WWW.DISSERTATION.XLIBX.INFO
FREE ELECTRONIC LIBRARY - Dissertations, online materials
 
<< HOME
CONTACTS



Pages:   || 2 | 3 |

«1. Introduction The trigeminal nerve (TN) is a mixed cranial nerve that consists primarily of sensory neurons. It exists the brain on the lateral ...»

-- [ Page 1 ] --

5

The Mandibular Nerve:

The Anatomy of Nerve Injury and Entrapment

M. Piagkou1, T. Demesticha2, G. Piagkos3,

Chrysanthou Ioannis4, P. Skandalakis5 and E.O. Johnson6

1,3,4,5,6Department of Anatomy,

2Department of Anesthesiology, Metropolitan Hospital

Medical School, University of Athens

Greece

1. Introduction

The trigeminal nerve (TN) is a mixed cranial nerve that consists primarily of sensory

neurons. It exists the brain on the lateral surface of the pons, entering the trigeminal ganglion (TGG) after a few millimeters, followed by an extensive series of divisions. Of the three major branches that emerge from the TGG, the mandibular nerve (MN) comprises the 3rd and largest of the three divisions. The MN also has an additional motor component, which may run in a separate facial compartment. Thus, unlike the other two TN divisions, which convey afferent fibers, the MN also contains motor or efferent fibers to innervate the muscles that are attached to mandible (muscles of mastication, the mylohyoid, the anterior belly of the digastric muscle, the tensor veli palatini, and tensor tympani muscle). Most of these fibers travel directly to their target tissues. Sensory axons innervate skin on the lateral side of the head, tongue, and mucosal wall of the oral cavity. Some sensory axons enter the mandible to innervate the teeth and emerge from the mental foramen to innervate the skin of the lower jaw.

An entrapment neuropathy is a nerve lesion caused by pressure or mechanical irritation from some anatomic structures next to the nerve. This occurs frequently where the nerve passes through a fibro-osseous canal, or because of impingement by an anatomic structure (bone, muscle or a fibrous band), or because of the combined influences on the nerve entrapment between soft and hard tissues. Any mechanical injury of the nerve therefore could be considered a compression or entrapment neuropathy (Kwak et al., 2003). A usual position of TN compression is the ITF (Nayak et al., 2008), a deep retromaxillary space, situated below the middle cranial fossa of the skull, the pharynx and the mandibular ramus.

The ITF contains several of the mastication muscles, the pterygoid venous plexus, the maxillary artery (MA) and the MN ramification (Prades et al., 2003) (Figure 1). The MA is in contact with the inferior alveolar nerve (IAN) and lingual nerve (LN) (Trost et al., 2009).

Recently, it is believed that some cases of temporomandibular joint syndrome (TMJS), persistent idiopathic facial pain (PIFP) and myofascial pain syndrome (MPS) may be due to entrapment neuropathies of the MN in the ITF (Loughner et al., 1990). Various muscle anomalies in the ITF have been reported when considering unexplained neurological

–  –  –

symptoms attributed to MN branches. The variations of the typical nerve course are important for adequate local anaesthesia, dental, oncological and reconstructive operations (Akita et al., 2001). Whenever observed these variations must be reported as they can cause serious implications in any surgical intervention in the region, and may lead to false neurological differential diagnosis. If anomalous branches occur in combination with the ossified ligaments, then cutaneous sensory fibres might pass through one of the foramina formed by the ossified bars (Shaw, 1993). The MN can be compressed as a result of both its course and its relation to the surrounding structures, particularly when passing between the medial pterygoid (MPt) and lateral pterygoid (LPt) muscles. When the pterygoid muscles contract, both the IAN and the LN may be compressed. This results in pain, particularly during chewing; and may eventually cause trigeminal neuralgia (TGN) (Anil et al., 2003). MN entrapment can lead to numbness of all peripheral regions innervated from it. It could also lead to pain during speech (Peuker et al., 2001).

