Imaging description

Acute infections and abscesses of the neck are most commonly odontogenic in origin and occur in the vicinity of the oral cavity, and they may spread in some cases from there into the deep neck spaces. Acute infections of the salivary glands and lymph nodes (suppurative adenitis) account for the majority of the remaining cases. An abscess occurring within or in the vicinity of the thyroid is rare and should raise the suspicion of an underlying third branchial pouch anomaly, particularly in the pediatric population [1]. A sinus tract connecting the piriform sinus to the thyroid lobe has been recognized as the cause of childhood thyroid/perithyroid abscesses, and it may lead to recurrent infections if left untreated [1,2].

CT is the most commonly performed initial exam for a suspicion of neck abscess, and it shows a loculated fluid collection with variable rim enhancement in the region of the thyroid gland (Fig. 81.1). The overwhelming majority of cases occur in the left neck. Demonstration of a sinus tract emanating from the apex of the piriform sinus is diagnostic, and can be accomplished by barium swallow pharyngogram, CT with oral contrast, or endoscopic exam. However, exams performed during the acute inflammatory phase may be false negative [2]. It is believed that the sinuses or fistulas of the third or fourth branchial pouches are responsible, although there is a scarcity of thoroughly documented cases, and more recent studies have implicated the thymopharyngeal duct of the third branchial pouch as the more likely culprit [3,4].