Surgical Anatomy of the Infratemporal Fossa PDF

Surgical Anatomy of the Infratemporal Fossa Surgical Anatomy of the Infratemporal Fossa John D.Langdon Professor and Head of Department Department of Oral and Maxillofacial Surgery King’s College London, UK Barry K.B.Berkovitz Reader in Anatomy Division of Anatomy, Cell and Human Biology King’s College London, UK Bernard J.Moxham Professor of Anatomy and Head of Teaching in Biosciences Cardiff School of Biosciences Cardiff University, UK MARTIN DUNITZ © 2003 Martin Dunitz, a member of the Taylor & Francis Group First published in the United Kingdom in 2003 by Martin Dunitz, Taylor & Francis Group plc, 11 New Fetter Lane, London EC4P 4EE Tel.: +44 (0) 20 7583 9855 Fax.: +44 (0) 20 7842 2298 E-mail: [email protected] Website: http://www.dunitz.co.uk This edition published in the Taylor & Francis e-Library, 2005. “To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.” All rights reserved. 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ISBN 0-203-62701-6 Master e-book ISBN ISBN 0-203-63088-2 (Adobe eReader Format) ISBN 1-899066-79-9 (Print Edition) Distributed in the USA by Fulfilment Center Taylor & Francis 10650 Tobben Drive Independence, KY 41051, USA Toll Free Tel.: +1 800 634 7064 E-mail: [email protected] Distributed in Canada by Taylor & Francis 74 Rolark Drive Scarborough, Ontario M1R 4G2, Canada Toll Free Tel.: +1 877 226 2237 E-mail: [email protected] Distributed in the rest of the world by Tomson Publishing Services Cheriton House North Way Andover, Hampshire SP10 5BE, UK Tel.: +44 (0)1264 332424 E-mail: [email protected] Project management: Top Draw Design Medical illustrators: Philip Wilson FMAA, RMIP Debbie Maizels CBiol, MIBiol Contents Contributors vii Preface ix Chapter 1 Regional and sectional anatomy of the infratemporal fossa 1 B.J.MOXHAM AND B.K.B.BERKOVITZ The boundaries of the infratemporal fossa 1 The contents of the infratemporal fossa 1 The masticatory muscles 2 The mandibular nerve 6 The otic ganglion 10 The maxillary artery 11 The pterygoid venous plexus 12 Other features of the infratemporal fossa 13 The relationships of structures within the infratemporal fossa 14 References 14 Chapter 2 The temporomandibular joint and pterygopalatine fossa 23 B.K.B.BERKOVITZ, B.J.MOXHAM AND J.D.LANGDON The temporomandibular joint 23 The pterygopalatine fossa 30 Some surgical aspects of the temporomandibular joint 40 References 44 Chapter 3 Local anaesthesia and the infratemporal fossa 47 J.D.LANGDON AND J.P.ROOD Background 47 Maxillary anaesthesia 49 Mandibular anaesthesia 53 References 58 Chapter 4 Infection and the infratemporal fossa and associated tissue spaces 60 J.D.LANGDON, B.J.MOXHAM AND B.K.B.BERKOVITZ Tissue spaces associated with the infratemporal fossa 60 Tissue spaces adjacent to the infratemporal fossa 62 The fascia and tissue spaces of the neck 64 Infection of the infratemporal fossa region and its spread 68 v Spread of infection by vascular pathways and the lymphatics 74 References 75 Chapter 5 The significance of the infratemporal fossa in maxillofacial trauma and orthognathic surgery 78 D.T.LANIGAN Introduction 78 Haemorrhage 82 False aneurysms, arteriovenous fistulae, and thrombosis 84 Ophthalmic complications 86 Sensory deficits of the second and third divisions of the trigeminal nerve 91 Muscle dysfunction 92 Summary and conclusions 92 References 92 Chapter 6 Tumours and tumour-like disorders of the infratemporal fossa 97 R.M.TIWARI Introduction and historical background 97 Surgical landmarks 97 Classification 98 Diagnosis 99 Surgical approaches 99 References 107 Chapter 7 Surgical approaches to the infratemporal fossa 109 B.T.EVANS, D.WIESENFELD, L.CLAUSER AND C.CURIONI Introduction 109 Pathology 109 Applied anatomy 109 Surgical approaches 99 References 145 Chapter 8 The facial nerve and the parotid gland 147 B.K.B.BERKOVITZ, J.D.LANGDON AND B.J.MOXHAM Introduction 147 Development of the parotid gland 147 The parotid gland 147 Parotid capsule 148 Form and relations of the parotid gland 149 Contents of the parotid gland 152 Lymph nodes associated with the parotid gland 160 Parotid duct 160 The innervation of the parotid gland 160 References 163 vi Chapter 9 Trigeminal pain 168 C.SHIEFF AND J.ALLIBONE Introduction 168 Classification 98 Anatomy of the trigeminal nerve 169 Primary (idiopathic) trigeminal neuralgia 170 Pathophysiology of trigeminal neuralgia 171 Treatment 174 Summary 180 References 181 Index 183 Contributors James Allibone Consultant Spinal Neurosurgeon Royal National Orthopaedic Hospital Stanmore, Middlesex, UK Barry K.B.Berkovitz Reader in Anatomy Division of Anatomy, Cell and Human Biology GKT School of Biomedical Sciences King’s College London London, UK Luigi Clauser Professor and Head of Department of Craniomaxillofacial Surgery and Centre for Orbital Surgery and Pathology St Anna Hospital and University Ferrara, Italy Camillo Curioni Professor of Maxillofacial Surgery University of Ferrara Ferrara, Italy Barrie T.Evans Consultant Oral and Maxillofacial Surgeon Southampton University Hospitals Southampton, UK John D.Langdon Professor and Head of Department Department of Oral and Maxillofacial Surgery GKT Dental Institute King’s College London London, UK Dennis T.Lanigan Head, Division of Oral and Maxillofacial Surgery Department of Biological, Diagnostic, and Surgical Sciences College of Dentistry University of Saskatchewan Saskatoon, Saskatchewan, Canada Bernard J.Moxham Professor of Anatomy and Head of Teaching in Biosciences Cardiff School of Biosciences Cardiff University Cardiff, UK J.Phillip Rood Professor, Department of Oral and Maxillofacial Surgery GKT Dental Institute King’s College London London, UK Colin Shieff viii Consultant Neurosurgeon Department of Neurosurgery Royal Free Hospital London, UK Ram M.Tiwari Head, Neck, Skull Base and Reconstructive Surgeon Bangalore Institute of Oncology and Chief, Division of Surgical Oncology and Head and Neck Surgery Manipal Hospital Bangalore, India David Wiesenfeld Oral and Maxillofacial Surgeon Head of Oral and Maxillofacial Surgery Unit The Royal Melbourne Hospital and Oral and Maxillofacial Surgeon Peter MacCallum Cancer Institute Senior Associate, Department of Surgery and School of Dental Science The University of Melbourne Melbourne, Australia Preface Specialisation in the medical and dental professions has always been an important issue. With the development of new undergraduate and postgraduate training schemes, together with the concomitant reduction in the teaching of basic science, particularly anatomy, the issue is assuming even greater significance. This book takes cognisance of educational, and political, concerns and also takes account of the rapid clinical and surgical developments that have taken place in recent years. The infratemporal fossa is of particular importance to the dentist and to the oral and maxillofacial surgeon. However, as its anatomical boundaries impinge onto other regions of clinical interest, it is also relevant to other medical specialities. For example, an infratemporal approach is now used for certain neurosurgical procedures. The main aim of this book is to bring together descriptions of the anatomy of this area with coverage of the main aspects of clinical and surgical relevance, topics not normally found in a single text. In relation to the anatomy of the infratemporal fossa, attention has also been given to the temporomandibular joint, parotid gland and pterygopalatine fossa. Clinical aspects that are covered concern local anaesthesia, spread of infection, surgical approaches to the infratemporal fossa and to the facial nerve, tumours and tumour-like disorders in the region and maxillofacial trauma and orthognathic surgery. The scope and specialisation of the subject matter requires contributions from experts in a variety of disciplines. Inevitably, there will be some overlap between chapters. The editors regard this as a positive feature, giving the reader the opportunity to hear the views of different experts in the field of head and neck surgery. We hope that our attempts to provide a guide to the infratemporal fossa by correlating anatomical, clinical and surgical subject matter, and our efforts to provide a visual commentary by the use of numerous colour illustrations, will prove beneficial to our readers whatever their level of specialisation. J.D.Langdon B.K.B.Berkovitz B.J.Moxham Figure 1.1 Skull showing osteology related to the infratemporal fossa. Chapter 1 Regional and sectional anatomy of the infratemporal fossa B.J.MAXHOM AND B.K.B BERKOVITZ THE BOUNDARIES OF THE INFRATEMPORAL FOSSA The infratemporal fossa is the space located deep to the ramus of the mandible. Further reading of the anatomy of this region is available from Hollingshead,1 Berkovitz and Moxham,2 Gray’s Anatomy3 and Lang.4 Together with the temporal fossa, pterygoid processes and maxillary tuberosity, the infratemporal fossa has been thought of by some anatomists as part of a ‘masticatory muscle compartment’ or ‘masticatory space’.4 The fossa is bounded anteriorly by the posterior surface of the maxilla and posteriorly by the styloid apparatus, carotid sheath and deep part of the parotid gland. Medially lies the lateral pterygoid plate and the superior constrictor muscle of the pharynx. Laterally lies the ramus of the mandible. The roof is formed by the infratemporal surface of the greater wing of the sphenoid. The infratemporal fossa has no anatomical floor, being continuous with tissue spaces in the neck. The infratemporal fossa communicates with the temporal fossa deep to the zygomatic arch. It also Chapter 1 municates with the pterygopalatine fossa through the pterygomaxillary fissure (Fig. 1.1). At the base of the cranium, the foramen ovale, the foramen spinosum and the sphenoidal emissary foramen (of Vesalius) enter the fossa through the sphenoid bone. The foramen lacerum and the petrotympanic, squamotym-panic and petrosquamous fissures are also found close to the infratemporal fossa. On the medial surface of the ramus of the mandible is the mandibular foramen. THE CONTENTS OF THE INFRATEMPORAL FOSSA The major structures that occupy the infratemporal fossa are: The lateral and medial pterygoid muscles The mandibular division of the trigeminal nerve The chorda tympani branch of the facial nerve The otic parasympathetic ganglion 2 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.2 The masseter muscle. (Courtesy of Professor