Spazio Parafaringeo mdOTO_08

Otolaryngol Clin N Am

Imaging of the Parapharyngeal Space

Hilda E. Stambuk, MDa,b,*, Snehal G. Patel, MDb,c

aDepartment of Radiology, Memorial Sloan-Kettering Cancer Center,

1275 York Avenue, New York, NY 10021, USAbWeill Cornell Medical College, New York, NY, USA

cDepartment of Surgery, Memorial Sloan-Kettering Cancer Center,

1275 York Avenue, New York, NY 10021, USA

The parapharyngeal space (PPS) is a fascial space of the suprahyoid neckthat largely contains fat and is surrounded by several other important fascialspaces. Surgeons may be familiar with the older nomenclature of the ‘‘pre-styloid’’ and ‘‘post-styloid’’ parapharyngeal spaces. The post-styloid com-partment of the PPS is now designated as the carotid space, whereas theprestyloid compartment is now considered the true PPS. The presence offat in the PPS allows the radiologist to identify displacement patterns ofthe PPS and to use a logical algorithm in identifying the anatomic originof tumors in this region. A clear understanding of spatial anatomy is essen-tial for accurate diagnosis and appropriate treatment of pathology arisingfrom this region. This article covers the basic anatomy of the PPS andsurrounding spaces to describe the spatial approach to the differential diag-nosis of lesions in this area. Other spaces in the suprahyoid neck, includingthe retropharyngeal space, the perivertebral space, and the posterior cervicalspace, are not discussed. Boxes and figures are used to list and illustratesome common conditions in the differential diagnosis pertaining to eachspace but the reader is referred elsewhere for a more detailed discussionof pathology [1,2].

41 (2008) 77–101

Spatial approach to differential diagnosis

The PPS is an inverted cone-shaped space that extends from the skullbase to the level of the hyoid bone on either side of the pharynx (Fig. 1).

* Corresponding author. Department of Radiology C-278, Memorial Sloan-Kettering

Cancer Center, 1275 York Avenue, New York, NY 10021.

E-mail address: [email protected] (H.E. Stambuk).

0030-6665/08/$ - see front matter � 2008 Elsevier Inc. All rights reserved.

doi:10.1016/j.otc.2007.10.012 oto.theclinics.com

mailto:[email protected]

http://www.oto.theclinics.com

Fig. 1. The PPS is an inverted cone-shaped space that extends from the skull base to the hyoid

bone. (Courtesy of Memorial Sloan-Kettering Cancer Center, New York, NY; with permission.

Copyright � 2007 MSKCC.)

78 STAMBUK & PATEL

The anatomic boundaries of the PPS are listed in Box 1. The PPS is sur-rounded by other spaces that are bound by the superficial (investing), middle(buccopharyngeal), and deep (prevertebral) layers of the deep cervicalfascia. The reader is referred to other sources for detailed anatomy of thefacial layers [3,4].

An understanding of the fascial anatomy and spaces of the neck allowsa logical approach to differential diagnosis of lesions arising from the PPSor surrounding spaces. The carotid space is actually the designation givento the previously named post-styloid space and is separated from the presty-loid space, or PPS, by the tensor-vascular-styloid fascia overlying the tensorveli palatini muscle (Fig. 2). Unlike squamous cell carcinoma (SCC) that islocally infiltrative and tends to spread across fascial boundaries in the neck,other tumors tend to be limited in local extent by fascial compartments.

The PPS is centrally located in relation to surrounding spaces that areenclosed by the layers of the deep cervical fascia (Fig. 3). The PPS is a rela-tively rare site of primary pathology but its significance is that it predomi-nantly contains fat and therefore has a distinct appearance on CT andMRI. The displacement pattern of the PPS fat is an excellent indicator ofthe possible space of origin of a lesion (Fig. 4) and helps limit the differential

Box 1. Anatomic boundaries of the parapharyngeal space

SuperiorTemporal bone lateral to the attachment of the pharyngobasilar

fascia and medial to the foramen ovale and foramen spinosum.Note that none of the skull base foramina are included withinthe boundaries of the PPS.

InferiorThe greater cornu of the hyoid bone and the posterior belly

of the digastric muscle. The PPS blends into the posterioraspect of the submandibular space at this level.

MedialThe buccopharyngeal fascia that covers the pharyngobasilar

fascia and constrictor muscles.

