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Head and Neck 05 -- Carotid Space


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What encloses the carotid space?
A tenacious fascial space
Why is it tenacious?
It is a condensation of all three layers of deep cervical fascia
What is this tenacious fascial enclosure named?
Carotid sheath
What are the contents of the carotid space?
1) Carotid artery (common or internal, level dependent)

2) Internal jugular vein

3) Sympathetic plexus

4) Lymph nodes

5) Cranial nerves
Which cranial nerves are in the carotid sheath?

But not all are at every level of the space.
What cranial nerves are present in the carotid space at the level of the nasopharynx?
All mentioned above
What cranial nerves are present in teh carotid space at the level of the oropharynx and hypopharynx?
CN X only
Where do the other nerves go?
IX, XI, XII end up innervating oropharyngeal or oral cavity structures
What is true of the carotid sheath?
It is thick, and able to prevent disease from entering or leaving its bounds
What is the caveat to this?
It is well defined below the carotid bifurcation only. In the region of the oropharynx and nasopharynx, it is often incomplete.
At what level does the internal carotid artery originate?
What can mimic tumor of the CS?
Carotid pseudoaneurysm
What can mimic necrotic tumor of the CS?
Jugular venous thrombosis
What is the most important nerve in the CS?
What is the anteromedial structure in the carotid space?
Carotid artery (common or internal)
What is the posterolateral structure in the carotid space?
Jugular vein
Where is the vagus nerve located?
In the posterior notch formed by the carotid and jugular
Where are the other three nerves located at nasopharyngeal level?
Same area as vagus
At about what level to the other 3 nerves leave the CS?
Level of the soft palate
Why does it make sense that the carotid sheath is often incomplete or absent at the level of the oropharynx and nasopharynx?
Because things like these nerves have to get out (just a way to remember it, probably not necessarily true)
Where are the highest lymph nodes of the deep cervical chain located?
With the carotid sheath at the level of the oropharynx
What are these nodes called?
What is the carotid space closely associated with in the infrahyoid neck?
Deep cervical nodal chain
What is the superior extent of the carotid space?
Skull base
What is the inferior extent of the carotid space?
Aortic arch
What are the three subdivisions of the carotid space that you should describe a CS lesion to be involving?



What foramen does it lead to in the skull base?
Jugular foramen
Why is this important to know
This is an important communication by which extracranial spread of cisternal and skull base lesions can spread extracranially, and carotid sheath lesions can spread intracranially.
What is an outdated term used to describe the nasopharyngeal carotid space?
Retrostyloid parapharyngeal space
What space is lateral to the CS?
The lateral recess of the retropharyngeal space.
What space is anterior to the CS?
Parapharyngeal space
Why is this important to remember?
Because lesions of the lateral recess of the retropharyngeal space can be mistaken for occuring within the CS if the close relationship between these two spaces is not remembered.
What portion of the CS are we discussing in this chapter?
Only the suprahyoid portion of the CS. The infrahyoid portion will be discussed in the chapter related to infrahyoid neck
How can a lesion be identified with certainty to be arising within the CS?
1) The center of the mass is within the area of the ICA and internal jugular vein.

2) The mass invades or pushes on the parapharyngeal space from posterior to anterior, displacing the PPS fat anteriorly.
What other finding is seen when the mass is in the nasopharyngeal CS?
Anteriolateral displacement of the styloid process
What masses begin in the posterior portion of the CS?
Tumors of nerve origin. i.e. vagal schwannoma or neurofibroma, or paraganglioma.
What is seen when the mass begins in the posterior portion of the of the CS?
The ICA is seen draping over the anterior surface of the mass.
What is done once the lesion is placed within the CS?
Use the characteristic radiologic features of the lesion to narrow the differential diagnosis for CS lesions.
What is true of CS lesions versus lesions of other deep facial spaces?
CS lesions are more characteristic in their radiologic appearance, making histopathologic diagnosis easier.
What three lesions of the CS are statistically the most common?


