Tarlov cyst seen by chance on a spine MRI
An MRI or CT of the low back or pelvis done for something else may report a "Tarlov cyst" or "perineural cyst". This means a small pouch of spinal fluid on a nerve root, most often at the base of the spine. They are often found by chance and most cause no symptoms. (Klepinowski 2021)(Murphy 2024) This page covers what the report means, how common they are and when they matter, not treatment.
What the report words mean
- Tarlov cyst or perineural cyst. A pouch filled with spinal fluid that forms in the covering of a nerve root, where the nerve leaves the spine. (Klepinowski 2021)(Shoyab 2021)
- Sacral and level names. Most are in the sacrum, the triangle-shaped bone at the base of the spine. Levels are numbered S1, S2 and so on from the top, and S2 is the most common place. A few are higher up the spine. (Klepinowski 2021)
- Size. The average size in the pooled studies was about 12 mm across. A report may give a size in millimetres in one or more directions. (Klepinowski 2021)(Shoyab 2021)
- Single or multiple. Across the pooled studies, 57% of people with Tarlov cysts had one and 43% had more than one. (Klepinowski 2021)
- Bony scalloping. A large cyst can press a shallow dent into the bone around it over time. A radiology paper suggests reports mention this, along with any narrowing where the nerve leaves the spine. (Shoyab 2021)
- On a pelvic ultrasound. A cyst that reaches forward into the pelvis can be mistaken on ultrasound for a cyst or mass near the ovary. (Murphy 2024) About 5% of Tarlov cysts reach into the pelvis. (Shoyab 2021) See ovarian cyst found by chance.
How common they are, by age and sex
A review of 22 imaging studies with 13,266 people found Tarlov cysts in about 4% of people overall. They were found in about 6% of women and 3% of men, and in about 0.5% of children. (Klepinowski 2021)
| Group | Share with a Tarlov cyst |
|---|---|
| Women | 5.8% |
| Men | 3.0% |
| Children | 0.5% |
| Everyone | 4.2% |
In a French study of 1000 adults aged 18 to 94 who had an MRI of the sacrum, 13% had a Tarlov cyst, 101 women and 31 men, and none were found in 100 children and teenagers. A review reports that in these studies cysts were more common in women and with older age. (Murphy 2024) Numbers are higher when the whole sacrum is scanned, so a cyst can show up on one scan and not have been seen on an older one that did not include that area. (Murphy 2024)(Shoyab 2021)
When they matter
- Most need nothing. Tarlov cysts are usually found by chance and most cause no symptoms. (Klepinowski 2021)(Murphy 2024) A radiology paper says they need no specific treatment unless they are the cause of symptoms. (Shoyab 2021)
- Sometimes linked to symptoms. In the review of 22 studies, about 16% of cysts matched a person's symptoms, such as nerve pain down a leg. (Klepinowski 2021) When disc wear or other spine changes are on the same scan, it can be hard to tell which one is causing symptoms. (Murphy 2024)
- Change over time. In one study that repeated MRI over 4 years, none of the cysts got smaller and 17% got slightly longer. (Murphy 2024)
- Repeat scans. The sources here do not set a routine repeat scan for a Tarlov cyst found by chance, and a review says there is no agreed approach. (Murphy 2024) Whether another scan or a referral is needed depends on your symptoms and the rest of the report. Your doctor decides.
- Seeing a GP. The NHS says to see a GP for back pain that does not improve after a few weeks, stops you doing day-to-day things, comes with weight loss without trying, a lump or swelling or a change in the shape of your back, does not improve with rest or is worse at night, is worse when sneezing, coughing or pooing, or is between the shoulders. (NHS back pain)
- Worry is real. See after an abnormal screening result.
The NHS says to ask for an urgent GP appointment or get help from NHS 111 (your local urgent care line elsewhere) if you have back pain and feel hot, cold, shivery or generally unwell, or the pain is severe and starts suddenly or gets worse quickly. It says to call 999 or go to A&E (your local emergency number elsewhere) for back pain with pain, tingling, weakness or numbness in both legs, loss of feeling around the genitals or anus, changes in bladder or bowels, changes in sexual feeling or function, chest pain, or pain after a serious accident. (NHS back pain)
Other things a scan may show
The same scan may mention other chance findings, each with its own page: a disc bulge or wear, Schmorl nodes and a spine hemangioma. A fluid-filled cyst found by chance in the head is covered on arachnoid cyst on a brain scan.
Who it applies to
Adults told that an MRI or CT of the spine or pelvis, done for something else, shows a Tarlov or perineural cyst. Children, people already being seen for a Tarlov cyst, and a scan done because of leg weakness, numbness or bladder or bowel changes are outside this page.
Routine age-based screening
A spine finding on a scan does not replace the routine screenings for your age. See screenings by age and gender.
Where they differ:
- How common they are. The pooled review gives about 4%. (Klepinowski 2021) Single MRI studies range from 1.5% to 13.2%, with the highest on dedicated MRI of the sacrum. (Murphy 2024) A study of spine MRI for back pain in Bangladesh found 6.5%. (Shoyab 2021)
- Women and men, and age. The pooled review found them about twice as often in women, (Klepinowski 2021) and a review reports more with older age. (Murphy 2024) The Bangladesh study found no link with sex or age. (Shoyab 2021)
- How many cause symptoms. The pooled review found about 16%. (Klepinowski 2021) A radiology paper says most studies put it at 1% to 2%, while others suggest up to 25%. (Shoyab 2021) Studies used different scans and groups of people.
Your doctor decides what your result means for you.
Questions people ask
What is a Tarlov cyst?
A Tarlov cyst, also called a perineural cyst, is a small pouch filled with spinal fluid on the covering of a nerve root. Most are in the sacrum, the bone at the base of the spine, and the S2 level is the most common place. (Klepinowski 2021) (Shoyab 2021)
How common are Tarlov cysts?
A review of 22 imaging studies with 13,266 people found them in about 4% of people. Single studies range from about 1.5% to 13%, with the highest numbers when the whole sacrum is scanned. (Klepinowski 2021) (Murphy 2024)
Do Tarlov cysts cause symptoms?
Most do not and are found by chance. In the review of 22 studies, about 16% of cysts matched a person's symptoms. Other studies give lower or higher shares. (Klepinowski 2021) (Shoyab 2021)
Do Tarlov cysts grow?
Little is known. One study that followed cysts on MRI for 4 years found that none got smaller and 17% got slightly longer. Your doctor decides what your result means for you. (Murphy 2024)
When should I get help for back pain?
The NHS says to call 999 or go to A&E for back pain with pain, tingling, weakness or numbness in both legs, loss of feeling around the genitals or anus, or changes in bladder or bowels. It lists other signs that need a GP or urgent help. (NHS back pain)
Related
- Baker's cyst behind the knee seen by chance on a scan
- Disc bulge or wear seen by chance on a spine scan
- Schmorl nodes seen by chance on a spine scan
- Spine hemangioma seen by chance on a scan
- Arachnoid cyst found by chance on a brain scan
- Ovarian cyst found by chance: follow-up scans
- After an abnormal screening result
- Screenings by age and gender