LateralThe fascia overlying the pterygoid muscles and the

sphenomandibular ligament. The parotid space communicateswith the PPS laterally through the stylomandibular tunnel.This tunnel is enclosed by the stylomandibular ligamentwhich extends from the styloid process to the angle of themandible, the ascending ramus, and the skull base.

AnteriorThe pterygomandibular raphe that extends from the hamulus

of the medial pterygoid plate to the posterior aspect of themylohyoid line on the lingual surface of the mandible.

PosteriorThe tensor-vascular-styloid fascia overlying the tensor veli

palatini muscle from the medial pterygoid plate to the styloidprocess.

79IMAGING OF THE PARAPHARYNGEAL SPACE

diagnosis based on the contents of that space. For example, a tumor arisingfrom the deep lobe of the parotid gland grows medially and thus displacesthe adjacent PPS fat anteromedially (see Fig. 4C). The displacement pat-terns typical of each space along with some common lesions are describedunder separate sections.

The pharyngeal mucosal space

The pharyngeal mucosal space (PMS) is the nasopharyngeal and oropha-ryngeal mucosal lining on the luminal side of the middle layer of the deep

Fig. 2. The prestyloid parapharyngeal space (now designated PPS) is separated from the post-

styloid parapharyngeal space (now designated CS) by the tensor-vascular-styloid fascia (white

line) that overlies the tensor veli palatini muscle and extends medially toward the pharynx

from the styloid process (S). (Courtesy of Memorial Sloan-Kettering Cancer Center, New

York, NY; with permission. Copyright � 2007 MSKCC.)

Fig. 3. The PPS contains fat and is surrounded by several fascial-bound spaces. (Courtesy of

Memorial Sloan-Kettering Cancer Center, New York, NY; with permission. Copyright �2007 MSKCC.)

80 STAMBUK & PATEL

Fig. 4. Displacement patterns of PPS fat from tumors of the (A) pharyngeal mucosal space

(PMS), (B) masticator space (MS), (C) parotid space (PS), (D) carotid space (CS). (Courtesy

of Memorial Sloan-Kettering Cancer Center, New York, NY; with permission. Copyright �2007 MSKCC.)


cervical fascia. It is lined on the outside by the pharyngeal constrictormuscles and on the inside by squamous mucosa. The space contains minorsalivary glands and lymphoid tissue of the Waldeyer ring. Since the PMS islined by squamous mucosa, squamous cell carcinoma (SCC) is the mostcommon tumor but other tumors, such as minor salivary gland tumors,lymphoma (Fig. 5), and sarcoma, can also occur.

Fig. 5. (A) Precontrast T1-weighted magnetic resonance image (T1WI) shows lymphoma (M)

involving the left PPS. The lesion presents as a homogeneous lesion that is isointense to muscle.

The lesion arises from the PMS as evidenced by the absence of a fat plane between the lesion

and the PMS. (B) The lesion is hyperintense on T2-weighted magnetic resonance image

(T2WI) making it easier to delineate from adjacent normal soft tissue.

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Tumors of the PMS are based on the mucosa or wall of the space with noclear delineating plane between it and the tumor. They may infiltrate thePPS diffusely and replace it (Fig. 6). Alternatively, with benign or lessaggressive tumors the PPS fat is displaced posteriorly and laterally (Fig. 7).

The masticator space

The masticator space (MS) is enclosed by the split layers of the superficiallayer of the deep cervical fascia and extends from the skull base to the

Fig. 6. SCC of the left base of tongue (T) that extends into and infiltrates the adjacent PPS fat.

SCC does not respect fascial boundaries in the neck and infiltrates across compartments.

Fig. 7. (A) Displacement of PPS fat by a tumor of the PMS. (Courtesy of Memorial Sloan-Ket-

tering Cancer Center, New York, NY; with permission. Copyright � 2007 MSKCC.) (B) Pre-

contrast axial T1WI of a patient who has a tumor (T) of the right tonsil that displaces the PPS

fat posterolaterally (arrow).


inferior border of the mandible. It contains the ascending ramus, the poste-rior body of the mandible, and the muscles of mastication (masseter, medialand lateral pterygoids, and temporalis), the motor and sensory branches ofmandibular branch of the trigeminal nerve (V3), and the inferior alveolarartery and vein. The MS extends superolaterally along the lateral surfaceof the temporalis muscle, divided by the zygoma into supra and infrazygo-matic portions (Fig. 8). Anteriorly it is continuous with the buccal spacewhere there is no discrete fascial boundary so that disease processes havefree access from one space to the other.

