Most Frequently Missed

Diagnosis: Retropharyngeal

Suppurative Lymphadenitis

J Shah, MD; L Lanier, MD; C L Sistrom, MD; D Rajderkar, MD;

A Ghaffari, MD; A Mancuso, MD;I M Schmalfuss, MD

University of Florida, Department of Radiology

Contact: shahjl@radiology.ufl.edu

The authors have no financial disclosure in regard to this educational

exhibit.

Background:

Computer aided online simulation (SIM) of

emergency imaging studies was developed

Designed to test residents for readiness for call

Providing proficient & objective assessment of

resident competence in the emergency/critical

care imaging & affirmation of milestone

achievements

8 hour simulation of 65 emergent & critical care

cases of varying degrees of difficulty, including

normal studies

Presentation via full DICOM image sets

Dictation of free responses into text boxes labelled:

o Critical findings

o Incidental findings

o Acuity ranking

Background:

SIM was taken by 103 first (R1) & second (R2) year residents from 9 USA radiology training programs in 2014

Suppurative retropharyngeal space (RPS) lymphadenitis was presented

o 100% of residents failed to make the correct diagnosis

o Incorrect answers included:• RPS abscess (48%)

• Peritonsillar abscess (24%)

• Tonsillar abscess (15%)

• Abscess without localization (1%)

Results:

SIM was taken by 103 first (R1) & second (R2) year residents from 9 USA radiology training programs in 2014

Suppurative retropharyngeal space (RPS) lymphadenitis was presented

o 100% of residents failed to make the correct diagnosis

Results:

Conclusion: Significant cognitive gap exists in

differentiating suppurative RPS lymphadenitis from

abscess placing patients at risk for unnecessary surgical

procedure

Teaching Points:

Familiarize the radiologist with clinical and imaging

findings of RPS suppurative lymphadenitis

Discuss clinical and imaging features of mimics of RPS

suppurative lymphadenitis to improve diagnostic

competency

Outline:

SIM case presentation

Discussion of normal RPS anatomy

Presentation of clinical & imaging findings of RPS suppurative lymphadenitis and potential complications

Review of mimics of RPS suppurative lymphadenitis

SIM Case: 9 month old male with fever &

decreased neck movement

Axial contrast enhanced CT (CECT) shows mild narrowing of the upper airway (*) caused by a focal, rim enhancing hypodensity in

the right RPS with marked surrounding edema. The lateral nature of the disease is not consistent with a RPS abscess but rather with

suppurated RPS lymphadenitis.

*

RPS Anatomy

Boundaries:o Anterior: Middle layer of deep cervical fascia

o Posterior: Deep layer of deep cervical fascia

o Lateral: Alar fascia (arises from deep cervical fascia)

o Superior: Skull base

o Inferior: Fusion of middle & deep cervical fascia from

T2 to T6

Contents:o Loose connective tissue

o Lateral and medial RPS lymph nodes

RPS Imaging Anatomy: Axial plane - CT

Axial CECT shows thin layer of fat in the RPS between the pharyngeal constrictor & longus colli muscles. RPS lymph nodes are divided into lateral & medial groups (2) with the lateral being located medial to the

internal carotid artery (ICA) while the medial ones are in midline.

RPS Imaging Anatomy: Axial plane - MRI

Axial T1+Gd image reveals a normal lateral RPS lymph node located immediately

medial to the ICA and lateral to the longus colli muscle. Axial T2 image in an

infant shows a normal medial RPS lymph node located in the midline between the

longus colli muscles and a normal left lateral RPS lymph node medial to the ICA.

RPS Imaging Anatomy: Sagittal plane

Danger space is a potential space while RPS is an actual space. In a normal patient, the two cannot be distinguished with a small fat plane seen

in the RPS on T1 image.

RPS Imaging Anatomy: Sagittal plane

Sagittal CT in bone algorithm in a different patient shows air tracking

inferiorly into the mediastinum posterior to the esophagus consistent with

the danger space as the RPS stops at the thoracic inlet level.

RPS Suppurative Lymphadenitis

Demographics:

o Most common in children between ages of 2 to 6 yearso Teens and young adults occasionally affected

o No gender predilection

Presentation:

o Young children - high fevers, feeding problems and airway compromise

o Older children - fevers, sore throat, odynophagia, and neck pain

Pathophysiology:

o Staphylococcus or Streptococcus head & neck infection -> RPS reactive lymphadenopathy -> RPS suppurativelymphadenitis -> RPS abscess

RPS Diagnostic Confusion

In RPS space:o RPS suppurative lymphadenitis

o RPS abscess

o RPS edema

o Necrotic RPS nodal metastasis

In adjacent anatomical structures:o Tonsillar abscess

o Peritonsillar abscess

o Longus colli calcific tendinitis

o Soft tissue tumors / cysts

Increasing Diagnostic Accuracy

Characteristic RPS Suppurative

LymphadenitisRPS Abscess RPS Edema

Fluid Distribution Unilateral Fills the RPS from

side to side

Fills the RPS from

side to side

Configuration

and mass effect

Rounded or ovoid,

mass effect

depends on size

Rounded or ovoid;

mass effect

depends on size

“Bow-Tie”

configuration on

axial images,

sagittal images

demonstrates

tapered margins.

