A Tarlov cyst is a fluid-filled sac that forms on the nerve roots near the base of the spine, most commonly in the sacrum (the triangular bone at the bottom of your spinal column). These cysts are found in roughly 1% to 5% of the population, usually discovered by accident on an MRI ordered for something else entirely. The vast majority never cause problems, but in about 1% of cases they become symptomatic and can significantly affect quality of life.
What Makes Tarlov Cysts Different
Your spinal nerves are surrounded by protective membranes. Tarlov cysts develop in a specific spot: the space between two of these membrane layers, right where nerve roots exit the spinal canal. What sets them apart from other spinal cysts is that their walls contain actual nerve tissue, including nerve fibers and sometimes nerve cell bodies. This is the key distinction. Other types of spinal cysts sit outside the nerves, but Tarlov cysts are woven into them, which is part of what makes treatment more complicated.
Inside the cyst is cerebrospinal fluid, the same liquid that normally cushions your brain and spinal cord. The cysts typically form at or below the junction where nerve roots branch off from the spinal cord, which is why the sacral region is the most common location.
How These Cysts Form
The exact cause isn’t fully settled, but the leading theory involves a one-way valve effect. Cerebrospinal fluid flows into the nerve root sheath but can’t easily flow back out. Over time, this trapped fluid increases pressure inside the space, stretching the nerve lining and creating a cyst. Activities that raise spinal fluid pressure, like coughing, straining, or standing for long periods, may contribute to gradual enlargement.
Other proposed causes include inflammation following trauma, which could damage the nerve sheath and create the conditions for fluid to accumulate. Some researchers have observed immune cells surrounding certain cysts, suggesting an inflammatory process. There’s also evidence pointing to a genetic component, particularly in people with connective tissue disorders that affect collagen. In reality, multiple factors likely work together: a structural vulnerability in the nerve sheath, combined with fluid pressure dynamics that slowly expand the cyst over months or years.
Symptoms When Cysts Become Problematic
Most Tarlov cysts sit quietly and never cause trouble. When they do become symptomatic, it’s because the cyst has grown large enough to compress the nerve root it sits on, or the increased pressure within the cyst itself irritates the surrounding nerves. Larger cysts are generally more likely to cause symptoms, though size alone doesn’t always predict who will have problems.
The most common symptom is lower back pain, often concentrated in the sacral area. Many people experience sciatica: a burning or shock-like pain that travels from the lower back through the buttocks and down one leg, sometimes reaching below the knee. Because the sacral nerves control sensation and movement in the lower body, a compressed nerve root can also cause numbness, tingling, weakness, or reduced control in the legs and feet.
Sacral nerves also govern bladder, bowel, and sexual function, so symptomatic cysts can lead to urinary incontinence, constipation, and sexual dysfunction. Some people develop headaches related to changes in spinal fluid pressure. In severe cases, prolonged pressure on surrounding structures can cause the nearby bone to deteriorate.
How Tarlov Cysts Are Diagnosed
MRI is the primary tool for identifying Tarlov cysts. On imaging, they appear as fluid-filled pouches along the nerve root sleeves, most often at the S1-S2 or S2-S3 levels of the sacrum. A standard lumbosacral MRI without contrast is typically sufficient to spot them. CT scans with dye injected into the spinal canal are rarely needed but can help confirm the diagnosis in ambiguous cases.
The challenge with diagnosis isn’t finding the cyst. It’s determining whether the cyst is actually responsible for your symptoms. Because these cysts are so common as incidental findings, a doctor needs to carefully match the cyst’s location and size to the specific nerve distribution where you’re experiencing pain or dysfunction. Other conditions, like herniated discs or spinal stenosis, can produce overlapping symptoms and may even coexist with a Tarlov cyst.
Living With an Asymptomatic Cyst
If your Tarlov cyst was discovered incidentally and isn’t causing symptoms, treatment is typically unnecessary. Your doctor may recommend periodic MRI scans to monitor whether the cyst is growing, but many people live their entire lives without ever knowing the cyst is there. The key is being aware of the symptoms that would signal a change, particularly new sacral pain, leg weakness, or bladder issues, so you can follow up if something shifts.
Treatment for Symptomatic Cysts
When a Tarlov cyst is clearly causing symptoms, treatment options range from conservative management to surgery. Initial approaches often focus on managing pain and maintaining function through physical therapy, activity modification, and medications that target nerve pain. These measures don’t shrink or eliminate the cyst, but they can make symptoms manageable for some people.
For cysts that don’t respond to conservative care, procedural options include percutaneous aspiration (draining the cyst fluid through a needle, sometimes combined with injecting fibrin glue to prevent refilling) and open surgery. Two common surgical techniques are cyst fenestration, which involves opening and draining the cyst, and nerve root imbrication, a more involved procedure that reconstructs the nerve root sheath to prevent the cyst from refilling.
Surgical outcomes are generally favorable. A 2024 meta-analysis covering 283 patients found that 81% experienced complete or substantial resolution of symptoms one year after surgery. A separate prospective study reported that 82.3% of surgical patients noted improvement in their quality of life. Cyst recurrence rates after surgery sit around 8%, compared to about 20% for percutaneous drainage procedures, though symptom recurrence rates are similar between the two approaches (roughly 20-21%).
Risks of Surgical Treatment
Because Tarlov cysts contain nerve tissue within their walls, surgery carries inherent risks that don’t apply to simpler fluid collections. The most significant complication is cerebrospinal fluid leakage after the procedure, which historically has sometimes required additional surgeries to seal. Infection is another concern, and some patients have developed aseptic meningitis, an inflammatory reaction in the membranes surrounding the brain and spinal cord, after treatment. These risks are part of why surgery is reserved for cases where symptoms are significant and haven’t responded to less invasive management.
The presence of nerve fibers in the cyst wall also means surgeons must work carefully to preserve nerve function during the procedure. This is a meaningful difference from treating a simple fluid-filled sac and is one reason why experience with this specific condition matters when choosing a surgical team.