Face and oral cavity part 4

Question 1

Summarise the masseter

Answer 1

The masseter muscle is a powerful muscle of mastication that elevates the mandible (Fig. 8.137 and Table 8.11). It overlies the lateral surface of the ramus of the mandible.

zygomatic arch to lat surface of ramus and angle of mandible
elevates mandible (allows forced closure of mouth)

Question 2

Summarise the temporalis muscle

Answer 2

temporal fossa to coronoid process of mandible
elevates and retracts mandible
fan-shaped and thin

Question 3

Summarise the lateral pterygoid

Answer 3

sphenoid /lat pterygoid plate to neck of mandible

depresses and protracts mandible to open mouth

Question 4

Show the medial pterygoid

Answer 4

lat pterygoid plate/ maxilla/palate to angle of mandible

elevates, protracts and lateral movement of mandible for chewing

Question 5

Describe the AFI of the masseter muscle

Answer 5

origin- zygomatic arch (superficial) and maxillary process of the zygomatic bone (deep)
insertion - lateral surface of ramus of mandible and angle of mandible (superficial)
innervation- masseteric nerve from anterior trunk of mandibular nerve
function- elevation of mandible

Question 6

Describe the AFI of the temporalis muscle

Answer 6

origin- bone of temporal fossa and temporal fascia
insertion- Coronoid process of mandible and anterior margin of ramus of mandible almost to last molar tooth
innervation- Deep temporal nerves from the anterior trunk of the mandibular nerve [V3]
function- elevation and retraction of mandible

Question 7

Describe the AFI of the medial pterygoid

Answer 7

origin- Deep head—medial surface of lateral plate of pterygoid process and pyramidal process of palatine bone; superficial head—tuberosity of the maxilla and pyramidal process of palatine bone
insertion- medial surface of angle near mandible
innervation- Nerve to medial pterygoid from the mandibular nerve [V3]
function- Elevation and side-to-side movements of the mandible (when both activated- mandible will move to one side).

Question 8

Describe the AFI of the lateral pterygoid

Answer 8

origin- Upper head—roof of infratemporal fossa; lower head—lateral surface of lateral plate of the pterygoid process
insertion- Capsule of temporomandibular joint in the region of attachment to the articular disc and to the pterygoid fovea on the neck of mandible
innervation- Nerve to lateral pterygoid directly from the anterior trunk of the mandibular nerve [V3] or from the buccal branch
function- Protrusion and side-to-side movements of the mandible

Question 9

Summarise the temporal fossa

Answer 9

The temporal fossa is a narrow fan-shaped space that covers the lateral surface of the skull

Question 10

Describe the upper margin of the temporal fossa

Answer 10

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Its upper margin is defined by a pair of temporal lines that arch across the skull from the zygomatic process of the frontal bone to the supramastoid crest of the temporal bone.

Question 11

Describe the lateral margin of the temporal fossa

Answer 11

It is limited laterally by the temporal fascia, which is a tough, fan-shaped aponeurosis overlying the temporalis muscle and attached by its outer margin to the superior temporal line and by its inferior margin to the zygomatic arch.

Question 12

Describe the anterior margin of the temporal fossa

Answer 12

Anteriorly, it is limited by the posterior surface of the frontal process of the zygomatic bone and the posterior surface of the zygomatic process of the frontal bone, which separate the temporal fossa behind from the orbit in front.

Question 13

Describe the inferior margin of the temporal fossa

Answer 13

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Its inferior margin is marked by the zygomatic arch laterally and by the infratemporal crest of the greater wing of the sphenoid medially (Fig. 8.138B)—between these two features, the floor of the temporal fossa is open medially to the infratemporal fossa and laterally to the region containing the masseter muscle.

Question 14

What are the contents of the temporal fossa

Answer 14

The major structure in the temporal fossa is the temporalis muscle.
Also passing through the fossa is the zygomaticotemporal branch of the maxillary nerve [V2], which enters the region through the zygomaticotemporal foramen on the temporal fossa surface of the zygomatic bone.

