic suppurative otitis media and cholesteatoma, as compared with normal. Methods: Five chorda tympani specimens were collected from healthy middle ears of patients subjected to surgery for acoustic neuroma, to be used as normal controls, and five from middle ears with chronic otitis media or cholesteatoma, where the nerve could not be saved during the operation. Light and electron microscopy were performed. Results: For all five nerves from diseased ears, microscopy showed a higher percentage of axon and myelin sheath degeneration than in the normal controls. Furthermore, three of the five also exhibited sprouting.

Keyword
Taste, otosurgery, degeneration, sprouting
National Category
Otorhinolaryngology
Identifiers
urn:nbn:se:uu:diva-255041 (URN)10.3109/00016489.2014.999875 (DOI)000354215700004 ()25719908 (PubMedID)
Funder
Swedish Research Council, 2010-7209
Available from: 2015-06-23 Created: 2015-06-12 Last updated: 2017-03-07Bibliographically approved
3. Taste disturbance after stapes surgery: an evaluation of frequency, severity, duration, and quality-of-life
Open this publication in new window or tab >>Taste disturbance after stapes surgery: an evaluation of frequency, severity, duration, and quality-of-life
Show others...
2017 (English)In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 37, no 1, 39-43 p.Article in journal (Refereed) Published
Abstract [en]

 

Conclusion: The incidence of taste disturbance after stapes surgery is high (61.9 %), whereas the majority (94.8 %) recovers within 1 year. More severe surgical nerve trauma caused more disturbance, implying that the nerve should be handled carefully during surgery.

 

Objectives: Patients operated on for otosclerosis seem more often to complain about post-operative taste disturbance than those operated on for chronic otitis media, although the chorda tympani nerve more seldom becomes maltreated in stapedotomy. These observations seem paradoxical. It is unclear to what extent a post-operative taste disturbance affects the quality-of-life. This study aims to shed light on the occurrence of post-operative taste disturbances, on possible prognostic factors, and to what extent post-operative taste disturbance impairs the quality-of-life.

 

Methods: One hundred and thirty-four adults undergoing primary stapedotomy were included. Questionnaires on taste disturbance and quality-of-life (SF-36) were answered before and after surgery, until 1 year post-operatively.

 

Results: Eighty-three (61.9%) study persons reported post-operative taste disturbance. Seven (5.2%) reported persisting disturbance at 1 year. Surgically more traumatized chorda tympani nerves correlated with more severe taste disturbance post-operatively than less traumatized.  Taste disturbance at 1 year post-operatively correlate with a decrease of the physical function domain in the SF-36.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2017
Keyword
Chorda tympani nerve, otosclerosis, stapedotomy, taste, questionnaire, QoL, SF-36
National Category
Otorhinolaryngology
Research subject
Oto-Rhino-Laryngology
Identifiers
urn:nbn:se:uu:diva-315775 (URN)10.1080/00016489.2016.1217562 (DOI)
Available from: 2017-02-21 Created: 2017-02-21 Last updated: 2017-03-07Bibliographically approved
4. Surgery for chronic otitis media causes greater taste disturbance than surgery for otosclerosis
Open this publication in new window or tab >>Surgery for chronic otitis media causes greater taste disturbance than surgery for otosclerosis
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Objectives: Patients with otosclerosis more often complain about postoperative taste disturbance than those with chronic otitis media, which seems paradoxical. During surgery, the chorda tympani nerve (CTN) is thought to be severely traumatized less frequently, in the former than in the latter.

Study design: Objective and subjective measurements of taste impairment were obtained to document the occurrence of taste disturbance before and after surgery, possible prognostic factors, and to what extent such complications affect quality of life (QoL).

Methods: Sixty-five adults undergoing primary middle ear surgery were included. Thirty-seven were operated on for chronic suppurative otitis media (CSOM) and 28 for otosclerosis. Taste was assessed using electrogustometry (EGM) and the filter paper disc (FPD) method before and up to 1 year after surgery.  Questionnaires on taste disturbance and on QoL were completed before and up to 1 year after surgery.

Results: The FPD method indicated preoperative taste disturbance for participants with CSOM, who reported more postoperative taste disturbance than did those with otosclerosis. Severe traumatization of the CTN during surgery or an abnormal CTN before surgery predicted more severe symptoms after surgery. Younger people and females were also at higher risk for postoperative taste disturbance. QoL was slightly impairment after surgery in patients with abnormal CTN status at start of surgery.

Conclusion: People operated for CSOM had greater postoperative taste disturbances than did those operated on for otosclerosis. Females and younger people seemed to be more prone to postoperative taste disturbance. Traumatization of the CTN significantly reduced taste ability. 

Keyword
Chorda tympani nerve, ear surgery, taste, electrogustometry, chronic otitis media, otosclerosis
National Category
Medical and Health Sciences
Research subject
Oto-Rhino-Laryngology
Identifiers
urn:nbn:se:uu:diva-315778 (URN)
Available from: 2017-02-21 Created: 2017-02-21 Last updated: 2017-03-07

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