Tarlov Cysts¶

Definition¶

Tarlov cysts (perineural cysts) are CSF-filled cysts arising from the nerve root sheaths, most commonly in the sacral spine (S2–S3). They are very common — found in approximately 5–9% of spine MRIs — and are almost always incidental and asymptomatic.

Imaging Findings¶

MRI¶

CSF-signal cysts (T1 dark, T2 bright) in the sacral spinal canal, arising from the nerve root sleeves
The nerve root fibers may be seen traversing the cyst wall or within the cyst
Can be unilateral or bilateral, single or multiple
May cause sacral bone remodeling (scalloping) when large

CT Myelography¶

Delayed filling with contrast (hours after intrathecal injection) — the cyst communicates with the subarachnoid space through a narrow neck (ball-valve mechanism)
This delayed filling distinguishes Tarlov cysts from simple meningeal diverticula

Clinical Pearl

Tarlov cysts are almost always incidental findings that should NOT be attributed as the cause of low back pain or radiculopathy without exhaustive exclusion of other causes. Large cysts (>1.5 cm) occasionally cause symptoms from mass effect on adjacent nerve roots, but this is rare. Over-attributing symptoms to Tarlov cysts leads to unnecessary interventions.

Key Points¶

CSF-signal sacral perineural cysts — very common incidental finding (5–9%)
Almost always asymptomatic — do not attribute symptoms without excluding other causes
Nerve root fibers within or on the cyst wall distinguish from simple meningeal cysts
Large cysts may remodel sacral bone
Delayed filling on CT myelography is characteristic

References¶

Lim Y, Selbi W. Tarlov Cyst. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jun 12. Available from: https://www.ncbi.nlm.nih.gov/books/NBK582154/
Tarlov cyst. Radiopaedia.org. Available from: https://radiopaedia.org/articles/tarlov-cyst
Nabors MW, Pait TG, Byrd EB, Karim NO, Davis DO, Kobrine AI, Rizzoli HV. Updated assessment and current classification of spinal meningeal cysts. J Neurosurg. 1988;68(3):366-77. doi:10.3171/jns.1988.68.3.0366
Murphy K, Nasralla M, Pron G, Almohaimede K, Schievink W. Management of Tarlov cysts: an uncommon but potentially serious spinal column disease—review of the literature and experience with over 1000 referrals. Neuroradiology. 2023;66(1):1-30. doi:10.1007/s00234-023-03226-6
Paredes Mogica JA, Feigenbaum F, Pilitsis JG, Schrot RJ, Oaklander AL, De EJB. Sacral Tarlov perineurial cysts: a systematic review of treatment options. J Neurosurg Spine. 2024;40(3):375-388. doi:10.3171/2023.9.SPINE23559
Fletcher-Sandersjöö A, Mirza S, Burström G, Pedersen K, Kuntze Söderqvist Å, Grane P, et al. Management of perineural (Tarlov) cysts: a population-based cohort study and algorithm for the selection of surgical candidates. Acta Neurochir (Wien). 2019;161(9):1909-1915. doi:10.1007/s00701-019-04000-5