Head And Neck 03 (Masticator Space)

Front 1

What is the central structure in the masticator space?

Back 1

The mandibular ramus.

Front 2

Where is the masseter located?

Back 2

Lateral to the mandibular ramus, at the inferior aspect of the masticator space.

Front 3

Where are the pterygoid muscles located?

Back 3

Medial to the mandibular ramus.

Front 4

What pterygoid muscles are there?

Back 4

Medial and lateral

Front 5

How does the medial pterygoid appear?

Back 5

It is elongated, and is thickest at the inferior aspect of the masticator space.

Front 6

How does the lateral pterygoid appear?

Back 6

It is rounded and located in the superior aspect of the masticator space.

Front 7

What is the other muscle of mastication?

Back 7

The temporalis

Front 8

What space is it located in?

Back 8

The suprazygomatic portion of the masticator space.

Front 9

What other bone is part of the masticator space?

Back 9

The zygomatic arch.

Front 10

How far up does the suprazygomatic portion of the masticator space extend?

Back 10

Way up the temporal bone to the origin of the temporalis m. on the floor of the temporal fossa.

Front 11

What is the fascial anatomy of the masticator space?

Back 11

The superficial layer of deep cervical fascia splits along the inferior aspect of the mandible, and creates a sling which encloses the masticator space. (Fig 3-2)

Front 12

What is the deal with the lateral slip of superficial layer of deep cervical fascia?

Back 12

After splitting from the medial layer on the bottom of the mandible,it travels up superficial to the masseter, and inserts on the zygomatic arch. Then continues upward on the surface of the temporalis m.

Front 13

What is the deal with the medial slip of superficial layer of deep cervical fascia?

Back 13

It travels up deep to the medial pterygoid muscle.

Front 14

Where does the medial slip insert?

Back 14

On the skull base, just MEDIAL to the foramen ovale (fig 3-2).

Front 15

What is the significance of this relationship?

Back 15

Lesions traveling cephalad within the masticator space will enter the skull base through the foramen ovale.

Front 16

Contents of masticator space?

Back 16

Muscles of mastication
Masticator nerve (V3 motor branch)
Inferior alveolar nerve (V3 sensory)
Inferior alveolar vein/artery
Ramus and posterior body of the mandible.

Front 17

Which is the largest muscle of mastication?

Back 17

Masseter

Front 18

What is another way tumor or infection in the MS can access the intracranial compartment?

Back 18

Along the muscles of mastication.

Front 19

What is the main clinical symptom resulting from tumor or infection involving the masticator space?

Back 19

Trismus

Front 20

What is trismus?

Back 20

Difficulty opening the mouth secondary to spasm of muscle(s) of mastication.

Front 21

Masseter origin?

Back 21

Zygomatic arch

Front 22

Masseter insertion?

Back 22

Lateral surface of manbible (ramus, angle, posterior body)

Front 23

Lateral pterygoid origin?

Back 23

There are 2 heads of the lateral pterygoid muscle. One originates on skull base contained by the masticator space. The other on the lateral pterygoid plate.

Front 24

Lateral pterygoid insertion?

Back 24

Medial aspect of mandibular condyle.

Front 25

Medial pterygoid origin?

Back 25

Fossa between medial and lateral pterygoid plates.

Front 26

Medial pterygoid insertion?

Back 26

Medial aspect of mandibular angle.

Front 27

How many nerves enter the masticator space?

Back 27

2

Front 28

What nerves are they.

Back 28

The senory and motor branches of V3.

Front 29

What is the motor branch of V3 called?

Back 29

Masticator nerve

Front 30

What is the sensory branch of V3 called>

Back 30

Inferior alveolar nerve.

Front 31

What is the significance of this?

Back 31

The inferior alveolar nerve ends up in the inferior alveolar foramen in the mandible, where it innervates the mandibular teeth. The masticator nerve supplies the muscles of mastication with its terminal branches.

If there is a tumor in a region supplied, there can be perineural spread.

Front 32

Where does the spread occur?

Back 32

Back up the nerves, superiorly through the MS, passing through the foramen ovale. Spread can progress further into Meckel's cave, and then even further into the root entry zone of CN V at the lateral pons.

Front 33

What is a syndrome you should be aware of related to perineural spread along V3?

Back 33

Masticator muscle atrophy, mandibular dental pain, and serous otitis media.

