Multiplanar CT and MRI of Collections in the Retropharyngeal Space: Is It an Abscess?

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1 Neuroradiology/Head and Neck Imaging Pictorial Essay Hoang et al. Multiplanar Imaging of Retropharyngeal Space Neuroradiology/Head and Neck Imaging Pictorial Essay Downloaded from by on 12/06/17 from IP address opyright RRS. For personal use only; all rights reserved Jenny K. Hoang 1 arton F. ranstetter IV 2 James D. Eastwood 1 hristine M. Glastonbury 3 Hoang JK, ranstetter F IV, Eastwood JD, Glastonbury M Keywords: retropharyngeal abscess, retropharyngeal cellulitis, retropharyngeal edema, retropharyngeal nodes, retropharyngeal space DOI: /JR Received June 8, 2010; accepted after revision ugust 23, M. Glastonbury is an investor and consultant for mirsys. J. K. Hoang is a GE-UR fellow for Department of Radiology, Division of Neuroradiology, Duke University Medical enter, ox 3808, Erwin Rd, Durham, N ddress correspondence to J. K. Hoang (jenny.hoang@duke.edu). 2 Department of Radiology, University of Pittsburgh, Pittsburgh, P. 3 Departments of Radiology and iomedical Imaging, Otolaryngology Head and Neck Surgery, and Radiation Oncology, University of alifornia, San Francisco, San Francisco,. WE This is a Web exclusive article. JR 2011; 196:W426 W X/11/1964 W426 merican Roentgen Ray Society Multiplanar T and MRI of ollections in the Retropharyngeal Space: Is It an bscess? OJETIVE. The purpose of this article is to describe a practical imaging approach to evaluating collections in the retropharyngeal space. ONLUSION. The differential diagnoses for fluid in the retropharyngeal space include both noninfectious and infectious processes. The multiplanar capabilities of T and MRI are ideal for characterizing and delineating collections. In this pictorial essay, we describe the anatomy of the retropharyngeal space and offer a four-step approach to evaluating retropharyngeal collections on multiplanar imaging. T he retropharyngeal space spans the skull base to the mediastinum and normally contains fat and lymph nodes. The main causes of fluid expanding the retropharyngeal space can be divided into noninfectious retropharyngeal edema and retropharyngeal infection, including suppurative retropharyngeal nodes and retropharyngeal abscess. The multiplanar capabilities of T and MRI are ideal for characterizing and delineating collections. In this pictorial essay, we present the anatomy of the retropharyngeal space and offer a practical approach to evaluating retropharyngeal collections on multiplanar imaging. Important points to remember are that one, a suppurative retropharyngeal node is contained by the nodal capsule; two, a retropharyngeal space abscess is contained only by the fascia of the retropharyngeal space and has the potential for devastating complications from mass effect and the spread of infection; and three, retropharyngeal space edema is noninfectious and resolves spontaneously as its cause is treated. Normal natomy Understanding the anatomy of the retropharyngeal space is the key to appreciating the spread of infection and formation of a retropharyngeal abscess [1] (Fig. 1). The retropharyngeal space is posterior to the pharynx and esophagus and anterior to the prevertebral muscles. It is bound by the visceral fascia anteriorly, the prevertebral fascia posteriorly, and the carotid sheaths laterally. The alar fascia, a deep layer of the deep cervical fascia, divides the retropharyngeal space into two components: the true retropharyngeal space and the danger space (Fig. 1). The anterior true retropharyngeal space extends from the clivus to a variable level from T1 to T6 vertebrae, where the alar fascia fuses with the visceral fascia to obliterate the true retropharyngeal space [2]. The posteriorly located danger space, however, extends further inferiorly into the posterior mediastinum and to the level of the diaphragm. ecause the alar fascia is very thin, the danger space and true retropharyngeal space cannot be distinguished on imaging in a healthy patient. The normal contents of the retropharyngeal space include fat, small vessels, and lymph nodes. The retropharyngeal nodes drain the nasopharynx, oropharynx, nasal cavity, paranasal sinuses, middle ears, and prevertebral space. Retropharyngeal nodes are often large in children and begin to atrophy before puberty. Imaging pproach We recommend that the interpretive approach to a retropharyngeal space collection include an evaluation of multiplanar imaging for four characteristics: distribution of fluid, configuration and mass effect, presence or absence of a thick enhancing wall, and ancillary findings (Table 1). Retropharyngeal Edema Retropharyngeal edema is the presence of nonpurulent fluid in the retropharyngeal space. The accumulation of fluid is thought to be due W426 JR:196, pril 2011

