Pus in lymph node = intranodal abscess

Thick enhancing nodal walls with central hypodensity

Edema in surrounding fat (cellulitis)

± thickening of muscles (myositis)

Associated nonsuppurative adenopathy

Nontuberculous mycobacterial adenitis lacks surrounding inflammatory changes

Conglomeration of suppurative nodes or rupture of node extranodal abscess

Superficial abscesses: Anterior or posterior cervical or submandibular space

Deep neck abscesses: Retropharyngeal, parapharyngeal, or tonsillar; may grow rapidly airway compromise, ± mediastinal extension

If anterior to left thyroid lobe, think 4th branchial apparatus anomaly

Exclude dental infection and salivary gland calculus as cause of H&N infection

Wide prevertebral soft tissue = cellulitis and edema ± frank abscess

False-positive in children if neck not in extended position

Rim-enhancing mass with low-attenuation center; majority drainable pus, up to 25% may be phlegmon without drainable pus

Edema in surrounding fat (cellulitis), ± thickening of muscles (myositis), occasionally air in abscess cavity

Remnant of thyroglossal duct, anywhere from foramen cecum at base of tongue to thyroid bed in infrahyoid neck

Treatment = resect cyst, tract, and midline hyoid bone (Sistrunk procedure)

Cyst with minimal rim enhancement

At hyoid > suprahyoid = infrahyoid

Most in suprahyoid neck are midline; may be paramidline in infrahyoid neck

Infrahyoid embedded in strap muscles

May contain hyperechoic debris without hemorrhage or infection

Increased enhancement and surrounding inflammatory change when infected

± nodularity or calcifications if associated thyroid carcinoma (adults)

Congenital vascular malformation

Variably sized lymphatic channels

Present at birth

Grows with child

Hemorrhage sudden increase in size

Unilocular or multilocular; macrocystic or microcystic

1 space or trans-spatial

Only septations enhance, unless associated with venous malformation

Lack high-flow vessels on flow sensitive MR sequences and angiography

Fluid-fluid levels

Simple = postinflammatory retention cyst with epithelial lining; arising in sublingual gland or minor salivary gland, in sublingual space (SLS)

Diving = extravasation pseudocyst when ruptures out of SLS into submandibular space (SMS)

Simple = well-defined cyst in SLS

Diving = cyst in SLS and SMS; if SLS component collapsed “tail”

Characteristic location = at or inferior to angle of mandible, posterolateral to submandibular gland, lateral to carotid space, and anteromedial to sternocleidomastoid muscle (SCM)

Uncommon locations = parapharyngeal space, beaking in between internal and external carotid artery, anterior surface of infrahyoid carotid space

Well-defined unilocular cyst in typical location

No significant contrast enhancement unless infected

Remnant of 1st branchial apparatus

In or superficial to parotid gland, around pinna or external auditory canal

May extend to angle of mandible

Proximity to facial nerve important for surgical planning

Well-defined nonenhancing cyst; contrast-enhancing wall with surrounding inflammation if infected

Remnant of thymopharyngeal duct

3rd branchial pouch remnant

Wall contains Hassall corpuscles

Cystic neck mass along course of thymopharyngeal duct

± solid enhancing thymic tissue

Closely associated with carotid sheath

May be connected to mediastinal thymus

Rarely ruptures into parapharyngeal space