Laryngitis and tonsillitis are the most common inflammatory lesions in the oral pharynx however usually no imaging is necessary as this area is very amenable to direct visualization. However, if tonsillitis goes untreated and becomes complicated by peritonsillar abscess which can spread to the parapharyngeal and lateral retropharyngeal spaces easily, MRI may be necessary to evaluate spread to the deep spaces. In children, a retropharyngeal abscess can develop in response to an underlying inflammation usually from tonsillitis however a traumatic perforation of the posterior pharyngeal wall can also be a cause. Masticator space infections are often due to dental infections that become complicated, but sometimes they can be due to otitis externa. Ludwig's angina which is usually due to complicated streptococcus or staphyloccoccus infections are often of dental origin. This represents an extensive infection of the floor of the mouth and can extend inferiorly along deep spaces to the mediastinum.
On imaging abscesses typically contain fluid centrally with a wall that enhances brightly when contrast is administered. A phlegmon, cellulitis, or fasciitus involves an area of soft tissue enhancement without fluid or gas formation.
In this age of intravenous drug abuse and aids, one may find unusual
abscesses often with multiple large nodes, that can easily be mistaken for
malignancy with metastatic lymphadenopathy. Clinical history of intravenous
drug abuse and in particular attempted needle access to the jugular veins
would be helpful in considering a different diagnosis.