Fig. 1. The distribution of the mandibular nerve and its branches in the infratemporal fossa (ITF)

–  –  –

2. Typical course of mandibular nerve and its branches The MN, the largest of the three divisions of the Τ, leaves the skull through the foramen ovale (FO) and enters the ITF and medial to the LPt; it divides into a smaller anterior trunk and a larger posterior trunk. The anterior trunk passes between the roof of the ITF and the LPt and the posterior trunk descends medially to the LPt, which might entrap the nerve (Isberg et al., 1987; Loughner et al., 1990) (Figure 2).

Fig. 2. The mandibular division of the TN emerging for the Foramen Ovale deep in the ITF.

3. The anterior trunk of the MN The Buccal Nerve (BN) mainly supplies the LPt while passing through it and may give off the Anterior Deep Temporal Nerve (ADTN). It supplies the skin over the anterior part of the buccinator and the buccal mucous membrane, together with the posterior part of the buccal gingivae, adjacent to the 2nd and 3rd molar teeth. It proceeds between the two parts of the LPt, descending deep then anteriorly to the tendon of the temporalis muscle. This normal course is a potential site of entrapment. If LPt spasm occurs, the BN could be compressed, and this compression could provoke in cheek numbness. BN compression has been reported by a hyperactive temporalis muscle and may result in neuralgia-like paroxysmal pain (Loughner al., 1990). Kim et al (2003) found that in 8 cadavers (33.3%) the BN was entrapped within the anterior muscle fibres of the temporalis.





The Masseteric nerve passes laterally, above the LPt, on the skull base, anterior to the TMJ and posterior to the tendon of the temporalis; it crosses the posterior part of the mandibular coronoid notch with the masseteric artery, ramifies on, and enters the deep surface of masseter. It also supplies the TMJ. Compression of the masseteric nerve anterior to the TMJ was found in 1 joint with excessive condylar translation (Johansson et al., 1990).

www.intechopen.com 74 Maxillofacial Surgery The Deep temporal nerves (DTN) usually an anterior and a posterior branch pass above the LPt to enter the deep surface of the temporalis. The small Posterior Deep Temporal Nerve (PDTN) sometimes arises in common with the masseteric nerve. The Anterior Deep Temporal Nerve (ADTN), a branch of the BN, ascends over the upper head of the LPt. A middle branch often occurs. Johannson et al. (1990) found that the DPTN may pass close to the anterior insertion of the joint capsule on the temporal bone, exposing them to the risk of mechanical irritation in condylar hypermobility. Loughner et al. (1990) observed the mylohyoid nerve and ADTN passing through the LPt. A spastic condition of the LPt may be causally related to compression of an entrapped nerve that leads to numbness, pain or both in the respective nerve distribution areas. Compression of sensory branches of the DTN by the temporalis muscle is a cause of neuropathy, (neuralgia or paresthesia) neuralgia or paresthesia (Madhavi et al., 2006).

The Nerve to the LPt enters the deep surface of the muscle and may arise separately from the anterior division or with the BN.

4. The posterior trunk of the MN The Auriculotemporal Nerve (ATN) usually has 2 roots, arising from the posterior division of MN. It encircles the middle meningeal artery (MMA) and runs posteriorly passing between the sphenomandibular ligament (SML) and the neck of the mandible. It then runs laterally behind the TMJ to emerge deep in the upper part of the parotid gland. The nerve carries somatosensory and secremotor fibres of the MN and the glossopharyngeal nerve (GPhN). The ATN communicates with the facial nerve (FN) at the posterior border of the ramus where the ATN passes posterior to the neck of the condyle. If fibres cross over from the ATN to the FN and not vice versa, this communication may represent a pathway for FN sensory impairment; i.e. pain in the muscles of facial expression may occur due to an entrapped and compressed ATN. An entrapped ATN in the LPt could be the aetiology behind a painful neuropathy in a distal ATN branch supplying sensory innervation to a deranged TMJ (Akita et al., 2001).

The ATN is in close anatomic relation to the condylar process, the TMJ, the superficial temporal artery (STA) and the LPt. ATN compression by hypertrophied LPt may result in neuralgia or paresthesia of TMJ, exernal acoustic meatus and facial muscles. Further it may result in functional impairment of salivation ipsilaterally. In addition, the altered position of the ATN and its extensive or multiple loops may render the ATN more liable to entrapment neuropathy. Temple headaches occur frequently due to entrapment of ATN, which sometimes is throbbing in nature, due to its proximity to STA (Soni et al., 2009). Johannson et al. (1990) revealed the existence of topographical prerequisites for mechanical influence upon the MN branches passing in the TMJ region. In joints, with a displaced disc, the ATN trunk was almost in contact with the medial aspect of the condyle instead of exhibiting its normal sheltered course at the level of the condylar neck, thus exposing the nerve possible mechanical irritation during anteromedial condylar movements.