Question 15

Summarise the muscles of mastication

Answer 15

Of the four muscles of mastication (masseter, temporalis, medial pterygoid, and lateral pterygoid) that move the lower jaw at the temporomandibular joint, one (masseter) is lateral to the infratemporal fossa, two (medial and lateral pterygoid) are in the infratemporal fossa, and one fills the temporal fossa.

Question 16

Describe the role of the buccinator muscle in mastication

Answer 16

Pushes food towards the inside of the mouth
also involved in facial expression
innervated by the facial nerve

Question 17

Summarise the temporo-mandibular joints

Answer 17

The temporomandibular joints, one on each side, allow opening and closing of the mouth and complex chewing or side-to-side movements of the lower jaw.
Each joint is synovial and is formed between the head of the mandible and the articular fossa and articular tubercle of the temporal bone

Question 18

How do temporo-mandibular joints differ to most other synovial joints

Answer 18

Unlike most other synovial joints where the articular surfaces of the bones are covered by a layer of hyaline cartilage, those of the temporomandibular joint are covered by fibrocartilage. In addition, the joint is completely divided by a fibrous articular disc into two parts:
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The lower part of the joint allows mainly the hinge-like depression and elevation of the mandible.
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The upper part of the joint allows the head of the mandible to translocate forward (protrusion) onto the articular tubercle and backward (retraction) into the mandibular fossa.

Question 19

What does opening the mouth involve

Answer 19

Opening the mouth involves both depression and protrusion (Fig. 8.134B).
The forward or protrusive movement allows greater depression of the mandible by preventing backward movement of the angle of the mandible into structures in the neck.

Question 20

Describe the synovial membrane of the joint capsule

Answer 20

The synovial membrane of the joint capsule lines all nonarticular surfaces of the upper and lower compartments of the joint and is attached to the margins of the articular disc.

Question 21

Describe the fibrous membrane of the joint capsule

Answer 21

The fibrous membrane of the joint capsule encloses the temporomandibular joint complex and is attached:
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above along the anterior margin of the articular tubercle,
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laterally and medially along the margins of the articular fossa,
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posteriorly to the region of the tympanosquamous suture, and
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below around the upper part of the neck of the mandible.
The articular disc attaches around its periphery to the inner aspect of the fibrous membrane.

Question 22

Describe the extracapsular ligaments

Answer 22

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The lateral ligament is closest to the joint, just lateral to the capsule, and runs diagonally backward from the margin of the articular tubercle to the neck of the mandible.
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The sphenomandibular ligament is medial to the temporomandibular joint, runs from the spine of the sphenoid bone at the base of the skull to the lingula on the medial side of the ramus of the mandible.
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The stylomandibular ligament passes from the styloid process of the temporal bone to the posterior margin and angle of the mandible

Question 23

Compare the two different actions of the temporo-mandibular joints

Answer 23

Jaw slightly opened- hinge action predominates (between articular discs and head of mandible)
Jaw widely opened- hinge and gliding (articular tubercle will move forward) action combined

Question 24

What does depression of the mandible involve

Answer 24

Depression is generated by the digastric, geniohyoid, and mylohyoid muscles on both sides, is normally assisted by gravity, and, because it involves forward movement of the head of the mandible onto the articular tubercle, the lateral pterygoid muscles are also involved.

Question 25

What does elevation of the mandible involve

Answer 25

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Elevation is a very powerful movement generated by the temporalis, masseter, and medial pterygoid muscles and also involves movement of the head of the mandible into the mandibular fossa.

Question 26

What does protraction of the mandible involve

Answer 26

Protraction is mainly achieved by the lateral pterygoid muscle, with some assistance by the medial pterygoid.

Question 27

What does retraction of the mandible involve

Answer 27

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Retraction is carried out by the geniohyoid and digastric muscles, and by the posterior and deep fibers of the temporalis and masseter muscles, respectively.

Question 28

What can cause dislocation of the temporo-mandibular joints

Answer 28

Extensive gliding movement- head of mandible and articular tubercle get pushed into infratemporal fossa- can damage the nerve and vessels there.

