Imaging Recommendations for Tarlov Cysts
MRI of the lumbosacral spine is the imaging modality of choice for diagnosing Tarlov cysts, demonstrating characteristic hypointense signal on T1-weighted images and hyperintense signal on T2-weighted images. 1, 2, 3, 4, 5
Primary Imaging Modality
- MRI provides superior soft tissue contrast and is the gold standard for identifying Tarlov cysts, showing the cystic nature, size, location, and relationship to adjacent nerve roots 1, 2, 3, 4, 5
- The cysts appear hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences, similar to cerebrospinal fluid 1
- MRI allows assessment of cyst size (critical for surgical planning, as cysts >1.5 cm predict better surgical outcomes), nerve root compression, and bone remodeling changes 6, 1
Complementary Imaging
- CT myelography can demonstrate communication between the cyst and subarachnoid space, which is a key diagnostic feature distinguishing Tarlov cysts from other perineural lesions 2
- CT imaging may identify bone erosion or remodeling of the sacral vertebrae caused by chronic cyst expansion 1
- Bone scintigraphy has been reported in multilocular disseminated cases but is not routinely indicated for diagnosis 5
Imaging Protocol Specifics
- Target imaging to the lumbosacral spine, as Tarlov cysts most commonly affect sacral nerve roots (S2-S3 levels) 1, 2, 3, 4
- Standard MRI sequences (T1-weighted and T2-weighted) are sufficient for diagnosis without requiring contrast administration 1, 2, 3
- For surgical planning in symptomatic cases, MRI should clearly delineate the cyst ostium and its communication with the subarachnoid space 6, 2
Follow-Up Imaging Strategy
- For asymptomatic incidentally discovered Tarlov cysts, the American College of Radiology recommends no routine imaging surveillance 6
- Consider a single follow-up MRI at 1 year to demonstrate stability, then discontinue surveillance if the cyst remains stable 6
- Repeat imaging is only indicated if new symptoms develop (radicular pain, bladder/bowel dysfunction, or progressive neurological deficits) 6, 1, 3
Critical Diagnostic Pitfalls
- Do not confuse Tarlov cysts with other cystic lesions of the spine such as arachnoid cysts, synovial cysts, or schwannomas—Tarlov cysts specifically arise between the perineurium and endoneurium near the dorsal root ganglion 2, 3, 4
- The presence of nerve root fibers within the cyst wall (visible on high-resolution MRI) is pathognomonic for Tarlov cysts 2, 4
- Most Tarlov cysts (>80%) remain asymptomatic and stable over time, so imaging findings must be correlated with clinical symptoms before attributing pain or neurological deficits to the cyst 6, 4