The Inferior alveolar Nerve (IAN) normally descends medial to the LPt. At its lower border, the nerve passes between the SML and the mandibular ramus, and then enters the mandibular canal through the mandibular foramen. In the mandibular canal it runs downwards and forwards, generally below the apices of the teeth until below the first and www.intechopen.com 75 The Mandibular Nerve: The Anatomy of Nerve Injury and Entrapment second premolars, where it divides into the terminal incisive and mental branches (Khan et al., 2009). Because the IAN is a mixed nerve, it is suggested that during development, the sensory and motor fibres are guided separately, and take different migration pathways. When the motor component of the nerve leaves for its final destination, the sensory fibres reunite (Krmpotic-Nemanic et al., 1999). It was also found that the IAN and the LN may pass close to the medial part of the condyle. In joints with this nerve topography, a medially displaced disc could interfere mechanically with these nerves.

These findings could explain the sharp, shooting pain felt locally in the joint with jaw movements and the pain and other sensations projecting to the terminal area of distribution of the nerve branches near the TMJ such as the ear, temple, cheek, tongue, and teeth (Johansson et al., 1990).

The Mylohyoid Nerve branches from the IAN as the latter descends between the SML and the mandibular ramus. The mylohyoid nerve (motor nerve) passes forward in a groove to reach the mylohyoid muscle and the anterior belly of the digastric muscle. Loughner et al.

(1990) found an unusual entrapment of the mylohyoid nerve in the LPt in one cadaver.

Nerve compression may cause a poorly localized deep pain from the muscles it innervates.

Chronic compression of the nerve results in muscular paresis. Nerve entrapment bilaterally may provoke swallowing difficulties.

The Lingual Nerve (LN) is the smallest sensory branch of the posterior trunk of the MN.



Pages:   || 2 | 3 |


Similar works:

«Solo System ® User Manual Form 94006 May 29, 2002 / ISO Reference 7.2.2 DEVICE Congratulations! You are now the owner of a Sunlighten sauna! Are you ready to experience ultimate relaxation and rejuvenation? Just follow our assembly and usage guidelines and you will soon be in Sunlighten heaven!DISCLAIMER: The Solo System® is a Personal Sauna. Any information presented within this manual is for educational or reference purposes only. The content of this manual is not intended for diagnosis or...»

«Package leaflet: Information for the patient Vanatex HCT 80 mg/12.5 mg film-coated tablets Vanatex HCT 160 mg/12.5 mg film-coated tablets Vanatex HCT 160 mg/25 mg film-coated tablets Valsartan/hydrochlorothiazide Read all of this leaflet carefully before you start taking this medicine because it contains important information for you.Keep this leaflet. You may need to read it again.If you have any further questions, ask your doctor or pharmacist. This medicine has been prescribed for you only....»

«Estimates of Medical Device Spending in the United States Roland “Guy” King, F.S.A., M.A.A.A. Gerald F. Donahoe1 Abstract Advances in medical technology have long been believed to be a major driver of health care costs, but surprisingly little is known about the aggregate value and prices of one of the major types of medical technology, medical devices and diagnostics. This data note analyzes spending on medical devices for 1989-2004. Prices for medical devices consistently grew more slowly...»

«Neuropathic orofacial paiN The brochure is provided compliments of This brochure in intended for informational purposes only and should be considered a replacement for a professional treatment for a health care professional.To locate knowledgeable and experienced expert in orofacial pain, contact: The American Academy of Orofacial Pain 174 S. New York Ave. POB 478 Oceanville, NJ 08231 P: 609-504-1311 E: aaopexec@aaop.org W: www.aaop.org To locate knowledgeable and experienced expert in...»