Front 34

Why is there serous accumulation in the middle ear?

Back 34

The motor division of V3 also supplies the tensor veli palatini, resulting in dysfynction of the eustachian tube.

Front 35

What is the most common source of abscess in the masticator space?

Back 35

The mandibular ramus, angle, and posterior body form the central strut of the MS. The posterior body contains teeth, and odontogenic infection is the most common reason for masticator space abscess.

Front 36

What is the relationship of the parotid duct to the MS?

Back 36

It passes just superficial to it, coursing over the lateral surface of the masseter.

Front 37

What is the significance of this?

Back 37

Lesions of the MS can result in involvement of the parotid duct by direct lateral invasion.


Also, lesions of the parotid duct may seem to be within the masticator space.

Front 38

What must be recognized about the temporal fossa?

Back 38

It is actually the superior extension of the masticator space (SZMS)

Front 39

What is the significance of this?

Back 39

Lesions occurring in the infrazygomatic portion of the masticator space will commonly involve the suprazygomatic portion (temporal fossa) as well.


Therefore, careful examination of the suprazygomatic portion of the MS is the rule anytime a lesion of the infrazygomatic MS is found.

Front 40

What is the infratemporal fossa?

Back 40

The area between the pterygopalatine fossa (medially) and the zygomatic arch (laterally).

Front 41

What is this region actually?

Back 41

It is just the nasopharyngeal portion of the masticator space. There is no fascia separating it from any other part of the MS.

Front 42

What is the more anatomically correct name for this region?

Back 42

Nasopharyngeal masticator space

Front 43

What is the anterior boundary of the MS?

Back 43

Buccal space

Front 44

What constitutes the posteromedial border of the masticator space?

Back 44

Parapharyngeal space.

Front 45

What constitutes the posterior border of the masticator space?

Back 45

Parotid space.

Front 46

What are the boundaries of the buccal space?

Back 46

No fascial boundaries

Front 47

What is its relationship to infection or malignancy in the MS?

Back 47

Disease often spreads to it

Front 48

What are contents of buccal space?

Back 48

1) Buccal fat pad


2) Facial artery and vein


3) Distal portion of parotid duct


4) Buccinator muscle

Front 49

What is the most important information to be gleaned from a CT or MRI examination of disease in the buccal space?

Back 49

Its relationship to the distal parotid duct

Front 50

When is a mass radiographically in the MS?

Back 50

Center of mss is anterior to the parapharyngeal space, within muscles of mastication or the mandible.


The mass invades the PPS from A to P, posteriorly displacing the PPS fat.

Front 51

When are these rules most helpful?

Back 51

When mass is large. When small, easy to spot its location within the muscles or the bone.

Front 52

After answering the question of what space the lesion is in, and coming up with answer MS, what is the next step?

Back 52

Is there perineural spread along V3?

Front 53

What patients need evaluation for perineural spread?

Back 53

Any non-infectious mass in the masticator space

Front 54

What are the ways tumor of the MS invades the skull base?

Back 54

Within muscles of mastication


Along V3 (gains access to main trunk of V3 via masticator or inferior alveolar nerve)

Front 55

What is most common clinical symptom related to perineural spread along V3?

Back 55

Pain or numbness along ipsilaeral chin and jaw

Front 56

What are the early imaging features of perineural spread during its early phases?

Back 56

Normal

Front 57

What about when spread is macroscopic?

Back 57

Continuous or discontinuous perineural tumor.

Front 58

What is important about this?

Back 58

Must evaluate the ENTIRE V3, from mental foramen, through mandible, back out the mandibular foramen, as it ascends through the masticator space, through the foramen ovale, into Meckel's cave, and finally into its preganglionic segment to the dorsal entry zone at the lateral pons. All of this must be imaged every time, or else there will be areas that are improperly resected or irradiated, leading to "early recurrence" along V3.

Front 59

How is perineural spread along V3 evaluated?

Back 59

MRI

Front 60

Why not CT?

Back 60

Does not depict soft tissue differences well.

Lack of destruction at foramen ovale does not mean there is no perineural spread.

CT can't do jack **** for evaluating the intracranial portion of V3.

Front 61

What is the third question that must be answered

Back 61

What is the status of the skull base, and suprazygomatic masticator space.

Front 62

What patients need evaluation of the skull base and suprazygomatic MS?

