eRadiograph Volume 7: Imaging of Oral Cavity | Page 224
Lymphoepithelial cysts: These nearly always are seen in relation to HIV. They are
usually bilateral and multi cystic occuring due to obstruction of the parotid lymph
nodes and associated cystic changes. The appearances depend on the contents which
can range from fluid to mucoid or caseous. Due to their hyperintensity on T2 WI they
are difficult to distinguish from true branchial cyst, cystic Warthin tumor or low grade
mucoepidermoid carcinoma.
Branchial cleft cyst: Within the parotid gland is very rare ,these may be intraparotid in
location or preauricular. The preauricular are more commonly and seen as a well
defined fluid filled mass with peripheral enhancement. Intraparotid are seen as well
defined cystic masses.
Polycystic dysgenic disease: This is similar to as seen as polycystic disease of the
kidney. The entire gland is replaced by cysts usually bilaterally.
Acquired cysts: Sialocysts these occur due to duct obstruction which may be due to
a calculus, trauma, post inflammatory stricture, or post surgical – These appear as well
defined fluid density lesions with or without enhancing margins.
Pneumatoceles are air filled cysts which occur in trumpet players, glass blowers as air
coll ects in the ducts due to increased intrabuccal pressure.
Sialadenitis
Infection of the salivary gland is known as sialadenitis. This may be caused by viruses,
bacteria, mycobacteria, fungi, parasites, though most commonly due to bacterial/viral
infections. Mumps which is caused by paramyxovious is the most common viral
injection affecting the salivary glands with the parotid gland being most commonly
affected. The clinical presentation and disease progression is sufficient for a definitive
diagnosis – imaging findings are nonspecific and further not required.
Chronic sialadenitis
This may be due to infectious or noninfectious process like sarcoidosis, post radiation
or autoimmune disease. On imaging in chronic sialadenitis the gland is shrunken,
there may be duct ectasia, imaging is also required to differentiate between
obstructive and non obstructive causes of chronic sialedenitis. Sarcoidosis involves the
parotid glands in 10 – 30 % cases. They may present as parotid masses which are
solitary or multinodular with or without associated adenopathy. These should not be
confused with malignancy – presence of unilateral facial palsy, mediastinal
adenopathy, pulmonary granulomas helps establish the diagnosis. Radiation causes
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Parotid Space
Bacterial infections are retrograde via oral cavity through the salivary ducts. These
occur more commonly in the parotid gland as the orifice of stensons duct is wide.
Clinically they present with acute sialadenitis. On imaging the gland is enlarged with
enlarged intraparotid lymph nodes. There is dilatation of the ducts with enhancement
of the ductal wall. Subsequently an intraparotid abscesses may develop as a focal
peripherally enhancing hypodense lesion on CT scan and a T2 hyperintense lesion with
peripheral enhancement on MRI.