2 Multiplanar Imaging of Retropharyngeal Space Downloaded from by on 12/06/17 from IP address opyright RRS. For personal use only; all rights reserved TLE 1: Four-Step Interpretive pproach to Retropharyngeal Space ollection on Multiplanar Imaging Step Retropharyngeal Edema Suppurative Retropharyngeal Node Retropharyngeal bscess Fluid distribution Fills the retropharyngeal space from Unilateral Fills the retropharyngeal space from side to side side to side onfiguration and mass effect to altered lymphatic drainage or excess lymph production. There are multiple causes of retropharyngeal edema, including radiotherapy, internal jugular vein (IJV) thrombosis (Fig. 2), and retropharyngeal calcific tendinitis (Fig. 3). The latter is an inflammatory condition due to calcium hydroxyapatite deposition in the longus colli tendons [3]. Rupture of crystal deposits provokes an inflammatory response and results in acute neck pain and retropharyngeal space edema. nother common cause of retrophar yngeal edema is infection in spaces surrounding the retropharyngeal space. In an adult, the prevertebral space is the most common source of infection (Fig. 4), compared with the pharynx in children (Figs. 5 and 6). Our four-step approach for evaluating retropharyngeal edema is as follows: first, with regard to fluid distribution, edema uniformly fills the retropharyngeal space from side to side. Second, edema has a smooth ovoid, rectangular, or bow-tie configuration on axial imaging and a diffuse craniocaudal distribution on sagittal images, with tapered inferior and superior margins; there is only mild mass effect. Third, there is no wall thickening or enhancement. Fourth, ancillary findings include IJV thrombosis, adjacent neck infection, and focal calcification anterior to 1 2 in the longus colli tendons [4, 5]. Retropharyngeal edema does not require surgical drainage. Most cases resolve as the cause of edema is treated. Suppurative Retropharyngeal Node suppurative retropharyngeal node is a reactive lymph node that has undergone liquefactive necrosis but is contained by the nodal capsule (also known as retropharyngeal adenitis or intranodal abscess) (Figs. 5 and 6). The process begins as a bacterial infection in the pharynx, paranasal sinuses, middle ear, or xial images show ovoid, rectangular, or bow-tie configuration; sagittal images show diffuse configuration with tapered inferior and superior margins; mild mass effect Rounded or ovoid configuration; mass effect varies the prevertebral space. s infection drains to the retropharyngeal node, the node enlarges as the result of proliferation and invasion of inflammatory cells (i.e., reactive lymphadenopathy). Next, the node can become edematous and this is referred to as the presuppurative phase [6]. Finally, necrosis and pus formation occur to create a suppurative retropharyngeal node. Such infections are most commonly seen in early childhood before the retropharyngeal nodes atrophy. Our four-step approach for evaluating suppurative retropharyngeal nodes is as follows: first, with regard to fluid distribution, such nodes are laterally located. Second, these nodes have a rounded or oval configuration, and the mass effect varies depending on the degree of nodal enlargement. Third, with regard to the wall, a thin hyperdense or enhancing rim may be found around this low-density node [7, 8]; an edematous node in the presuppurative phase can also be low density. Fourth, ancillary findings include evidence of the primary infectious source, such as otitis media or tonsillitis. Retropharyngeal edema is a common associated finding. There is confusion in the literature about the terms suppurative retropharyngeal node and retropharyngeal abscess. Suppurative retropharyngeal node, or adenitis, is regarded as a more accurate description for infection contained by the nodal capsule. The distinction from abscess is important because many cases do not have purulent material at surgery and can be successfully managed medically. The sign of rim enhancement and a low-density center is less than 57% specificity for purulent material at surgery [6]. Shefelbine et al. [6] found that the volume of the hypodense focus is a better predictor of pus at surgery. In that study, patients with purulence present at surgery had a mean hypodense volume on Rounded or ovoid configuration; moderate-to-marked mass effect Thick enhancing wall No an have an enhancing wall Most have an enhancing wall ncillary findings Neck infection adjacent to the retropharyngeal space or suppurative retropharyngeal node; internal jugular vein thrombosis; focal calcification anterior to 1 2; other inflammatory signs of radiotherapy Primary infectious source such as otitis media or tonsillitis; retropharyngeal edema is a common associated finding Primary