«Community Champion Network Meeting Thursday 10th July 2014 Attendees John Black (JB) Breathe Easy group Brian Clark (BC) North Southport Individual Locality Representative Lionel Johnson (LJ) Central Southport Individual Locality Representative Ken Lowe (KL) Ainsdale/Birkdale Individual Locality Representative Denise Grant (DG) Southport Community Service Station Carole Holt (CH) Parenting 2000 Louise Malone (LM) Healthy Sefton Gill Mason (GM) The Independent Social Work Partnership Liz Brooks...»

«Recovering Ordinary Lives The strategy for occupational therapy in mental health services 2007–2017 Results from service user and carer focus groups College of Occupational Therapists About the publisher The College of Occupational Therapists is a wholly owned subsidiary of the British Association of Occupational Therapists (BAOT) and operates as a registered charity. It represents the profession nationally and internationally, and contributes widely to policy consultations throughout the UK....»

«SIGNIFICANT ITEMS (Sis) FY 2010 House Appropriations Committee Report 111-220 and FY 2010 Senate Appropriations Committee Report 111 -66 T a b l e of Contents National Institutes of Health Institutes and Centers National Cancer Institute (NCI) 1 National Heart, Lung, and Blood Institute (NHLBI) 24 National Institute of Dental and Craniofacial Research (NIDCR) 42 National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) 45 National Institute of Neurological Disorders and Stroke...»

«National Medical Policy Subject: Capsular Tension Rings Policy Number: NMP89 Effective Date*: January 2004 Updated: February 2016 This National Medical Policy is subject to the terms in the IMPORTANT NOTICE at the end of this document For Medicaid Plans: Please refer to the appropriate State's Medicaid manual(s), publication(s), citations(s) and documented guidance for coverage criteria and benefit guidelines prior to applying Health Net Medical Policies The Centers for Medicare & Medicaid...»

«  No. _ IN THE Supreme Court of the United States _ WHOLE WOMAN’S HEALTH; AUSTIN WOMEN’S HEALTH CENTER; KILLEEN WOMEN’S HEALTH CENTER; NOVA HEALTH SYSTEMS D/B/A REPRODUCTIVE SERVICES; SHERWOOD C. LYNN, JR., M.D.; PAMELA J. RICHTER, D.O.; AND LENDOL L. DAVIS, M.D., on behalf of themselves and their patients, Applicants, v. KIRK COLE, M.D., Commissioner of the Texas Department of State Health Services; MARI ROBINSON, Executive Director of the Texas Medical Board, in their official...»

«Patanjali’s Yoga-Sûtra Compiled by: Trisha Lamb Last Revised: April 27, 2006 © 2004 by International Association of Yoga Therapists (IAYT) International Association of Yoga Therapists P.O. Box 2513 • Prescott • AZ 86302 • Phone: 928-541-0004 E-mail: mail@iayt.org • URL: www.iayt.org The contents of this bibliography do not provide medical advice and should not be so interpreted. Before beginning any exercise program, see your physician for clearance.Alix, Paul JJ. The Yoga Sutras of...»

«SEXUAL OFFENDER TREATMENT: A PARADIGM ANALYSIS OF ACADEMIC JOURNALS by VIJAY F. CHILLAR A thesis submitted in partial fulfillment of the requirements for the Honors in the Major Program in Criminal Justice in the College of Health and Public Affairs and in The Burnett Honors College at the University of Central Florida Orlando, Florida Spring Term 2014 Thesis Chair: Dr. Roberto Potter ABSTRACT Many criminologists and psychologists have theorized the possible causes behind an individual who...»

«MEDICATION GUIDE Oral Transmucosal Fentanyl Citrate (OTFC) CII (fentanyl citrate) oral transmucosal lozenge 200 mcg, 400 mcg, 600 mcg, 800 mcg, 1200 mcg, 1600 mcg IMPORTANT: Do not use Oral Transmucosal Fentanyl Citrate (OTFC) unless you are regularly using another opioid pain medicine around-the-clock for at least one week or longer for your cancer pain and your body is used to these medicines (this means that you are opioid tolerant). You can ask your healthcare provider if you are opioid...»





 
<<  HOME   |    CONTACTS
2016 www.dissertation.xlibx.info - Dissertations, online materials

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.