S.Standring, GKT School of Biomedical Sciences, London.) The maxillary artery and branches The pterygoid venous plexus The deep ‘lobe’ of the parotid gland. The key to understanding the relationships of structures within the infratemporal fossa is the lateral pterygoid muscle. This lies in the roof of the fossa, running anteroposteriorly in a horizontal plane from the region of the pterygoid plates to the mandibular condyle. Deep to the muscle arise the branches of the mandibular nerve and the main origin of the medial pterygoid muscle. The maxillary artery generally passes superficial to the lower head of the lateral pterygoid. The buccal branch of the mandibular nerve passes between the two heads that comprise the lateral pterygoid muscle. Emerging below the inferior border of the muscle are the medial pterygoid muscle and the lingual and inferior alveolar nerves. At the upper border emerge the deep temporal nerves and vessels. Concentrated around and within the lateral pterygoid muscle lies a venous network, the pterygoid venous plexus. THE MASTICATORY MUSCLES The four primary masticatory muscles are the masseter, temporalis, lateral and medial pterygoid muscles. Being derived from the first branchial arch, the muscles are supplied by the mandibular nerve. The pterygoid muscles lie within the infratemporal fossa. The masseter muscle arises from the zygomatic arch and is attached to the lateral surface of the ramus of the mandible (Fig. 1.2). The temporalis muscle arises from the floor of the temporal fossa and the overlying temporal fascia, passes behind the zygomatic arch, and is attached to the anterior and medial surface of the coronoid process (Fig. 1.3). THE LATERAL PTERYGOID MUSCLE4–7 (FIGS 1.4–1.6) This muscle has two separate and distinct heads.5,8–10 The larger, lower head is sometimes referred to as the pterygoid head. The smaller, upper head has been termed the infratemporal head. Some anatomists claim that the lateral pterygoid has three heads—the upper head having two slips of muscle.7 Attachments The bulk of the muscle is formed by its lower head. This arises mainly from the lateral surface of the lateral pterygoid plate of the sphenoid bone, although some fibres may arise from the maxillary surface of the pterygoid plate. The most superior fibres of the lower head run more horizontally than the more inferior fibres. The length and thickness of the lower head varies considerably from site to site and from individual to individual.4 The smaller upper head takes origin from the infratemporal CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 3 Figure 1.3 The temporalis muscle, revealed following reflection of the zygomatic arch. (Courtesy of Professor S.Standring, GKT School of Biomedical Sciences, London.) surface of the greater wing of the sphenoid (usually medial to the infratemporal crest) and, under cover of the temporalis muscle, runs in a groove-like depression in the infratemporal roof. The two heads converge near the point of insertion (about 1 cm anterior to the neck of the mandibular condyle). The fibres of the upper head are said to insert primarily into the capsule and articular disc of the temporomandibular joint.11 Indeed, the articular disc has sometimes been thought of as a (cartilaginous) tendon of the upper head of the lateral pterygoid muscle.12 The fibres from the lower head insert into the pterygoid fovea on the mandibular condyle.13–15 Some anatomists have reported that there are no or few muscle fibres inserting into the articular disc of the temporomandibular joint.16 The attachment of the lateral pterygoid muscle is discussed further on pages 35–36. Innervation The nerves to the lateral pterygoid (one for each head) arise from the anterior trunk of the mandibular nerve, deep to the muscle. The upper head and the lateral part of the lower head receive their innervation from a branch of the buccal nerve. However, the medial part of the lower head has a branch arising directly from the anterior trunk of the mandibular division of the trigeminal nerve.4,17 Vasculature The arterial supply is derived from the maxillary artery (pterygoid branches) as it crosses the lateral pterygoid muscle and from the ascending palatine artery (a branch of the facial artery).4 Actions The main action of the muscle is to assist in opening the jaws by pulling the mandibular condyle and the articular disc of the temporomandibular joint forwards and downwards along the posterior slope of the articular eminence. In addition, the muscle is involved in protrusion and in lateral movements of the mandible. The muscle is involved in stabilising the disc-condyle complex. From EMG findings, it has also been reported that the upper head of the lateral pterygoid muscle is inactive during jaw opening and might help to elevate the mandible. Furthermore, this head can restrain backward movements of the articular disc of the temporomandibular joint. EMGs also suggest that the lower head is a synergist of the suprahyoid muscles and the upper head is an antagonist.6,9 It has been estimated that the upper head of the lateral pterygoid muscle can exert a tensile force of about 40 N and the lower head a greater force of approximately 130 N.18 4 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.4 The pterygoid muscles viewed laterally. (Courtesy of Professor S.Standring, GKT School of Biomedical Sciences, London.) THE MEDIAL PTERYGOID MUSCLE4,6 Attachments This muscle is the deepest of the four muscles of mastication. It consists of two heads. The bulk of the muscle arises as a deep head from the medial surface of the lateral pterygoid plate. Thus, the lateral pterygoid plate of the sphenoid bone gives rise to both pterygoid muscles. A common mistake is the belief that the medial pterygoid muscle arises from the medial pterygoid plate. However, the medial pterygoid plate gives origin only to a small proportion of the superior constrictor muscle of the pharynx. The smaller, superficial head of the medial pterygoid muscle (sometimes called the tuberal head) originates from the maxillary tuberosity and the neighbouring part of the palatine bone (pyramidal process).4,6 From these sites, the fibres pass downwards and backwards to insert into the roughened surface of the angle of the mandible on its medial aspect. In terms of the muscle’s dimension, the medial pterygoid muscle has on average a cross-section of 1.5 cm2, being larger in males than females.4 In relation to the long axis of the ramus of the mandible, the muscle shows an obliquity of approximately 30° on the medial side. At its origin on the pterygoid plate, the width of the muscle can vary between 20 mm and 35 mm. At its insertion, the muscle varies between 10 mm and 18 mm. The length of the main deep head of the muscle varies from 43 mm to 50 mm, although the most anterior fibres are usually shorter (32–50 mm). Within the muscle can be discerned up to six tendinous plates. The intramuscular tendinous plates form a multipennate structure.6,18 Following analysis by CT scanning, the maximum cross-sectional area of the medial pterygoid was centred at the level of the mandibular foramen. The maximum cross-sectional area was also found to be highly correlated with volume.19 Other work20 showed that the cross-sectional area of the medial pterygoid significantly decreases with age, with a greater decrease in edentulous subjects. Furthermore, there is a significant decrease in the density of the muscle with increasing age (previously interpreted to indicate an increase in fat and fibrous tissue). CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 5 Figure 1.5 The pterygoid muscles viewed medially. (Courtesy of Professor L.Garey, Anatomy Department, Imperial College Medical School, London.) Innervation The nerve to the medial pterygoid muscle arises from the mandibular nerve (deep to the lateral pterygoid muscle), before the nerve divides into anterior and posterior trunks. Vasculature Like the lateral pterygoid muscle, the medial pterygoid derives its arterial supply from the maxillary artery. Actions The medial pterygoid muscle is an elevator of the mandible. It assists in lateral and protrusive movements. The medial pterygoid muscle is synergistic to the masseter muscle. In addition, the medial pterygoid muscle and the masseter muscle together provide a ‘sling’ to support the angle of the mandible.4 It has been estimated that the elevating force provided by this pterygoid masseter sling can be as great as 420 N.18 It has been reported21 that similar bite-force efficiencies for the medial pterygoid muscle can be found in persons with disparate facial features. THE PTERYGOID HIATUS4,14 This is the space bounded superiorly by the inferior margin of the lower head of the lateral pterygoid muscle and inferiorly by the posterior margin of the medial pterygoid muscle. In this space run the lingual and inferior alveolar nerves, the first part of the maxillary artery, part of the pterygoid venous plexus and the sphenomandibular ligament. Its dimensions are of some 6 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.6 The pterygoid muscles viewed posteriorly. (Courtesy of Professor LGarey, Anatomy Department, Imperial College Medical School, London.). importance to maxillofacial surgeons, the superior margin being approximately 14–21 mm, the posterior border 14–31 mm and the frontal dimension 3–8 mm. THE SPHENOMANDIBULAR MUSCLE22 It has been reported in the scientific and medical literature that a previously unknown muscle, termed the ‘sphenomandibular muscle’, exists within the infratemporal fossa. It has been proposed that this muscle is a fifth member of the ‘muscles of mastication’. It appears to take origin from the greater wing of the sphenoid bone (at the base of the temporal fossa) and extends downwards and backwards to be inserted onto the inner and anterior aspect of the mandibular coronoid process and the anterior edge of the mandibular ramus. It would appear from its orientation that the muscle aids elevation (and perhaps protrusion) of the mandible. An alternative explanation for the muscle is that it is a previously unidentified component of a known muscle. Indeed, it may therefore be linked to the medial pterygoid muscle or be considered part of the temporalis muscle. THE MANDIBULAR NERVE (FIGS 1.7–1.9) This is the largest division of the trigeminal nerve and is the only one to contain motor as well as sensory fibres. Developmentally, it is the nerve of the