Question 29

How do you put a dislocated temporo-mandibular joint back into place

Answer 29

have to use thumbs to push mouth down and back

put something in mouth to prevent the patient from biting you

Question 30

What is key to remember about the internal carotid artery

Answer 30

It has no branches

Question 31

At the level of what anatomical landmark does the common carotid artery bifurcate.

Answer 31

At the level of the laryngeal prominence

Question 32

List the branches of the external carotid artery

Answer 32

Superior thyroid
Ascending pharyngeal
Lingual
Facial
Occipital
Posterior auricular
Maxillary
Superficial temporal

Question 33

Describe the common carotid arteries

Answer 33

Common carotid arteries: begin the carotid system, branching off the brachiocephalic trunk on the right and directly from the aortic arch on the left; pass superiorly to enter neck near sternoclavicular joint
Ascension: travel upwards lateral to trachea and oesophagus within the carotid sheath and do not branch
Bifurcation: divide to external and internal carotids near superior edge of thyroid cartilage and within the carotid triangle
Carotid sinus: at bifurcation, common and internal carotid arteries are dilated, forming a sinus where the carotid pulse can be palpated, and baroreceptors monitor blood pressure (CN IX)/chemistry (CN IX/X)

Question 34

Describe the internal carotid arteries

Answer 34

Internal carotid arteries: supply cerebral hemispheres, orbit and forehead
Origin: formed at bifurcation of the common carotid in carotid triangle
Course: ascends towards base of skull, entering cranial cavity via carotid canal in petrous part of temporal bone
Major branches: none in the neck

Question 35

Describe the external carotid arteries

Answer 35

External carotid arteries: supply the muscles, face and visceral structures
Origin: formed at bifurcation of the common carotid in carotid triangle
Course: ascends anterior to the internal carotids
Major branches: SALF-OPSM
Superior thyroid: thyroid and muscles
Ascending pharyngeal: palate and pharynx
Lingual: tongue, epiglottis and mouth
Facial: face
Occipital: sternocleidomastoid and meninges
Posterior auricular: parotid gland and ear
Superficial temporal: masseter and lateral face
Maxillary: large supply

Question 36

Describe the course of the facial artery

Answer 36

Tortuous passage around the inferior border of the mandible to inferior border of eye
If tight/taut around mandible- it would rupture when the mouth is opened- so it loops to get around the mandible.

Question 37

Describe the middle meningeal artery

Answer 37

Comes from maxillary artery to supply the dura
pierces skull through foramen spinosum.
divides into anterior and posterior branches:

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The anterior branch passes in an almost vertical direction to reach the vertex of the skull, crossing the pterion during its course.

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The posterior branch passes in a posterosuperior direction, supplying this region of the middle cranial fossa.

Question 38

Describe the clinical importance of the middle meningeal artery

Answer 38

In lateral blows to the head the middle meningeal artery can be ruptured, leading to extradural hemorrhage and eventual death if not treated.

Lateral blows to the head can fracture the internal table of bone of the skull and tear the middle meningeal artery in the outer layer of dura mater that is fused to the cranium. Blood under pulsatile arterial pressure leaks out of the vessel and gradually separates the dura from the bone, forming a progressively larger extradural hematoma.

Question 39

Which part of the middle meningeal artery is most likely to be torn

Answer 39

The anterior branch of the middle meningeal artery is the part of the vessel most often torn. This branch is in the temple region of the head, approximately midway between the superior margin of the orbit and the upper part of the external ear in the pterion region. The pterion is a small circular area enclosing the region where the sphenoid, frontal, parietal, and temporal bones of the skull come together.

Question 40

Summarise the role of the buccinator muscle in mastication

Answer 40

Pushes food towards inside of mouth
Sucking in your cheeks is a result of contraction of the buccinator muscle
Contraction of the buccinator presses the cheek against the teeth. This keeps the cheek taut and aids in mastication by preventing food from accumulating between the teeth and the cheek. The muscle also assists in the forceful expulsion of air from the cheeks.