infectious source such as otitis media or tonsillitis; presence of a foreign body in traumatic causes; complications in the airway, mediastinum, or vessels T of 4.4 cm 3 [6]. Patients without purulence at surgery were grouped with those who responded to medical therapy. This group had T scans with a smaller mean volume in the low-attenuation focus (2.2 cm 3 ). The current treatment for suppurative retropharyngeal nodes is a trial of IV antibiotics if the patient s condition is stable [9, 10]. Surgical drainage is considered if there is progression after medical therapy or if the suppurative node is large at presentation. Retropharyngeal bscess Retropharyngeal abscess is most commonly due to rupture of a suppurative retropharyngeal node into the retropharyngeal space (Fig. 7) and is contained only by the fascia surrounding the retropharyngeal space. Other less common causes of a retropharyngeal abscess are spread of infection from contiguous spaces across the fascial boundaries or direct inoculation from penetrating trauma (Fig. 8). efore infection evolves into a walled abscess, it is known as retropharyngeal cellulitis or phlegmon. This condition can be difficult to differentiate from retropharyngeal edema. The typical clinical presentation of retropharyngeal abscess is acute to subacute onset of neck pain, dysphagia or odynophagia, and a low-grade fever. Our four-step approach for evaluating retropharyngeal abscess is as follows: first, with regard to fluid distribution, a retropharyngeal abscess fills the retropharyngeal space from side to side [7, 8]. Second, retropharyngeal abscesses have an oval or rounded configuration; moderate-to-marked mass effect can produce anterior displacement of the pharynx and flattening of prevertebral muscles. Third, retropharyngeal abscess usually has a thick enhancing wall. Fourth, ancillary findings include evidence of primary infection or presence of a JR:196, pril 2011 W427

3 Hoang et al. Downloaded from by on 12/06/17 from IP address opyright RRS. For personal use only; all rights reserved foreign body in traumatic causes. In addition, the radiologist should search carefully for complications [10, 11]. The mortality rate for retropharyngeal abscess is less than 1% [12] and has declined in the last 50 years because of the availability of antibiotics and early diagnosis with T. The most urgent complication is airway compression from mass effect on the larynx and pharynx. irway compromise is suggested in up to 3% of patients by the clinical symptom of stridor [12]. The other feared complications are rare and documented in the literature as case reports and case series. Infection can spread inferiorly via the danger space to the mediastinum, where it can result in mediastinitis, pericarditis, pleuritis, and empyema [13] (Fig. 9). Infection can also break through the surrounding fascial planes and cause infection in the airway, spine, or carotid space. Vascular complications of carotid space infection include IJV thrombosis, carotid artery rupture, and pseudoaneurysm [14 16]. Finally, the infection itself can evolve into necrotizing fasciitis and sepsis [13]. ecause these complications are associated with significant morbidity and mortality, a true retropharyngeal abscess usually requires prompt surgical drainage. onclusion The accurate diagnosis of retropharyngeal collections will help triage patients for appropriate management. four-step imaging assessment with multiplanar imaging will help to recognize key imaging findings that differentiate between noninfectious and infectious causes. cknowledgment We thank Roxana Gafton for her editorial assistance in preparing the manuscript. References 1. ranstetter F 4th, Weissman JL. Normal anatomy of the neck with T and MR imaging correlation. Radiol lin North m 2000; 38: [ix] 2. Davis WL, Harnsberger HR, Smoker WR, Watanabe S. Retropharyngeal space: evaluation of normal anatomy and diseases with T and MR imaging. Radiology 1990; 174: Ring D, Vaccaro R, Scuderi G, Pathria MN, Garfin SR. cute calcific retropharyngeal tendinitis: clinical presentation and pathological characterization. J one Joint Surg m 1994; 76: Kanzaria H, Stein J. severe sore throat in a middle-aged man: calcific tendonitis of the longus colli tendon. J Emerg Med 2008 [epub ahead of print] 5. Eastwood JD, Hudgins P, Malone D. Retropharyngeal effusion in acute calcific prevertebral tendinitis: diagnosis with T and MR imaging. JNR 1998; 19: Shefelbine SE, Mancuso, Gajewski J, Ojiri H, Stringer S, Sedwick JD. Pediatric retropharyngeal lymphadenitis: differentiation from retrophar yngeal abscess and treatment implications. Otolaryngol Head Neck Surg 2007; 136: ranstetter F 4th, Weissman JL. Infection of the facial area, oral cavity, oropharynx, and retropharynx. Neuroimaging lin N m 2003; 13: [ix] 8. Hudgins