The PPS is located posteromedial to the MS so that lesions of the MStend to displace the PPS fat posteromedially (Fig. 9). Infectious or in-flammatory lesions are the most common lesions arising within the MS(Box 2). If imaging is required for evaluation of infectious or inflammatorylesions of the MS, CT should be the initial modality of choice becauseinflammation, abscess, dental infection, and osteomyelitis are more easilyidentified on CT compared with MRI.

Malignant tumors of adjoining mucosal sites, such as the oral cavity,oropharynx, or maxillary sinus, not infrequently invade the muscles of theMS causing trismus. Lymphoma is an exception to this rule since trismusmay not occur despite gross infiltration of the MS (Fig. 10). Radiologic im-aging may be able to identify early infiltration of the MS before the onset oftrismus. Tumor invasion of the MS places the branches of V3 at risk forperineural spread, which is a particular feature with some tumors, such asadenoid cystic carcinoma. Perineural spread can occur contiguous to theprimary tumor mass or as skip areas and can occur in retrograde and

Fig. 8. Coronal T1WI demonstrates the normal anatomy of the MS. Note that the space

extends from the superior attachment of temporalis muscle (upper white arrow) to the inferior

border of the mandible (lower white arrow). The MS is divided into suprazygomatic and infra-

zygomatic compartments by the zygoma (white arrowhead). The contents of the MS include the

mandible (*) which is flanked on either side by the muscles of mastication: T, temporalis; M,

masseter; LP, lateral pterygoid muscle; MP, medial pterygoid muscle.

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antegrade directions along the nerve at risk. Radiologic findings with earlyperineural spread may be minimal, and conclusive diagnosis requires bothabnormal enlargement and enhancement of the nerve (Fig. 11). Perineuralspread may not always be readily apparent and it is helpful for the radiolo-gist to look for certain indirect signs, such as an enlarged foramen ovale(Fig. 12), abnormal soft tissue in the Meckel’s cave, and denervationatrophy of the masticatory muscles. MRI is superior to CT for the evalua-tion of perineural spread (see article by Drs. Ahmad and Branstetter, else-where in this issue).

Primary tumors of the MS are rare in adults but a solid tumor in the MSin a child should prompt the diagnosis of rhabdomyosarcoma until provenotherwise. Although these tumors can be restricted to the MS, extensionacross fascial compartments can occur with destruction of the mandibleor erosion of the skull base (Fig. 13).

The parotid space

The superficial layer of the deep cervical fascia splits to enclose theparotid space (PS), which is located posterolateral to the PPS. In additionto the parotid gland, the PS contains the facial nerve that divides the parotidinto a superficial and deep lobe. Since the parotid gland is encapsulated late

Fig. 9. (A) Lesions originating in the MS tend to displace the fat of the PPS in a posteromedial

direction. (Courtesy of Memorial Sloan-Kettering Cancer Center, New York, NY; with permis-

sion. Copyright � 2007 MSKCC.) (B) Axial precontrast CT scan shows a soft tissue mass orig-

inating from the ascending ramus of the left mandible with extraosseous extension into the

pterygoid muscles. The fat in the left PPS is displaced posteromedially by the MS mass. (C)

Bone window of axial CT scan shows sunburst-like periosteal new bone formation which is clas-

sically found in osteosarcoma.


in embryonic development, it contains intraparenchymal lymph nodes.Common lesions of the PS are listed in Box 3.

As might be expected, the most common lesions in the PS arise from theparotid gland. Since the majority of the parotid gland parenchyma is locatedsuperficial to the plane of the facial nerve, lesions arise more commonlyfrom the superficial lobe of the parotid compared with the deep lobe. This

Box 2. Common lesions of the masticator space

Inflammatory/infectiousOdontogenic infection: cellulitis, abscessMyositis

Congenital/developmentalHemangiomaVenolymphatic malformation

NeoplasticBenign tumor of muscle or boneRhabdomyosarcomaOsteosarcomaNerve sheath tumorNon-Hodgkin lymphomaDeep extension of mucosal carcinomaMetastatic disease

86 STAMBUK & PATEL

distinction is helpful in surgical planning, but imaging is generally not ableto delineate the normal facial nerve. However, the plane of the facial nervecan be estimated by identifying the retromandibular vein on imaging sincethe nerve lies lateral to the vein after exiting the stylomastoid foramen.

