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Emergency Head & Neck Imaging: Infections and Inflammatory Processes
Emergency Head & Neck Imaging: Infections and Inflammatory Processes Jason A. McKellopa,b,*, Wessam Bou-Assalya,c,d and Suresh K. Mukherjie KEYWORDS Deep neck infection Neck mass Computed tomography Magnetic resonance imaging Emergency
INFECTIONS OF THE LYMPH NODE The development of the lymphatic system begins in early fetal life and continues through early neonatal growth. The lymphatic system comprises a combination of lymphocytes and surrounding cellular structures that include epithelial and stromal elements. Lymph nodes are a secondary lymphoid structure where primary immune responses are initiated. Like other secondary
lymphoid organs of the body, lymph nodes have specialized architecture that promotes controlled interactions of immune cells to facilitate an appropriate immune response to infectious agents.1 The ultimate anatomy of the head and neck lymphatic system consists of an elegant meshwork of lymphatic drainage. This network can be simplified broadly into 3 groups: the ring of Waldeyerda circle of adenoidal, tonsillar, and lymphoid tissue; a more superficial ring consisting of the facial groups, parotids, preauricular, postauricular, and occipital nodes; and finally the nodes of the neck, which include the submaxillary, submental, and superficial and deep cervical chains.2 Pathologically, an infective agent within the head and neck will spread into the surrounding tissues and be partially inactivated by the host’s immune response. A portion of the infective antigenic focus will be passively drained into the afferent lymphatic channels of the lymph node causing a cascade of events including the activation of T and B lymphocytes, the formation of multiple germinal centers with active cell proliferation, and ultimately enlargement of the lymph node. A variety of infectious and noninfectious processes may cause enlargement of the cervical
a Department of Radiology at the University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48105, USA b Radiology Department, NYU Langone Medical Center/Bellevue Hospital Center, 462 First Avenue, NBV 3W38, New York, NY 10016, USA c Neuroradiology Division, Department of Radiology, University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48105, USA d Neuroradiology and Nuclear Medicine Division, Department of Radiology, Ann Arbor VA Health System, 2215 Fuller Road, Ann Arbor, MI 48105, USA e Department of Radiology, University of Michigan Health System, B2 A209-0030, 1500 East Medical Center Drive, Ann Arbor, MI 48109-0030, USA * Corresponding author. E-mail address: [email protected]
Neuroimag Clin N Am 20 (2010) 651–661 doi:10.1016/j.nic.2010.07.007 1052-5149/10/$ e see front matter Ó 2010 Elsevier Inc. All rights reserved.
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Emergency neck infections are diverse in both their presentation and their affected patient population; with pathology ranging from a transient enlargement of a child’s cervical lymph node to a rapidly spreading necrotizing fasciitis in an adult diabetic. Despite the widespread availability of antibiotics and early surgical intervention, deep neck infections still present significant morbidity and mortality in clinical centers. Complex neck anatomy can frequently obscure or delay diagnoses, so timely and appropriate radiological interpretation are critical to patient care. This article reviews common neck infections that may be encountered in the emergency room and details some of their most salient findings on imaging.
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McKellop et al lymph nodes. The stimulated node is often referred to as “reactive.” Ongoing and untreated infection may eventually result in necrosis of the node leading to suppurative adenitis.
Cervical Adenitis The term cervical adenitis denotes an inflammation of the lymph nodes of the neck due to an infectious process (Fig. 1A). Suppurative adenitis indicates an infected node that has undergone liquefaction necrosis (Fig. 1B). The likelihood of developing cervical adenitis, especially suppurative forms, decreases with age, although the incidence of suppurative adenitis is increasing in older patients.3 The pediatric population, not surprisingly, comprises a large proportion of infectious head and neck emergency room presentations. The most common cause of cervical lymph node enlargement in children is viral infections of the upper respiratory tract.4 The true incidence of viral infections is unknown because the majority of such infections are benign, and do not require any form of biopsy or incision and drainage. Noteworthy virions include adenovirus, rhinovirus, enterovirus, and herpes simplex virus. EpsteinBarr virus, the causative agent in infectious mononucleosis, is characterized by generalized lymphadenopathy, weakness, fever, and malaise. Infection with cytomegalovirus and Varicella zoster is also a well-documented cause of generalized lymph node enlargement. Another noteworthy viral infection is the acquired immunodeficiency syndrome (AIDS), caused by human T-cell lymphotrophic virus type III (HTLV-III), a potentially
devastating disease of childhood. Nearly 90% of human immunodeficiency viruseinfected children acquire their infection vertically, during gestation or, more commonly, during labor and delivery.5 Patients affected by congenital transmission usually develop symptoms during the first year of life. Symptoms include localized or generalized lymphadenopathy, thrush, parotid swelling, interstitial pneumonitis, hepatosplenomegaly, and diarrhea. Affected patients also have an increased risk of bacterial superinfection including meningitis and sepsis. Bacterial infections are the most common cause of suppurative cervical adenitis, with Staphylococcus aureus and Group A streptococcus being the most common etiologic agents.6e8 Infected patients typically present with fever and upper respiratory tract infections. Early in the course of infection, discrete nodes are palpated. With uncontrolled infection, the firm nodes are replaced by a palpable fluctuant mass (suppurative adenitis), which may require drainage. Other noteworthy bacteria that may cause suppurative cervical lymph nodes include Streptococcus pyogenes, Group B streptococcus, and Pseudomonas aeruginosa.4 Computed tomography (CT) is the preferred modality to evaluate patients suspected of having cervical lymphadenitis. CT has the advantage of a shorter acquisition time relative to magnetic resonance (MR) imaging, which in children may necessitate sedation to reduce motion artifact. Early involvement by infection is characterized by homogeneous enlargement, loss of the fatty hilum, and increased enhancement of the involved lymph node on CT (see Fig. 1A). Reticulation of the
Fig. 1. Cervical and suppurative adenitis. (A) Axial contrast-enhanced computed tomography (CT) shows homogeneous enlargement of multiple various-sized lymph nodes (arrows) in a patient with neck pain due to cervical adenitis. (B) Axial contrast-enhanced CT shows a suppurative cervical lymph node (large arrow) with surrounding phlegmon.
Emergency Head & Neck Imaging adjacent fat surrounding a suppurative lymph node or the presence of a circumferential rim of soft tissue may be helpful in differentiating an inflammatory origin as the cause of the abnormal node as opposed to metastases.3
Cat-Scratch Disease Cat-scratch disease (CSD) is a very common cause of enlarged cervical lymph nodes in the pediatric age group, and has been reported to be the most common cause of chronic unilateral regional lymphadenitis in children in the United States.2,9 The disorder is caused by the bacteria Bartonella henselae and usually presents within 3 to 10 days following contact. A prior history of a cat scratch, lick, bite, or other exposure is present in more than 90% of cases.10 These patients present clinically with tender, enlarged cervical lymph nodes, fever, and malaise. Approximately 10% of patients develop overlying erythema and fluctuant lymph nodes that require drainage. Diagnosis is confirmed by a positive cat-scratch antigen or demonstration of the bacillus on a Warthin-Starry stain of infected material. The typical findings on CT are a unilateral clumped group of enlarged lymph nodes clustered in the primary echelon drainage of the site of contact. Central areas of decreased attenuation within the lymph nodes are rare (Fig. 2). There may be some subtle reticulation of the fat surrounding the lymph nodes; however, gross findings of extracapsular extension is rare. On MR imaging, the signal characteristics are nonspecific and can be seen in a variety of disorders. The nodes typically enhance with contrast and contain high T2 signal.3
Tuberculous Lymphadenitis There has been a dramatic increase in the prevalence of tuberculosis in industrialized countries due to the AIDS epidemic, drug abuse, and increased migration.11 The most common form of head and neck tuberculosis is lymphadenitis.12 This form of tuberculosis represents 15% of cases of extrapulmonary disease and 1% to 2% of all new cases of tuberculosis.3 Cervical lymphadenopathy is usually painless. Involvement is commonly bilateral and most frequently involves the internal jugular, posterior triangle, and supraclavicular nodes. In advanced stages, the overlying skin may be inflamed and sinus tracts may appear. Pathologically, tuberculosis typically shows tubercles with marked fibroblastic response. These tubercles show characteristic amorphous caseating necrosis, which may rupture into
Fig. 2. Cat-scratch disease. Axial contrast-enhanced CT shows enlarged level II and V lymph nodes in a patient with pathologically proven cat-scratch disease (arrows).