P. Nodal and nonnodal inflammatory processes of the pediatric neck. Neuroimaging lin N m 2000; 10: [ix] 9. raig FW, Schunk JE. Retropharyngeal abscess in children: clinical presentation, utility of imaging, and current management. Pediatrics 2003; 111: Johnston D, Schmidt R, arth P. Parapharyngeal and retropharyngeal infections in children: argument for a trial of medical therapy and intraoral drainage for medical treatment failures. Int J Pediatr Otorhinolaryngol 2009; 73: Page N, auer EM, Lieu JE. linical features and treatment of retropharyngeal abscess in children. Otolaryngol Head Neck Surg 2008; 138: oulthard M, Isaacs D. Retropharyngeal abscess. rch Dis hild 1991; 66: Papalia E, Rena O, Oliaro, et al. Descending necrotizing mediastinitis: surgical management. Eur J ardiothorac Surg 2001; 20: eningfield, Nehus E, hen Y, Yellin S. Pseudoaneurysm of the internal carotid artery after retropharyngeal abscess. Otolaryngol Head Neck Surg 2006; 134: Hudgins P, Dorey JH, Jacobs IN. Internal carotid artery narrowing in children with retropharyngeal lymphadenitis and abscess. JNR 1998; 19: Ide, odart E, Remacle M, De oene, Nisolle JF, Trigaux JP. n early MR observation of carotid involvement by retropharyngeal abscess. JNR 1998; 19: Fig. 1 Normal anatomy of retropharyngeal space., Diagram of fascial layers of retropharyngeal space (double-headed arrow). True retropharyngeal space is between visceral fascia and alar fascia of deep layer of deep cervical fascia. Danger space is between alar and prevertebral layers of deep cervical fascia. These two components cannot be distinguished on MRI and T in healthy patient. and, xial enhanced T () and T2-weighted MRI () images show normal thin fat-containing retropharyngeal space (arrowheads, ; single arrowhead, ). nterior visceral fascia surrounds pharynx and esophagus. Posterior prevertebral fascia invests longus colli and other prevertebral muscles. arotid spaces form lateral walls of retropharyngeal space and contain internal or common carotid artery () and internal jugular vein (IJV). Lymph nodes lie in true retropharyngeal space and are subdivided into lateral and medial groups. Lateral lymph nodes are located lateral to longus colli and capitis muscles and extend from skull base to 3. (Fig. 1 continues on next page) W428 JR:196, pril 2011

4 Multiplanar Imaging of Retropharyngeal Space Fig. 1 (continued) Normal anatomy of retropharyngeal space. D and E, Sagittal enhanced T (D) and T1-weighted MRI (E) images show normal thin fat-containing retropharyngeal space (arrowheads, D and E). Fascial layers that form anterior and posterior walls attach to clivus. Danger space of retropharyngeal space extends from clivus to mediastinum. Downloaded from by on 12/06/17 from IP address opyright RRS. For personal use only; all rights reserved D E D Fig year-old man with retropharyngeal edema due to internal jugular vein (IJV) thrombophlebitis. Infected catheter used for renal dialysis was removed 3 weeks earlier. New subclavian catheter was placed. One week later, patient presented with fever and right neck tenderness. and, xial unenhanced T images show collection (arrowheads, and ) filling from side to side in retropharyngeal space, with mild mass effect. This is consistent with retropharyngeal edema. There is high-density thrombosis in right IJV (arrow, and ) and edema in surrounding carotid space., Sagittal unenhanced reformatted T image shows fluid expanding in retropharyngeal space (arrowheads). D, xial enhanced T image performed 10 hours later shows reduction in amount of retropharyngeal edema (arrowheads). There is contrast-filling defect (arrow) in thrombosed IJV. JR:196, pril 2011 W429

5 Hoang et al. Downloaded from by on 12/06/17 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with retropharyngeal edema secondary to calcific tendinitis. He presented with 2-day history of neck pain, stiffness, and tenderness. and, xial unenhanced () and sagittal reformatted () T images show diffuse low attenuation collection (arrowheads, and ) in retropharyngeal space with mild mass effect and tapered margins. These findings are in keeping with retropharyngeal edema., Parasagittal reformatted T image in bone windows shows focal calcification (arrow) in right longus colli tendon at 1 2 level. (ourtesy of Everton KL, Durham, N) Fig year-old man with retropharyngeal edema due to cervical spine epidural abscess. Patient had history of IV heroin use and presented with 1-week history of neck pain., xial fat-suppressed gradient-echo MRI scan shows fluid collection (arrowheads) filling retropharyngeal space from side to side with mild mass effect. There is also hyperintensity in right longus colli muscle and other prevertebral muscles (curved arrow). = common carotid artery, IJV = internal jugular vein, L = longus collis. and, T1-weighted () and T2-weighted () MRI scans show anterior epidural collection (arrow, and ) extending from 2 to 4 vertebral levels. T1-weighted image shows hyperintense stripe (arrowheads, ) in keeping with fat-containing true retropharyngeal space. Posterior to fat stripe is thin diffuse T1 isointense and T2 hyperintense signal collection (arrowhead, ) in danger space (asterisks, and ) from 2 to mediastinum. These findings are consistent with retropharyngeal edema in danger space secondary to prevertebral space infection. W430 JR:196, pril 2011