SCCa nodal metastasis
What types of paragangliomas are most common?
Glomus jugulare

Glomus vagale

Carotid body tumor
What type of schwannoma is most common?
What are schwannomas a type of?
Neural sheath tumor
What else is a neural sheath tumor?
What is the categorical differential diagnosis of a carotid space mass?
1) Inflammatory

2) Vascular lesions

3) Pseudomass

4) Benign tumor

5) Malignant tumor
Once the lesion is placed in the CS, what is the next question that must be asked?
Does the lesion appear vascular?
What findings on CT suggest a vascular lesion?
Mass should have about the same density as the adjacent vessels.
What findings on MR suggest a vascular lesion?
Serpininous flow or flow voids.
What other lesion is suspected when bright enhancement on CT or flow voids on MR are seen?
What other lesion cannot be distinguished from paraganglioma on this vascular-appearing basis?
Vascular neural sheath tumors
Which neural sheath tumor is most likely to present as a vascular mass?
Why is the differentiation between paraganglioma and vascular neural sheath tumor not so important?
Because both are treated the same way.
How are they treated?
Both require preoperative embolization and a transcervical surgical approach.
What is the second question that must be asked once a lesion is placed within the CS?
What is the relationship of the mass to the ICA and internal jugular?
What does this mean?
1) When lesion occurs at carotid bifurcation = carotid body tumor

2) When lesion occurs above the bifurcation to the skull base = glomus vagale

3) When lesion originates in jugular foramen, and involves CS from above = glomus jugulare
Why is this so important?
Pseudomasses of the ICA or nonsurgical vascular lesions must be identified so that no one actually tries to resect one of these, thinking it is a mass.
What are examples of nonsurgical vascular lesions?
Thrombosed ICA

Thrombosed internal jugular
What is the third question that must be asked when a lesion of the CS is found?
Does the lesion extand into the jugular foramen or basal cisterns?
What lesions can do this?
Lesions of the nasopharyngeal CS
Why is this identification so important?
Head and neck surgeons view the skull base as the end of their surgical expertise. Therefore, involvement of a neurosurgeon or head and neck surgeon trained in skull base must be involved if lesion penetrates the skull base and basal cisterns.
What other type of lesion can cause this confusion?
A lesion that begins in the jugular foramen can spread into the nasopharyngeal CS.
What lesions begin in the jugular foramen?
Glomus jugulare paraganglioma

Jugular foramen meningioma
What is important about identifying whether a jugular foramen mass extends into the nasopharyngeal CS?
Neurosurgeons see the lower margins of the skull base as the inferior extent of their zone of expertise, so if the lesion extends into the CS, a head and neck surgeon must also be involved in the surgery.
What are the lesions that can involve the basal cisterns, jugular foramen, and the nasopharyngeal CS?
1) Jugular foramen paraganglioma = glomus jugulare paraganglioma

2) Cranial nerves IX--XI schwannoma

3) Cranial nerves IX--XI neurofibroma

4) Jugular foramen meningioma
What are inflammatory lesion of the CS?
CS cellulitis or abscess
How are infections of the CS usually incurred?
By spread from adjacent spaces, similar to how infections of the PPS occur.
What clinical sign may be seen with CS infection?
Why hoarseness?
Due to vagus nerve malfunction
How is CS cellulitis diagnosed on imaging?
Loss of soft tissue planes within the CS, without focal fluid collection.
How is CS abscess diagnosed on imaging?
Focal area of fluid contained within the tenacious carotid sheath.
What is important about CS abscess?
It is a surgical emergency!
Compressive ischemia of the nerves.
What are the vascular lesions of the CS?
Jugular vein thrombosis or thrombophlebitis

Carotid thrombosis

Carotid mural thrombus

Carotid aneurysm

Carotid pseudoaneurysm
What types of patients get jugular thrombosis or thrombophlebitis?
History of previous central venous catheterization

History of drug abuse

History of malignancy
What does the acute thrombophlebitic phase mimic?
Infection--tender red mass with fever
What does the chronic thrombotic phase mimic?
Tumor--Hard, nontender mass
What does CT show in the acute thrombophlebitic phase?
Enlarged, thrombus filled internal jugular

Loss of soft tissue planes surrounding it

Vasa vasorum may enhance as a thin white rim
What does the chronic thrombotic phase appear like on CT?
Well-marginated tubular mass without loss of surrounding soft tissue planes
What does subacute jugular vein thrombus appear like on MRI?
Tubular mass with high signal on T1W images secondary to T1 shortening from methemoglobin.
What is the clinical presentation of carotid artery thrombosis and mural thrombus?