surrounding structures such as the airway and blood stream, causing endobronchial or hematogenous dissemination. CT imaging of the early stages of tuberculous lymphadenitis reveals nodes with homogeneous contrast enhancement. As the disease evolves, central necrosis can be detected as foci of low density associated with rim enhancement (Fig. 3). One may also note a relative lack of fat stranding and effacement.13 Healed lesions and nodes undergoing chemotherapy may show calcifications. MR imaging shows nonspecific homogeneous enhancement on T1-weighted images and high signals on T2-weighted images. In nodes undergoing necrosis, contrast-enhanced MR imaging shows rim enhancement with a central area of no enhancement representing caseating necrosis. These nodes typically show high signal intensity on T2-weighted images. MR imaging, though helpful in demonstrating lymphadenitis, cannot detect nodal calcifications.3
SUBLINGUAL SPACE INFECTIONS The sublingual space (SLS) is located inferior to intrinsic muscles of the oral tongue, lateral to the genioglossus-geniohyoid complex and superomedial to the mylohyoid muscle, forming an attachment to a line on the medial surface of the
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Fig. 3. Tuberculous lymphadenitis. Axial contrastenhanced CT shows a necrotic suppurative lymph node in a patient with tuberculosis (arrow).
mandible. Posteriorly, the SLS communicates with the submandibular space (SMS) with no fascia separating these spaces.
Sublingual Space Abscess \Abscesses originating in this space are usually due to sublingual or submandibular duct stenosis or calculus disease. Dental infection or mandibular osteomyelitis, however, may also extend into the SLS. The most commonly encountered organisms in SLS abscess formation are Staphylococcus aureus and Streptococcus viridans.
Clinically, patients with SLS abscess usually present with pain, tenderness, and swelling in the anterior floor of the mouth. There may be a history of salivary colic, recent dental disease, or dental manipulation. Treatment of an SLS abscess should commence with antibiotic therapy followed by surgical drainage. CT remains the imaging modality of choice for such infections.14 Noncontrast CT may show a rounded low-attenuation lesion on the floor of the mouth (Fig. 4) while delayed postcontrast CT may show a peripherally enhancing mass.15 These lesions are often associated with subcutaneous streaking and thickening of the platysmus muscle. The genioglossus-geniohyoid complex is often displaced medially or across the midline. If an SMS component is present, this abscess may track into the parapharyngeal space where further spread can take place in a craniocaudal axis. Infection may also spread to the medial pterygoid (see Fig. 4B) or masseter muscles.3,14 MR imaging is rarely used for inflammatory disease of the sublingual space. An SLS abscess shows the typical enhancing mass on T1-weighted images and high signal intensity on T2-weighted images. On contrast-enhanced images, a central area of absent enhancement indicating pus collection can readily be demonstrated. Mandibular marrow edema is more readily demonstrated on MR imaging as intermediate signal tissues replacing high signal intensity fat on T1-weighted images.3
Ludwig Angina The term Ludwig angina refers to cellulitis involving the floor of the mouth. It is an infection
Fig. 4. Sublingual space abscess after dental extraction. (A) The bone algorithm shows focal cortical erosion in the region of the right second molar, postextraction of a “rotten” tooth (arrow). (B) Axial contrast-enhanced CT shows abscess extending into the right sublingual space and pterygoid muscles (arrow).
Emergency Head & Neck Imaging of the submental, sublingual, and SMSs causing elevation and posterior displacement of the tongue and tense induration between the hyoid bone and the genu of the mandible. This infection is usually caused by Streptococcus or Staphylococcus species. Once thought to be only of dental origin, numerous cases arising from the sinuses and pharynx, among other locations, have recently been described.15,16 Patients usually present with pain, tenderness, and swelling of the mouth floor. The infection is usually precipitated by an odontogenic infection.17 In neglected cases, Ludwig angina may spread inferiorly through fascial planes into the mediastinum. Hence some patients may present with chest pain. Because the tongue can rapidly become posteriorly displaced in this condition, securing a patent airway is a priority. Early signs of airway collapse may be subtle and many patients may require awake fiberoptic intubation or tracheostomy.18 Definitive treatment requires intravenous antibiotics and, if necessary, surgical drainage of secondary abscesses.19 Contrast-enhanced CT shows swelling of the floor of the mouth (Fig. 5). This finding is frequently associated with streaky changes in the adjacent subcutaneous fat and thickening of the overlying platysmus muscle. Enlargement of the submental or submandibular lymph nodes may also be seen. In late cases, pus or gas formation may take place and the airway may be compressed. Contrast-enhanced MR images show a thickened floor of the mouth with strong enhancement. On T2-weighted images, diffuse high signal is evident on the floor of the mouth and adjacent soft tissues.3
NECK INFECTIONS Retropharyngeal Space Infections The retropharyngeal space is a potential space that lies immediately posterior to the pharynx and extends from the base of the skull superiorly to the upper mediastinum inferiorly. It is bordered anteriorly by the buccopharyngeal fascia, posteriorly by the alar fascia and laterally by the carotid sheaths and parapharyngeal spaces. Pathology within this space can cause rapid airway compromise and requires immediate clinical attention. Infection of this space is usually the consequence of one of two mechanisms: direct inoculation or spreading infection. In adults, infection of the retropharyngeal space is usually caused by a penetrating injury. Iatrogenic causes such as endotracheal intubation and nasogastric tube placement, and incidental causes such as fish bone ingestion, are frequent culprits. Gram-positive cocci are the most common pathogen implicated in such cases.20 In children, however, retropharyngeal space infections are most commonly the result of a spreading upper respiratory tract infection. Acute pharyngitis, for example, may spread from the pharyngeal space to the retropharyngeal lymph nodes that may ultimately communicate with the retropharyngeal space. Such infections are common in childhood and frequently affect children younger than 3 years.8 Similarly, microorganisms from the nose, paranasal sinuses, and eustachian tube can drain to the retropharyngeal nodes, resulting in suppurative adenitis. If treatment is delayed, suppurated lymph nodes may rupture and result in formation of retropharyngeal abscess or retropharyngeal cellulitis. Patients with retropharyngeal space infection often present clinically with fever, neck pain, sore throat, and neck mass21; they may
Fig. 5. Ludwig angina. (A) Contrast-enhanced CT shows multiple abscess (arrows) on the mouth floor in a patient with Ludwig angina. (B) This patient also had edema of the larynx as demonstrated by thickening of the left aryepiglottic fold (arrow).
