The presentation gave a detailed anatomy of the pterygomandibular space and how the space is clinically significant

1. ANATOMY OF THE
PTERYGOMANDIBULAR SPACE
AND ITS CLINICAL RELEVANCE
BY
DR. HOPE INEGBENOSUN

2. OUTLINE
 Introduction
 General anatomy
 Anatomic boundaries
 Communications
 Contents
 Clinical relevance
 Methods of inferior alveolar nerve block
 Potential anatomical causes for failure of anaesthesia
 Conclusion
 References

3. INTRODUCTION
 A thorough understanding of the anatomy of the pterygomandibular
space is fundamental to the successful administration of inferior
alveolar nerve blocks (IANBs), which are frequently used for
mandibular anaesthesia.
 The relationships of structures in the pterygomandibular space have
significant bearing on the effectiveness of the IANB, as well as its
safety.
 It has been suggested that many of the failures are associated with
vascular damage and/or variations in the anatomical pattern of the
relevant nerves and surrounding fibrous tissue.

4. GENERAL ANATOMY OF THE PTERYGOMANDIBULAR
SPACE
 The pterygomandibular space is a small fascial-lined cleft/space
containing mostly loose areolar tissue.
It is a potential space in the head, paired, on each side
It is located between the medial pterygoid muscle and the medial
surface of the ramus of the mandibble

5. ANATOMIC BOUNDARIES
 The boundaries of each pterygomandibular space are;
 The pterygomandibular raphe anteriorly
 The parotid gland (deep lobe) posteriorly
 The lateral pterygoid muscle superiorly
 The inferior border of the mandible (lingual surface) inferiorly
 The medial pterygoid muscle medially (the space is superficial to
the medial pterygoid)
 The ascending ramus of the mandible laterally (the space is deep
to the ramus of the mandible)
o Anteriorly, the buccinators and superior constrictor muscle come
together to form a fibrous junction, the pterygomandibular raphe

6. KEY
1 — retromandibular vein;
2 — masseter muscle;
3 — inferior alveolar nerve, artery and vein; 4
— medial pterygoid muscle;
5 — superior constrictor muscle;
6 — buccinator muscle;
7 — parotid gland;
8 — deep portion of temporalis muscle tendon;
9 — sphenomandibular ligament;
10 — facial nerve;
11 — mandibular ramus;
12 — external carotid artery;
13 — buccal nerve;
14 — styloid process of temporal bone.
Fig 1. Diagrammatic representation of a transverse
section of the right mandibular ramus showing the
anatomical boundaries of the pterygomandibular
space

7. COMMUNICATIONS
 The communications of each pterygomandibular space are;
 to the buccal space anteriorly
 to the lateral pharyngeal space and peritonsillar space medially
(around the medial pterygoid muscle)
 to the submasseteric space laterally (around the ramus of the
mandible)
 to the parotid space posteriorly
 to the deep temporal/infratemporal space superiorly

8. Fig 3 – Diagrammatic representation of
the mandibular fascial spaces
Fig 2 – Diagrammatic illustration of the
comunication between the
pterygomandibular space and lateral
pharyngeal space and also the spread of
dentoalveolar abscess into contiguous
fascial spaces

9. CONTENTS
 The pterygomandibular space contains the;
 Inferior alveolar nerve, artery and vein
 Lingual nerve
 Nerve to mylohyoid
 Sphenomandibular ligament and fascia

10. KEY
M = masseter
R = ramus
IAN = inferior alveolar nerve;
IAV = inferior alveolar vein;
IAA = inferior alveolar artery;
SML = sphenomandibular ligament;
MP = medial pterygoid muscle;
LN =lingual nerve;
B = buccinator;
PMR = pterygomandibular raphe;
SCM= superior constrictor muscle;
P= parotid gland;
TT= tendon of temporalis
L = lingula
The LN is located anterior and medial to the
IAN.
Fig 4. Diagrammatic representation of a
transverse section of the right mandibular
ramus showing the contents of the
pterygomandibular space

11. CLINICAL RELEVANCE OF THE PTERYGOMANDIBULAR
SPACE
A. SITE FOR INFERIOR ALVEOLAR NERVE BLOCK INJECTION
 The pterygomandibular space is the area where local anaesthetic
solution is deposited during an inferior alveolar nerve block (IANB), a
common procedure to anaesthesize the distribution of the inferior
alveolar nerve
Fig. 5

12. B. PTERYGOMANDIBULAR SPACE INFECTION
AETIOLOGY
1. Rarely, pathogenic microorganisms from the mouth may be seeded into
the pterygomandibular space during this injection and cause a needle
tract infection of the space [Hupp JR, Ellis E, Tucker MR 2008].
2. Odontogenic infections may spread to involve the pterygomandibular
space and the most common teeth responsible are the mandibular
second and third molar teeth [Hargreaves KM, Cohen S, 2010].
3. The pterygomandibular space is one of the possible spaces into which a
tooth may be displaced into during exodontia, e.g. of a maxillary wisdom
tooth [Ozer N, et al, 2013].
4. A mandibular fracture in the angle region may also cause
pterygomandibular space infection [Hupp JR, Ellis E, Tucker MR 2008].

