Glossary of Head and Neck 06 -- Retropharyngeal Space
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- What is the retropharyngeal space?
- A potential space
- What is it a potential space between?
- Middle and deep layers of deep cervical fascia
- Practically, on imaging, where is it located?
- Between the pharyngeal constrictor muscles anteriorly, and the prevertebral muscles posteriorly.
- How is the RPS sometimes seen directly?
- As a thin line of fat
- In which patients may this retropharyngeal space fat line be more prominent?
- What are the lateral walls of the retropharyngeal space formed by?
- A slip of deep cervical fascia
- What is this slip called?
- Alar fascia
- What is located immediately posterior to the retropharyngeal space?
- Danger space
- What is the importance of the danger space?
- Conduit for retropharyngeal space infection and tumor to reach the mediastinum
- What separates the retropharyngeal space from the danger space?
- A slip of deep cervical fascia
- How are lesions of the RPS distinguished from lesions of the DS on imaging?
- They cannot be. Therefore this discussion of RPS is inclusive of the DS as well.
- What is an important anatomic feature of the RPS?
- It has a median raphe which divides the RPS into two halves
- When is this median raphe identified on imaging?
- Only when the RPS is distended
- What are the important structures within the RPS?
- What classification of lymph nodes are there in the RPS?
- Lateral nodes
- What is another name for the lateral retropharyngeal nodal group?
- Nodes of Rouviere
- Where are these lateral retropharyngeal nodes located?
- Only in the nasopharynx and high oropharynx
- When are these nodes considered normal?
- < 1 cm
- How are they best visualized?
- Not normally seen on CT or MRI
- In which patients are they best seen?
- Young patients
- Where are the medial retropharyngeal nodes located?
- From nasopharynx to upper hypopharynx
- What lymph nodes are located in the RPS below the hyoid?
- What is the significance of this?
- In the suprahyoid neck, disease of the RPS will typically begin intranodally, and will be asymmetric, eventually spreading to involve the entire RPS.
In the infrahyoid neck, since there are no nodes to initially confine disease, the pathologic process will start out more diffusely, involving the entire space, with tumor or infection spreading freely through the RPS fat.
- What is the superoinferior extent of the RPS?
- Skull base to T4 level
- What is the most important thing to remember about disease of the RPS?
- It can spread directly into the mediastinum
- What does this mean for imaging?
- Scan must be extended to include mediastinum if disease of the RPS is encountered
- What space is anterior to the RPS?
- Pharyngeal mucosal space
- What space is lateral to the RPS?
- Carotid space
- What space is posterior to the RPS?
- Perivertebral space
- Which spaces enter the mediastinum? Danger space or RPS?
- Both do. And for purposes of this discussion, they will just be classed together.
- Where is the danger space in relation to the RPS?
- Posterior, between RPS and perivertebral space
- What does danger space contain?
- When is a suprahyoid mass considered primary to the RPS?
- 1) Center of mass is posteromedial to PPS
2) Center of mass is directly medial to carotid space
3) Mass encroaches on the PPS posteromedially to anterolaterally.
4) Mass is anterior to the prevertebral muscles
- What does RPS mass do to prevertebral muscles?
- Posteriorly displaces them
- What does RPS mass do to pharyngeal mucosal space?
- May anteriorly compress posterior wall of pharyngeal mucosal space, narrowing the aerodigestive tract.
- What effect does RPS mass have on the styloid process?
- None, unless it is very large.
Then it would displace styloid anteriorly.
- When is an infrahyoid or lower oropharyngeal mass considered primary to the RPS?
- 1) Mass is "bow-tie" shaped or oval in the posterior midline
2) Mass flattens and remains anterior to the prevertrbral muscles.
- When as abscess in the RPS is identified, are there CT or MRI findings consitent with spread into the RPS?
- Mediastinal extension is not a subtle finding.
The mistake is made when the scan is terminated before the complete extent of the abscess is seen.
- What must be done if a nodal-appearing RPS mass is found?
- Image the nasopharynx
- Why image the nasopharynx in this setting?
- The nasopharynx is the most common primary site for SCCa that spreads to the nodes of the RPS.
The nasopharyngeal mucosa is also the most common site to harbor a clinically occult primary SCCa.
- What are the classes of RPS lesions?
- What are the congenital lesions of the RPS?
- Lesions in the Hemangioma-Lymphangioma spectrum
- What is true of RPS involvement by a lesion in the hemangioma-lymphangioma spectrum?
- Lesion is usually transspatial, involving multiple contiguous spaces.
- What is CT appearance of hemangioma?
- Hypervascular infiltrating mass
- What is CT appearance of lymphangioma?
- Hypodense lobular mass
- Where do pediatric infections of the RPS begin?
- In the lymphatic tissues of Waldeyer's ring
- How does this get into the RPS?
- The RPS nodes get seeded.
- Then what happens?
- Swelling of the posterior pharyngeal wall, difficulty swallowing, fever
- How does infection get to the RPS in adults?
- Spread from vertebral osteomyelitis
Following cervical spine surgery
- What is a typical way for vertebral osteomyelitis to occur?
- Seeding from genitourinary tract infection
- What is the initial stage of infection spreading to the nasopharyngeal and oropharyngeal RPS?
- Reactive adenopathy
- How is this manifested?
- Swelling of the node without suppuration
- What does this look like on imaging?
- Looks like enlarged (>1 cm) version of normal node in this area
No central cystic or necrotic change
- What is the next stage in RPS infection in the suprahyoid neck?
