The surgical anatomy of the extra-temporal portion of the facial nerve in relation to parotidectomy

Rea, Paul Michael (2003) The surgical anatomy of the extra-temporal portion of the facial nerve in relation to parotidectomy. MSc(R) thesis, University of Glasgow.

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Abstract

The facial nerve passes through the substance of the parotid gland and therefore, surgery on this gland (commonly for parotid tumours) places the nerve at great risk. The facial nerve needs to be preserved as it supplies the muscles of facial expression and therefore damaging it will have severe cosmetic and functional consequences. There has been dispute in the past as to whether to locate the facial nerve during parotid gland surgery from an anterograde approach, where the main trunk is identified early in the procedure (Corcione and Califano, 1990) or, by a retrograde approach, where the peripheral branches are identified first (Yu, 2001). In Glasgow, the facial nerve is identified in parotidectomy by the anterograde approach. This means that the facial nerve is identified after it leaves the skull at the stylomastoid foramen but before it enters the parotid gland. A landmark at this point which can be used to identify the facial nerve is the tympanomastoid suture, although other landmarks have been used in the past (Holt, 1996; Conley, 1978; Heeneman, 1975 and Boswell, 1959). The null hypotheses which are to be tested are that in parotid surgery: The tympanomastoid suture is not a reliable landmark to use to locate the extra-temporal portion of the facial nerve. The tympanomastoid suture is not a safe landmark to use to locate the extra-temporal portion of the facial nerve. o The tympanomastoid suture is not any more reliable in locating the extratemporal portion of the facial nerve compared to other landmarks which have been used in the past. To test this proposition the following work will be undertaken: To test the reliability of using the tympanomastoid suture in locating the facial nerve: 1. The tympanomastoid suture will be identified in the cadaver. 2. The suture will be used to identify the facial nerve. 3. The distance will be measured from the tympanomastoid suture to the main trunk of the facial nerve (ie. its extra temporal portion) and this will be repeated on a series of cadavers. To test the safety of the tympanomastoid suture in locating the facial nerve: 1. The relationship of the suture line to the facial nerve and other surrounding structures will be examined. 2. The facial nerve will be traced distally and surrounding structures to it will be examined. 3. A parotidectomy (which involves identifying the facial nerve early in the operation) will be carried out on the cadaver to see the other structures which may be at risk. To test the reliability of the tympanomastoid suture against other landmarks: 1. Three other surrounding landmarks will be identified: the "tragal pointer", the posterior belly of digastric muscle and the junction of the cartilaginous and bony external auditory canal to examine their relationship to the facial nerve. 2. Distances will be measured from the main trunk of the facial nerve to each of these landmarks and serial measurements will be undertaken. Finally, the identification of the facial nerve at operation will be observed to judge the safety and reliability of identifying the main trunk early in the operation and to see if any other complications arise. It is hoped these types of measurements above may also be useful in the future in terms of computer-guided surgery.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Adviser: J Shaw-Dunn
Keywords: Morphology, Surgery
Date of Award: 2003
Depositing User: Enlighten Team
Unique ID: glathesis:2003-41127
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 15 Apr 2019 15:21
Last Modified: 15 Apr 2019 15:21
URI: http://theses.gla.ac.uk/id/eprint/41127

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