What are the situations that carotid artery pseudoaneurysm occurs?
Penetrating injury

Deceleration injury with carotid dissection and associated pseudoaneurysm formation.
What is CT appearance of mural thrombus?
Partial luminal obliteration
What is CT appearance of carotid thrombosis?
Complete luminal obliteration
What does pseudoaneurysm appear as on CT?
Carotid space mass with at least partial filling of its lumen
What does MRI show in carotid mural thrombus, thrombosis, or pseudoanerysm?
Partial or complete loss of carotid artery flow void.

Associated clot will show a complex mixture of signal intensities on T1W images due to multiple ages of blood within clot.
What is jugular or carotid artery thrombosis sometimes associated with?
SCCa of the head and neck
What is the thrombotic vessel often misdiagnosied as?
Necrotic adenopathy. Avoid this by noticing that the abnormality is present on multiple sequential axial images.
What are pseudomasses of the carotid space?
1) Ectatic carotid artery

2) Asymmetric internal jugular vein
What is the clinical presentation of ectatic common or internal carotid artery?
Pulsatile mass seen or felt in the anterolateral neck or posterolateral pharyngeal wall.
What diagnosis is the clinician concerned about when seeing this?
What is the imaging appearance of ectatic carotid?
Tubular tortuous sometimes dilated common or internal carotid artery.
When can it be mistaken for an enhancing mass on CT?
May appear as enhancing mass when it folds sharply upon itself
What if after CT you are still not sure whether this is a real mass or a pseudomass?

This is not usually necessary, however.
What is clinical presentation of asymmetric internal jugular?
Vague fullness in neck

Or incidental finding on a scan
What is appearance of asymmetric internal jugular vein?
Large tubular enhancing structure on CT, or large flow void on MRI in the normal location of the jugular
What is the normal range of variation in symmetry between the two jugular veins?
From perfect symmetry to complete absence of the jugular on one side. All normal variants.
What are the benign tumors occurring in the CS?
1) Paraganglioma

2) Nerve sheath tumors

3) Meningioma
What nerve sheath tumors occur in the CS?

What is the clinical presentation of paraganglioma?
Slowly enlarging mass of the CS.
What are the different types of paraganglioma occurring in the CS?
Glomus Jugulare

Glomus vagale

Carotid body tumor
What is the other type of paraganglioma (does not occur in the CS)
Glomus tympanicum
Where does glomus jugulare occur?
Jugular foramen
In what normal structure does the GJ occur?
Jugular ganglion
Where does glomus vagale occur?
Naso and oropharyngeal carotid space
In what normal structure does the GV occur?
Nodose gangion of the vagus nerve
Where does carotid body tumor occur?
Carotid bifurcation within the carotid body.
What types of cells to all paragangliomas occur in?
Neural crest paraganglion cells
What percentage of patients with paraganglioma have multiple tumors?
What percentage of patients with paraganglioma who have a positive family history have multiple tumors?
What is an additional presentation that occurs when the tumor involves the jugular foramen?
Neuropathy of CN IX through XI
How else can paragangliomas involving the skull base present?
Pulsatile tinnitus
What is the CT appearance of paraganglioma?
INTENSELY enhancing mass
What is the only other common diagnosis in the CS that can have this appearance?
Vascular schwannoma
What occurs when the bone of the jugular foramen is involved
1) Erosion of jugular spine

2) PERMEATIVE changes of the involved bone
What are the bony features of paraganglioma in contradistinction to?
Bone findings seen in nerve sheath tumors
What is the MRI appearance of paraganglioma?
Tubular mass within the CS.

When the lesion is greater than 2cm, MRI appearance is distinctive.
What is the distinctive appearance is lesions greater than 2cm?
Serpiginous flow voids within the mass = focal hypointensities = PEPPER

Small areas of subacute hemorrhage on T1W images = focal hyperintensities = SALT
Which of these is seen less frequently?

But when seen together as salt and pepper, diagnostic of paraganglioma.
How are the different types of paraganglioma named?
Simply by anatomic location.
What is true once a diagnosis of paraganglioma is suspected on imaging?
Careful search for a second synchronous paraganglioma, especially of there is a family history.
From what cells to schwannomas arise?
Schwann cells
Where do Schwann cells live?