Fig. 10. (A) Infiltrative lesion of the right MS that had infiltrated the pterygoid muscles on

imaging but had not produced trismus. (B) The lesion was accessed by transfacial CT-guided

FNA, which confirmed the diagnosis of lymphoma.

Fig. 11. Coronal postcontrast T1WI shows abnormal enlargement and enhancement of left V3

(*) from foramen ovale at the skull base into the MS. These features are consistent with

perineural spread of tumor in this patient who had a history of melanoma.


If a lesion of the PS comes into relation to the PPS, such as a tumor of thedeep lobe of the parotid gland, it displaces the PPS fat anteromedially(Fig. 14). The most common deep lobe parotid lesion is a pleomorphicadenoma or benign mixed tumor. Unlike most solitary well-defined lesions

Fig. 12. Bone window of axial CT of the skull base in the patient shown in Fig. 11 demonstrates

widening of the left foramen ovale (arrowheads) compared with the normal right side (*). Nerves

involved by perineural spread tend to cause uniform enlargement of the bony canal or foramen

without osseous destruction as demonstrated in this case.

Fig. 13. (A) Axial CT scan of a patient who has rhabdomyosarcoma shows a large, multicom-

partmental soft tissue mass occupying the right MS. The mass (M) infiltrates the pterygoid

muscles, surrounding fat, including the PPS, with extension into the right maxillary sinus (S),

nasal cavity, nasopharynx, and destruction of the pterygoid plates (arrow). Note the normal

fat in the contralateral PPS that is labeled for comparison. (B) There is destruction of the skull

base (arrows) with extension of tumor into the right sphenoid sinus and the right cavernous

sinus (*). On MRI, rhabdomyosarcomas are generally isointense to muscle on T1WI, of inter-

mediate signal on T2WI, and are generally homogenous on postcontrast images, but can have

variable enhancement depending on the extent of necrosis.

88 STAMBUK & PATEL

of the parotid, this tumor classically is intensely T2-bright matching theintensity of cerebrospinal fluid (CSF) (Fig. 15). MRI is therefore the pre-ferred modality to evaluate the parotid bed for recurrent lesions after surgi-cal excision of benign mixed tumor (Fig. 16). This is not a consistent, nor anexclusive, characteristic of pleomorphic adenomas, however, because othertumors, such as lymphangioma/hemangioma (Fig. 17), lymphoepithelialcysts, and occasionally mucoepidermoid carcinoma (Fig. 18) can also be hy-perintense on T2-weighted MRI. Malignant tumors of the deep lobe of theparotid gland are uncommon and are difficult to differentiate from the morecommon benign lesions in the absence of certain features, such as extrapar-enchymal extension, perineural invasion, regional lymph node metastases,skull base erosion (Fig. 19), or distant metastases.

The parapharyngeal space

The PPS is an inverted, cone-shaped, fat-filled space that is surroundedby several fascia-defined spaces (see Figs. 3 and 4). Adipose tissue is the pri-mary content of the PPS. Other contents include arteries, veins, and minorsalivary gland rests. Primary lesions of the PPS are therefore rare, althoughlipoma or minor salivary gland tumors can occur. Small lesions arising fromthe PPS are recognizable by the presence of fat around their periphery rather

Box 3. Common lesions of the parotid space

NeoplasticPleomorphic adenomaWarthin tumorLipomaMucoepidermoid carcinomaAdenoid cystic carcinomaAcinic cell carcinomaCarcinoma ex pleomorphic adenomaSquamous cell carcinomaExtranodal or nodal non-Hodgkin lymphomaNodal metastases, commonly skin cancers of the face and scalp.

Inflammatory/infectiousParotitis/parotid abscessReactive lymphadenopathyLymphoepithelial cysts/lesions

Congenital/developmentalHemangiomaVenolymphatic malformationFirst branchial cleft cyst


than displacement of the fat. Most lesions arising from the PPS itself are be-nign and therefore well-defined. Malignant tumors can occasionally arisefrom the minor salivary gland rests and are also generally well-defined sothat differential diagnosis from benign tumors is not possible on imaging(Fig. 20). An ill-defined lesion of the PPS, however, should raise suspicionfor malignancy.