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McKellop et al also complain of a choking feeling and difficulty in swallowing. Inspection of the pharynx reveals edema and redness. On imaging, plain films typically demonstrate thickening of the soft tissues in the prevertebral space. This finding is nonspecific and may be seen in retropharyngeal cellulitis, retropharyngeal suppurative adenitis, or retropharyngeal abscess.3,15 On CT, retropharyngeal cellulitis is identified by symmetric low attenuation in the retropharyngeal space (Fig. 6A). There is anterior displacement of the posterior wall of the pharynx from the prevertebral muscles. However, the symmetric displacement does not typically exceed a few millimeters as compared with retropharyngeal edema of other origin (Fig. 6B). Retropharyngeal suppurative adenitis is identified by enlarged paramedian retropharyngeal lymph nodes that have a lowattenuation center (Fig. 7). A retropharyngeal abscess is identified by a low-attenuation fluid collection that causes anterior displacement of the posterior wall of the pharynx from the prevertebral muscles (Fig. 8). The collection may be asymmetric. Retropharyngeal abscesses usually do not have a thick enhancing wall.3 On MR imaging, enlarged retropharyngeal nodes show intermediate signal intensity on T1-weighted images and marked contrast enhancement. Rim enhancement indicates suppurative lymphadenitis. On T2-weighted images, the inflamed nodes show increased signal intensity. Soft tissue thickening, secondary to cellulitis, also shows contrast enhancement and increased signal intensity on T2-weighted imaging.3
Tonsillar Abscess In contrast to acute tonsillitis, which is more common in children, a tonsillar abscess is more
common in young adults. The average age is 25 years with more than 65% of patients falling between the ages of 20 and 40 years.22,23 The most common symptoms are sore throat, dysphagia, fever, and trismus. Nearly all patients have a history of recurrent pharyngitis. Management typically includes incision and drainage with antibiotic coverage.24 CT should be used to evaluate a suspected tonsillar abscess because it is quicker and cheaper than MR imaging. CT shows an enhancing mass in the tonsillar fossa that may or may not show pus formation (Fig. 9). MR imaging demonstrates hyperintensity on T2-weighted imaging (and hypointensity on T1) in the region of the abscess (Fig. 10). Extension into the parapharyngeal space may involve the medial pterygoid muscles (leading to trismus). In extensive disease, the inflammatory process may spread posterolaterally to involve the carotid sheath. It is important to evaluate this entity for possible jugular vein thrombosis or carotid artery erosion.3
Parapharyngeal Abscess The parapharyngeal space is the area within the deep neck medial to the masseter muscle and lateral to the superior pharyngeal constrictor. The space is divided into anterior and posterior compartments by the styloid process, the latter of which contains the carotid artery and internal jugular vein. An abscess in this space may arise from direct extension of infection from the pharynx through the pharyngeal wall, as a consequence of odontogenic infection, local trauma, and occasionally tonsillar abscess.25 Diabetes is the most common systemic condition predisposing one to parapharyngeal abscess.
Fig. 6. Retropharyngeal space cellulitis and edema. (A) Patient with retropharyngeal space cellulitis. There is symmetric low attenuation in the retropharyngeal space (arrows) without evidence of a focal fluid collection. (B) Retropharyngeal space edema secondary to internal jugular vein thrombosis: there is symmetric low attenuation in the retropharyngeal space (arrow) without evidence of a focal fluid collection. Also note ring-enhancing wall of left jugular vein with a nonenhancing lumen, representing thrombus (arrowhead).
Emergency Head & Neck Imaging
Fig. 7. Suppurative adenitis of the retropharyngeal lymph node with retropharyngeal space edema. (A) Axial CT shows a suppurative retropharyngeal lymph node (arrow). (B) Contrast-enhanced axial CT shows low attenuation in the retropharyngeal space (arrowheads) representing retropharyngeal space edema.
Parapharyngeal abscess often presents clinically with fever, sore throat, and neck swelling. Erythema, odynophagia, and dysphagia often accompany such infections.26 Trismus is most commonly associated with anterior compartment abscesses. On imaging, plain film findings are typically nonspecific, and include thickening of the soft tissues in the prevertebral space and loss of cervical lordosis. Contrast-enhanced CT is the imaging examination of choice to diagnose parapharyngeal abscess. CT shows a single or multiloculated low-density lesion with an air and/ or fluid center (Fig. 11). Contrast-enhanced
sequences may occasionally enhancement of the abscess wall.
demonstrate
Fig. 8. Retropharyngeal space abscess. Contrastenhanced CT shows fluid (large arrow) and gas (small arrow) in the retropharyngeal space.
Fig. 9. Tonsillar abscess. Contrast-enhanced axial CT demonstrates an abscess involving the left tonsil (arrow).
Necrotizing Fasciitis Cervical necrotizing fasciitis is a rapidly spreading bacterial infection of the soft tissue that can quickly become a life-threatening condition. It is commonly caused by either streptococcal or polymicrobial infections; however, methicillinresistant Staphylococcus aureus species have been seen with increasing prevalence.27 Patients commonly present with high fevers and appear acutely ill. The overlying skin of the affected tissue
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Fig. 10. Tonsillar abscess. (A) T2-weighted axial MR imaging image demonstrates an abscess involving the right tonsil (arrow). (B) Postcontrast T1-weighted image demonstrates hypodense fluid collection within an enhanced abscess wall and swollen right tonsil.
may be erythematous and tender. One might appreciate crepitus with gas-producing bacterium. Patients with necrotizing fasciitis are best managed in the intensive care unit, and are typically treated with parenteral antibiotics and frequent surgical debridement.28 CT imaging reveals nonspecific findings of diffuse reticulation of subcutaneous fat along with thickening and enhancement of the platysma. One may also find multiple abscesses extending along the fascial planes. Presence of gas within the soft tissue in the absence of prior surgery or
Fig. 11. Parapharyngeal space abscess. Contrastenhanced CT shows a low-attenuation fluid collection deep to the right tonsil located in the parapharyngeal space (arrow).
radiation therapy is pathognomonic for necrotizing fasciitis (Fig. 12).3
Bezold Abscess A Bezold abscess is a rare complication of otomastoiditis characterized by necrosis of the mastoid tip and spread of infection from bone to the adjacent soft tissue. Inflammatory collections form inferior to the mastoid process and may course along the plane of the sternocleidomastoid muscle to the lower neck. If left untreated, the
Fig. 12. Cervical necrotizing fasciitis. Contrastenhanced CT scan showing diffuse thickening of the soft tissues of the neck associated with small fluid collection (large arrow). The presence of air (small arrows) in a patient with a fever who has never had surgery or radiation therapy is strongly suggestive of necrotizing fasciitis.
