Parapharyngeal & Masticator Spaces

Nicholas A. Koontz, MD Director of Fellowship Programs

Dean D.T. Maglinte Scholar in Radiology Education Assistant Professor of Radiology

Department of Radiology and Imaging Sciences, Indiana University School of Medicine

Disclosures

•  None

Introduction

•  Parapharyngeal space (PS) & Masticator space (MS) •  Two really important spaces of the neck •  Close proximity •  Very different contents •  Thus, each space has a unique set of pathology

•  Identifying space of origin of a lesion will immediately narrow your differential diagnosis

Parapharyngeal Space Contents

•  Fat •  Minor salivary gland rests •  Internal maxillary artery •  Ascending pharyngeal

artery •  Pterygoid venous plesxus

(minimal portion)

•  Predicts space of origin of suprahyoid neck mass •  Pharyngeal mucosal space mass

•  Displaces PPS posterolateral

•  Masticator space mass •  Displaces PPS posteromedial

•  Carotid space mass •  Displaces PPS anterolateral

•  Parotid space mass •  Displaces PPS anteromedial

Parapharyngeal Space Displacement Parapharyngeal Space Displacement

LeftPPS

Masticator Space

Parotid Space

Pharyngeal Mucosal

Space

Carotid Space

Masticator Space Contents

•  Mandible •  Ramus, posterior body,

condyle, and temporomandibular joint

•  Muscles of mastication •  Temporalis, masseter,

medial pterygoid, and lateral pterygoid

•  CN V3 and branches •  Pterygoid venous plexus

Parapharyngeal Space Pathology

•  Primary lesions •  Minor salivary gland tumor •  Lipoma •  Nerve sheath tumor •  Vascular malformation •  2nd branchial cleft cyst

•  Secondary lesions •  Squamous cell carcinoma (palatine tonsil) •  Nasopharyngeal carcinoma •  Abscess

Masticator Space Pathology

•  Mandibular disease •  Odontogenic infection •  Osteo(radio)necrosis •  Pigmented villonodular synovitis

•  Tumors •  Sarcomas •  Schwannoma •  Perineural tumor spread •  Pseudolesions

Masticator Space Pathology

•  Mandibular disease •  Odontogenic infection •  Osteo(radio)necrosis •  Pigmented villonodular synovitis

•  Tumors •  Sarcomas •  Schwannoma •  Perineural tumor spread •  Pseudolesions

Odontogenic Infection

•  Edema, phlegmon, cellulitis, and myositis within masticator space •  +/- Abscess

•  Due to infected molar or prior dental procedure

•  Pain, trismus, fever •  Concurrent mandibular

osteomyelitis

Masticator Space Abscess

•  Rim-enhancing fluid collection

•  Osteomyelitis ! cortical dehiscence ! pus ruptures into the masticator space

•  Associated myositis, parotitis

•  Extract diseased teeth, aggressive antibiotics, +/- drain

Axial CECT

Osteo(radio)necrosis

•  Necrosis of the mandible associated with bisphosphonate use or radiotherapy

•  Non-healing, exposed bone •  +/- Fracture

•  Mixed sclerosis and lysis at extraction site

•  Low signal intensity sequestra

Axial NECT Coronal NECT

Pigmented Villonodular Synovitis (PVNS)

•  Benign, locally destructive disease of synovial proliferation

•  Mainly large joints •  Uncommonly TMJ

•  T1/T2 dark, blooming artifact (hemosiderin), enhancing, FDG avid •  Mimics giant cell tumor,

amyloid, gout, & malignancy

Axial CECT Axial T2WI FS Axial T1WI C+ FS

Masticator Space Pathology

•  Mandibular disease •  Odontogenic infection •  Osteo(radio)necrosis •  Pigmented villonodular synovitis

•  Tumors •  Sarcomas •  Schwannoma •  Perineural tumor spread •  Pseudolesions

Masticator Space Pathology

•  Mandibular disease •  Odontogenic infection •  Osteo(radio)necrosis •  Pigmented villonodular synovitis

•  Tumors •  Sarcomas •  Schwannoma •  Perineural tumor spread •  Pseudolesions

Masticator Space Sarcomas

•  Masticator space harbors bone, joint, fat, and vascular components

•  Many sarcomas may arise: •  Rhabdomyosarcoma •  Osteosarcoma •  Chondrosarcoma •  Fibrosarcoma •  Lymphangiosarcoma •  Ewing sarcoma…and more!

Masticator Space Sarcomas

•  Imaging often non-specific •  Invasive, ill-defined mass •  Aggressive bone destruction •  Ugly periosteal reaction

•  Matrix mineralization may help differentiate •  Chondroid matrix

•  Rings & arcs, T2 bright •  Osteoid matrix

•  Cloudlike, amorphous calcs

Axial CECT Images courtesy of Rick Wiggins, III, MD

Schwannoma

•  Relatively uncommon site of a common mass

•  Identical appearance of schwannomas in other places

•  Extends along CN V3 and its branches

•  Typically sporadic •  If multiple, think NF2 or

Schwannomatosis

Axial NECT Axial T1WI C+ FS

Perineural Tumor Spread

•  CN V3 and branches •  Oral or mandibular SCCa •  Lip SCCa •  Facial melanoma or SCCa

•  Don’t forget spread along the auriculotemporal nerve! •  Parotid malignancy

Axial T1WI C+ FS

CN V3 Motor Denervation

•  Most commonly due to surgical trauma

•  Tumors along CN V3 •  Acute

•  Enlarged, edematous, enhancing muscles of mastication

•  Chronic •  Marked atrophy Axial T2WI FS Axial T1WI C+ FS Axial T1WI

Asymmetric Pterygoid Venous Plexus

•  Unilateral prominence of pterygoid venous plexus

•  Usually incidental finding •  Incredibly common •  Pitfall

•  Can be secondary to a carotid cavernous fistula

•  MUST have the appropriate clinical context

Axial CECT

Summary

•  Overview of parapharyngeal and masticator spaces •  Anatomic contents •  Common pathologies •  Mimics •  Don’t miss lesions

•  Understanding the contents of each space helps to generate a succinct, appropriate differential diagnosis

•  Recognizing displacement of parapharyngeal spaces helps to identify space of origin of suprahyoid neck mass

Delicate Arch Arches National Park, UT

Email: nakoontz@iupui.edu Twitter: @nakoontz

Parapharyngeal & Masticator Spaces

Nicholas A. Koontz, MD Director of Fellowship Programs

Dean D.T. Maglinte Scholar in Radiology Education Assistant Professor of Radiology

Department of Radiology and Imaging Sciences, Indiana University School of Medicine