Back 62

Any patient with infectious or neoplastic lesion

Front 63

How does infection spread within the MS?

Back 63

Superiorly (path of least resistance)

Front 64

What can happen with infection in the MS?

Back 64

Skull base osteomyelitis (pterygoid wing area)

Front 65

How does malignancy spread usually?

Back 65

Also cephalad. Involvement of skull base usually makes tumor unresectable, and radiation ports have to include this region.

Front 66

What is the 4th question to be answered (1--where is lesion, 2--is there perineural spread, 3--what is status of skull base and SZMS)

Back 66

What is status of the mandible?

Front 67

Why is mandibular involvement important in infection?

Back 67

Because a longer course of Abx and subperiosteal surgical drainage is necessary in mandibular osteomyelitis.

Front 68

Why is mandibular involement important in the case of tumor.

Back 68

Malignancy involving the mandible commonly results in perineural spread (distally, along the inferior alveolar canal, and/or proximally)

Front 69

What is the 5th question that must be answered in the case of a lesion of the MS?

Back 69

Is the parotid duct involved?

Front 70

Why is this question important in infection involving the MS?

Back 70

A calculus of the parotid duct may be causal. If the MS infection is drained without treating the cause (possibly a tiny stone of the parotid), then effect of treatment will not be lasting.

Front 71

In case of suspected infection of the MS, what modality should be used?

Back 71

CT

Front 72

Why is CT better?

Back 72

Ease of identifying sialolith.


Ease of diagnosis of mandibular osteomyelitis.

Front 73

When a lesion (mass) of the MS is encountered, what are the 3 technical questions that must be asked after Q#1 (what space is the lesion in)?

Back 73

1) Is the entire course of CN V3 imaged?


2) Is the entire MS imaged, including the suprazygomatic masticator space?


3) Is the lesion a masticator space pseudomass?

Front 74

What are the pseudomasses of the masticator space?

Back 74

1) Asymmetric accessory parotid gland.


2) Benign masseteric hypertrophy


3) CN V3 motor atrophy

Front 75

What is the incidence of accessory parotid gland?

Back 75

21%

Front 76

Where is the accessory parotid gland?

Back 76

Just lateral to the masseter, superficial to the masticator space.

Front 77

What does imaging reveal?

Back 77

Salivary gland tissue on the surface of the masseter muscle. May appear prominent.

Front 78

How is the diagnosis made?

Back 78

The tissue has the same density or signal intensity as the adjacent parotid gland.

Front 79

What is benign masseteric hypertrophy?

Back 79

Hypertrophy of masseters.

Front 80

What is the cause?

Back 80

Usually bruxism, thus usually bilateral process.

Front 81

When is diagnosis pathognomonic?

Back 81

Bilateral enlargement of the masseters, with discrete outer margins.

Front 82

What makes diagnosis even more confident?

Back 82

Concommitent hypertrophy of the pterygoids and temporalis.

Front 83

When is diagnosis slightly less confident?

Back 83

When hypertrophy is unilateral, but appearance is otherwise the same.

Front 84

When should one be concerned about malignancy?

Back 84

When there is unilateral masseteric mass, and the margins are not discrete.

Front 85

What is crainial nerve V3 motor atrophy?

Back 85

Occurs when there is compression (i.e. by tumor) or surgical cutting of V3.

Front 86

What does V3 innervate?

Back 86

Muscles of mastication


Mylohyoid


Anterior belly of digastric


Tensor tympani and palatini.

Front 87

What happens when V3 is disrupted.

Back 87

Atrophy and fatty replacement of the innervated muscles occurs within 6 weeks.

Front 88

What is the imaging issue?

Back 88

To not diagnose the normal contralateral masticator space as tumor.

Front 89

Why is there a limited variety of pathology in the masticator space?

Back 89

Because limited variety of normal tissues there:

Muscle


Mandible


V3

Front 90

What is the most common pathology encountered in the MS?

Back 90

Odontogenic abscess

Front 91

What is clinical presentation in odontogenic abscess?

Back 91

Trismus. Also fever, swelling, etc.

Front 92

What are the most common causes of odontogenic abscess.

Back 92

There are two:

Poor dental hygeine


Recent dental manipulation

Front 93

What is seen in odontogenic abscess?

Back 93

Fluid collection within the masticator space, surrounded by swollen tissue.

Front 94

What modatlity is best for suspected odontogenic abscess?