Emergency Head & Neck Imaging abscess may spread as far as the larynx and mediastinum, which results in a poor prognosis. Clinically, patients present with fever, neck pain, restricted neck motion, and otalgia. Because the secondary abscesses lie deep to the superficial fascial planes surrounding the sternocleidomastoid and trapezius muscles, the contours of the fluctuant soft tissue mass may be difficult to palpate.29 On CT, one can identify unilateral opacification of the middle ear and mastoid cavities, often associated with bone erosion, especially of the mastoid tip (Fig. 13A). The abscess involves the adjacent musculature surrounding the mastoid and extends inferiorly (Fig. 13B).25,30 Surrounding the abscess, one may see obliteration of the fat planes, reticulation of the subcutaneous tissues, and thickening of the overlying skin.
compartments, which may result in abscess formation in the adjacent spaces such as the retropharyngeal space. Children present clinically with respiratory distress, drooling, or regurgitation, but adults usually present with pain and dysphagia. Senile, psychiatric, or stuperous patients may present late with evidence of fever or sepsis. Noncontrast CT of the neck may be performed to confirm the presence or absence of an ingested foreign body. Contrast-enhanced CT demonstrates the site and level of the resultant inflammation or abscess. Frequently, gas translucencies are detected within the retropharyngeal space. MR imaging is seldom used for foreign body ingestion as it cannot define reliably the presence of foreign body or gas collections.3
Calcific Tendinitis
OTHER PATHOLOGIES Foreign Body Ingestion Among other complications, inadvertent swallowing of foreign objects may also result in retropharyngeal space infections, most notably retropharyngeal abscess formation. Nearly 80% of all swallowed pharyngeal and esophageal foreign bodies take place in the pediatric population.31 However, adult patients who are stuperous, senile, or have psychiatric illness are also prone to swallowing a variety of foreign objects including animal bones and dentures. These objects are usually lodged in areas of normal anatomic narrowing in the cricopharyngeus area, the aortic arch, or the distal esophagus. Sharp objects may perforate the pharynx or esophagus and migrate along tissue planes and
Calcific tendinitis is a benign inflammatory condition that may mimic infectious pathology of the neck. Calcific tendinitis is caused by deposition of hydroxyapatite in the tendon fibers of the longus colli muscles.32 Patients present clinically with either sudden onset or subacute pain in the neck and throat worsened by head movement and swallowing.33 Due to its rare occurrence, it is often mistaken clinically for traumatic injury, retropharyngeal abscess, or infectious spondylitis, causing patients to frequently undergo unnecessary tests and treatment. The condition, however, is selflimited and resolves after 1 to 2 weeks on calcium resorption. Lateral neck radiography may show extensive soft tissue swelling between C1 through C4 with amorphous calcific deposits anterior to C1 and C2.34 Likewise, CT imaging may demonstrate the
Fig. 13. Bezold abscess. (A) Axial contrast-enhanced CT shows opacification of the mastoid air cells with associated bone erosion indicating an aggressive inflammatory process. (B) The soft tissue algorithm demonstrates a multiloculated abscess involving the paraspinal musculature.
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Fig. 14. Calcific tendinitis. (A) Axial contrast-enhanced CT of the neck demonstrates retropharyngeal space edema (large arrows). Note the preservation of the alar fascia (small arrows), which indicates that the low attenuation is edema and not an abscess. (B) The bone algorithm shows an ossific mass anterior to the dens, confirming that the edema in the retropharyngeal space is due to calcific tendinitis.
same findings along with prevertebral edema, an image finding that must be distinguished from that found within retropharyngeal space infection (Fig. 14). Though typically unnecessary for diagnosis, MR imaging demonstrates a signal void anterior to C1 and C2 representing an amorphous calcification. In addition, MR may demonstrate marrow edema in adjacent vertebrae.3
IMAGING MODALITIES FOR NECK INFECTION The range of inflammatory and infectious processes of the neck is diverse, requiring a thorough appreciation for neck anatomy as well as the appropriate imaging modalities to investigate such pathology. In the emergency setting, timely interpretation of these images is critical to the care of acutely ill patients, especially those with a threatened airway. While plain film, ultrasonography, and MR imaging play a part in the investigation of inflammatory and infectious pathology of the neck, cross-sectional imaging with CT plays a central role.
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3. Mukherji SK, Chong V. Atlas of head and neck imaging: the extracranial head and neck. New York: Thieme; 2004. 4. Peters T, Edwards K. Cervical lymphadenopathy and adenitis. Pediatr Rev 2000;21:399e404. 5. Murray DL. Infectious diseases. In: Rudolph CD, Rudolph AM, Hostetter MK, et al, editors. Rudolph’s pediatrics. 21st edition. New York (NY): The McGraw-Hill Companies Inc; 2003. p. 867e1165. 6. Baker CJ. Group B streptococcal cellulitis-adenitis in infants. Am J Dis Child 1982;136(7):631e3. 7. Dajani AS, Garcia RE, Wolinski E. Etiology of cervical lymphadenitis in children. N Engl J Med 1963;268: 1329. 8. Schweinfurth J. Demographics of pediatric head and neck infections in a tertiary care hospital. Laryngoscope 2006;116(6):887e9. 9. Bass JW, Vincent JM, Person DA. The expanding spectrum of Bartonella infections II: Cat-scratch disease. Pediatr Infect Dis J 1997;16:163e79. 10. Heyman DL. Control of communicable diseases manual. 19th edition. Washington, DC: American Public Health Association Press; 2008. p. 98. 11. Frieden TR, Sterling TR, Munsiff SS, et al. Tuberculosis. Lancet 2003;362:887. 12. Menon K, Bem C, Gouldesbrough D, et al. A clinical review of 128 cases of head and neck tuberculosis presenting over a 10-year period in Bradford, UK. J Laryngol Otol 2007;121(4):362e8. 13. Hanck C, Fleisch F, Katz G. Imaging appearance of nontuberculous mycobacterial infection of the neck. AJNR Am J Neuroradiol 2004;25(2):349e50. 14. Branstetter BF, Weissman JL. Infection of the facial area, oral cavity, oropharynx, and retropharynx. Neuroimaging Clin N Am 2003;13:393e410.
Emergency Head & Neck Imaging 15. Hurley MC, Heran MK. Imaging studies for head and neck infections. Infect Dis Clin North Am 2007;21: 305e53. 16. Djupesland P. Necrotizing fasciitis of the head and neck: report of three cases and review of the literature. Acta Otolaryngol 2000;543:186e9. 17. Weed HG, Forest LA. Deep neck infection. In: Cummings CW, Flint PW, Harker LA, et al, editors Otolaryngology: head and neck surgery, vol. 3. 4th edition. Philadelphia: Elsevier Mosby; 2005. p. 2515e24. 18. Marple, BF. Ludwig angina: a review of current airway management. Arch Otolaryngol Head Neck Surg 1999;125(5):600. 19. Bross-Soriano D, Arrieta-Gomez J, PradoCalleros H, et al. Management of Ludwig’s angina with small neck incisions: 18 years experience. Otolaryngol Head Neck Surg 2004;130(6):712e7. 20. Brook I. Microbiology and management of peritonsillar, retropharyngeal, and parapharyngeal abscesses. J Oral Maxillofac Surg 2004;62(12): 1545e50. 21. Craig FW, Schunk JE. Retropharyngeal abscess in children: clinical presentation, utility of imaging, and current management. Pediatrics 2003;111(6): 1394e8. 22. Steyer TE. Peritonsillar abscess: diagnosis and treatment. Am Fam Physician 2002;65(1):937e96. 23. Belleza WG, Kalman S. Otolaryngologic emergencies in the outpatient setting. Med Clin North Am 2006;90(2):329e53. 24. Johnson RF, Stewart MG. The contemporary approach to diagnosis and management of
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peritonsillar abscess. Curr Opin Otolaryngol Head Neck Surg 2005;13(3):157e60. Glynn F, Skinner LJ, Riley N, et al. Parapharyngeal abscess in an insulin dependent diabetic patient following an elective tonsillectomy. J Laryngol Otol 2007;121(9):e16. Page C, Biet A, Zaatar R, et al. Parapharyngeal abscess: diagnosis and treatment. Eur Arch Otorhinolaryngol 2008;265:681e6. Smouha EE, Levenson MJ, Anand VK, et al. Modern presentations of Bezold’s abscess. Arch Otolaryngol Head Neck Surg 1989;115:1126e9. Miller LG, Perdreau-Remington F, Rieg G, et al. Necrotizing fasciitis caused by community-associated methicillin-resistant Staphylococcus aureus in Los Angeles. N Engl J Med 2005;352:1445e53. Castillo M, Albernaz VS, Mukherji SK, et al. Imaging of Bezold’s abscess. AJR Am J Roentgenol 1998; 171:1491e5. Gaffney RJ, O’Dwyer TP, Maguire AJ. Bezold’s abscess. J Laryngol Otol 1991;105:765e6. Digoy GP. Diagnosis and management of upper aerodigestive tract foreign bodies. Otolaryngol Clin North Am 2008;41(2):485e96. Vieira F, Allen SM, Stocks RM, et al. Deep neck infection. Otolaryngol Clin North Am 2008;41: 459e83, vii. Eastwood JD, Hudgins PA, Malone D. Retropharyngeal effusion in acute calcific prevertebral tendinitis: diagnosis with CT and MR imaging. AJNR Am J Neuroradiol 1998;19:1789e92. Haun CL. Retropharyngeal tendinitis. AJR Am J Roentgenol 1978;130:1137e40.