Question 41

Summarise the buccinator muscle

Answer 41

Innervated by the facial nerve
The buccinator forms the muscular component of the cheek and is used every time air expanding the cheeks is forcefully expelled (Figs. 8.56 and 8.57). It is in the space between the mandible and the maxilla, deep to the other facial muscles in the area.

Question 42

Summarise the muscles of the face

Answer 42

The muscles of the face (Fig. 8.53) develop from the second pharyngeal arch and are innervated by branches of the facial nerve [VII]. They are in the superficial fascia, with origins from either bone or fascia, and insertions into the skin.

Question 43

Summarise the functions of the muscles of the face

Answer 43

Because these muscles control expressions of the face, they are sometimes referred to as muscles of “facial expression.” They also act as sphincters and dilators of the orifices of the face (i.e., the orbits, nose, and mouth). This organizational arrangement into functional groups provides a logical approach to understanding these muscles

Question 44

Summarise the orbicularis oculi muscles

Answer 44

The orbicularis oculi is a large muscle that completely surrounds each orbital orifice and extends into each eyelid (Fig. 8.54). It closes the eyelids. It has two major parts:

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The outer orbital part is a broad ring that encircles the orbital orifice and extends outward beyond the orbital rim.

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The inner palpebral part is in the eyelids and consists of muscle fibers originating in the medial corner of the eye that arch across each lid to attach laterally.

Question 45

Distinguish between the two functions of the palpebral part and the orbital part of the orbicularis oculi muscle

Answer 45

The orbital and palpebral parts have specific roles to play during eyelid closure. The palpebral part closes the eye gently, whereas the orbital part closes the eye more forcefully and produces some wrinkling on the forehead.

Question 46

Summarise the corrugator supercilii

Answer 46

The second muscle in the orbital group is the much smaller corrugator supercilii (Fig. 8.54), which is deep to the eyebrows and the orbicularis oculi muscle and is active when frowning. It arises from the medial end of the superciliary arch, passing upward and laterally to insert into the skin of the medial half of the eyebrow. It draws the eyebrows toward the midline, causing vertical wrinkles above the nose.

Question 47

Summarise the nasalis muscle

Answer 47

The largest and best developed of the muscles of the nasal group is the nasalis, which is active when the nares are flared (Fig. 8.55). It consists of a transverse part (the compressor naris) and an alar part (the dilator naris):

Question 48

Distinguish between the two parts of the nasalis muscle

Answer 48

The transverse part of the nasalis compresses the nares—it originates from the maxilla and its fibers pass upward and medially to insert, along with fibers from the same muscle on the opposite side, into an aponeurosis across the dorsum of the nose.

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The alar part of the nasalis draws the alar cartilages downward and laterally, so opening the nares—it originates from the maxilla, below and medial to the transverse part, and inserts into the alar cartilage.

Question 49

Summarise the procerus muscle

Answer 49

The procerus is a small muscle superficial to the nasal bone and is active when an individual frowns (Fig. 8.55). It arises from the nasal bone and the upper part of the lateral nasal cartilage and inserts into the skin over the lower part of the forehead between the eyebrows. It may be continuous with the frontal belly of the occipitofrontalis muscle of the scalp.

The procerus draws the medial border of the eyebrows downward to produce transverse wrinkles over the bridge of the nose

Question 50

Summarise the depressor septi nasi

Answer 50

The final muscle in the nasal group is the depressor septi nasi, another muscle that assists in widening the nares (Fig. 8.55). Its fibers arise from the maxilla above the central incisor tooth and ascend to insert into the lower part of the nasal septum.

The depressor septi nasi pulls the nose inferiorly, so assisting the alar part of the nasalis in opening the nares.

Question 51

Summarise the oral group of muscles

Answer 51

The muscles in the oral group move the lips and cheek. They include the orbicularis oris and buccinator muscles, and a lower and upper group of muscles (Fig. 8.56). Many of these muscles intersect just lateral to the corner of the mouth on each side at a structure termed the modiolus.