Conversely, tumors from the surrounding spaces more commonly affectthe PPS and cause eccentric displacement of the PPS fat. Some malignanttumors, such as low-grade salivary tumors, can also displace fat makingdifferential diagnosis difficult, but obvious infiltration of the PPS fat is a re-liable indicator of malignancy. Most malignant tumors that invade the PPSare squamous cell carcinomas of PMS (see Fig. 6) or lymph node origin(Fig. 21), but occasionally lymphomas of the PMS or PS can also be infiltra-tive (see Fig. 5).

The carotid space

The carotid space (CS) is contained by the carotid sheath and is formedfrom all three layers of the deep cervical fascia. It spans the entire neck andextends from the skull base to the aortic arch. The suprahyoid portion of the

Fig. 14. (A) A lesion of the PS displaces the PPS fat in an anteromedial direction. (Courtesy of

Memorial Sloan-Kettering Cancer Center, New York, NY; with permission. Copyright � 2007

MSKCC.) (B) Anteromedial displacement of the PPS fat (arrow) on this axial T1WI from a tu-

mor (T) of the deep lobe of the left parotid gland (P). (C) The tumor is intermediate signal on

T2WI and (D) the tumor enhances homogeneously on the post-contrast T1W fat-saturated se-

quence. Histopathology of the resected deep lobe parotid tumor was low-grade myoepithelial

carcinoma.

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CS is anatomically related to the PPS and is located posterior to it (seeFig. 3). The CS communicates with the carotid canal and jugular foramensuperiorly at the skull base and contains the carotid artery, internal jugularvein, cranial nerves IX through XII, and the sympathetic chain. Cranialnerve X lies posterior and lateral to the carotid artery, whereas the sympa-thetic chain lies posterior and medial to the artery. The anatomic relation-ships of the contents of the CS to each other are often helpful indiscerning the precise anatomic origin of tumors within this space. Vascular

Fig. 15. (A) Axial T1WI shows a well-defined hypointense lesion (T) arising from the deep lobe

of the left parotid gland. The tumor is distinct from the normal surrounding fatty parotid tissue

(P). (B) The lesion is extremely hyperintense on T2WI similar to the CSF signal. (C) The lesion

does not enhance significantly on postcontrast T1WI. Pleomorphic adenomas exhibit variable

enhancement after gadolinium administration and may enhance increasingly on delayed imag-

ing so that differentiating the lesion from surrounding normal parotid tissue may become

difficult.


and neurogenic tumors are therefore the most common lesions in this space(Box 4). Common anatomic variations, such as a dominant jugular vein ortortuous carotid artery, may be mistaken for a lesion of the CS if care is nottaken in examining contiguous slices on CT or MRI. Specific studies, suchas MR angiography (MRA) or CT angiography (CTA), can easily resolvethe issue if required. Tumors of the suprahyoid CS cause anterior displace-ment of the PPS fat and the internal carotid artery with lateral displacementof the internal jugular vein (Fig. 22).

The two most common soft tissue masses in the CS are paragangliomasand nerve sheath tumors. These tumors are most commonly asymptomaticand are often incidentally detected on imaging studies performed for inves-tigation of unrelated conditions. When symptomatic, clinical findings may

Fig. 16. Recurrent pleomorphic adenoma in the right parotid bed following previous surgical

excision. (A) T1WI shows a mass (arrow) in the right parotidectomy bed that is isointense to

muscle. Differentiating postoperative scar from recurrent pleomorphic adenoma is extremely

difficult on this sequence. T2WI shows intensely bright clusters of nodules that represent recur-

rent tumor in the parotidectomy bed on axial (B) and coronal (C) sequence.

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include a pulsatile neck mass, submucosal lateral pharyngeal wall mass, orvery rarely lower cranial neuropathy or Horner’s syndrome.