first branchial arch and is thus responsible for supplying structures derived from it. Its sensory fibres supply the mandibular teeth and their supporting structures, the mucosa of the anterior two-thirds of the tongue CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 7 and the floor of the mouth, the skin of the lower part of the face (including the lower lip) and parts of the temporal region and auricle. Its motor fibres supply the four ‘muscles of mastication’ and the mylohyoid, anterior belly of digastric, tensor veli palatini and tensor tympani muscles. The mandibular nerve is formed in the infratemporal fossa by the union of the sensory and motor roots immediately after they leave the skull at the foramen ovale. Within the foramen ovale, the motor root (or roots) lie posteromedially to the sensory root and these roots are accompanied by emissary veins, the lesser petrosal nerve (from the glossopharyngeal nerve) going to the otic ganglion and by the accessory meningeal artery. As the mandibular nerve leaves the foramen ovale, it lies on the tensor veli palatini muscle and is covered laterally by the upper head of the lateral pterygoid muscle (slightly anterior to the neck of the mandible). After a short course, the nerve divides into a smaller anterior trunk and a larger posterior trunk. Before this division, the main trunk gives off two branches—the meningeal branch and the nerve to medial pterygoid. The anterior trunk of the mandibular nerve is mainly motor, the posterior trunk mainly sensory. BRANCHES Meningeal branch (nervus spinosus) Nerve to medial pterygoid Anterior trunk: Masseteric nerve Deep temporal nerves Nerve to lateral pterygoid Buccal nerve Posterior trunk: Auriculotemporal nerve Lingual nerve Inferior alveolar nerve The meningeal branch of the mandibular nerve (nervus spinosus) This arises from the main trunk of the mandibular nerve. It is a ‘recurrent nerve’ as it runs back into the middle cranial fossa through the foramen spinosum. It supplies the dura mater lining the middle and anterior cranial fossae and the mucosa of the mastoid antrum and mastoid air cells. The nerve to the medial pterygoid muscle (Figs 1.8, 1.9, 1.12) This enters the deep surface of the muscle and also gives slender branches that pass uninterrupted through the otic ganglion to supply the tensor tympani and tensor veli palatini muscles. The masseteric nerve This is usually the first branch of the anterior trunk of the mandibular nerve. It passes above the upper border of the lateral pterygoid muscle (accompanying the posterior deep temporal nerve) and then crosses the mandibular notch (between the condylar and coronoid processes) to be distributed into the masseter muscle. It also gives an articular branch to the temporomandibular joint. The nerve enters the masseter muscle as two branches. The upper branch is smaller and runs to the deeper layers of the muscle. The larger, lower trunk innervates the more superficial layers of the masseter muscle. The deep temporal nerves (Fig. 1.5) These nerves also pass above the lateral pterygoid muscle. Anatomists have provided varying descriptions for them. Anterior, middle and posterior deep temporal nerves may be recognised. 8 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA The nerve to the lateral pterygoid muscle17 This may arise separately or may run with the buccal nerve before entering the deep surface of the lateral pterygoid muscle. The buccal branch of the mandibular nerve23 This is the only sensory branch of the anterior trunk of the mandibular nerve. On emerging between the upper and lower heads of the lateral pterygoid muscle (Figs 1.4, 1.7), it passes downwards and forwards across the lower head to contact the medial surface of the temporalis muscle as it inserts onto the coronoid process of the mandible (Figs 1.4, 1.7–1.9). It then clears the ramus of the mandible to lie on the lateral surface of the buccinator muscle in the cheek. At this point, it is close to the retromolar fossa of the mandible. It now gives branches to the skin of the cheek before piercing the buccinator to supply its lining mucosa, the buccal sulcus and the buccal gingiva related to the mandibular molar and premolar teeth. It may also carry secretomotor fibres to minor salivary glands in the buccal mucosa, these being post-ganglionic fibres from the otic ganglion. The buccal branch of the mandibular nerve may be seen to ‘anastomose’ with the buccal branches of the facial nerve. The auriculotemporal nerve24–26 This is the first branch of the posterior trunk of the mandibular nerve. It is essentially sensory but it also distributes autonomic fibres to the parotid gland derived from the otic ganglion. It usually arises as two roots (approx. 75% of cases) that encircle the middle meningeal artery and unite behind the artery (Figs 1.8, 1.12). The nerve then runs backwards under the lateral pterygoid muscle to lie beneath the mandibular condyle (between the condyle and the sphenomandibular ligament) (Fig.1.9). On entering the parotid region, it turns to emerge superficially between the temporomandibular joint and the external acoustic meatus (Fig. 1.8). From the upper surface of the parotid gland, the auriculotemporal nerve ascends on the side of the head with the superficial temporal vessels (Figs 8.3, 8.19), passing over the posterior part of the zygomatic arch. It gives several branches along its course: Ganglionic branches which communicate with the otic ganglion. Articular branches which enter the posterior part of the temporomandibular joint; these carry proprioceptive information important in mastication. Parotid branches which convey parasympathetic secretomotor fibres and sympathetic fibres to the parotid gland; these fibres are related to the otic ganglion. Sensory fibres from the auriculotemporal nerve supply the gland (with the exception of the capsule, which is innervated by the great auricular nerve). Auricular branches (usually two) which supply the tragus and crus of the helix of the auricle, part of the external acoustic meatus, and the outer (lateral) surface of the tympanic membrane. Superficial temporal branches which are cutaneous nerves supplying part of the skin of the temple. The lingual nerve (Figs 1.4, 1.7–1.9, 1.12) This is the second branch of the posterior trunk of the mandibular nerve. It is essentially a sensory nerve but, following union with the chorda tympani branch of the facial nerve, it also contains parasympathetic fibres. Initially, the nerve lies on the tensor veli palatini muscle deep to the lateral pterygoid muscle. Here, the chorda tympani nerve (which has entered the infratemporal fossa via the petrotympanic fissure and passed over the spine of the sphenoid bone) joins the posterior surface of the lingual nerve (Figs 1.8, 1.12). Emerging from the inferior border of the lateral pterygoid muscle, the lingual nerve curves downwards and forwards in the space between the ramus of the mandible and the medial pterygoid muscle (pterygomandibular space) (Fig. 1.9). At this level, it lies anterior to, and slightly deeper than, the inferior alveolar nerve. The lingual nerve then leaves the infratemporal fossa, passing downwards and forwards to lie close to the lingual alveolar plate of the mandibular third molar. Before curving forwards into the tongue, the nerve is found above the origin of the mylohyoid muscle and lateral to the hyoglossus muscle. The close relationship of the lingual nerve to the third molar tooth makes the nerve susceptible to damage during removal of the tooth. In addition, in about one in seven cases, the lingual nerve is actually located above the lingual bony plate in the third molar region and is liable to damage during surgery.27–29 The lingual nerve supplies the mucosa covering the anterior two-thirds of the dorsum of the tongue, the ventral surface of the tongue, the floor of the mouth and the lingual gingivae of the mandibular teeth. The chorda tympani fibres travelling with the lingual nerve are of two types: sensory and parasympathetic. The sensory fibres are associated with taste for the anterior two-thirds of the dorsum of the tongue. The parasympathetic fibres are preganglionic fibres that pass to the submandibular ganglion. Postganglionic fibres are distributed to the submandibular and sublingual salivary glands. CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 9 Figure 1.7 The mandibular nerve viewed buccally. (Courtesy of Professor LGarey, Anatomy Department, Imperial College Medical School, London.) The chorda tympani branch of the facial nerve (Figs 1.8, 1.12, 2.19) This is distributed through the lingual nerve and has two types of fibres. Sensory fibres are associated with taste to the anterior two-thirds of the tongue. Parasympathetic fibres are preganglionic to the submandibular ganglion (Fig. 1.12). Postganglionic fibres are secretomotor to the submandibular and sublingual glands. The inferior alveolar nerve (Figs 1.4, 1.7–1.9, 1.12) This is the largest branch of the mandibular division of the trigeminal nerve. It is the third branch of the posterior trunk of the mandibular nerve. Although it is essentially a sensory nerve, it also carries motor fibres which are given off as the mylohyoid nerve. Indeed, the mylohyoid nerve contains all the motor fibres of the posterior trunk of the mandibular nerve. The inferior alveolar nerve descends deep to the lateral pterygoid muscle, posterior to the lingual nerve in the pterygoid hiatus. Here, it is crossed by the maxillary artery. On emerging at the inferior border of the muscle, it passes between the sphenomandibular ligament and the ramus of the mandible to enter the mandibular foramen. It is accompanied in its course by inferior alveolar blood vessels. The mylohyoid nerve is given off just before the mandibular foramen (Figs 1.8, 2.23). It pierces the sphenomandibular ligament and runs in a groove (the mylohyoid groove) which lies immediately below the mandibular foramen. The mylohyoid nerve supplies the mylohyoid muscle and the anterior belly of the digastric. The mylohyoid nerve may also contain sensory fibres that supply the skin of the chin and medial parts of the submandibular triangle in the suprahyoid region. 