Mild to no mass

effect

Enhancing Wall Sometimes Always No

• Necrotic metastatic RPS lymph nodes mimic RPS suppurative

lymphadenitis but affect elderly patients.

RPS Suppurative Lymphadenitis

Axial CECT images in a 8 year old boy with dysphagia, fever & neck pain reveals a hypodense, rim enhancing lesion in the right RPS as the lesion is medial to ICA & posterior to the pharyngeal constrictor muscle. Notice the reactive lymphadenopathy in level II with subtle

edema in the RPS. The unilateral nature of the lesion is consistent with RPS suppurative lymphadenitis with clear fluid & negative cultures on

aspiration, confirming the diagnosis and ruling out RPS abscess.

RPS Abscess

CECT reveals an irregular, rim enhancing hypodensity in the RPS. The small air pockets & bilateral nature of the disease indicates RPS abscess rather than suppurated RPS lymph node. This requires search for underlying etiology, e.g. discitis/osteomyelitis as seen on sagittal

T1+Gd image in this patient.

RPS Abscess

CECT reveals a rim enhancing hypodensity in the RPS bilaterally

consistent with RPS abscess which was related to recent anterior

fusion surgery. The diagnosis of RPS abscess requires CT imaging to

the carina to exclude thoracic involvement as seen in this patient.

Notice also the small abscess in the sternocleidomastoid muscle.

RPS Edema

CECT of a 60 year old male following anterior fusion surgery reveals

hypodensity in the RPS bilaterally. The lack of enhancement is

consistent with RPS edema rather than RPS abscess as seen in the

patient on the prior slide. The RPS edema spontaneously resolved with

the lateral cervical spine plain film performed 2 months later showing

normal thickness of the prevertebral stripe.

RPS Edema

Non-contrasted CT in a 65 year old shows hypodensity in the RPS bilaterally. The lack of mass effect, the tapered margins and additional subcutaneous stranding are consistent with RPS edema rather than

RPS abscess. Search for venous thrombosis / obstruction is required in every patient with unexplained RPS edema. Superior vena cava

syndrome due to mediastinal adenopathy was confirmed in this patient.

RPS Edema

Bilateral RPS edema in two different patients related to venous thrombophlebitis with involvement of the internal jugular vein only in

the patient on the left and extension into smaller neck veins in the patient on the right. Notice that the degree of the edema does not

indicate the extent of thrombophlebitis.

Necrotic RPS Nodal Metastasis

CECT in a 58 year old male reveals a focal rim enhancing hypodensity in the right RPS. The age of the patient & the associated large

abnormal group IIB nodal conglomerate without adjacent inflammatory changes are consistent with metastatic disease rather than suppurative RPS adenitis. Fullness & fat plane obscuration was seen in the right

nasopharynx and confirmed as cancer on subsequent biopsy.

Necrotic RPS Nodal Metastasis

CECT in a 49 year old male reveals a right, oval hypodensity with rim

enhancement & inflammatory thickening of the adjacent soft tissues

mimicking suppurative RPS adenitis. However, in an adult patient this is a

necrotic RPS metastasis until proven otherwise and requires search for

an underlying malignancy in particular of the oropharynx & thyroid gland

as in this patient.

RPS Pathology - Management

Varies based on pathology

ManagementRPS Suppurative

LymphadenitisRPS Abscess RPS Edema

Treatment

Intravenous

antibiotics; most

patients improve in

24 to 48 hours

Surgical drainage

Non-surgical &

depending on

cause of edema

Additional

Recommen-

dations

Airway protection;

Incision & drainage if

progression to RPS

abscess or if the

lymph node exceeds

3 cm in short axis

Airway protection;

Chest CT to exclude

extension into

mediastinum; Search

for underlying cause

e.g. discitis /

osteomyelitis

Airway protection;

Search for

underlying cause

e.g. venous

thrombosis /

thrombophlebitis

RPS Pathology – Reporting Guidelines

Is the process centered in the RPS lymph node or truly in the RPS?

If in RPS lymph node, is it inflammatory indicating suppurativeadenitis or neoplastic?

