Tarlov Cyst on MRI: What Is It and When Does It Matter?

A Tarlov cyst is a small sac filled with fluid, usually cerebrospinal fluid, that forms on a nerve root near the bottom of the spine, most often in the sacrum. It is also called a perineural or meningeal cyst. Most are found by chance on an MRI or CT done for something else, such as back pain, and most never cause symptoms.

This guide is for adults reading an existing scan report that mentions a Tarlov or perineural cyst. It explains what the wording usually means and what to ask. It cannot tell you whether a cyst explains your own symptoms.

The sacrum is the triangle-shaped bone at the base of the spine, between the hips and above the tailbone. The nerve roots that pass through it help control sensation and movement in the legs, as well as bladder, bowel and sexual function. That is why symptoms, when they occur, can involve these areas. Cleveland Clinic notes that the size of a cyst can change with the pressure of the surrounding spinal fluid.

A Tarlov cyst on a report does not make back pain an emergency on its own. But some symptoms can signal pressure on the nerves at the base of the spine and need same-day emergency assessment. The NHS advises calling emergency services or going to an emergency department if back pain comes with:

• Loss of feeling around the genitals or anus.
• New difficulty passing urine, or losing control of bladder or bowels.
• Pain, tingling, weakness or numbness in both legs.
• New changes in genital sensation or sexual function.
• Pain that started after a serious accident.

Cleveland Clinic suggests seeing a healthcare provider for lower back pain without a known cause, ongoing constipation or incontinence, or numbness or weakness in the legs. Arrange a prompt review if symptoms are new, are getting worse, or are different from what you had when the scan was done.

Estimates vary because most people with a Tarlov cyst never know they have one. Cleveland Clinic cites one study suggesting just under 4% of people in the United States have one, while the National Organization for Rare Disorders (NORD) gives an estimate of about 4.6% to 9% of adults when cysts with and without symptoms are counted.

They are more common in women, and Cleveland Clinic lists age 30 to 60, earlier spine injury and some connective tissue conditions, such as Marfan syndrome or Ehlers-Danlos syndrome, as risk factors. The cause is not well understood. Some people have more than one cyst.

Sometimes, but not usually. Cleveland Clinic states that only 5% to 8% of people diagnosed with a Tarlov cyst have symptoms, and that larger cysts are more likely to cause them. NORD notes that small cysts can grow over time.

When symptoms do occur, the sources describe:

• Pain in the lower back, buttocks or legs, sometimes with burning or shock-like sensations.
• Numbness, tingling or weakness in the legs or feet.
• Bladder or bowel problems, such as difficulty emptying the bladder, incontinence or constipation.
• Changes in sexual function.
• Pelvic, genital or rectal pain in some people.
• Symptoms that worsen with sitting, standing, walking, coughing or sneezing, and ease when lying down, in some people.

Often the answer is no. Back pain is very common, and many spine MRIs show findings that are not the source of pain. A cyst that is small and does not press on a nerve is often an incidental finding, meaning it was seen by chance.

Deciding whether a cyst is relevant usually involves a full history, a neurological examination and a review of the images, including the cyst's size and its relationship to the nerves. Sometimes further imaging is used; NORD mentions that a myelogram can show whether a cyst connects with the fluid around the spinal cord. If your symptoms match the area of the cyst, ask whether a referral to a spine specialist is appropriate.

A cyst that causes no symptoms does not need treatment. Cleveland Clinic notes that some providers may suggest periodic check-ups to watch for changes in size or symptoms, so ask what your own plan is.

For cysts that do cause symptoms, there is no single agreed treatment. Care is usually tailored to the person and often starts with symptom relief. Options described by Cleveland Clinic and NORD include:

• Pain-relief medicines, nerve-pain treatments or steroid injections, chosen with a clinician.
• TENS, which uses mild electrical pulses on the skin to ease nerve pain.
• Draining the cyst with a needle and then filling or sealing it, for example with fibrin glue, because a drained cyst often refills.
• Surgery, generally reserved for people whose symptoms do not respond to other treatment.
• No option reliably prevents a cyst from coming back, and some people do not improve even after treatment.

A radiologist writes the report for the clinician who requested the scan. Take the full report to that clinician, along with a short note of your symptoms and when they started. Questions to consider:

• Where exactly is the cyst, how large is it, and is it pressing on a nerve?
• Do you think it explains any of my symptoms, or is it likely incidental?
• Is any follow-up scan or examination planned?
• Which new symptoms should make me seek care urgently?
• If treatment is ever considered, what are the options, side effects and chance of the cyst returning?
• Would a referral to a spine specialist help in my situation?

On SameCase, patients and verified doctors share de-identified cases. Reading how others with a Tarlov cyst on their report described their symptoms, scan wording and follow-up can help you organise your own timeline and questions.

Other people's cases cannot show whether your cyst is causing symptoms or which treatment would suit you. We suggest using them only to prepare for a conversation with your own clinician.