10 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.8 The mandibular nerve with the lateral pterygoid muscle removed. (Courtesy of Professor C.Dean, Department of Anatomy and Developmental Biology, University College London.) The main distribution of the inferior alveolar nerve is to the mandibular teeth and their supporting structures, there being molar and incisive branches. The mental nerve is a cutaneous branch that supplies the skin of the chin and the lower lip. It arises within the mandible in the premolar region, but soon exits onto the face via the mental foramen. THE OTIC GANGLION (Figs 1.9, 1.10, 1.12) This parasympathetic ganglion lies immediately below the foramen ovale on the medial surface of the main trunk of the mandibular nerve. It is concerned primarily with supplying the parotid gland (Fig. 1.10). Like other parasympathetic ganglia in the head, three types of fibres are associated with it: parasympathetic, sympathetic and sensory fibres. However, only the parasympathetic fibres synapse in the ganglion. The preganglionic parasympathetic fibres originate from the inferior salivatory nucleus in the brainstem. The fibres pass out in the glossopharyngeal nerve, appearing as the lesser (superficial) petrosal nerve from the tympanic plexus in the middle ear cavity. The lesser petrosal nerve reaches the otic ganglion by a complex course. Passing through the petrous part of the temporal bone, the lesser petrosal nerve comes to lie in the floor of the middle cranial fossa. Here, it is lateral to the FIGURE 1.10 THE OTIC PARASYMPATHETIC GANGLION AND INNERVATION OF THE PAROTID GLAND. CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 11 Figure 1.9 The mandibular nerve viewed medially. (Courtesy of Professor C.Dean, Department of Anatomy and Developmental Biology, University College London.) greater (superficial) petrosal branch of the facial nerve. The lesser petrosal nerve usually enters the infratemporal fossa through the foramen ovale to join the otic ganglion. On occasion, the lesser petrosal nerve passes through the sphenopetrosal fissure. The sympathetic root of the otic ganglion is derived from postganglionic fibres from the superior cervical ganglion. They are said to reach the otic ganglion from the plexus on the middle meningeal artery. Other descriptions have it that the sympathetic root arises from the deep petrosal nerve or directly from the internal carotid plexus. The sensory root is derived from the auriculotemporal nerve. The postganglionic parasympathetic fibres (with sympathetic and sensory components) reach the parotid gland by way of the auriculotemporal nerve. Parasympathetic fibres may also innervate the minor salivary glands in the cheek, passing with the buccal branch of the mandibular nerve. The innervation of tensor veli palatini and tensor tympani is derived from the nerve to the medial pterygoid by a branch that passes through the otic ganglion. THE MAXILLARY ARTERY (Figs 1.4, 1.7, 1.11–1.13) The maxillary artery is a terminal branch of the external carotid artery. It arises within the parotid gland at the level of the neck of the condyle of the mandible. It enters the infratemporal fossa between the deep surface of the condyle and the sphenomandibular ligament. At this point, it lies below the auriculotemporal nerve and above the maxillary vein. The artery can be quite firmly adherent to the capsule of the temporomandibular joint. In the infratemporal fossa, it is closely related to the lateral pterygoid muscle. Initially, it lies near the inferior border of the muscle, crossing the inferior alveolar nerve. Its subsequent course is variable, although it usually passes superficial to the lower head of the lateral pterygoid24,30–35 before entering the pterygopalatine fossa through the pterygomaxillary fissure. The maxillary artery has many branches. It is convenient to subdivide the artery into three parts: before the lateral pterygoid muscle (first or (retro)mandibular part), on the lateral pterygoid muscle (second or pterygoid part), and in the pterygopalatine fossa (third or pterygopalatine part) (see page 52). The relationship of the maxillary artery to the lateral pterygoid muscle is variable, but it runs superficial to the muscle in nearly 60% of cases.34 However, there can be asymmetry between the right and left infratemporal fossae and there appears also to be ethnic differences. In Japanese, for example, the maxillary artery runs superficial to the lateral pterygoid muscle in 12 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA over 90% of persons, a much higher percentage than in Western populations.35 In most cases, where the maxillary artery runs superficial to the lower head of the lateral pterygoid, the artery passes lateral to the inferior alveolar, lingual and buccal nerves (in 37% of persons). In 16% of cases, only the buccal nerve crosses the artery laterally FIGURE 1.11 THE MAXILLARY ARTERY. and in about 5% of cases the artery passes deep to all the branches of the mandibular nerve.34 The first part of the maxillary artery has five branches and all enter bone. The first branch is the deep auricular artery, supplying the skin of the external acoustic meatus and part of the tympanic membrane. A small branch contributes to the arterial supply of the temporomandibular joint. The second branch, the anterior tympanic artery, passes through the petrotympanic fissure to supply part of the lining of the middle ear. This is the companion artery to the chorda tympanic nerve. The middle meningeal artery is the main source of blood to the meninges and to the bones of the vault of the skull. The artery may arise either directly from the first part of the maxillary artery or from a common trunk with the inferior alveolar artery.4,30 When the maxillary artery lies superficial to the lateral pterygoid muscle, the middle meningeal artery is usually the first branch of the maxillary artery. However, when the maxillary artery takes a deep course in relation to the muscle it is not usually the first branch.24 The middle meningeal artery ascends between the two roots of the auriculotemporal nerve and leaves the infratemporal fossa through the foramen spinosum (Fig. 1.12). An accessory meningeal artery runs through the foramen ovale into the middle cranial fossa. This artery can arise directly from the maxillary artery or as a branch of the middle meningeal artery (Fig. 2.24b).4,36 In its course in the infratemporal fossa, it is closely related to the tensor and levator veli palatini muscles and usually runs deep to the mandibular nerve. Although the accessory meningeal artery runs intracranially, its blood is mainly distributed extracranially to the pterygoid muscles, tensor veli palatini, the otic ganglion and to branches of the mandibular nerve. The inferior alveolar artery accompanies the inferior alveolar nerve and has a similar distribution (Fig. 1.13). It very occasionally arises directly from the external carotid artery. Immediately before the inferior alveolar artery enters the mandible (at the mandibular foramen), it gives off a mylohyoid branch. There are considerable variations in the patterns of entry of the inferior alveolar artery into the mandibular foramen.37 In the mandibular canal, the inferior alveolar artery usually runs lateral to the inferior alveolar nerve. The artery gives off branches supplying the cheek teeth before terminating in mental and incisive branches. The mental artery passes through the mental foramen onto the face to supply the lower lip, the chin and the labial mucosa related to the anterior teeth. The incisive branch continues along the incisive canal to supply the anterior teeth. The second part of the maxillary artery also has five branches, but they differ from those of the first part in not entering bone. Muscular branches include deep temporal arteries (anterior, middle and posterior branches), pterygoid arteries and masseteric arteries. The deep temporal arteries pass between the temporalis muscle and the pericranium, producing shallow grooves in the bone. The masseteric arteries pass through the mandibular notch to enter the muscle. They can also supply the temporomandibular joint. A buccal artery accompanies the buccal nerve to supply structures in the cheek. A small lingual branch may be given off to accompany the lingual nerve and supply structures in the floor of the mouth. Detailed knowledge of the blood supply to the human temporalis muscle is required clinically for successful flap operations. This supply is derived from three main arteries: anterior deep temporal (supplying about 20% of the muscle anteriorly), posterior deep temporal (supplying about 40% of the muscle in the posterior region) and the middle temporal arteries (supplying about just under 40% of the muscle in the middle region). A venous network accompanies the arteries, and double veins pairing one artery is a common finding.38 THE PTERYGOID VENOUS PLEXUS39 This is situated around, and within, the lateral pterygoid muscle and it surrounds the maxillary artery. Its tributaries correspond to the various branches of the maxillary artery (the plexus receives blood from the pterygoid muscles, the deep temporal veins, the middle meningeal veins and from parotid veins) (Fig. 1.14). Although it is sometimes difficult to demonstrate in the cadaver, it is very prominent in life (although the density varies considerably from individual to individual). The plexus allows for the rapid take-up of blood from regions around the infratemporal fossa. The plexus communicates with the cavernous sinus, the facial vein, the inferior ophthalmic vein and the pharyngeal plexus. The connections with the cavernous sinus are via emissary veins passing through the foramen ovale, foramen lacerum and, where present, the emissary sphenoidal foramen. The communication with the facial vein is via the deep facial vein which CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 13 Figure 1.12 Dissection of maxillary artery showing middle meningeal artery. (Courtesy of the Royal College of Surgeons of England.) accompanies the buccal nerve. The inferior ophthalmic vein communicates with the pterygoid plexus through a branch passing through the inferior orbital fissure. The pterygoid venous plexus chiefly drains posteriorly into the maxillary vein. The maxillary vein runs with the first part of the maxillary artery, passing deep to the neck of the condyle of the mandible to enter the parotid gland. Here, it joins the superficial temporal vein to form the retromandibular vein. OTHER FEATURES OF THE INFRATEMPORAL FOSSA In addition to the major contents described above, the infratemporal fossa also contains the sphenomandibular ligament, the