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INFECTIONS OF THE LYMPH NODE The development of the lymphatic system begins in early fetal life and continues through early neonatal growth. The lymphatic system comprises a combination of lymphocytes and surrounding cellular structures that include epithelial and stromal elements. Lymph nodes are a secondary lymphoid structure where primary immune responses are initiated. Like other secondary
lymphoid organs of the body, lymph nodes have specialized architecture that promotes controlled interactions of immune cells to facilitate an appropriate immune response to infectious agents.1 The ultimate anatomy of the head and neck lymphatic system consists of an elegant meshwork of lymphatic drainage. This network can be simplified broadly into 3 groups: the ring of Waldeyerda circle of adenoidal, tonsillar, and lymphoid tissue; a more superficial ring consisting of the facial groups, parotids, preauricular, postauricular, and occipital nodes; and finally the nodes of the neck, which include the submaxillary, submental, and superficial and deep cervical chains.2 Pathologically, an infective agent within the head and neck will spread into the surrounding tissues and be partially inactivated by the host’s immune response. A portion of the infective antigenic focus will be passively drained into the afferent lymphatic channels of the lymph node causing a cascade of events including the activation of T and B lymphocytes, the formation of multiple germinal centers with active cell proliferation, and ultimately enlargement of the lymph node. A variety of infectious and noninfectious processes may cause enlargement of the cervical
a Department of Radiology at the University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48105, USA b Radiology Department, NYU Langone Medical Center/Bellevue Hospital Center, 462 First Avenue, NBV 3W38, New York, NY 10016, USA c Neuroradiology Division, Department of Radiology, University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48105, USA d Neuroradiology and Nuclear Medicine Division, Department of Radiology, Ann Arbor VA Health System, 2215 Fuller Road, Ann Arbor, MI 48105, USA e Department of Radiology, University of Michigan Health System, B2 A209-0030, 1500 East Medical Center Drive, Ann Arbor, MI 48109-0030, USA * Corresponding author. E-mail address: [email protected]
Neuroimag Clin N Am 20 (2010) 651–661 doi:10.1016/j.nic.2010.07.007 1052-5149/10/$ e see front matter Ó 2010 Elsevier Inc. All rights reserved.
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Emergency neck infections are diverse in both their presentation and their affected patient population; with pathology ranging from a transient enlargement of a child’s cervical lymph node to a rapidly spreading necrotizing fasciitis in an adult diabetic. Despite the widespread availability of antibiotics and early surgical intervention, deep neck infections still present significant morbidity and mortality in clinical centers. Complex neck anatomy can frequently obscure or delay diagnoses, so timely and appropriate radiological interpretation are critical to patient care. This article reviews common neck infections that may be encountered in the emergency room and details some of their most salient findings on imaging.
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McKellop et al lymph nodes. The stimulated node is often referred to as “reactive.” Ongoing and untreated infection may eventually result in necrosis of the node leading to suppurative adenitis.
Cervical Adenitis The term cervical adenitis denotes an inflammation of the lymph nodes of the neck due to an infectious process (Fig. 1A). Suppurative adenitis indicates an infected node that has undergone liquefaction necrosis (Fig. 1B). The likelihood of developing cervical adenitis, especially suppurative forms, decreases with age, although the incidence of suppurative adenitis is increasing in older patients.3 The pediatric population, not surprisingly, comprises a large proportion of infectious head and neck emergency room presentations. The most common cause of cervical lymph node enlargement in children is viral infections of the upper respiratory tract.4 The true incidence of viral infections is unknown because the majority of such infections are benign, and do not require any form of biopsy or incision and drainage. Noteworthy virions include adenovirus, rhinovirus, enterovirus, and herpes simplex virus. EpsteinBarr virus, the causative agent in infectious mononucleosis, is characterized by generalized lymphadenopathy, weakness, fever, and malaise. Infection with cytomegalovirus and Varicella zoster is also a well-documented cause of generalized lymph node enlargement. Another noteworthy viral infection is the acquired immunodeficiency syndrome (AIDS), caused by human T-cell lymphotrophic virus type III (HTLV-III), a potentially
devastating disease of childhood. Nearly 90% of human immunodeficiency viruseinfected children acquire their infection vertically, during gestation or, more commonly, during labor and delivery.5 Patients affected by congenital transmission usually develop symptoms during the first year of life. Symptoms include localized or generalized lymphadenopathy, thrush, parotid swelling, interstitial pneumonitis, hepatosplenomegaly, and diarrhea. Affected patients also have an increased risk of bacterial superinfection including meningitis and sepsis. Bacterial infections are the most common cause of suppurative cervical adenitis, with Staphylococcus aureus and Group A streptococcus being the most common etiologic agents.6e8 Infected patients typically present with fever and upper respiratory tract infections. Early in the course of infection, discrete nodes are palpated. With uncontrolled infection, the firm nodes are replaced by a palpable fluctuant mass (suppurative adenitis), which may require drainage. Other noteworthy bacteria that may cause suppurative cervical lymph nodes include Streptococcus pyogenes, Group B streptococcus, and Pseudomonas aeruginosa.4 Computed tomography (CT) is the preferred modality to evaluate patients suspected of having cervical lymphadenitis. CT has the advantage of a shorter acquisition time relative to magnetic resonance (MR) imaging, which in children may necessitate sedation to reduce motion artifact. Early involvement by infection is characterized by homogeneous enlargement, loss of the fatty hilum, and increased enhancement of the involved lymph node on CT (see Fig. 1A). Reticulation of the
Fig. 1. Cervical and suppurative adenitis. (A) Axial contrast-enhanced computed tomography (CT) shows homogeneous enlargement of multiple various-sized lymph nodes (arrows) in a patient with neck pain due to cervical adenitis. (B) Axial contrast-enhanced CT shows a suppurative cervical lymph node (large arrow) with surrounding phlegmon.
