Tarlov cyst

Tarlov cysts, also known as perineural cysts, are fluid-filled protrusions of the nerve root sheaths that usually occur in the area of the sacral spine. They are asymptomatic in many cases, but can also cause pain in the back, buttocks and legs, as well as neurological deficits. The exact cause of their development is not fully understood. Treatment varies from conservative measures such as pain medication and physiotherapy to surgical intervention for severe symptoms.

Drawing of a sacral Tarlov cyst with pressure effect (red) on surrounding nerve roots
Sacral Tarlov cyst. The cyst originates from the S2 root and exerts pressure (red) on the surrounding nerve roots. Image: University Department of Neurosurgery, Inselsptial Bern © CC BY-NC 4.0

Tarlov cysts most commonly occur in the sacral area and typically affect the sacral nerve roots S2 or S3  *. In principle, however, they can occur anywhere along the spine. *, *

They develop when fluid leaks into the space between the perineurium (which surrounds individual nerve fiber bundles) and the epineurium (which surrounds the entire nerve) *. Usually there is a small connection to the cerebral spinal fluid space, which can cause nerve roots to be compressed *, *. In contrast to other meningeal cysts, Tarlov cysts take longer to fill with contrast agent during myelography, an imaging technique used to visualize the cerebrospinal fluid space, and do not collapse immediately during CSF drainage. *, *, *

How are Tarlov cysts classified?

Classically, cysts associated with the meninges of the spinal column are categorized into three types  *:

  • Type I: extradural (outside the original meninges) meningeal cysts without nerve fibers
  • Type II: extradural meningeal cysts with nerve fibers
  • Type III: intradural meningeal cysts

The classic Tarlov cysts are type II cysts according to Nabors et al. *

How common is a Tarlov cyst?

Depending on the imaging technique and analysis used, a Tarlov cyst can be found in approximately 1–13% of all individuals and is an incidental finding in the vast majority of cases *, *, *, *. Women are affected more often than men *, *. This high number makes it clear that only a very small proportion of the cysts actually cause symptoms, which often makes diagnosis difficult.

What is the cause of a Tarlov cyst?

The exact cause of Tarlov cysts is still unclear. It is assumed that factors such as inflammation, injury, degenerative changes or a genetic predisposition can contribute to the formation of these cysts. The most common hypotheses include an inherited risk, an enlargement of the soft meninges with subsequent encapsulation or increased pressure in the cerebral fluid space due to connective tissue weakness *.

What symptoms does a Tarlov cyst cause?

Most Tarlov cysts do not cause any symptoms *. Only a small percentage of them lead to symptoms, usually when they grow due to the pressure of the cerebral fluid *, *, *, *, *. This can cause the cysts to stretch nerve fibers or press against surrounding bone *, *. Depending on their location, various symptoms of nerve compression *, *, * may occur, such as:

  • pain radiating along the nerve roots, similar to sciatica
  • problems with the bladder or bowe
  • localized low back pain, especially with larger cysts *, *, *, *

In rare cases, Tarlov cysts have also been associated with sexual dysfunction, but this has not been sufficiently studied *, *, *. Most commonly, pain radiates to the thigh, the area around the anus or the perineum and can be aggravated by standing, coughing or pressing *. Large cysts also exert pressure on the periosteum of the sacrum, causing local pain.

Even relatively small cysts can cause symptoms. In addition, problems such as bladder, bowel or sexual dysfunction are often not addressed or asked about during the doctor's appointment. As a result, Tarlov cysts are often considered an incidental finding and left untreated, which can lead to long-term psychological strain for those affected. In addition, incorrect or inadequate treatment can lead to recurring symptoms, lasting discomfort and frustration for the treating physicians. *

How is a Tarlov cyst diagnosed?

Tarlov cysts are usually visible in magnetic resonance imaging (MRI) of the spine. Based on this, further diagnostic measures such as CT myelography and urodynamic examination are used selectively.

Diagnosis flowchart. In cases of suspected Tarlov cyst, a fixed diagnostic protocol is recommended (adapted from Fletcher-Sandersjöö et al., 2019).

How is a Tarlov cyst treated?

If a Tarlov cyst is detected by imaging, careful investigation is needed to determine whether it is actually the cause of the symptoms, as it is not always responsible for them *. As mentioned earlier, the majority of Tarlov cysts do not cause any symptoms and should therefore not be treated *. This does not mean that patients' complaints are not credible, but that they often exist independently of the cyst. 

Larger cysts (>1–1.5 cm) can, however, cause radicular pain or bladder and bowel dysfunction, and in such cases treatment should be considered *, *. In particular, patients whose symptoms worsen when they change position or strain could benefit from therapy *. A thorough examination and additional diagnostic tests are essential.

Surgical treatment

To determine whether surgery is appropriate, it may be helpful to first drain the cyst using a CT-guided needle. If patients experience symptom relief, they are likely to benefit from surgical treatment. *

Treatment options

The optimal surgical approach for Tarlov cysts is still a matter of debate *, *. There are various approaches that can be divided into three categories:

  • reducing the pressure of the cyst: This is done by draining the cerebral fluid to reduce the pressure in the cyst (e.g. lumboperitoneal shunt). *, *
  • removing fluid from the cyst: The cyst is punctured to drain the fluid. However, this method has a high rate of relapse. *, *, *
  • open surgical cyst lifting: This is usually done by ligating the communication with the dural tube . *, *, *, *, *, *

Careful patient selection and individually tailored therapy are crucial for successful treatment.

Possible complications

According to studies, the rate of complications after surgery is between 5 and 20%. The most common complications are infections, cerebrospinal fluid loss (CSF leaks), temporary pain intensification, sexual dysfunction and problems with bladder and bowel emptying. In addition, cyst recurrence can be expected in about 30% of patients. *, *

The frequency of complications also depends to a large extent on the surgeon's experience with this procedure.

Our experience at Inselspital

Many patients benefit from surgical treatment if they have been carefully selected. However, a significant improvement in symptoms can only be expected in about 50% of patients, although higher numbers are reported in many studies. *, *, *, *, *, *, *, *

The treatment is most successful for radicular pain, i.e. pain that originates from one or more nerve roots in the area of the spine. It has a rather limited effect on sexual dysfunction. *, *, * For voiding problems, the duration of the symptoms plays an important role: the shorter they have been present, the better the prognosis. 

Ideal candidates for surgery are patients with large cysts (over 1.5 cm) and short-term radicular symptoms. *

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