tensor veli palatini muscle, the insertion of the temporalis muscle on to the coronoid process of the mandible, the maxillary nerve as it passes from the pterygopalatine fossa into the inferior orbital fissure, the posterior superior alveolar nerve(s), a loop of the facial artery (together with its ascending palatine and tonsillar branches) and the deep ‘lobe’ of the parotid gland (see Chapter 8). FIGURE 1.14 THE VEINS OF THE NECK. 14 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.13a The maxillary artery in the infratemporal fossa. (Courtesy of Professor S.Standing, GKT School of Biomedical Sciences, London.) Figure 1.13b Maxillary artery in the infratemporal following removal of the pterygoid muscles. (Courtesy of the Royal College of Surgeons of England.) THE RELATIONSHIPS OF STRUCTURES WITHIN THE INFRATEMPORAL FOSSA The relationships of structures within the infratemporal fossa are best visualised in sectional anatomy and these are illustrated in Figs 1.15–1.22. REFERENCES 1. Hollingshead W H. Anatomy for surgeons: the head and neck (3rd edn). New York: Harper Row, 1982 2. Berkovitz B K B, Moxham B J. A textbook of head and neck anatomy. London: Wolfe Medical Publications, 1988 3. Williams P L (ed) Gray’s anatomy (38th edn). Edinburgh: Churchill Livingstone, 1995 4. Lang J. Clinical anatomy of the masticatory apparatus and peripharyngeal spaces. New York: Thieme Medical Publishers, Inc., 1995 5. Juniper R P. The superior pterygoid muscle? Br J Oral Surg 1981; 19:121–128 6. McDevitt W E. Functional anatomy of the masticatory system. London: Butterworth and Co., 1989 CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 15 Figure 1.15 A horizontal section of the head at the level of the top of the condyle. 7. Bertilsson O, Strom D. A literature survey of a hundred years of anatomic and functional lateral pterygoid muscle research. J Orofac Pain 1995; 9:17–23 8. Prentiss H J. Regional anatomy, emphasising mandibular movements with specific reference to full denture construction. J Am Dent Assoc 1923; 10:1085–1099 9. McNamara J A Jr. The independent functions of the two heads of the lateral pterygoid muscle. Am J Anat 1973: 138:197–206 10. Widmalm S E, Lillie J H, Ash M M Jr. Anatomical and electronmyographic studies of the lateral pterygoid muscle. J Oral Rehabil 1987; 14:429–446 11. Honée G L J M. The anatomy of the lateral pterygoid muscle. Acta Morphol Neerl (Scand) 1972; 10:331–340 12. Petersen H. Histologie und mikroskopische anatomie. Munchen: Bergmann, 1935 13. Porter M R. The attachment of the lateral pterygoid muscle of the meniscus. J Prosthet Dent 1970; 24:555–562 14. Mosolov N N. On the anatomy of human masticatory musculature. In: Schumacher G H (ed) Morphology of the maxillo-mandibular apparatus. Leipzig: Thieme, 1972 15. LeToux G, Duval J M, Darnault P. The human temporomandibular joint: current anatomic and physiologic sta-tus. Surg Radiol Anat 1989; 11:283–288 16. Wilkinson T M. The relationship between the disc and the lateral pterygoid muscle in the human temporomandibular joint. J Prosthet Dent 1988; 60: 715–724 17. Lau H. Innervation of the jaw muscles in representatives of various chewing types. In: Morphology of the maxillomandibular apparatus. Leipzig: Thieme, 1972; 133–137 18. Schumacher G H. Funktionsbedingter strukturwandel des M. masseter. Gegenbaurs Morphol Jb 1961; 102: 150–169 19. Xu J A, Yuasa K, Yoshiura K, Kanda S. Quantitative analysis of masticatory muscles using computed tomography. Dentomaxillofac Radiol 1994; 23:154–158 20. Newton J P, Yemm R, Able R W, Menhinick S. Changes in human jaw muscles with age and dental state. Gerodontology 1993; 10: 16–22 21. Hannam A G, Wood W W. Relationships between the size and spatial morphology of human masseter and medial pterygoid muscles, the craniofacial skeleton, and jaw biomechanics. Am J Phys Anthropol 1989; 40: 429–445 22. Dunn G F, Robinson W L. Anatomical observation of a craniomandibular muscle originating from the skull base: the sphenomandibularis. J Craniomandibular Prac 1996; 14:97–103 23. Zenker W. Uber einige befunde am M. temporalis des menschen. Z Anat Entwickl Gesch 1955; 118:355–368 24. Lurje A. On the topographical anatomy of the internal maxillary artery. Acta Anat 1947; 2:219–231 16 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.16 A horizontal section of the head at the upper part of the ramus. 25. Krizan Z. Beitrag zur kenntnis des dritten trigeminusastes. Pract Otol Rhinol Laryngol 1956; 18:144 26. Baumel J J. Vanderheiten J P, McElenney J E. The auriculotemporal nerve of man. Am J Anat 1971; 130:431^40 27. Kiesselbach J E, Chamberlain J E. Clinical and anatomic observations on the relationship of the lingual nerve to the mandibular third molar. J Oral Maxillofac Surg 1984; 42:565–567 28. Kiesselbach J E. Discussion in J Oral Maxillofac Surg 1995; 53:1181 29. Pogrel M A, Renaut A, Schmidt B, Ammar A. The relationship of the lingual nerve to the mandibular third molar region. J Oral Maxillofac Surg 1995; 53:1178–1181 30. Adachi B. Das Arteriensystem der Japaner. Bd I und II. Kyoto: Verlag der Kaiserlich-Japanischen Universitat, 1928. (Quoted in ref. 4) 31. Lasker G W, Opdyke D L, Miller H. The position of the internal maxillary artery and its questionable relation to the cephalic index. Anat Rec 1951; 109:119–126 32. Skopakoff C. Uber die variabilitat im verlauf der A. maxillaris. Anat Anz 1968:123:534–546 33. Urban A. Topographie der pars pterygopalatina der A. maxillaris aus frontaler sicht. [thesis] Wurzburg. (Quoted in ref. 4), 1974 34. Pretterklieber M L, Skopakoff C, Mayr R. The human maxillary artery reinvestigated: 1. Topographical relations in the infratemporal fossa. Acta Anat Basel 1991; 142: 281–287 35. Sashi R, Tomura N, Hashimoto M, Kobayashi M, Watarai J. Angiographic anatomy of the first and second segments of the maxillary artery. Radiat Med 1996; 14: 133–138 36. Baumel J J, Beard D Y. The accessory meningeal artery of man. J Anat 1961; 95:386–402 37. Bast R A. Alveolaris inferior, Verlauf und Verzweigungstypen. (Dissertation) Wurzburg. (Quoted in ref. 4), 1982. 38. Chung L K. The vascular anatomy of the human temporalis muscle: Implications for surgical splitting techniques. Int J Oral Maxillofac Surg 1996; 25:414–421 39. Deplus S, Bremond-Gignac D, Gillot C, Lassau J P. The pterygoid venous plexuses. Surg Radiol Anat 1996; 18: 23–27 CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 17 Figure 1.17 A horizontal section of the head at the level of the palate. 18 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.18 A horizontal section of the head at the level of the tongue. CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 19 Figure 1.19 A coronal section of the head at the anterior border of the ramus of the mandible. 20 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.20 A coronal section of the head towards the back of the ramus of the madible. CHAPTER 1 REGIONAL AND SECTIONAL ANATOMY OF THE INFRATEMPORAL FOSSA 21 Figure 1.21 Axial MRI scan of the head at the level of the palate. 22 CHAPTER 1 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 1.22 Coronal MRI scan of the head towards the back of the ramus. Figure 2.1 The skull from the side showing articulation of the temporomandibular joint. Chapter 2 The temporomandibular joint and pterygopalatine fossa B.K.B.BERKOVITZ, B.J.MOXHAM AND J.D.LANGDON For a full understanding of the surgical and clinical aspects of the infratemporal fossa, an appreciation of its relationship to adjacent structures is of importance. This chapter will consider the anatomy of the temporomandibular joint and the pterygopalatine fossa, while Chapter 8 will deal with the parotid gland. THE TEMPOROMANDIBULAR JOINT The temporomandibular (craniomandibular) joint (TMJ) is a synovial joint. It is formed by the condylar process of the mandible articulating in the mandibular (glenoid) fossa of the temporal bone (Fig. 2.1). Unlike most other synovial joints, the joint cavity is divided into upper and lower compartments by an articular disc. Although basically a hinge joint, the TMJ also allows for some gliding movements. Movement of the condylar head occurs within the mandibular fossa and down a bony prominence termed the articular eminence (tubercle) of the temporal bone, which is located immediately anterior to the mandibular fossa. That there are two TMJs associated with a single mandible has considerable functional significance in that movement at one joint must imply additional movement at the other. The reader is referred to additional accounts of the joint.1–7 THE MANDIBULAR FOSSA The mandibular fossa is an oval depression in the temporal bone lying immediately anterior to the external acoustic meatus (Figs 1.1, 2.2, 2.15). Its mediolateral dimension is greater than its anteroposterior one in order to accommodate the mandibular condyle, and it is wider laterally than medially. The curvature of the mandibular fossa varies and may show some relationship to the nature of the occlusion. The mandibular fossa is bounded anteriorly by the articular eminence, laterally by the zygomatic process, and posteriorly by the tympanic plate. The posterior margin is elevated to form the posterior auricular ridge, which may be enlarged laterally as the postglenoid tubercle just anterior to the external acoustic meatus. Medially, the mandibular fossa may be defined by a ridge, the medial glenoid plane. The squamous and tympanic parts of the temporal bone are delineated laterally by the squamotympanic fissure. Medially, this fissure bifurcates due to the presence of a small 24 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.2 The base of the skull showing the mandibular fossa and related structures. component of the petrous portion, the tegmen tympani, giving rise to the petrosquamous fissure anteriorly and the petrotympanic fissure immediately behind (Fig. 1.1). The petrotympanic fissure is the site at which the chorda tympani nerve exits from the cranium into the infratemporal fossa. The shape of the mandibular fossa does not exactly conform to the shape of the mandibular condyle, the articular disc moulding together the joint surfaces. The bone of the central part of the fossa is thin. This indicates that masticatory loads are not dissipated through the mandibular fossa but through the teeth and thence the facial bones and base of the cranium. THE CONDYLAR PROCESS OF THE MANDIBLE The mandibular condyle (Figs 2.1–2.4) varies considerably both in size