13. Fig 6: A diagrammatic illustration
showing the various pathways of
spread of infection from the mandibular
third molar
1 = Peritonsillar and
parapharyngeal spaces
2 = Pterygomandibular space
3 = Submasseteric space
4 = Buccal space
5 = Vestibular space
mandibular

14. CLINICAL FEATURES
1. Trismus (difficulty opening the mouth)
2. There is usually not any externally visible facial swelling
3. Intraorally, there may be swelling and erythema (redness) of the anterior
tonsillar pillar (the palatoglossal arch)
4. There is deviation of the uvula to the unaffected side
5. The airway may be compressed leading to air hunger
6. There may be general constitutional symptoms
7. There may also be dysphagia

15. SPREAD OF THE INFECTION
Upward Infratemporal space
Below Submandibular space
Medial Lateral pharyngeal space
TREATMENT
o Treatment is by surgical incision and drainage, and the incision may
be placed inside the mouth or two incisions may be used, one inside
the mouth and one outside followed with antibiotics.

16. C. FRACTURE OF ANAESTHETIC NEEDLE
 Fortunately, needle fracture is a rare complication following the
administration of dental local anaesthetic injections.
 Evidence seems to suggest that needle fracture is more common
when giving an inferior dental nerve block than it is with other dental
infiltration and block techniques [Ethunandan M, et al, 2012].
 Since the introduction of disposable needles in the 1960s, along with
improvements in metal alloys and manufacturing processes, needle
fracture has become even less common [Bedrock RD, et al 1999].

17.  Needle fracture may occur due to:
Poor technique;
Patient movement during administration;
Needle manufacturing faults.

18. MANAGEMENT
 Upon realizing that a needle has fractured, the dentist should
immediately attempt retrieval with a fine mosquito/ haemostatic clip if
the needle is visible.
 If the needle cannot be retrieved, the patient should be informed,
advised of the clinical risks of leaving the needle in situ.
 Following appropriate radiographic imaging and patient consent, the
patient should undergo surgical exploration and retrieval of the
fractured needle under general anaesthesia.
 Retrieval should be performed as soon as possible to prevent
complications, such as migration of the needle, tissue space infection,
and also to prevent the pain and discomfort caused by having a
needle imbedded in the soft tissues [Ethunandan M, et al, 2012].

19. D. RISK OF INTRAVASCULAR INJECTION
 Due to the high vascularity of the area, injections into the
pterygomandibular space carry a high risk of intravascular injection
(injecting into a blood vessel).
E. INJURY TO FACIAL NERVE
 A possible complication of IANB occurs when the needle is placed too
deep, passing through the pterygomandibular space and into the
parotid gland behind.
 Branches of the facial nerve (which gives motor supply to the muscles
of facial expression) run through the substance of the parotid gland
and so this manifest as a transient facial palsy

20. METHODS OF INFERIOR ALVEOLAR NERVE BLOCK
 Anesthesia of the inferior alveolar nerve can be achieved by:
1. Classical method by Halsted
2. Kenneth-Reed method
3. Gow-Gates method.
o Other available techniques includes approaches described by
Vazirani/Akinosi’s closed mouth technique, Malamed’s method and
Fischer’s three stage technique [Zanette G et al, 2011, Skrzat J et al, 2012 and Thangavelu K
et al, 2012].

21. CLASSICAL METHOD BY HALSTED
 The classical method proposed by Halsted involves the insertion of a
needle into the pterygomandibular space by piercing the buccinator
muscle.
 In this method the needle is inserted about 10 mm above the plane of
lower teeth with mouth widely opened.
 Once in the pterygomandibular space, the aim of the technique is to
deposit local anaesthetic solution at a level just superior to the tip of
the lingula.
 Diffusion of local anaesthetic solution from the needle tip to the IAN
anaesthetizes the nerve just prior to it entering the mandibular
foramen.

22.  The lingual nerve lies medial and anterior to the IAN and it can be
anaesthetized during an IANB. This is achieved by withdrawing the needle
and swinging the barrel of the syringe toward the dental midline.
 Generally, as a guide, the syringe barrel should be over the premolars on
the contralateral side.
 This angulation can be modified if bone has not been contacted by the
needle tip at an appropriate insertion depth of around 20–25 mm.
 Once the correct needle position and angulation have been determined,
the needle is then withdrawn one or two millimetres and aspiration
performed before injection [Skrzat J, et al, 2003].