Emergency Head & Neck Imaging adjacent fat surrounding a suppurative lymph node or the presence of a circumferential rim of soft tissue may be helpful in differentiating an inflammatory origin as the cause of the abnormal node as opposed to metastases.3
Cat-Scratch Disease Cat-scratch disease (CSD) is a very common cause of enlarged cervical lymph nodes in the pediatric age group, and has been reported to be the most common cause of chronic unilateral regional lymphadenitis in children in the United States.2,9 The disorder is caused by the bacteria Bartonella henselae and usually presents within 3 to 10 days following contact. A prior history of a cat scratch, lick, bite, or other exposure is present in more than 90% of cases.10 These patients present clinically with tender, enlarged cervical lymph nodes, fever, and malaise. Approximately 10% of patients develop overlying erythema and fluctuant lymph nodes that require drainage. Diagnosis is confirmed by a positive cat-scratch antigen or demonstration of the bacillus on a Warthin-Starry stain of infected material. The typical findings on CT are a unilateral clumped group of enlarged lymph nodes clustered in the primary echelon drainage of the site of contact. Central areas of decreased attenuation within the lymph nodes are rare (Fig. 2). There may be some subtle reticulation of the fat surrounding the lymph nodes; however, gross findings of extracapsular extension is rare. On MR imaging, the signal characteristics are nonspecific and can be seen in a variety of disorders. The nodes typically enhance with contrast and contain high T2 signal.3
Tuberculous Lymphadenitis There has been a dramatic increase in the prevalence of tuberculosis in industrialized countries due to the AIDS epidemic, drug abuse, and increased migration.11 The most common form of head and neck tuberculosis is lymphadenitis.12 This form of tuberculosis represents 15% of cases of extrapulmonary disease and 1% to 2% of all new cases of tuberculosis.3 Cervical lymphadenopathy is usually painless. Involvement is commonly bilateral and most frequently involves the internal jugular, posterior triangle, and supraclavicular nodes. In advanced stages, the overlying skin may be inflamed and sinus tracts may appear. Pathologically, tuberculosis typically shows tubercles with marked fibroblastic response. These tubercles show characteristic amorphous caseating necrosis, which may rupture into
Fig. 2. Cat-scratch disease. Axial contrast-enhanced CT shows enlarged level II and V lymph nodes in a patient with pathologically proven cat-scratch disease (arrows).
surrounding structures such as the airway and blood stream, causing endobronchial or hematogenous dissemination. CT imaging of the early stages of tuberculous lymphadenitis reveals nodes with homogeneous contrast enhancement. As the disease evolves, central necrosis can be detected as foci of low density associated with rim enhancement (Fig. 3). One may also note a relative lack of fat stranding and effacement.13 Healed lesions and nodes undergoing chemotherapy may show calcifications. MR imaging shows nonspecific homogeneous enhancement on T1-weighted images and high signals on T2-weighted images. In nodes undergoing necrosis, contrast-enhanced MR imaging shows rim enhancement with a central area of no enhancement representing caseating necrosis. These nodes typically show high signal intensity on T2-weighted images. MR imaging, though helpful in demonstrating lymphadenitis, cannot detect nodal calcifications.3
SUBLINGUAL SPACE INFECTIONS The sublingual space (SLS) is located inferior to intrinsic muscles of the oral tongue, lateral to the genioglossus-geniohyoid complex and superomedial to the mylohyoid muscle, forming an attachment to a line on the medial surface of the
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Fig. 3. Tuberculous lymphadenitis. Axial contrastenhanced CT shows a necrotic suppurative lymph node in a patient with tuberculosis (arrow).
mandible. Posteriorly, the SLS communicates with the submandibular space (SMS) with no fascia separating these spaces.
Sublingual Space Abscess \Abscesses originating in this space are usually due to sublingual or submandibular duct stenosis or calculus disease. Dental infection or mandibular osteomyelitis, however, may also extend into the SLS. The most commonly encountered organisms in SLS abscess formation are Staphylococcus aureus and Streptococcus viridans.
Clinically, patients with SLS abscess usually present with pain, tenderness, and swelling in the anterior floor of the mouth. There may be a history of salivary colic, recent dental disease, or dental manipulation. Treatment of an SLS abscess should commence with antibiotic therapy followed by surgical drainage. CT remains the imaging modality of choice for such infections.14 Noncontrast CT may show a rounded low-attenuation lesion on the floor of the mouth (Fig. 4) while delayed postcontrast CT may show a peripherally enhancing mass.15 These lesions are often associated with subcutaneous streaking and thickening of the platysmus muscle. The genioglossus-geniohyoid complex is often displaced medially or across the midline. If an SMS component is present, this abscess may track into the parapharyngeal space where further spread can take place in a craniocaudal axis. Infection may also spread to the medial pterygoid (see Fig. 4B) or masseter muscles.3,14 MR imaging is rarely used for inflammatory disease of the sublingual space. An SLS abscess shows the typical enhancing mass on T1-weighted images and high signal intensity on T2-weighted images. On contrast-enhanced images, a central area of absent enhancement indicating pus collection can readily be demonstrated. Mandibular marrow edema is more readily demonstrated on MR imaging as intermediate signal tissues replacing high signal intensity fat on T1-weighted images.3
Ludwig Angina The term Ludwig angina refers to cellulitis involving the floor of the mouth. It is an infection
Fig. 4. Sublingual space abscess after dental extraction. (A) The bone algorithm shows focal cortical erosion in the region of the right second molar, postextraction of a “rotten” tooth (arrow). (B) Axial contrast-enhanced CT shows abscess extending into the right sublingual space and pterygoid muscles (arrow).
Emergency Head & Neck Imaging of the submental, sublingual, and SMSs causing elevation and posterior displacement of the tongue and tense induration between the hyoid bone and the genu of the mandible. This infection is usually caused by Streptococcus or Staphylococcus species. Once thought to be only of dental origin, numerous cases arising from the sinuses and pharynx, among other locations, have recently been described.15,16 Patients usually present with pain, tenderness, and swelling of the mouth floor. The infection is usually precipitated by an odontogenic infection.17 In neglected cases, Ludwig angina may spread inferiorly through fascial planes into the mediastinum. Hence some patients may present with chest pain. Because the tongue can rapidly become posteriorly displaced in this condition, securing a patent airway is a priority. Early signs of airway collapse may be subtle and many patients may require awake fiberoptic intubation or tracheostomy.18 Definitive treatment requires intravenous antibiotics and, if necessary, surgical drainage of secondary abscesses.19 Contrast-enhanced CT shows swelling of the floor of the mouth (Fig. 5). This finding is frequently associated with streaky changes in the adjacent subcutaneous fat and thickening of the overlying platysmus muscle. Enlargement of the submental or submandibular lymph nodes may also be seen. In late cases, pus or gas formation may take place and the airway may be compressed. Contrast-enhanced MR images show a thickened floor of the mouth with strong enhancement. On T2-weighted images, diffuse high signal is evident on the floor of the mouth and adjacent soft tissues.3
NECK INFECTIONS Retropharyngeal Space Infections The retropharyngeal space is a potential space that lies immediately posterior to the pharynx and extends from the base of the skull superiorly to the upper mediastinum inferiorly. It is bordered anteriorly by the buccopharyngeal fascia, posteriorly by the alar fascia and laterally by the carotid sheaths and parapharyngeal spaces. Pathology within this space can cause rapid airway compromise and requires immediate clinical attention. Infection of this space is usually the consequence of one of two mechanisms: direct inoculation or spreading infection. In adults, infection of the retropharyngeal space is usually caused by a penetrating injury. Iatrogenic causes such as endotracheal intubation and nasogastric tube placement, and incidental causes such as fish bone ingestion, are frequent culprits. Gram-positive cocci are the most common pathogen implicated in such cases.20 In children, however, retropharyngeal space infections are most commonly the result of a spreading upper respiratory tract infection. Acute pharyngitis, for example, may spread from the pharyngeal space to the retropharyngeal lymph nodes that may ultimately communicate with the retropharyngeal space. Such infections are common in childhood and frequently affect children younger than 3 years.8 Similarly, microorganisms from the nose, paranasal sinuses, and eustachian tube can drain to the retropharyngeal nodes, resulting in suppurative adenitis. If treatment is delayed, suppurated lymph nodes may rupture and result in formation of retropharyngeal abscess or retropharyngeal cellulitis. Patients with retropharyngeal space infection often present clinically with fever, neck pain, sore throat, and neck mass21; they may
Fig. 5. Ludwig angina. (A) Contrast-enhanced CT shows multiple abscess (arrows) on the mouth floor in a patient with Ludwig angina. (B) This patient also had edema of the larynx as demonstrated by thickening of the left aryepiglottic fold (arrow).