and shape. When viewed from above, the condyle is roughly ovoid in outline, the anteroposterior dimension of the condyle (approximately 1 cm) being approximately half the mediolateral dimension. The medial aspect of the condyle is wider than the lateral. The long axis of the condyle is not, however, at right angles to the ramus, but diverges posteriorly from a strictly coronal plane. Thus, the lateral pole of the condyle lies slightly anterior to the medial pole and, if the long axes of the two condyles are extended, they meet at an obtuse angle (approximately 145°) at the anterior border of the foramen magnum. The articular surfaces of the condyle are the anterior and superior surfaces. These surfaces are convex. The articular surface area of the condyle is of the order of 200 mm2, which is about half that of the mandibular fossa.8 The non-articular posterior surface of the condyle is broad and flat. The articular surface may be separated from the nonarticular surface by a slight ridge indicating the site of attachment of the joint capsule. The articular head of the condyle joins the ramus through a thin bony projection termed the neck of the condyle. A small depression (the pterygoid fovea) marks part of the attachment of the lateral pterygoid muscle. This fovea is situated on the anterior surface of the neck, below the articular surface. The condyle is composed of a core of cancellous bone covered by a thin layer of compact bone. During the period of growth, however, a layer of hyaline cartilage lies immediately beneath the fibrous articulating surface of the condyle. THE JOINT CAPSULE The capsule of the TMJ is a thin slack cuff which, of itself, does not limit mandibular movements and is too weak to provide much support for the joint (Fig. 2.5). Below, it is attached to the neck of the condyle of the mandible. Above, it is attached to the mandibular fossa, extending anteriorly to just in front of the crest of the articular eminence, posteriorly to the squamotympanic and petrotympanic fissures, medially to the medial glenoid plane and laterally between the lateral margin of the articular eminence and the postglenoid process. The capsule posteriorly is associated with the thicker, vascular, but loosely arranged connective tissue of the bilaminar zone of the articular disc. Internally, the capsule gives attachment to the articular disc.9,10 The collagen fibres of the capsule run predominantly in a vertical direction.5 CHAPTER 2 THE TEMPOROMANDIBULAR JOINT AND PTERYGOPALATINE FOSSA 25 Figure 2.3 The condyle viewed laterally. A synovial membrane lines the inner surface of the fibrous capsule and the margins of the articular disc but does not cover the articular surfaces of the joint. The synovial membrane secretes the synovial fluid that occupies the joint cavities. The synovial fluid lubricates the joint and may also have nutritive functions. Important components of the fluid are the proteoglycans, which aid the lubrication. At rest, the hydrostatic pressure of the synovial fluid has been reported as being subatmospheric, but this is greatly elevated during mastication.11,12 THE ARTICULAR DISC (Figs 2.6–2.10) The articular disc (meniscus) is of a dense, fibrous consistency and is moulded to the bony joint surfaces above and below. Blood vessels are only evident at the periphery of the articular disc, the bulk of it being avascular. Above, it covers the slope of the articular eminence in front while below it covers the condyle. When viewed in sagittal section, the upper surface of the disc is concavoconvex from before backwards and the lower surface is concave (Figs 2.6–2.8). Viewed superiorly, the articular disc is somewhat oval in outline. The disc is of variable thickness, being thinnest centrally over the articular surface of the mandibular condyle and thickest posteriorly in the region above, and behind, the mandibular condyle. The lateral half of the disc is thinner than the medial half. The medial and lateral margins of the disc are slightly thickened (Fig. 2.9). The articular disc has been subdivided into three portions: anterior, intermediate and posterior (Fig. 2.8). The intermediate zone is the thinnest and is the area in contact with the articular surface of the condyle. In the intermediate part, the collagen bundles have been described as running preferentially in an anteroposterior direction, while in the anterior and posterior bands, they run both anteroposteriorly and mediolaterally. The collagen fibres are crimped, perhaps evidence that the disc is subjected to tensional forces. The overall shape of the articular disc is thought to provide a self-centring mechanism, which automatically acts to maintain its correct relationship to the articular surface of the mandibular condyle during mandibular movements. The margin of the articular disc merges peripherally with the joint capsule. Anteriorly, fibrous bands connect the disc to the anterior margin of the articular eminence above and to the anterior margin of the condyle below. Medially and laterally, the articular disc is attached to the joint capsule and, just below the medial and lateral poles of the condyle, by triangular zones of connective tissue. Posteriorly, the disc is attached to the capsule by a looser connective tissue, the retrodiscal tissue (pad) that has a bilaminar appearance. The superior lamina is loose and possesses numerous vascular elements and elastin fibres.13 It attaches to the anterior margin of the squamotympanic fissure. The inferior lamina is relatively avascular, less extensible (as it has few elastin fibres) and is attached to the posterior margin of the condyle. The volume of the retrodiscal tissue appears to increase four to five times as a result of venous engorgement as the jaw is opened and the condyle moves downwards and forwards. This venous engorgement of the retrodiscal veins is not the result of the tissue having erectile properties,13 but more the result of their continuity with the pterygoid venous plexus lying medial to the condyle. This activity fills the vacated space in the mandibular fossa and rapidly equilibrates any changes in intracapsular pressures which may hinder jaw movement. Changes in tissue fluid pressures during mandibular movements could also help regulate the flow of blood in the retrodiscal 26 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.4 The condyle viewed anteriorly showing the pterygoid fovea. pad.2 As the mandibular condyle moves backwards during jaw closure, blood leaves the retrodiscal tissues. The close relationship of elastin fibres to the walls of the blood vessels in the retrodiscal tissues has led to the view that the fibres function as a pump, facilitating blood flow during venous dilatation and compression.14,15 It has been suggested that the retrodiscal pad may serve as an absorber of sounds produced by the temporomandibular joint.13 The return of the articular disc to its original position may be aided by the elastic recoil of the superior lamella. However, the finding that the superior lamina is folded on itself when the jaw is closed and only increased in length by one quarter by the time the condyle reached the crest of the articular eminence argues against this view.16 This indicates that movement of the disc may be passive, due to the shape of the disc and its firm insertion to the lateral and medial poles of the condyle of the mandible, and also due to the finding that the superior head of the lateral pterygoid is only active on final closure.17 The articular disc of the TMJ divides the joint cavity into superior and inferior joint cavities. About 1 ml of synovial fluid occupies the inferior joint cavity, while a little more occupies the slightly larger superior joint cavity. Numerous studies have been undertaken to determine the precise attachment of the lateral pterygoid muscle to the articular disc, as this may help us understand TMJ disorders such as internal derangement of the articular disc, when the disc is displaced generally in an anteromedial direction.18–21 These numerous studies have produced variable results which have been summarised in a major review of the literature.22 The findings indicate that, in the majority of studies (60%), fibres from the superior head of the lateral pterygoid muscle gain a direct attachment into the capsule of the joint and to the medial aspect of the anterior border of the articular disc (as well as to the condyle). In 30% of articles, only a few muscle fibres are inserted into the disc, while in the remaining 10% of studies the superior head of the lateral pterygoid muscle is attached only to the condyle. Very rarely, some fibres from the inferior head of the lateral pterygoid may insert into the articular disc.23 Such CHAPTER 2 THE TEMPOROMANDIBULAR JOINT AND PTERYGOPALATINE FOSSA 27 Figure 2.5 The capsula viewed laterally. (Courtesy of Professor S.Standing. GKT School of Biomedical Sciences, London.) differences may reflect biological variation or the particular techniques used. In one recent study trying to explain the different results, the differing methodology was blamed and it was con cluded that part of the superior head of the lateral pterygoid muscle is attached only to the capsule and did not extend into the disc. As there is a firm adhesion between the capsule, disc and muscle, this arrangement allows them to act as a unit without the necessity of muscle fibres passing into the disc.24 Some reports have suggested that fibres of the masseter muscle may be attached to the anterolateral part of the articular disc of the temporomandibular joint.25 However, there are other studies which dispute this and maintain that there is no direct muscular attachment, but rather a blending of fibrous tissue.9,26 Rarely, fibres of the temporalis muscle may gain attachment to the disc.25,26 Whereas some regard the functions of the articular disc as helping to spread the joint forces and to stabilise the condyle, others see its function as primarily permitting the condyle to move more freely.27 THE LIGAMENTS OF THE TEMPOROMANDIBULAR JOINT The joint capsule is attached to the neck of the condyle and to the margins of the mandibular fossa. It is strengthened by the lateral ligament (temporomandibular ligament) although this cannot readily be separated from the capsule (Fig. 2.11).5,28 Histological studies confirm the close attachment of the lateral ligament to the capsule.29 From the articular eminence, this ligament passes downwards