6 Multiplanar Imaging of Retropharyngeal Space Downloaded from by on 12/06/17 from IP address opyright RRS. For personal use only; all rights reserved D Fig. 5 3-year-old boy with retropharyngeal suppurative node and retropharyngeal edema. He presented with fever and neck pain and 1-week history of upper respiratory tract infection symptoms., xial enhanced T scan at level of nasopharynx shows unilateral collection in left retropharyngeal space (arrow). There is mild mass effect and thin high-density rim. This is consistent with retropharyngeal suppurative node., xial enhanced T scan at level of oropharynx shows fluid density bilaterally in retropharyngeal space (arrowheads) with mild mass effect and no rim enhancement. This is in keeping with reactive retropharyngeal edema. and D, oronal () and sagittal (D) reformatted T images show oval-shaped left retropharyngeal suppurative node (arrow, ) and retropharyngeal edema (arrowheads, and D). Patient improved with IV antibiotics and did not require surgical drainage. = common carotid artery, I = internal carotid artery, L = longus collis. Fig year-old boy with retropharyngeal suppurative node and retropharyngeal edema. He presented with 1-day history of fever after 3 days of odynophagia and left neck pain and stiffness. and, xial enhanced () and coronal reformatted () T images show rounded unilateral collection in left retropharyngeal space (straight arrow, and ). There is mild mass effect and thin high-density rim. This is consistent with retropharyngeal suppurative node. There is also enlarged right retropharyngeal node without low density (curved arrow, and ) in keeping with reactive lymphadenopathy., xial enhanced T image at higher level in oropharynx shows collection (arrowheads) filling retropharyngeal space from side to side with mild mass effect and no rim enhancement. This is in keeping with reactive retropharyngeal edema. Intraoperative examination found patient to have firm palpable mass behind tonsil pillars. From transoral approach, only tiny amount of pus was expressed. He improved with IV antibiotic therapy and was discharged on oral antibiotics. JR:196, pril 2011 W431

7 Hoang et al. Downloaded from by on 12/06/17 from IP address opyright RRS. For personal use only; all rights reserved Fig. 7 1-year-old girl with retropharyngeal abscess. She presented with fever and 1-week history of worsening stridor. This was preceded by otitis media treated with oral antibiotics. and, xial () and sagittal reformatted () enhanced T images show large collection (arrowheads, and ) filling both sides of retropharyngeal space. ollection has marked mass effect with obliteration of airway (asterisk, ). There are enhancing septations and thick enhancing wall. Endotracheal tube (arrow, ) was required before T scan. Fig. 8 3-year-old girl with retropharyngeal cellulitis due to penetrating injury to oropharynx, which resulted from fall while running with stick in her mouth. She presented 5 days later with fever and odynophagia. and, xial () and sagittal reformatted () enhanced T images show large mucosal defect (arrow, and ) in posterior oropharyngeal wall and gas (asterisks, and ) and fluid (arrowheads, and ) in retropharyngeal space. There is mild diffuse expansion of retropharyngeal space but no wall thickening or enhancement. On surgical exploration, breech in mucosa was noted in posterior pharyngeal wall. There was no purulent material or fluctuant mass. Patient improved with 2-day course of IV antibiotics and was discharged with oral antibiotics. Fig year-old man with retropharyngeal abscess and necrotizing fasciitis in neck complicated by descending mediastinitis., xial enhanced T image of neck at level of hyoid shows collection (arrowheads) filling retropharyngeal space from side to side. There is only mild mass effect, but thin wall enhancement is present. Edema is also noted in pharyngeal mucosal space (asterisk), parapharyngeal space, and submandibular space (arrows)., xial enhanced T image of upper thorax shows fluid collection (arrowheads) in posterior mediastinum tracking into right middle mediastinum. In comparison, there is normal low density fat in anterior mediastinum (curved arrow). Patient also had reactive bilateral pleural effusions. W432 JR:196, pril 2011