Question 52

Summarise the orbicularis oris muscle

Answer 52

The orbicularis oris is a complex muscle consisting of fibers that completely encircle the mouth (Fig. 8.56). Its function is apparent when pursing the lips, as occurs during whistling. Some of its fibers originate near the midline from the maxilla superiorly and the mandible inferiorly, whereas other fibers are derived from both the buccinator, in the cheek, and the numerous other muscles acting on the lips. It inserts into the skin and mucous membrane of the lips, and into itself.

Contraction of the orbicularis oris narrows the mouth and closes the lips

Question 53

Describe the depressor anguli oris

Answer 53

The depressor anguli oris is active during frowning. It arises along the side of the mandible below the canine, premolar, and first molar teeth and inserts into skin and the upper part of the orbicularis oris near the corner of the mouth. It depresses the corner of the mouth.

Question 54

Describe the depressor labii inferioris

Answer 54

The depressor labii inferioris arises from the front of the mandible, deep to the depressor anguli oris. Its fibers move superiorly and medially, some merging with fibers from the same muscle on the opposite side and fibers from the orbicularis oris before inserting into the lower lip. It depresses the lower lip and moves it laterally.

Question 55

Describe the mentalis

Answer 55

The mentalis helps position the lip when drinking from a cup or when pouting. It is the deepest muscle of the lower group arising from the mandible just inferior to the incisor teeth, with its fibers passing downward and medially to insert into the skin of the chin. It raises and protrudes the lower lip as it wrinkles the skin of the chin.

Question 56

Describe the risorius

Answer 56

The risorius helps produce a grin (Fig. 8.56). It is a thin, superficial muscle that extends laterally from the corner of the mouth in a slightly upward direction. Contraction of its fibers pulls the corner of the mouth laterally and upward.

Question 57

Describe the zygomaticus major and minor

Answer 57

The zygomaticus major and zygomaticus minor help produce a smile (Fig. 8.56). The zygomaticus major is a superficial muscle that arises deep to the orbicularis oculi along the posterior part of the lateral surface of the zygomatic bone, and passes downward and forward, blending with the orbicularis oris and inserting into skin at the corner of the mouth. The zygomaticus minor arises from the zygomatic bone anterior to the origin of the zygomaticus major, parallels the path of the zygomaticus major, and inserts into the upper lip medial to the corner of the mouth. Both zygomaticus muscles raise the corner of the mouth and move it laterally

Question 58

Describe the levator labii superioris

Answer 58

The levator labii superioris deepens the furrow between the nose and the corner of the mouth during sadness (Fig. 8.56). It arises from the maxilla just superior to the infra-orbital foramen, and its fibers pass downward and medially to blend with the orbicularis oris and insert into the skin of the upper lip.

Question 59

Describe the levator labii superioris alaeque nasi

Answer 59

The levator labii superioris alaeque nasi is medial to the levator labii superioris, arises from the maxilla next to the nose, and inserts into both the alar cartilage of the nose and skin of the upper lip (Fig. 8.56). It may assist in flaring the nares.

Question 60

Describe the levator anguli oris

Answer 60

The levator anguli oris is more deeply placed and covered by the other two levators and the zygomaticus muscles (Fig. 8.56). It arises from the maxilla, just inferior to the infra-orbital foramen and inserts into the skin at the corner of the mouth. It elevates the corner of the mouth and may help deepen the furrow between the nose and the corner of the mouth during sadness.

Question 61

Summarise the platysma

Answer 61

The platysma is a large, thin sheet of muscle in the superficial fascia of the neck. It arises below the clavicle in the upper part of the thorax and ascends through the neck to the mandible. At this point, the more medial fibers insert on the mandible, whereas the lateral fibers join with muscles around the mouth.

The platysma tenses the skin of the neck and can move the lower lip and corners of the mouth down.

Question 62

Summarise the auricular muscles

Answer 62

Three of these muscles, “other muscles of facial expression,” are associated with the ear—the anterior, superior, and posterior auricular muscles (Fig. 8.58):

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The anterior muscle is anterolateral and pulls the ear upward and forward.

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The superior muscle is superior and elevates the ear.