Radiographic distinction between paragangliomas and nerve sheathtumors is generally easy because paragangliomas are very vascular tumors.They arise from the neural crest and are most commonly located within thebifurcation of the common carotid artery (carotid body tumors), in the peri-neurium of the vagus nerve (glomus vagale), at the jugular bulb (glomus jug-ulare), or in the middle ear cavity (glomus tympanicum). Of these fourcommon sites, only glomus vagale and glomus jugulare are in direct rela-tionship to the PPS. They enhance intensely on CT and MRI and haveflow voids (Fig. 23). Flow voids are diagnostic of paragangliomas, but

Fig. 17. (A) Lymphangioma of the parotid gland can be hyperintense on T2WI but unlike pleo-

morphic adenoma, these tumors tend to be trans-spatial and compressible on palpation. (B) The

inferior PPS communicates directly with the submandibular and sublingual spaces. Note the

anterior extension of the lymphangioma from the PPS into the right sublingual space (*).


may not be readily apparent on MRI if the tumor is 2 cm in diameter orsmaller. Contrast-enhanced CT scan can help make the diagnosis becauseparagangliomas enhance intensely compared to nerve sheath tumors thatmay or may not enhance (Fig. 24). The classic carotid body tumor is located

Fig. 18. Mucoepidermoid carcinoma of the superficial lobe of the right parotid gland, which

appears as a well-circumscribed, hyperintense lesion (arrow) on T2WI. This finding is important

to consider in the differential diagnosis of parotid tumors since pleomorphic adenomas also ex-

hibit this characteristic, making precise histologic diagnosis difficult.

Fig. 19. Several radiographic features of malignancy are illustrated in this patient who has an

adenosquamous carcinoma of the deep lobe of the left parotid gland. (A) T1WI sequence shows

extraparotid extension with the tumor invading the posterior belly of the digastric muscle

(arrow). The contralateral normal muscle (M) is labeled for comparison. (B) Postcontrast fat-

saturated T1WI demonstrates the ill-defined lateral border (arrow) of the tumor within the

parenchyma of the left parotid gland. (C) A more caudal axial postcontrast fat-saturated

T1W image shows invasion (arrow) of the mastoid portion of the temporal bone. The contra-

lateral normal mastoid air cells (M) are normal.

94 STAMBUK & PATEL

within the carotid bifurcation in the infrahyoid neck and is not in immediateproximity to the PPS. It tends to splay the internal and external carotid ar-teries (Fig. 25) and this finding helps differentiate a carotid body tumor froma glomus vagale that tends to displace the carotid artery anteriorly (Fig. 26).Another distinction between other paragangliomas and carotid body tumorsis that unlike carotid body tumors, other paragangliomas often have demon-strable feeder vessels that most commonly arise from the ascending

Fig. 20. (A) Precontrast axial CT scan shows a well-defined mass centered in the left PPS. Note

the clear rind of PPS fat around the periphery of the lesion (arrows). The styloid process is

marked S and the opposite PPS fat is labeled (*) for comparison. (B) A large PPS tumor

may be difficult to differentiate from a tumor originating in the deep lobe of the parotid gland.

In this patient, however, the contrast-enhanced CT clearly demonstrates a fat plane (arrow)

between the PPS lesion and the deep lobe of the left parotid gland (P). The tumor was a poly-

morphous low-grade adenocarcinoma of minor salivary gland origin.

Fig. 21. (A) Axial contrast-enhanced CT shows a new necrotic nodal mass (arrow) at high-level

V in the right neck in this patient who had been previously treated for SCC of the right palatine

tonsil. (B) This nodal mass extends cephalad and infiltrates diffusely into the right PPS fat

(arrow).


Box 4. Common lesions of the carotid space

NeoplasticParagangliomaSchwannomaMeningioma (from posterior fossa via the jugular foramen)Direct extension of mucosal carcinoma or nodal metastases

VascularInternal jugular vein thrombosisCarotid artery thrombosisCarotid artery aneurysm, dissection, or pseudoaneurysm

Inflammatory/infectiousAbscess

96 STAMBUK & PATEL

pharyngeal artery. Conventional angiography can demonstrate vascularanatomy and is useful if embolization is part of the treatment plan, suchas for paragangliomas at the skull base.

Radiologic differential diagnosis of schwannoma versus neurofibromamay not be easy. Heterogeneity within the lesion is more commonly seen in

Fig. 22. Schematic of the relationship of the suprahyoid CS to the PPS fat showing a tumor of

the CS displacing the PPS fat and ICA anteriorly, and the IJV laterally. (Courtesy of Memorial

Sloan-Kettering Cancer Center, New York, NY; with permission. Copyright � 2007 MSKCC.)