Back 94

CT. Better defines osteomyelitis and calculus disease.

Front 95

What should be examined in case of swelling after ORIF for facial fractures requiring wires around zygomatic arch, before or after wire removal?

Back 95

The suprazygomatic masticator space.

Front 96

What are the questions that must be answered during imaging for masticator space abscess?

Back 96

1) In skull base or mandibular osteomyelitis present.


2) Is there evidence for parotid calculus disease?


3) Are there any other deep face spaces involved?


4) Is the suprazygomatic masticator space involved?

Front 97

Why does infection tend to spread supriorly (towards skull base and SZMS) in masticator space infection?

Back 97

Because of the firm attachment of the superficial layer of deep cervical fascia to the periosteum of the inferior mandible.

Front 98

How does odontogenic abscess form?

Back 98

1) Infection of tooth

2) Results in infection of tooth socket

3) Infected socket fistulizes into masticator space.

Front 99

What does masticator space abscess do to nearby structures?

Back 99

See bowing of soft palate and uvula medially, and the masseter muscle and cheek laterally.

Front 100

What kind of benign tumors occur in the masticator space?

Back 100

None really

Front 101

What class of malignant tumors is most common in masticator space?

Back 101

Sarcomas

Front 102

What are the tissue types that generate sarcomas in the masticator space, and the related tumors?

Back 102

Muscle--sott tissue sarcomas


Mandibular bone--Chondrosarcoma and osteosarcoma

Front 103

A tumor seen in the region of the TMJ?

Back 103

Chondrosarcoma


--Arises there (where there is a cartilage-bearing joint)

Front 104

Where in the mandible does osteosarcoma arise?

Back 104

Anywhere in mandible

Front 105

What distinguishes osteosarcoma and chondrosarcoma from other tumors in the MS?

Back 105

Only the matrix. Usually some degree of mandibular destruction. But may just appear as infiltrating mass indistinguishable from other tumors, and destruction of bone does not imply that the tumor arises from bone.

Front 106

What is tumor of V3 that occurs in the MS?

Back 106

Malignant schwannoma

Front 107

What are symptoms of malignant schwannoma?

Back 107

Same as perineural spread of tumor along the nerve? Pain and numbness along distribution of the inferior alveolar nerve.

Front 108

What is distribution of inferior alveolar nerve?

Back 108

Chin and jaw

Front 109

What parts of V3 can malignant schwannoma arise from?

Back 109

Both masticator and inferior alveolar nerves

Front 110

What is imaging appearance of malignant schwannoma?

Back 110

Tubular mass along course of V3, usually involving inferior alveolar nerve in the inf alv canal.

Front 111

What must be done in case of suspected malignant schwannoma?

Back 111

Image full extent of V3, all the way through foramen ovale, gasserian gangion in Meckels cave, to main CN V in lateral pons.

Front 112

Where does tumor commonly spread to?

Back 112

Gasserian gangion

Front 113

What is another malignancy of the masticator space?

Back 113

NHL

Front 114

What is unique about the appearance of NHL in the masticator space?

Back 114

Nothing. Just appears as infiltrating lesion.

Front 115

How can the diagnosis of NHL involving the MS be suggested on imaging?

Back 115

If there is associated:

1) Nodal disease


2) Extranodal lymphatic disease


3) Extranodal extralymphatic disease

Front 116

What are examples of extranodal lymphatic involvement?

Back 116

Waldeyer's ring

Pharynx

(although both of these could also represent SCCa)

Front 117

Wat are examples of extranodal extralymphatic involvement?

Back 117

Sinus


Nose


Orbit

Front 118

What is another tumor type that can occur in the masticator space?

Back 118

SCCa

Front 119

When should SCCa be suspected in the masticator space?

Back 119

Anytime there is history of oropharyngeal or oral cavity SCCa, even if primary lesion has already been treated.

SCCa does not occur primarily in the MS, as there is no squamous tissue normally there.

Front 120

How does it get there?

Back 120

Either by direct extension or perineural spread.

Front 121

How does it get there in cases of direct extension?

Back 121

Either via faucial tonsil or retromolar trigone.

Front 122

What is clincal picture usually?

Back 122

Usually known history of SCCa, usually already treated, presenting with Sx related to masticator space

Front 123

What are those symptoms?

Back 123

Trismus


Pain/Numbness in inferior alvelolar nerve dist'n.