OROPHARYNX: INFECTIOUS AND NONINFECTIOUS INFLAMMATORY CONDITIONS
- Imaging, especially computed tomography, is often useful in the management of acute pyogenic oropharyngeal infections and in the identification of potentially lethal although uncommon complications.
- Computed tomography can provide a safe and rapid assessment of the airway in a patient who is stable and under the control of the treating physician for airway management decisions.
- Imaging in noninfectious inflammatory diseases is generally nonspecific for diagnostic purposes.
- Atypical clinical and imaging features of oropharyngeal pathology should raise the possibility of an inflammatory process.
- Relatively few people undergo imaging for the latter group of noninfectious inflammatory diseases.
Most acute infections of the oropharynx present an obvious clinical picture, so imaging is reserved for establishing the extent rather than the cause of the disease, such as whether pyogenic tonsillitis is associated with an abscess that is tonsillar or peritonsillar. After physical examination, it may be difficult to decide whether an area of oropharyngeal swelling is inflammatory or infectious as opposed to neoplastic under less clear clinical circumstances. For instance, in a low-grade inflammatory process, this distinction might remain unclear even after biopsy, so watchful waiting might sometimes become the default strategy with imaging surveillance as an aid (Fig. 192.1).
Much inflammatory swelling in the oropharynx will have a nonspecific imaging appearance when considered independent of the clinical setting. Taken with clinical setting, the findings are often specific enough to confirm the suspected clinical etiology. Computed tomography (CT) and occasionally magnetic resonance imaging (MRI) are then used for their primary function of mapping the extent of the most commonly pyogenic, infectious inflammatory process.
For simplicity, this chapter is divided in two sections: one dealing with infections and one with the much less common noninfectious inflammatory conditions.
ANATOMIC AND DEVELOPMENTAL CONSIDERATIONS
Occasionally, a developmental lesion such as a thyroglossal duct cyst (Chapter 170) or branchial apparatus cyst (Chapter 153) will become infected and present as a primary oropharyngeal infection (Fig. 192.2). The embryology of those types of anomalies is discussed in chapters just shown in parentheses and elsewhere.
The critical anatomic knowledge necessary for the evaluation of inflammatory oropharyngeal processes is summarized here. The detailed anatomy of this region and the adjacent nasopharynx, oral cavity, larynx and hypopharynx, and related deep tissue spaces are reviewed in chapters indicated in parentheses.
- Regional anatomy of the oropharynx including the tonsillar pillars, palatine tonsils, tongue base, glossotonsillar sulci, and valleculae (including the normal variation of lymphoid tissue lining the mucosal surfaces) and that of the parapharyngeal space (Chapters 142 and 190)
- Related regional anatomy of the structures above and below the oropharynx, including the nasopharynx (Chapter 184), oral cavity (Chapter 196, mainly the anatomy of the floor of the mouth), larynx (Chapter 196, tongue base relationship to the pre-epiglottic space), and hypopharynx
- Bony anatomy: Hard palate, pterygoid plates, and mandible (Chapter 196)
- Neurovascular bundles: lingual and hypoglossal nerve and greater and lesser palatine and posterior superior alveolar neurovascular bundles
Techniques and Relevant Aspects
Computed Tomography and Magnetic Resonance Imaging
Inflammatory conditions of the oropharynx are studied with CT and MRI in essentially the same manner as benign and malignant oropharyngeal tumors, except the entire neck may not be included. The specifics and relative value of using these studies in this anatomic region are reviewed in Chapter 190. Problem-driven protocols for CT and MRI are presented in Appendixes A and B. In general, CT is more definitive than magnetic resonance (MR) in the evaluation of the oropharyngeal and deep space, primarily pyogenic, infectious processes.
Ultrasound has only a limited role in the evaluation of these conditions. Intraoral ultrasound has been reported as useful for detecting possible peritonsillar abscess.1 Radionuclide studies used to evaluate infectious disease (Chapter 5) have little or no diagnostic use in the evaluation of oropharyngeal conditions but may be used occasionally to monitor the response to therapy of a chronic infection. The normal anatomic variations in this region seen on fluorine-18 2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) studies and its lack of specificity significantly limit any potential diagnostic value of that study.
