Ludwig angina

Cellulitis involving the floor of the mouth and extends bilaterally to the oral cavity soft tissues.

Potentially life threatening due to posterior displacement of the tongue and obstruction of the oropharynx.

Most often caused by infection of the 3rd mandibular molar tooth or pericoronitis.

Imaging used to assess for airway patency, gas-forming organisms, underlying dental infection, drainable abscess.

Descending necrotizing mediastinitis

Infection commonly spreads from the oral cavity or oropharynx to the mediastinum through retropharyngeal ("danger") space, but may also spread via carotid space.

CT findings: mediastinal fluid collections +/- gas locules, hyperattenuating mediastinal fat, and pericardial or pleural effusions.

High mortality rate of 25%-40% is partially due to delayed diagnosis.

Peritonsillar abscess

Usually a clinical diagnosis.

Imaging can be used if diagnosis is uncertain, clinical exam is not possible, assess for deep space infection or complication, or patient not responding to therapy.

CT findings: tonsillar enlargement and linear, striated enhancement of palatine tonsils and posterior pharyngeal soft tissues. Rim enhancement is diagnostic of abscess, which requires drainage (as opposed to cellulitis which requires only antibiotics).

Sialadenitis

CT findings: enlarged, enhancing submandibular gland with ductal dilation secondary to obstructive calculus (within submandibular duct > parotid duct) or stenosis.

Secondary sialadenitis may result from SCC of the floor of mouth causing ductal obstruction.

Parotitis

CT findings: large and enhancing parotid gland, usually unilateral if bacterial and bilateral if viral.

Bacterial may be due to calculus obstructing parotid gland.

Bacterial complications: abscess formation, thrombophlebitis, cranial nerve VII dysfunction.

Discitis

Results from direct inoculation from trauma or surgery, extension of adjacent infection, or hematogenous spread.

CT findings: loss of disk height and endplate irregularity of 2 adjacent vertebrae and intervening disc, best seen on sagittal/coronal formats. Advanced disease may demonstrate vertebral body collapse, paraspinal or epidural soft tissue inflammation/fluid collection.

MR most sensitive for OM and epidural abscess.

Septic facet arthritis

Usually results from hematogenous spread and involves a single vertebral level.

CT findings: expansion of the joint, effusion, periarticular edema, diffuse rimlike enhancement, mixed lytic/sclerotic changes.

Complications: paraspinal or epidural abscess, foraminal compromise, meningitis, and progression to a more extensive spinal infection.

Periorbital (preseptal) cellulitis

Limited to soft tissues anterior to the orbital septum.

Often results from contiguous infection spread from face, teeth, or ocular adnexa.

Orbital (postseptal) cellulitis

Involves post septal fat.

Typically results from extension of paranasal sinus infection.

Complications: superior ophthalmic vein thrombosis, vision loss, meningitis, intracranial abscess.

Dacryocystitis

Inflammation of the lacrimal sac, secondary to obstruction/stenosis of the lacrimal duct.

CT findings: well defined cystic fluid collection along the inner canthus with rimlike enhancement and adjacent inflammatory findings.

Typically a clinical diagnosis but imaging may be performed to assess for underlying mass or complications such as orbital cellulitis.

Invasive fungal sinusitis

Almost exclusively occurs in immunocompromised patients.

CT findings: opacification of sinus, often with high attenuation secretions.

May erode sinus wall and invade adjacent structures.

Complications: vascular invasion and thrombosis, meningitis, epidural abscess, cerebral abscess, orbital infection, cavernous sinus involvement, osteomyelitis, and intracranial hemorrhage.

Infectious cervical lymphadenopathy

Multiple causative organisms.

Tuberculous lymphadenopathy (aka scrofula) is prevalent among immunocompromised patients, and often manifests as bilateral painless cervical lymphadenitis.

CT findings: enhancing and necrotic lymph nodes are seen in multiple nodal chains within the neck, which may calcify in the chronic phase of infection.