- Suppurative adenopathy
- What occurs in this phase?
- The center of the reactive node now transforms into an intranodal abscess.
- What is seen on imaging?
- Cystic mass in the location of known RPS nodes.
Cellulitis or early abscess may be seen in the adjacent RPS.
- What is the next phase?
- RPS cellulitis or abscess
- How does this occur?
- Either by rupture of the suppurative node (esp. pediatric pop'n) or spread from the suppurative node in the suprahyoid RPS.
Or direct spread from another source in the infrahyoid RPS
- What is clinical presentation of RPS cellulitis or abscess?
- Very sick patient, with high fever, sore throat, elevated WBCs.
- What happens to the posterior wall of the pharynx in RPS cellulitis or abscess?
- Anteriorly displaced. This can be seen clinically as well as on imaging.
- What is seen on plain film?
- During inspiration, see prevertebral STS.
- Why during inspiration?
- Expiratory films can cause false appearance of prevertebral STS, especially in pediatric pop'n.
- When is the term cellulitis used for RPS infection?
- Early infection, where tissues are swollen, without focal fluid.
- What can occur if RPS abscess remains untreated?
- Spread into:
2) Adjacent spaces
- What is abscess that spreads to adjacent spaces called?
- Transspatial abscess
- How is treatment of RPS infection performed?
- First, determine whether infection is early or late?
- What is early RPS infection?
- Reactive node, suppurative node, or cellulitis
- What is treatment for early RPS infection?
- What is treatment for RPS abscess?
- Surgical drainage
- How many pseudomasses of the RPS are there?
- What are the pseudomasses of the RPS?
- 1) Tortuous carotid artery
2) Edema fluid from deep venous obstruction
3) Lymphatic fluid from tumor-induced lymphatic obstruction in the neck
- Why does tortuous carotid artery appear to be inside the RPS?
- Bows the lateral alar fascia medially, so that the carotid appears to be in the lateral recess of the RPS
- What is the clinical presentation for tortuous carotid artery?
- Pulsatile mass in the lateral pharynx
- What is clinician thinking in his DDx?
- Paraganglioma or other vascular mass
- What does this pseudotumor appear as on CT?
- As a vascular mass or carotid artery aneurysm
- What can occur when both carotids are involved?
- "kissing carotids"
- What occurs in edema fluid from deep venous obstruction?
- Fluid is seen collecting in the RPS
- Where does the venous obstruction occur?
- Lower neck or mediastinum
- In which conditions is this commonly seen?
- SVC syndrome
Jugular vein thrombosis
- What can this edema fluid be confused for?
- RPS abscess
- What occurs to cause lymphatic fluid to collect in the RPS?
- Where are the tumors located?
- Lower neck
- What is seen in addition to fluid in the RPS in these cases?
- Lymphatic engorgement of other tissue spaces or skin.
- How are these non-infectious causes of fluid collection differentiated from RPS abscess?
- Look for the presence of venous obstruction or tumor.
If there is no clinical evidence for infection, then manage conservatively.
- What can be done in cases in which fluid collection is equivocal?
- CT guided or direct needle aspiration for fluid analysis to avoid unnecessary surgery.
- How common are benign tumors of the RPS?
- What benign tumor of the RPS occurs?
- What are the malignant tumors of the RPS?
- 1) Nodal mets from SCCa
2) Nodal mets from other tumors
4) Direct invasion of the RPS by SCCa
- What is the clinical presentation in cases of nodal mets to the RPS from SCCa?
- Usually, know primary tumor of the pharyngeal mucosal space.
- Where are the SCCa primaries that spread to RPS nodes?
Posteror wall of oropharynx and hypopharynx
- What is the most common cause of retropharyngeal nodal tumor?
- SCCa mets
- How do they appear on CT or MRI?
- Larger than 1 cm
May have central inhomogeneity
- How many other malignat tumors are known to spread to RPS nodes?
- What primaries are these?
- 1) Melanoma
2) Thyroid CA
- How may these nodes present clinically?
- Submucosal mass in the back of the throat.
- What is special about these nodes?
- They may be the first manifestation of systemic melanoma or nodal thyroid CA spread
- What are the MRI imaging features of these mets?
- Both may have high signal on T1W images
- Melanoma--if lesion is melanotic, melanin will cause T1 shortening
Thryroid CA--T1 shortening due to high protein content
- What protein is high in thryoid CA mets?
- What is special about NHL involving RPS nodes?
- Nothing. Just like NHL can involve any other nodal site in the extracranial head and neck, it can involve the nodes of the RPS.
- What appearance does NHL have in the suprahyoid RPS?
- Depends whether NHL is early or later phase.
- What does early phase NHL involvement of suprahyoid RPS look like?
- Unilateral involvement of node
Homogeneous nodal appearance
- What does later phase NHL involvement of suprahyoid RPS look like?
- Mass spreads from the node, becoming extranodal and filling the RPS with tissue density (CT) or intensity (MR) material.
- What is true in most cases of NHL involving the RPS nodes?
- Usually seen simultaneously in multiple nodal chains, besides RPS.
However, RPS nodal involvement may be the initial finding in some cases.
- What is clinical setting in SCCa invasion of the RPS?
- Known SCCa
- Where is the primary SCCa usually located?
- Nasopharynx or posterior wall of oropharynx/hypopharynx.
- What happens once the SCCa gets into the RPS?
- Can move freely in a cephalocaudad direction through the RPS fat, since there are no fascial boundaries.
- What is RPS adenopathy often associated with in SCCa?
- Direct invasion of SCCa
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