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The posterior muscle is posterior and retracts and elevates the ear.

Question 63

Summarise the occipitofrontalis muscle

Answer 63

The occipitofrontalis is the final muscle in this category of “other muscles of facial expression” and is associated with the scalp (see Fig. 8.53). It consists of a frontal belly anteriorly and an occipital belly posteriorly. An aponeurotic tendon connects the two:

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The frontal belly covers the forehead and is attached to the skin of the eyebrows.

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The occipital belly arises from the posterior aspect of the skull and is smaller than the frontal belly.

The occipitofrontalis muscles move the scalp and wrinkle the forehead.

Question 64

Describe the branches of the maxillary artery that supply the face

Answer 64

The infra-orbital artery enters the face through the infra-orbital foramen and supplies the lower eyelid, upper lip, and the area between these structures.

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The buccal artery enters the face on the superficial surface of the buccinator muscle and supplies structures in this area.

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The mental artery enters the face through the mental foramen and supplies the chin

Question 65

What is Bell’s Palsy and how may it present in a patient?

Answer 65

Facial nerve palsy

Inability to contract muscles of facial expression and altered taste

Question 66

Summarise Bell’s palsy

Answer 66

The complexity of the facial nerve [VII] is demonstrated by the different pathological processes and sites at which these processes occur.

The facial nerve [VII] is formed from the nuclei within the brainstem emerging at the junction of the pons and the medulla. It enters the internal acoustic meatus, passes to the geniculate ganglion (which gives rise to further branches), and emerges from the skull base after a complex course within the temporal bone, leaving through the stylomastoid foramen. It enters the parotid gland and gives rise to five terminal groups of branches that supply muscles in the face and a number of additional branches that supply deeper or more posterior muscles. A series of lesions may affect the nerve along its course, and it is possible, with good clinical expertise, to determine the exact site of the lesion in relation to the course of the nerve.

Question 67

Describe the impact of central lesions

Answer 67

A primary brainstem lesion affecting the motor nucleus of the facial nerve [VII] would lead to ipsilateral (same side) weakness of the whole face. However, because the upper part of the nucleus receives motor input from the left and right cerebral hemispheres a lesion occurring above the nucleus leads to contralateral lower facial weakness. In this example, motor innervation to the upper face is spared because the upper part of the nucleus receives input from both hemispheres. Preservation and loss of the special functions are determined by the extent of the lesion.

Question 68

Describe the impact of lesions at and around the genticulate ganglion

Answer 68

Typically lesions at and around the geniculate ganglion are accompanied by loss of motor function on the whole of the ipsilateral (same) side of the face. Taste to the anterior two-thirds of the tongue, lacrimation, and some salivation also are likely to be affected because the lesion is proximal to the greater petrosal and chorda tympani branches of the nerve.

Question 69

Describe the impact of lesions at and around the stylomastoid foramen

Answer 69

Lesions at and around the stylomastoid foramen are the commonest abnormality of the facial nerve [VII] and usually result from a viral inflammation of the nerve within the bony canal before exiting through the stylomastoid foramen. Typically the patient has an ipsilateral loss of motor function of the whole side of the face. Not only does this produce an unusual appearance, but it also complicates chewing of food. Lacrimation and taste may not be affected if the lesion remains distal to the greater petrosal and chorda tympani branches that originate deep in the temporal bone

Question 70

Describe trigeminal neuralgia

Answer 70

Trigeminal neuralgia (tic douloureux) is a complex sensory disorder of the sensory root of the trigeminal nerve. Typically the pain is in the region of the mandibular [V3] and maxillary [V2] nerves, and is usually of sudden onset, is excruciating in nature, and may be triggered by touching a sensitive region of skin.

The etiology of trigeminal neuralgia is unknown, although anomalous blood vessels lying adjacent to the sensory route of the maxillary [V2] and mandibular [V3] nerves may be involved.

If symptoms persist and are unresponsive to medical care, surgical exploration of the trigeminal nerve (which is not without risk) may be necessary to remove any aberrant vessels.