and backwards to attach on to the lateral surface and posterior border of the neck of the mandibular condyle. The lateral ligament is reinforced by a horizontal band of fibres running from the articular eminence to the lateral surface 28 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.6 Dissection showing articular disc attached to the lateral pterygoid. (Courtesy of Professor L Garey, Anatomy Department, Imperial College Medical School, London.) FIGURE 2.10 SAGITTAL SECTION OF THE TEMPOROMANDIBULAR JOINT. of the condyle. This band restricts posterior displacement of the condylar process.30 The lateral ligament is believed also to convert the potentially separating forces generated by the muscles opening the jaws into a force that compresses the condyle of the mandible on to the articular eminence.20 In addition to the usual type I collagen fibres, the lateral ligament also contains a considerable amount of type III collagen.28 In about 15% of cases, the collagen comprising the lateral ligament may not be organised into parallel-running fibre bundles, giving it an almost non-ligamentous appearance. Irregularly arranged collagen fibre bundles are encountered as a normal feature in the posterior part of the lateral ligament.28 FIGURE 2.11 THE TEMPOROMANDIBULAR JOINT AND ITS LIGAMENTS. Although a medial ligament has been described, it is much less conspicuous than the lateral ligament so that the medial displacement of the TMJ is likely to be prevented by the lateral ligament of the opposite side. The accessory ligaments of the temporomandibular joint are the stylomandibular ligament, the sphenomandibular ligament and the pterygomandibular raphe (Figs 2.11, 2.12). However, only the sphenomandibular ligament is likely to have any significant influence upon mandibular movements. CHAPTER 2 THE TEMPOROMANDIBULAR JOINT AND PTERYGOPALATINE FOSSA 29 Figure 2.7 Sagittal section of the articular disc. Figure 2.8a Low power histological section of the articular disc. Haematoxylin and eosin. The stylomandibular ligament is a reinforced lamina of the deep cervical fascia as it passes medial to the parotid salivary gland. It extends from the tip of the styloid process and from the stylohyoid ligament to the angle of the mandible. The sphenomandibular ligament is a remnant of the perichondrium of the embryonic first branchial arch cartilage. It runs from the spine of the sphenoid bone to the lingula near the mandibular foramen. From the spine of the sphenoid bone, it continues through the petrotympanic fissure into the middle ear to attach to the anterior process of the malleus. The sphenomandibular ligament is slack when the jaws are closed, but becomes tense at about the time when the condyle has passed in front of the lateral ligament.20 Recently, a new ligament has been described in association with the TMJ. This is the retinacular ligament which arises from the articular eminence, descends along the ramus of the mandible and is inserted into the fascia overlying the masseter muscle at the angle of the mandible. As the ligament is connected with the posterolateral aspect of the retrodiscal tissues, and contains an accompanying vein, it may function in maintaining blood circulation during masticatory jaw movements.31 THE INNERVATION AND VASCULATURE OF THE TEMPOROMANDIBULAR JOINT The TMJ is richly innervated, particularly its upper aspect. Of special significance are the encapsulated proprioceptive nerve endings important in the reflex control of mastication. Free nerve endings associated with nociception are also present. Innervation for the joint is provided by the auriculotemporal, masseteric and deep temporal nerves. 30 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.8b Micrograph of articular disc viewed with differential interference contrast microscopy revealing crimped nature of collagen (×150). The auriculotemporal branch of the mandibular division of the trigeminal nerve winds around the back of the TMJ, between it and the external acoustic meatus, before ascending in front of the tragus of the auricle to the temporal region (Figs 1.8, 1.9, 1.12). It provides multiple branches supplying the TMJ. The masseteric branch of the mandibular division of the trigeminal nerve passes through the mandibular notch to enter the posterior surface of the masseter muscle and, during its course, also gives multiple branches supplying the TMJ. The (posterior) deep temporal branch of the mandibular division of the trigeminal nerve arises in the infratemporal fossa and, passing up to supply the temporalis muscle (Fig. 1.9), provides a branch to the TMJ. Additional sources of supply for the TMJ have been reported to be provided by the facial nerve32 and the otic ganglion. The vascular supply is derived from the superficial temporal artery and the maxillary artery (Fig. 1.13) (anterior tympanic and deep auricular branches). Other branches from neighbouring arteries may also contribute (e.g. deep temporal and transverse facial arteries). HISTOLOGICAL CONSIDERATIONS The articular surfaces of the temporomandibular joint are lined by fibrous tissue. This reflects the development of the joint. Unlike other synovial joints whose articular surfaces develop endochondrally and are therefore lined by hyaline cartilage, the temporomandibular joint develops intramembranously. The histological appearance of the condylar cartilage is related to age, as a secondary cartilage is present until puberty. In the adult, the bony condylar head is covered superficially by the fibrous articular zone (Fig. 2.13). A layer containing an increased number of nuclei can be observed in the lower region of the covering fibrous articular layer, indicative of a proliferative zone. Two additional layers have been described below the proliferative layer: firstly, a region regarded as being composed of fibrocartilage, beneath which is a thin zone of calcified cartilage, representing the remains of the secondary condylar cartilage. In the condyle of a child, the articular surface is again lined by a layer of fibrous tissue. Beneath the articular layer is a proliferative layer of undifferentiated cells (Fig. 2.14). Cells from this proliferative layer passmore deeply where they differentiate into chondrocytes which form the secondary condylar cartilage. The chondrocytes subsequently hypertrophy and the site undergoes endochondral ossification. Unlike a primary cartilage, the secondary condylar cartilage has less extracellular matrix, the cartilage cells themselves do not undergo cell division and do not align themselves into columns. Although once thought to be a prime causative factor in controlling mandibular growth, the secondary condylar cartilage is now not thought to have any intrinsic growth potential. The condylar cartilage disappears at about the age of 16 years. Regions of cartilage cells may also be seen beneath the articular fibrous covering of the mandibular fossa, including the articular eminence, but these are less conspicuous than is the case with the condyle. The articular disc is comprised of dense fibrous tissue, the fibres being principally of type I collagen. The bulk of the cells are fibroblasts. However, more rounded, cartilage-like cells have been described within the disc (although whether their presence is age related or functionally related is not known). The disc, therefore, has been described as fibrocartilaginous. THE PTERYGOPALATINE FOSSA The pterygopalatine fossa lies beneath the infratemporal (posterior) surface of the maxilla and the pterygoid process of the sphenoid bone. The pterygopalatine fossa contains the maxillary nerve, the maxillary artery (third part) and the pterygopalatine parasympathetic ganglion. CHAPTER 2 THE TEMPOROMANDIBULAR JOINT AND PTERYGOPALATINE FOSSA 31 Figure 2.9 The articular disc viewed posteriorly. (Courtesy of the Royal College of Surgeons of England.) The elongated cleft between the posterior surface of the maxilla and the pterygoid process of the sphenoid bone is the pterygomaxillary fissure which forms the lateral aspect of the pterygopalatine fossa (Fig. 2.15). The anterior wall of the fossa is the infratemporal surface of the maxilla. The posterior wall of the fossa is the pterygoid process below and the greater wing of the sphenoid above. The medial wall is formed by the perpendicular plate of the palatine bone. The pyramidal process of the palatine bone is situated inferiorly and articulates with the tuberosity of the maxilla. It fills the triangular gap between the lower ends of the medial and lateral pterygoid plates. Laterally, the pterygopalatine fossa communicates with the infratemporal fossa through the pterygomaxillary fissure. The fissure continues above with the posterior end of the inferior orbital fissure in the floor of the orbit. The pterygomaxillary fissure transmits the maxillary artery from the infratemporal fossa, the posterior superior alveolar branches of the maxillary division of the trigeminal nerve and the sphenopalatine veins. Passing through the inferior orbital fissure from the pterygopalatine fossa are the infraorbital and zygomatic branches of the maxillary nerve, the orbital branches of the pterygopalatine ganglion and the infraorbital vessels. Entering the pterygopalatine fossa posteriorly are the foramen rotundum from the middle cranial fossa, and the pterygoid canal from the region of the foramen lacerum at the base of the skull (Fig. 2.16). The foramen rotundum (occupying the greater wing of the sphenoid bone) lies above, and lateral to, the pterygoid canal. The maxillary division of the trigeminal nerve passes through the foramen rotundum. The pterygoid canal transmits the greater petrosal and deep petrosal nerves (which combine to form the nerve of the pterygoid canal) and an accompanying artery derived from the maxillary artery. 