If truly in the RPS, is it infectious indicating RPS abscess or just edema?

Associated findings / complications, such as: o Airway compromise?o Venous obstruction or thrombophlebitis? o Osteomyelitis/discitis?o Epidural abscess with spinal canal or cord compromise?o Oropharyngeal or thyroid gland malignancy?

Extent of disease & relationship to carotid artery / jugular vein Are additional studies or intervention such as aspiration/biopsy

needed to establish the correct diagnosis?

Additional RPS Lymphadenitis Mimics:

Tonsillar abscess

Peritonsillar abscess

Longus colli calcific tendinitis

Soft tissue tumors / cysts

Tonsillar versus Peritonsillar Abscess

CECT in two different patients reveals focal fluid collections in the right tonsillar region. The differentiating feature between these two entities is the location of the tonsils. In the patient with tonsillar abscess, the fluid

collection is centered in the tonsil while the tonsil is normal but medially displaced in peritonsillar abscess. Both collections are markedly

anterior to the RPS.

Longus Colli Calcific Tendinitis

Clinical presentation mimics RPS infection:o Fevers, dysphagia, odynophagia & neck pain

o May have elevated inflammatory markers including ESR & WBC

Imaging findings on CT/MRI include:o Edema within the longus colli musculature & RPSo Calcification of the longus colli tendons = differentiating

feature; may be subtle

Treatment with NSAIDS

Longus Colli Calcific Tendinitis

54 year old male with dysphagia & fevers is referred to the hospital for

suspected discitis/osteomyelitis. CT scout image reveals marked

prevertebral soft tissue thickening that is caused by widened and

hypodense RPS without associated enhancement on the CECT

consistent with RPS edema. Notice the small calcifications at C2

leading to the correct diagnosis of calcific longus colli tendinitis.

Soft Tissue Tumors / Cysts

Axial T1 and T2 images in a 26 year female demonstrates a well-defined

T1 hypointense & T2 hyperintense mass medial to the ICA that

compresses the longus colli muscle. This could be mistaken for a

suppurative RPS adenitis. The marked enhancement on the T1+Gd

image is however not consistent with such a diagnosis. Pathology

revealed a schwanomma likely arising from the sympathetic chain as the

patient did not have vocal cord paralysis to indicate vagus nerve origin.

Soft Tissue Tumors / Cysts

T2 images in a 60 year old female reveal a well-defined, oval,

hyperintense lesion that might be mistaken for suppurative RPS

adenitis. Patient’s age, lack of inflammatory changes, location anterior to

the ICA and the heterogeneous internal enhancement on the T1+Gd

image contradict such a diagnosis. The location is characteristic of a

parapharyngeal space mass with the pathology revealing benign minor

salivary gland tumor.

Soft Tissue Tumors / Cysts

CECT in a 57 year old male shows a well-defined, oval, hypodense

lesion medial to ICA concerning for suppurative RPS adenitis. Patient’s

age & the lack of enhancement are contradicting such a diagnosis. Axial

T1 images reveal that the lesion is spontaneously hyperintense due to

proteinaceous fluid & located anterior to the pharyngeal constrictor

muscle consistent with a nasopharyngeal retention cyst.

Conclusion:

Identification of key clinical and imaging findings of

suppurative RPS lymphadenitis requires attention in

resident education

This exhibit focuses on improving competence in

diagnosing suppurative RPS lymphadenitis through

o Presentation of imaging features of common pathologies of the

RPS that are confused with suppurative RPS adenitis (e.g. RPS

abscess, RPS edema, & necrotic RPS nodal metastasis)

o Review of other mimics of RPS pathologies that affect adjacent

anatomical structures (e.g. nasopharynx, tonsillar &

paravertebral structures)

References

• Mancuso AA, Hanafee WN. Head and Neck Radiology. Head and Neck Radiology. Volumes I and II. Lippincott & Williams and Wilkins, 2011.

• Shefelbine SE, Mancuso AA, Gajewski B, Stringer S, Sedwick JD. Pediatric retropharyngeal lymphadenitis: differentiation from retropharyngeal abscess and treatment implications. Otolaryngol Head Neck Surg. 2007;136(2):182-8.

• Hoang JK, Branstetter BF, Eastwood JD, et al. Multiplanar CT and MRI of Collections in the Retropharyngeal Space: Is It an Abscess? AJR. 2011;196: W426-W432.

• Hoang JK, Vanka J, Ludwig BJ, et al. Evaluation of Cervical Lymph Nodes in Head and Neck Cancer With CT and MRI: Tips, Traps, and a Systematic Approach. AJR. 2013;200: W17-W25

• widionline.com