Fig. 23. (A) Contrast-enhanced axial CT scan demonstrates a densely enhancing mass in the left

CS. Note the anteromedial displacement of the internal carotid artery (arrow). The internal

jugular vein is effaced by the lesion and is therefore not visible on this section. (B) Axial

post-gadolinium T1WI at a slightly more cephalad level shows intense enhancement of the

mass. The internal jugular vein is displaced posterolaterally (black arrow) and the internal

carotid artery is displaced anteromedially (white arrow). (C) Multiple low-signal flow voids

are visible within the lesion on the T1WI, and a cluster is labeled (white arrow), confirming

the diagnosis of vagal paraganglioma.


schwannomas because of cystic change or hemorrhage. Schwannomas arisefrom the Schwann cells of the peripheral nerve sheath and in the CS, the vagusnerve and the sympathetic chain are the common nerves of origin. These well-encapsulated tumors appear as a round or ovoid mass that is isointense to

Fig. 24. (A) Postcontrast axial T1WI scan shows a fairly large right CS mass without flow

voids. The absence of flow voids is suggestive of nerve sheath tumor rather than paraganglioma.

(B) Relative non-enhancement of the mass on contrast-enhanced CT scan is consistent with

schwannoma. (C) Immediate delayed postcontrast image shows slightly more enhancement of

the schwannoma. Note that the degree of enhancement is not as intense as that seen in para-

ganglioma (Fig. 23A).

98 STAMBUK & PATEL

muscle on T1-weighted images, hyperintense on T2-weighted images, and en-hance following contrast administration (Fig. 27). These imaging character-istics are by no means unique to schwannomas, and paragangliomas canappear similar. However, schwannomas do not have flow voids even whenthey are large. Additionally, schwannomas at the skull base cause regressiveremodeling of bone, whereas permeative changes are seen withparaganglioma.

Fig. 25. (A) Schematic showing the classic location of a carotid body tumor that causes splay-

ing of the internal and external carotid arteries. (Courtesy of Memorial Sloan-Kettering Cancer

Center, New York, NY; with permission. Copyright � 2007 MSKCC.) (B) Sagittal precontrast

T1WI shows a soft tissue mass (M) nestled in the bifurcation of the common carotid artery with

splaying of the internal and external carotids. (C) Axial T2WI shows bilateral hyperintense

lesions in the carotid bifurcations. Flow voids are visible in these lesions that displace the exter-

nal carotid arteries (arrows) anteriorly and the internal carotid arteries (arrowheads) posterome-

dially. This patient has bilateral carotid body tumors.


Squamous cell carcinoma of the adjacent PMS or extracapsular spreadfrom metastatic lymphadenopathy can involve the CS (see Fig. 21). Theradiographic finding of SCC in the CS is of importance in determiningsurgical resectability of the primary or metastatic disease. Infiltration ofthe carotid artery and unresectability are features of tumors that encirclethe carotid artery by 270� or greater.

Fig. 26. Postcontrast axial T1WI shows a densely enhancing lesion of the CS that displaces the

internal (arrow) and external carotid arteries anteriorly instead of splaying them. The lesion has

the characteristic flow voids of paraganglioma, and the diagnosis of glomus vagale was con-

firmed at surgery.

Fig. 27. (A) Axial T2WI shows a heterogeneous mass in the left CS with focal central marked

hyperintensity. (B) The lesion enhances heterogeneously with focal low signal centrally on post-

contrast T1WI. A heterogeneous mass in the CS without flow voids is most indicative of

schwannoma.

100 STAMBUK & PATEL


Summary

The PPS is a suprahyoid space that largely contains fat and is surroundedby several other spaces defined by the fascial layers of the neck. A clearunderstanding of the spatial anatomy of the PPS and of the displacementpatterns of the PPS fat are essential for accurate diagnosis and appropriatetreatment for pathology arising in this region.

References

[1] Harnsberger H.Ric, Wiggins RH, Hudgins PA, editors. Diagnostic imaging: head and neck.

Salt Lake City (UT): Amirsys Inc.; 2004.

[2] Som PM, Curtin HD, editors. Head and neck imaging. 4th edition. St. Louis (MI): Mosby

Inc.; 2003.

[3] Harnsberger HR. CT andMRI of masses of the deep face. Curr Probl Diagn Radiol 1987;16:

141.

[4] Standring S, editor. Gray’s anatomy: the anatomical basis of clinical practice. 39th edition.

London: Elsevier Health Sciences; 2004.

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