23. o A string has been attached to indicate where the
pterygomandibular raphe would normally be
located.
o This structure attaches to the pterygoid hamulus
superiorly and descends to the inner aspect of
the mandible near the most posterior molar.
o The pterygomandibular fold refers to the fold of
mucosal tissue that overlies the
pterygomandibular raphe and the needle should
always be inserted lateral to the fold.
o The thumb or another finger can be used to
palpate the coronoid notch, as seen in the
photograph, to assist in establishing the correct
height of needle insertion.
o (L = lingula; PMR = pterygomandibular raphe; H
= pterygoid hamulus; CN = coronoid notch.)
Fig 7. Photograph of a skull with
simulated maximum opening of the
mouth.

24. Fig 8. Intraoral photograph of the right
side of the oral cavity showing key
anatomical landmarks observed when
giving an IANB.
o The site for needle penetration is the
pterygotemporal depression, which is
outlined. The needle travels through the
oral mucosa and underlying buccinator
muscle before entering the
pterygomandibular space.
o The height is at the level of the coronoid
notch, the most concave region on the
anterior border of the mandibular ramus.
o Approximate depth of needle penetration
required in most adult patients is about
20–25 mm.
o (CN = coronoid notch; PTD =
pterygotemporal depression; PMF =
pterygomandibular fold.)

25. KENNETH-REED METHOD
 In Kenneth-Reed technique the needle is inserted about 20 mm (not
like in Halsted method — about 10 mm) above the plane of lower
teeth with mouth widely opened.
 The place of injection is proposed to be at the crossing of two lines:
first, parallel to the plane of the lower teeth and second which
extends between coronoid notch and pterygomandibular raphe, in
anterior 2/3 of this line [Thangavelu K et al, 2012].

26. GOW-GATES METHOD
 Gow-Gates method was proposed in 1973 by Australian dentist who
defined the alternative method of anesthetizing all three nerves (inferior
alveolar, lingual and buccal) using single injection [Zanette G et al, 2011].
 George Gow-Gates distinguished two important topographical points:
tragus and mouth angle.
 The needle should be inserted going from the contralateral mouth angle
toward the cheek at the mesial palatine tubercle of the second upper
molar tooth.

27.  The needle should go upwards, externally and posteriorly, reaching
the medial surface of the condylar process, where these three
mentioned above nerves runs relatively near each to other.
 Positive aspiration in Gow-Gates method varies, however it never
exceed above 2%.
 Successful anesthesia can be achieved in 95-98%, comparing to 75–
85% obtained by the classical method.

28. Fig. 9. Gow-Gates method.

29. Fig. 10. Vazirani/Akinosi method.

30. POTENTIAL ANATOMICAL CAUSES FOR FAILURE OF ANAESTHESIA
 Anaesthetic failures occur frequently with IANBs, even with experienced
clinicians.
 There are many reasons why this may occur. The two major factors being poor
operator technique and anatomical variation (Lew K and Townsend G, 2006)
 Other potential reasons for anaesthetic failure include psychological issues
where patient fears and anxieties lead to either exaggerated or imagined pain
and discomfort, or in cases of acute localized infections within the
pterygomandibular space (Meechan J, 1999).

31.  The nerve to mylohyoid is primarily motor in nature, but it may contain a
sensory component that innervates mandibular teeth which may be relevant
when attempting an IANB.
 Variation in the height at which the nerve to mylohyoid branches off the the
IAN, may ultimately influence whether the nerve is anaesthetized during an
IANB
 Hence the greater the distance between the point at which the nerve to
mylohoid branches off the IAN and the location where the local anaesthetic
solution is deposited, the greater the likelihood that the nerve to mylohyoid may
not be fully anaesthetized, leading to potential failure in achieving anaesthesia.

32.  Bifid mandibular canals have the potential to increase the difficulty of
achieving adequate anaesthesia using the IANB technique [Lew K,
Townsend G., 2006].
 Mandibular prognathism is another anatomical variation that can
complicate IANBs. Prognathic mandibles generally have a lingula that
is positioned higher than the coronoid notch, making it more difficult
for the operator to insert the needle at the correct height [Jorgensen N,
Hayden J., 1967].
 The difference in height between the lingula and coronoid notch may
be as much as 1 cm. In these cases, needle insertion above normal is
indicated.

33. Fig 11. Four representative intraoral photographs of the right side of the oral cavity showing the key
intraoral landmarks observed and palpated when administering an IANB. (CN = coronoid notch; PTD =
pterygotemporal depression; PMF = pterygomandibular fold.)

34. CONCLUSION
 Just as an understanding of the basic anatomy of the pterygomandibular space
promotes safe and effective anaesthesia, improved knowledge about less
explored regions and relationships should make the administration of IANBs
even safer and more effective.
 Considering that IANBs is the main technique for achieving mandibular
anaesthesia, it is essential that clinicians are familiar with the relevant anatomy
and understand how anatomical variations can lead to anaesthetic failures.

35. REFERENCES
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pulp (10th ed.) St. Louis, Mo.: Mosby Elsevier. Pp. 590 – 594. ISBN 978-0 -323-06489-7.CS1
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