Plain film soft tissue views of the neck, while often done, are typically not definitive or cost effective and may add delay to the diagnostic process except when done to confirm possible croup or epiglottis in children (Chapter 204).
Pros and Cons
Infections of the oropharynx may involve or arise in bone, predominantly the mandible; therefore, CT becomes immediately preferable to MR. The patients are often very uncomfortable, and MRI will be motion degraded. A definitive CT study providing all necessary information can be accomplished in about 5 to 10 minutes, making it a more sensible first choice. MRI can be used for problem solving, such as in chronic conditions where it might help to choose the most productive biopsy site when it is difficult to differentiate tumor from a chronic inflammatory process.
Acute and Subacute Pyogenic Bacterial Infections, Viral Infections, and Chronic Infections
The vast majority of infections of the oropharynx that come to imaging are acute or subacute pyogenic bacterial infections, being mainly due to pharyngeal infections complicated by abscess formation and a few due to extension of dental infections (Figs. 192.3–192.11). Fungal infection occurs predominantly in the immune-compromised population and typically does not come to imaging except for an occasional case of candidiasis that might be initially mistaken clinically for a complicated bacterial infection in a critically ill patient. Some sporadic and relatively rare infections due to fungi may present in the oropharynx, usually from a site of origin in the jaw (Fig. 192.12). Tuberculosis (TB) may involve the Waldeyer ring (Fig. 192.13). Syphilis may cause an atrophic glossitis, and a mucosal gumma may mimic tumor until it is biopsied.
Viral infections are usually not so severe that they clinically mimic pyogenic infection enough to trigger imaging with CT or MRI. Epstein-Barr virus infection, including posttransplant lymphoproliferative disease (PTLD) (Fig. 192.14), may mimic lymphoma, and the related adenopathy may trigger imaging. Human immunodeficiency virus (HIV) infection can manifest in the lymphoid tissue of the Waldeyer ring.
Prevalence and Epidemiology
Pyogenic bacterial infections occur sporadically, primarily in the pediatric and young adult populations. In the older age group, diabetes—especially when poorly controlled—is a predisposing factor. HIV and other immune-compromising conditions will predispose to fungal infections and TB.
In infants, acute and subacute bacterial infections will present with fever and poor feeding and possibly lymphadenopathy. In older children and adults, these infections will cause fever, usually a very intense sore throat and altered voice, and lymphadenopathy. In the more indolent infections and in immune-compromised patients, there may be little if any fever, and local symptoms such as odynophagia may be less prevalent.
Pathophysiology and Patterns of Disease
Manifestations and Findings
Plain Film and Fluoroscopy
Plain films may show pharyngeal swelling, especially along the posterior pharyngeal wall, or extraluminal gas. Such study may rarely reveal an otherwise unsuspected causative radiodense foreign body. In general, this is a superfluous first step in a patient who requires a definitive imaging evaluation.
Computed Tomography and Magnetic Resonance Imaging
Contrast-enhanced CT and contrast-enhanced MR will show a pyogenic process that has a typical cellulitis pattern and may show an associated contained or spreading abscess (Chapter 13). Both modalities should almost always be able to differentiate “drainable” from “nondrainable” infectious processes.1,2 These findings will often have spread into the deep planes around the oropharynx and adjacent regions. Bone erosion (Chapter 14) and vascular complications (Chapter 15) may be present. The most well known vascular complication is Lemierre syndrome in acute pyogenic tonsillitis. Cortical bone erosion may not be as evident on MR as compared to CT. More indolent infections may show a similar morphology but are less likely to show frank abscess cavities (Chapter 16). Most of these infections will enhance more than muscle. They replace fat and may spread along paths of least resistance. It is important to understand differentiating features of the following conditions in this category.