Tarlov cyst

Tarlov cysts, also called perineural cysts, are CSF-filled dilatations of the nerve root sheath at the dorsal root ganglion (posterior nerve root sheath). These are type II spinal meningeal cysts that are, by definition, extradural but contain neural tissue.

Most Tarlov cysts are asymptomatic, but in some individuals can lead to neurological dysfunction and pain. This has been termed sacral symptomatic Tarlov cysts ⁶. 

Epidemiology

Tarlov cysts are common and are found in up to 10% of the population, more commonly in women ⁶.

Associations

They have been occasionally associated in patients with connective tissue disorders:

• Marfan syndrome ⁵
• Ehlers-Danlos syndrome
• Sjögren syndrome
• Loeys-Dietz syndrome

Clinical presentation

The prevalence and severity of symptoms in patients with Tarlov cysts is controversial. Traditionally, and still largely the dominant view, it has been believed that like other spinal meningeal cysts, the vast majority of Tarlov cysts are incidentally found and are entirely asymptomatic. Large cysts may cause local pressure effect and remodel bones. However, symptoms don't appear to correlate well with size ². 

In some patients, however, it appears that Tarlov cysts are the cause of symptoms, such as pelvic or perineal pain/discomfort, sphincter/sexual dysfunction, radicular pain/numbness and neurogenic claudication ^3,6. 

Radiographic features

While Tarlov cysts are most common in the lower lumbar spine and in the sacrum, they can occur anywhere in the spine. 

Tarlov cysts appear as very thin-walled CSF intensity simple cystic structures closely related to sacral and lower lumbar nerves. The sacral foramina may be widened. Morphology can vary from a simple rounded cyst to a complex loculated cystic mass with septations.

Treatment and prognosis

In asymptomatic individuals no treatment or further investigation is necessary. This accounts for the vast majority of Tarlov cysts. 

In patients with otherwise unexplained neurological symptoms potentially attributable to the cysts then further investigation and/or treatment may be warranted. 

Electromyography can be used to identify axonal damage in symptomatic patients ⁶. 

Cysts thought to be symptomatic can be aspirated under CT guidance using a two-needle technique and fibrin can be injected as a sealant ⁷. 

Numerous surgical approaches have also been described ⁷. 

History and etymology

Tarlov cysts were initially described by the American neurosurgeon Isadora Max Tarlov (1905-1977) in 1938 ^1,6,8.

Differential diagnosis

Usually, the diagnosis is self-evident and no alternatives should be entertained. Occasionally appearances are atypical and possible differential considerations include:

• dural ectasia
• spinal synovial cyst
• meningocele
• nerve sheath tumor
• spinal metastases