Tornwaldt cysts (also spelled as Thornwaldt cyst or Thornwald cyst) are common incidental benign midline nasopharyngeal mucosal cysts. A symptomatic cyst is also called Tornwaldt disease ^7,8.

Epidemiology

Tornwaldt cysts are developmental and usually asymptomatic. In most cases they are found incidentally; as such, age of diagnosis typically represents age of imaging of the nasopharynx. Peak incidence has been variably reported between the ages of 15 and 60 years ^1,3, which may be due to gradual accumulation of fluid in the cyst following obliteration of its neck.

Tornwaldt cysts have an autopsy prevalence of approximately 4%, with no gender predilection ³. These incidences found at autopsy studies in 1950s and 60s differ from findings in an incidence study using CT and/or MR, demonstrating an incidence of only 0.06% ⁷. The reason for this discrepancy is unclear.

Clinical presentation

Tornwaldt cysts are almost always asymptomatic. However, if they become infected, they can cause halitosis or periodic discharge of foul-tasting fluid into the mouth. Some may present with otitis media due to obstruction of the Eustachian tube ^7,8.

Pathology

Tornwaldt cysts are classified as crusting and cystic ⁸. They form as a result of retraction of the notochord where it contacts with the endoderm of the primitive pharynx.

This is believed to happen at about the 10^th week of embryonic development. Closure at the orifice results in the so-called cystic type, while crusts adhering to the orifice without closure result in the crust type ⁸. The cyst is lined by respiratory epithelium and accumulates fluid containing variable proteinaceous content. Inflammation can occur due to obstruction.

There is a report of Tornwaldt cyst formation following concurrent chemoradiotherapy for nasopharyngeal carcinoma ⁶.

Radiographic features

These lesions have a characteristic appearance and should usually not be confused with more sinister pathology. Typically, they are well-circumscribed rounded lesions immediately deep to the mucosa. They are usually nestled between and anterior to the longus colli muscles. They elevate the mucosa, forming a convex surface into the nasopharynx. They are variable in size, ranging from a few millimeters to a few centimeters in diameter, but are typically 2-10 mm in size ^1,3.

CT

On CT they appear as well-circumscribed low density (fluid density centrally) and are non-enhancing. If the fluid is protein-rich, it may be hyperattenuating and can even mimic a solid lesion.

MRI

Similarly, MRI demonstrates these cysts as being well-circumscribed with a thin wall.

Signal characteristics

• T1: signal is variable depending on protein content

• T2: high signal 

• T1 C+ (Gd): no enhancement

Treatment

Asymptomatic lesions require no treatment. If treatment is required, deroofing the cyst (marsupialization) is usually sufficient and can be performed via a transnasal approach ⁴.

Differential diagnosis

There is usually no real differential, however adenoidal/mucosal masses can sometimes have cystic components, and therefore the differential includes:

• normal/prominent adenoidal tissue

• mucous retention cyst

• intra-adenoid cyst: can be difficult to differentiate on MRI from a Tornwaldt cyst ¹⁰

• nasopharyngeal carcinoma (NPC): up to 12% are midline ²

• minor salivary gland tumors

• neurenteric cysts

• meningocoele

History and etymology

It is named after Gustav Ludwig Tornwaldt (1843-1910) ⁵, a German physician who described it as a pathological entity in 1885 ⁹. The original description of this cyst is thought to have been made by A F C J Meyer in 1840 ⁹.