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McKellop et al also complain of a choking feeling and difficulty in swallowing. Inspection of the pharynx reveals edema and redness. On imaging, plain films typically demonstrate thickening of the soft tissues in the prevertebral space. This finding is nonspecific and may be seen in retropharyngeal cellulitis, retropharyngeal suppurative adenitis, or retropharyngeal abscess.3,15 On CT, retropharyngeal cellulitis is identified by symmetric low attenuation in the retropharyngeal space (Fig. 6A). There is anterior displacement of the posterior wall of the pharynx from the prevertebral muscles. However, the symmetric displacement does not typically exceed a few millimeters as compared with retropharyngeal edema of other origin (Fig. 6B). Retropharyngeal suppurative adenitis is identified by enlarged paramedian retropharyngeal lymph nodes that have a lowattenuation center (Fig. 7). A retropharyngeal abscess is identified by a low-attenuation fluid collection that causes anterior displacement of the posterior wall of the pharynx from the prevertebral muscles (Fig. 8). The collection may be asymmetric. Retropharyngeal abscesses usually do not have a thick enhancing wall.3 On MR imaging, enlarged retropharyngeal nodes show intermediate signal intensity on T1-weighted images and marked contrast enhancement. Rim enhancement indicates suppurative lymphadenitis. On T2-weighted images, the inflamed nodes show increased signal intensity. Soft tissue thickening, secondary to cellulitis, also shows contrast enhancement and increased signal intensity on T2-weighted imaging.3
Tonsillar Abscess In contrast to acute tonsillitis, which is more common in children, a tonsillar abscess is more
common in young adults. The average age is 25 years with more than 65% of patients falling between the ages of 20 and 40 years.22,23 The most common symptoms are sore throat, dysphagia, fever, and trismus. Nearly all patients have a history of recurrent pharyngitis. Management typically includes incision and drainage with antibiotic coverage.24 CT should be used to evaluate a suspected tonsillar abscess because it is quicker and cheaper than MR imaging. CT shows an enhancing mass in the tonsillar fossa that may or may not show pus formation (Fig. 9). MR imaging demonstrates hyperintensity on T2-weighted imaging (and hypointensity on T1) in the region of the abscess (Fig. 10). Extension into the parapharyngeal space may involve the medial pterygoid muscles (leading to trismus). In extensive disease, the inflammatory process may spread posterolaterally to involve the carotid sheath. It is important to evaluate this entity for possible jugular vein thrombosis or carotid artery erosion.3
Parapharyngeal Abscess The parapharyngeal space is the area within the deep neck medial to the masseter muscle and lateral to the superior pharyngeal constrictor. The space is divided into anterior and posterior compartments by the styloid process, the latter of which contains the carotid artery and internal jugular vein. An abscess in this space may arise from direct extension of infection from the pharynx through the pharyngeal wall, as a consequence of odontogenic infection, local trauma, and occasionally tonsillar abscess.25 Diabetes is the most common systemic condition predisposing one to parapharyngeal abscess.
Fig. 6. Retropharyngeal space cellulitis and edema. (A) Patient with retropharyngeal space cellulitis. There is symmetric low attenuation in the retropharyngeal space (arrows) without evidence of a focal fluid collection. (B) Retropharyngeal space edema secondary to internal jugular vein thrombosis: there is symmetric low attenuation in the retropharyngeal space (arrow) without evidence of a focal fluid collection. Also note ring-enhancing wall of left jugular vein with a nonenhancing lumen, representing thrombus (arrowhead).
Emergency Head & Neck Imaging
Fig. 7. Suppurative adenitis of the retropharyngeal lymph node with retropharyngeal space edema. (A) Axial CT shows a suppurative retropharyngeal lymph node (arrow). (B) Contrast-enhanced axial CT shows low attenuation in the retropharyngeal space (arrowheads) representing retropharyngeal space edema.
Parapharyngeal abscess often presents clinically with fever, sore throat, and neck swelling. Erythema, odynophagia, and dysphagia often accompany such infections.26 Trismus is most commonly associated with anterior compartment abscesses. On imaging, plain film findings are typically nonspecific, and include thickening of the soft tissues in the prevertebral space and loss of cervical lordosis. Contrast-enhanced CT is the imaging examination of choice to diagnose parapharyngeal abscess. CT shows a single or multiloculated low-density lesion with an air and/ or fluid center (Fig. 11). Contrast-enhanced
sequences may occasionally enhancement of the abscess wall.
demonstrate
Fig. 8. Retropharyngeal space abscess. Contrastenhanced CT shows fluid (large arrow) and gas (small arrow) in the retropharyngeal space.
Fig. 9. Tonsillar abscess. Contrast-enhanced axial CT demonstrates an abscess involving the left tonsil (arrow).
Necrotizing Fasciitis Cervical necrotizing fasciitis is a rapidly spreading bacterial infection of the soft tissue that can quickly become a life-threatening condition. It is commonly caused by either streptococcal or polymicrobial infections; however, methicillinresistant Staphylococcus aureus species have been seen with increasing prevalence.27 Patients commonly present with high fevers and appear acutely ill. The overlying skin of the affected tissue
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Fig. 10. Tonsillar abscess. (A) T2-weighted axial MR imaging image demonstrates an abscess involving the right tonsil (arrow). (B) Postcontrast T1-weighted image demonstrates hypodense fluid collection within an enhanced abscess wall and swollen right tonsil.
may be erythematous and tender. One might appreciate crepitus with gas-producing bacterium. Patients with necrotizing fasciitis are best managed in the intensive care unit, and are typically treated with parenteral antibiotics and frequent surgical debridement.28 CT imaging reveals nonspecific findings of diffuse reticulation of subcutaneous fat along with thickening and enhancement of the platysma. One may also find multiple abscesses extending along the fascial planes. Presence of gas within the soft tissue in the absence of prior surgery or
Fig. 11. Parapharyngeal space abscess. Contrastenhanced CT shows a low-attenuation fluid collection deep to the right tonsil located in the parapharyngeal space (arrow).
radiation therapy is pathognomonic for necrotizing fasciitis (Fig. 12).3
Bezold Abscess A Bezold abscess is a rare complication of otomastoiditis characterized by necrosis of the mastoid tip and spread of infection from bone to the adjacent soft tissue. Inflammatory collections form inferior to the mastoid process and may course along the plane of the sternocleidomastoid muscle to the lower neck. If left untreated, the
Fig. 12. Cervical necrotizing fasciitis. Contrastenhanced CT scan showing diffuse thickening of the soft tissues of the neck associated with small fluid collection (large arrow). The presence of air (small arrows) in a patient with a fever who has never had surgery or radiation therapy is strongly suggestive of necrotizing fasciitis.