32 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.12 Posterior view of the jaws showing the stylomandibular and sphenomandibular ligaments. (Courtasy of the Royal Callege of Surgeons of England.) Figure 2.13 An histological section of part of an adult mandibular condyle. Haematoxylin and eosin, ×100 Lying high up on the medial wall of the pterygopalatine fossa is the sphenopalatine foramen. It is formed by the notch between the orbital and sphenoid processes of the perpendicular plate of the palatine bone (Fig. 2.17), articulating with the body of the sphenoid bone. This foramen communicates with the lateral wall of the nasal cavity. It transmits the nasopalatine and posterior superior nasal nerves (from the pterygopalatine ganglion) and the sphenopalatine vessels. At the base of the pterygopalatine fossa is found the opening of a palatine canal. This canal is formed when the greater palatine groove running down the posterior margin of the lateral surface of the perpendicular plate of the palatine bone (Fig. 2.17) articulates with the posterior surface of the maxillary bone and the medial pterygoid plate. Lower down, the canal divides into greater and lesser palatine canals. The lesser palatine canal runs backwards in the pyramidal process of the palatine bone. The greater palatine canal enters the hard palate at the greater palatine foramen in the region of the transverse palatine suture. The lesser palatine canal enters the hard palate at the lesser palatine foramen (foramina). The palatine canal CHAPTER 2 THE TEMPOROMANDIBULAR JOINT AND PTERYGOPALATINE FOSSA 33 Figure 2.14 A histological section of a condyle in a child. Haematoxylin and eosin, ×90. transmits the greater and lesser palatine nerves (and the posterior inferior nasal branches from the pterygopalatine ganglion), together with accompanying vessels, and these pass to the hard palate to emerge at the greater and lesser palatine foramina. THE MAXILLARY NERVE This division of the trigeminal nerve (the fifth cranial nerve) contains only sensory fibres. Functionally, it supplies the maxillary teeth and their supporting struc FIGURE 2.18 BRANCHES OF THE MAXILLARY NERVE. tures, the hard and soft palate, the maxillary air sinus, much of the nasal cavity, and skin overlying the middle part of the face (Figs 2.18, 2.19). The maxillary nerve arises from the trigeminal ganglion on the floor of the middle cranial fossa. It passes along the lateral dural wall of the cavernous sinus to exit the cranial cavity at the foramen rotundum (Fig. 2.19). It emerges from the foramen rotundum in the upper part of the pterygopalatine fossa, where most of the branches are derived. These branches can be classified into those which come directly from the maxillary nerve, and those which are associated with the pterygopalatine parasympathetic ganglion. Branches from the main maxillary nerve trunk: Meningeal nerve Ganglionic branches Zygomatic nerve zygomaticotemporal nerve zygomaticofacial nerve Posterior superior alveolar nerve 34 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.15 The skull showing the position of the pterygopalatine fossa. Infraorbital nerve middle superior alveolar nerve anterior superior alveolar nerve Branches from the pterygopalatine ganglion: Orbital nerve Nasopalatine nerve Posterior superior nasal nerve Posterior inferior nasal nerve Greater (anterior) palatine nerve Lesser (posterior) palatine nerve Pharyngeal branch The meningeal nerve This is the only branch from the main trunk of the maxillary nerve that does not originate in the pterygopalatine fossa; it arises within the middle cranial fossa, before the foramen rotundum. It runs with the middle meningeal artery and innervates the dura mater lining the middle cranial fossa. CHAPTER 2 THE TEMPOROMANDIBULAR JOINT AND PTERYGOPALATINE FOSSA 35 Figure 2.16 The anterior surface of the sphenoid bone showing the formen rotundum and pterygoid canal. The ganglionic branches These are usually two in number and connect the maxillary nerve to the pterygopalatine ganglion. The zygomatic nerve This leaves the pterygopalatine fossa through the inferior orbital fissure. It passes along the lateral wall of the orbit before dividing into zygomaticotemporal and zygomaticofacial branches. These pass through the zygomatic bone to supply overlying skin. The zygomaticotemporal nerve also gives a branch to the lacrimal nerve, which carries autonomic fibres to the lacrimal gland. The posterior superior alveolar nerve(s) (Figs 2.19, 2.20) This is one of three superior alveolar nerves that supply the maxillary teeth. The middle and anterior superior alveolar nerves are branches of the infraorbital nerve (see below). The posterior superior alveolar nerve(s) leaves the pterygopalatine fossa through the pterygomaxillary fissure. Thence, it runs onto the tuberosity of the maxilla and eventually pierces the bone to supply the maxillary molar teeth and the maxillary sinus (Fig. 2.20). Before entering the maxilla, the nerve provides a gingival branch which innervates the buccal gingivae around the maxillary molars. The extra-bony course of the posterior superior alveolar nerve is variable. The nerve can subdivide into several branches just before, or just after, it enters the maxilla. Alternatively, it may arise as several distinct branches at the main trunk of the maxillary nerve. The infraorbital nerve (Figs 2.19, 2.20) This can be regarded as the terminal branch of the maxillary nerve proper. It leaves the pterygopalatine fossa to enter the orbit at the inferior orbital fissure. Initially lying in a groove in the floor of the orbit (the infraorbital groove), the infraorbital nerve runs into a canal (the infraorbital canal) and passes onto the face at the infraorbital foramen. The middle and anterior superior alveolar nerves arise from the infraorbital nerve in the orbit. The branches of the maxillary nerve that arise with the pterygopalatine ganglion contain not only sensory fibres from the maxillary nerve, but also autonomic fibres from the ganglion, which are mainly distributed to glands and blood vessels. The orbital nerve This passes from the pterygopalatine ganglion into the orbit through the inferior orbital fissure. It supplies periosteum and, via sympathetic fibres, the orbitalis muscle. The orbital nerve can also supply part of the maxillary sinus and may pass through the posterior ethmoidal foramen to innervate posterior ethmoidal air cells and the sphenoid air sinus. 36 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.17 Lateral view of the palatine bone showing the sphenopalatine notch. The nasopalatine nerve (Fig. 2.21) This nerve runs medially from the pterygopalatine ganglion into the nasal cavity through the sphenopalatine foramen. It passes across the roof of the nasal cavity to reach the back of the nasal septum. The nasopalatine nerve then passes downwards and forwards within a groove on the vomer to supply the posteroinferior part of the nasal septum. It passes through the incisive canal, where it usually forms a single nerve with its fellow of the opposite side, and emerges on the hard palate at the incisive fossa to supply the oral mucosa around the incisive papilla and palatal gingiva of the anterior teeth. The posterior superior nasal nerve (Figs 2.19, 2.20) This nerve enters the back of the nasal cavity through the sphenopalatine foramen. It divides into lateral and medial branches. The lateral branches supply the posterosuperior part of the lateral wall of the nasal fossa. The medial branches cross the roof of the nasal cavity to supply the nasal septum overlying the posterior part of the perpendicular plate of the ethmoid. The posterior inferior nasal nerve This supplies the inferior part of the lateral wall of the nose in the region of the inferior nasal concha. It may arise directly from the pterygopalatine ganglion or appear as a branch from the anterior palatine nerve. The greater (anterior) palatine nerve (Figs 2.21, 2.23) This nerves passes downwards from the pterygopalatine ganglion, through the palatine canal, and onto the hard palate at the palatine foramen (Fig. 2.21). Within the greater palatine canal, it can give off nasal branches that innervate the posteroinferior part of the lateral wall of the nasal fossa. On the palate, it runs forwards at the interface between the palatine process and the CHAPTER 2 THE TEMPOROMANDIBULAR JOINT AND PTERYGOPALATINE FOSSA 37 Figure 2.19 Dissection of the maxillary and mandibular nerves. (Courtesy of the Royal College of Surgeons of England.) alveolar process of the maxilla to supply much of the mucosa of the hard palate and palatal gingivae (except around the incisive papilla). The lesser (posterior) palatine nerve(s) (Figs 2.21, 2.23) This passes downwards from the pterygopalatine ganglion initially through the palatine canal. It then passes through the lesser palatine canal in the pyramidal process of the palatine bone and onto the palate at the lesser palatine foramen (or foramina). It runs backwards to supply the soft palate. The pharyngeal branch This originates from the pterygopalatine ganglion and passes through the palatovaginal canal to supply the mucosa of the nasopharynx. The palatovaginal canal is formed when the groove on the undersurface of the vaginal process of the sphenoid bone articulates with the upper surface of the sphenoid process of the palatine bone. The pharyngeal branch has also been reported to pass through the vomerovaginal canal, which generally transmits the pharyngeal branch of the sphenopalatine artery. The vomerovaginal canal lies between the upper surface of the vaginal process of the sphenoid bone and the ala of the vomer and is often continuous with the pterygoid canal. THE PTERYGOPALATINE GANGLION (FIGS 2.21–2.23; SEE ALSO FIG. 1.5) This parasympathetic ganglion is situated below the maxillary nerve in the pterygopalatine fossa, connected by two ganglionic branches. It is concerned primarily with supplying the nose, palate, and lacrimal gland (Fig. 2.22). As with other parasympathetic ganglia in the head, three types of fibres enter the pterygopalatine ganglion: parasympathetic, sympathetic, and sensory fibres. However, only the parasympathetic fibres synapse in the ganglion. The preganglionic parasympathetic fibres originate from the superior salivatory nucleus in the brainstem. The fibres pass with the nervus intermedius of the facial nerve. They subsequently emerge as the greater (superficial) petrosal nerve. This occurs within the facial canal of the temporal bone, close to the geniculate ganglion of the facial nerve. The greater petrosal nerve then passes through the bone to appear on the floor of the middle cranial fossa. It then runs medially in a shallow groove to 38 CHAPTER 2 SURGICAL ANATOMY OF THE INFRATEMPORAL FOSSA Figure 2.20 Frontal aspect of the face showing the posterior superior alveolar and infraorbital nerves. (Courtesy of Professor C Dean, Department of Anatomy and Developmental Biology, University College London.) the foramen lacerum. Passing within the foramen lacerum,

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