What do they do?
Surround peripheral nerves.

Mechanically protect nerve, produce myelin sheath, serve as tract for nerve regeneration.
What are the most commonly involved peripheral nerves?
1) Cervical spinal roots

2) Vagus nerve

3) Sympathetic plexus
Is schwannoma encapsulated or unencapsulated?
What is the clinical presentation of schwannoma?
Painless, slow growing mass in the anterolateral neck or posterolateral oropharynx/nasopharynx.
When can schwannoma be painful?
When involving the jugular foramen and compressing CNs IX to XI.
When can schwannoma be multiple?
In patients with neurofibromatosis
What are the CT features of schweannoma?
Well encapsulated, fusiform, tissue density mass in the CS.

Displacement of ICA anteriorly (in the case of glomus vagale)
What is the appearance of the surrounding bone when schwannoma extends into the jugular foramen?
Bone is SMOOTHLY scalloped, clearly differentiating it from paraganglioma.
What is MRI appearence of schwannoma?
Fusiform shape

Well circumscribed

Uniformly enhancing

Absence of flow voids
In what case may schwannoma not be radiographically differentiated from paraganglioma?
Vascular schwannoma.
What still can be used to differentiate?
Bone changes
Why is the differentiation not so important?
Same treatment
Is neurofibroma encapsulated or unencapsulated?

However, still well circumscribed.
Where do neurofibromas occur?
Peripheral nerves.
What percent of patients with neurofibromas have von Recklinghausen syndrome?
Only 10%
Which patients often have solitary neurofibromas?
Young patients (20-30)
What is CT appearance of neurofibroma?
Well circumscribed


Why are neurofibromas low density?
Often undergo fatty degeneration
What is characteristic for neurofibroma on CT?
Low, almost water, density
What are MRI features of neurofibroma?
Indistinguishable from schwannoma
In what case can neurofibroma be distinguished from schwannoma on MRI?
Plexiform neurofibroma
What is seen in plexiform neurofibroma?
Central fibrous core, which gives central low intensity
What do lesions of the jugular foramen that extend into the basal cisterns and into the nasopharyngeal CS appear as?
Dumbell lesions
Where does meningioma involving the CS originate?
Jugular foramen.
What is clinical presentation of meningioma?
Nerve compressive symptoms, as CN IX through XI can be compressed in the jugular foramen.
What does CS meningioma appear like on imaging?
Well-circumscribed lesion hanging out bottom of jugular foramen, and possibly also extruding upward into basal cistern, creating a dumbell shape on coronal images.
What may be seen on CT?
Hypertrophic bony changes
What is seen on CT and MRI when contrast is given?
Intense enhancement
What also should be looked for to differentiate meningioma from other jugular foramen lesions?
Dural tail
What feature would distinguish meningioma from other jugular foramen lesions?
Calcification. (Although meningiomas calcify uncommonly)
What are common malignant tumors of the carotid space?
1) SCCa nodal metastasis

2) NHL
What is true of most cases of SCCa nodal metastasis to the CS?
Patient already has a diagnosis of SCCa of the upper aerodigestive tract.
What is the appearance of SCCa nodal metastases?
Single or multiple masses in or immediately adjacent to the carotid space.
What levels of the carotid space can be involved?
Oropharyngeal to clavicular region
What is a nodal mass in or adjacent to the CS at the level of the oropharynx?
Jugulodigastric node
What about nodes higher than the soft palate?
These are lateral retropharyngeal nodes. They are not in or associated with the CS.
What is the presentation of NHL in the CS?
Early NHL may present as nodal neck disease in the CS.

More advanced disease also involves throracic and abdominal nodes as well.
What is imaging appearance of NHL of the carotid space?
Homogeneous oval to round single or multiple CS masses.
How often will NHL nodes be necrotic?
Rarely, unless treated.

This is in contradistiction to SCCa nodal mets, which will often have evidence of central necrosis.
What are the three basic contents of the CS that produce disease?
1) Vessels

2) Nerves

3) Nodes
What is special about many CS lesions?
Characteristic radiologic features that allow the radiologist to make near-histopathologic diagnoses.

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