Emergency Head & Neck Imaging abscess may spread as far as the larynx and mediastinum, which results in a poor prognosis. Clinically, patients present with fever, neck pain, restricted neck motion, and otalgia. Because the secondary abscesses lie deep to the superficial fascial planes surrounding the sternocleidomastoid and trapezius muscles, the contours of the fluctuant soft tissue mass may be difficult to palpate.29 On CT, one can identify unilateral opacification of the middle ear and mastoid cavities, often associated with bone erosion, especially of the mastoid tip (Fig. 13A). The abscess involves the adjacent musculature surrounding the mastoid and extends inferiorly (Fig. 13B).25,30 Surrounding the abscess, one may see obliteration of the fat planes, reticulation of the subcutaneous tissues, and thickening of the overlying skin.
compartments, which may result in abscess formation in the adjacent spaces such as the retropharyngeal space. Children present clinically with respiratory distress, drooling, or regurgitation, but adults usually present with pain and dysphagia. Senile, psychiatric, or stuperous patients may present late with evidence of fever or sepsis. Noncontrast CT of the neck may be performed to confirm the presence or absence of an ingested foreign body. Contrast-enhanced CT demonstrates the site and level of the resultant inflammation or abscess. Frequently, gas translucencies are detected within the retropharyngeal space. MR imaging is seldom used for foreign body ingestion as it cannot define reliably the presence of foreign body or gas collections.3
Calcific Tendinitis
OTHER PATHOLOGIES Foreign Body Ingestion Among other complications, inadvertent swallowing of foreign objects may also result in retropharyngeal space infections, most notably retropharyngeal abscess formation. Nearly 80% of all swallowed pharyngeal and esophageal foreign bodies take place in the pediatric population.31 However, adult patients who are stuperous, senile, or have psychiatric illness are also prone to swallowing a variety of foreign objects including animal bones and dentures. These objects are usually lodged in areas of normal anatomic narrowing in the cricopharyngeus area, the aortic arch, or the distal esophagus. Sharp objects may perforate the pharynx or esophagus and migrate along tissue planes and
Calcific tendinitis is a benign inflammatory condition that may mimic infectious pathology of the neck. Calcific tendinitis is caused by deposition of hydroxyapatite in the tendon fibers of the longus colli muscles.32 Patients present clinically with either sudden onset or subacute pain in the neck and throat worsened by head movement and swallowing.33 Due to its rare occurrence, it is often mistaken clinically for traumatic injury, retropharyngeal abscess, or infectious spondylitis, causing patients to frequently undergo unnecessary tests and treatment. The condition, however, is selflimited and resolves after 1 to 2 weeks on calcium resorption. Lateral neck radiography may show extensive soft tissue swelling between C1 through C4 with amorphous calcific deposits anterior to C1 and C2.34 Likewise, CT imaging may demonstrate the
Fig. 13. Bezold abscess. (A) Axial contrast-enhanced CT shows opacification of the mastoid air cells with associated bone erosion indicating an aggressive inflammatory process. (B) The soft tissue algorithm demonstrates a multiloculated abscess involving the paraspinal musculature.
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Fig. 14. Calcific tendinitis. (A) Axial contrast-enhanced CT of the neck demonstrates retropharyngeal space edema (large arrows). Note the preservation of the alar fascia (small arrows), which indicates that the low attenuation is edema and not an abscess. (B) The bone algorithm shows an ossific mass anterior to the dens, confirming that the edema in the retropharyngeal space is due to calcific tendinitis.
same findings along with prevertebral edema, an image finding that must be distinguished from that found within retropharyngeal space infection (Fig. 14). Though typically unnecessary for diagnosis, MR imaging demonstrates a signal void anterior to C1 and C2 representing an amorphous calcification. In addition, MR may demonstrate marrow edema in adjacent vertebrae.3
IMAGING MODALITIES FOR NECK INFECTION The range of inflammatory and infectious processes of the neck is diverse, requiring a thorough appreciation for neck anatomy as well as the appropriate imaging modalities to investigate such pathology. In the emergency setting, timely interpretation of these images is critical to the care of acutely ill patients, especially those with a threatened airway. While plain film, ultrasonography, and MR imaging play a part in the investigation of inflammatory and infectious pathology of the neck, cross-sectional imaging with CT plays a central role.
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3. Mukherji SK, Chong V. Atlas of head and neck imaging: the extracranial head and neck. New York: Thieme; 2004. 4. Peters T, Edwards K. Cervical lymphadenopathy and adenitis. Pediatr Rev 2000;21:399e404. 5. Murray DL. Infectious diseases. In: Rudolph CD, Rudolph AM, Hostetter MK, et al, editors. Rudolph’s pediatrics. 21st edition. New York (NY): The McGraw-Hill Companies Inc; 2003. p. 867e1165. 6. Baker CJ. Group B streptococcal cellulitis-adenitis in infants. Am J Dis Child 1982;136(7):631e3. 7. Dajani AS, Garcia RE, Wolinski E. Etiology of cervical lymphadenitis in children. N Engl J Med 1963;268: 1329. 8. Schweinfurth J. Demographics of pediatric head and neck infections in a tertiary care hospital. Laryngoscope 2006;116(6):887e9. 9. Bass JW, Vincent JM, Person DA. The expanding spectrum of Bartonella infections II: Cat-scratch disease. Pediatr Infect Dis J 1997;16:163e79. 10. Heyman DL. Control of communicable diseases manual. 19th edition. Washington, DC: American Public Health Association Press; 2008. p. 98. 11. Frieden TR, Sterling TR, Munsiff SS, et al. Tuberculosis. Lancet 2003;362:887. 12. Menon K, Bem C, Gouldesbrough D, et al. A clinical review of 128 cases of head and neck tuberculosis presenting over a 10-year period in Bradford, UK. J Laryngol Otol 2007;121(4):362e8. 13. Hanck C, Fleisch F, Katz G. Imaging appearance of nontuberculous mycobacterial infection of the neck. AJNR Am J Neuroradiol 2004;25(2):349e50. 14. Branstetter BF, Weissman JL. Infection of the facial area, oral cavity, oropharynx, and retropharynx. Neuroimaging Clin N Am 2003;13:393e410.
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peritonsillar abscess. Curr Opin Otolaryngol Head Neck Surg 2005;13(3):157e60. Glynn F, Skinner LJ, Riley N, et al. Parapharyngeal abscess in an insulin dependent diabetic patient following an elective tonsillectomy. J Laryngol Otol 2007;121(9):e16. Page C, Biet A, Zaatar R, et al. Parapharyngeal abscess: diagnosis and treatment. Eur Arch Otorhinolaryngol 2008;265:681e6. Smouha EE, Levenson MJ, Anand VK, et al. Modern presentations of Bezold’s abscess. Arch Otolaryngol Head Neck Surg 1989;115:1126e9. Miller LG, Perdreau-Remington F, Rieg G, et al. Necrotizing fasciitis caused by community-associated methicillin-resistant Staphylococcus aureus in Los Angeles. N Engl J Med 2005;352:1445e53. Castillo M, Albernaz VS, Mukherji SK, et al. Imaging of Bezold’s abscess. AJR Am J Roentgenol 1998; 171:1491e5. Gaffney RJ, O’Dwyer TP, Maguire AJ. Bezold’s abscess. J Laryngol Otol 1991;105:765e6. Digoy GP. Diagnosis and management of upper aerodigestive tract foreign bodies. Otolaryngol Clin North Am 2008;41(2):485e96. Vieira F, Allen SM, Stocks RM, et al. Deep neck infection. Otolaryngol Clin North Am 2008;41: 459e83, vii. Eastwood JD, Hudgins PA, Malone D. Retropharyngeal effusion in acute calcific prevertebral tendinitis: diagnosis with CT and MR imaging. AJNR Am J Neuroradiol 1998;19:1789e92. Haun CL. Retropharyngeal tendinitis. AJR Am J Roentgenol 1978;130:1137e40.
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