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Neuroradiology Case of the Week
Case 336
Scott Cassar, MD
Clinical
Presentation: Patient is a a 45-year-old female with severe chronic lumbar spine pain and urinary incontinence.
Imaging Findings: A 1.0 cm cystic lesion in the region of the left sacral nerve root characteristic of CSF with high T2 and low T1 signal.
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Figure 1: Axial T2; high signal round lesion in the region of the left sacral nerve root.
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Figure 2: Sagittal T2: high-signal round lesion with nerve root traversing through the lesion. |
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Figure 3: Sagittal T1: low-signal round lesion in the region of the left sacral nerve root. |
Diagnosis: Tarlov cyst
Discussion: Tarlov or perineurial cysts were first described by Tarlov in 1938 as an incidental finding at autopsy. These cysts are collections of CSF fluid in the spinal nerve root sheath at or distal to the junction of the posterior nerve root and the dorsal root ganglion. Frequently found in the sacral vertebrae (S2 to S3), Tarlov cysts differ from meningeal diverticula by having only a potential communication with the subarachnoid space and therefore delayed or no filling on myelograms. They also occur in the perineurial space and have nerve fibers through or along the wall of the cyst.
The etiology of Tarlov cysts is unknown and hypotheses for their formation include inflammation, trauma, or congenital weakness of the dura in the setting of elevated CSF pressures. They are found in 4.6% of the population and are typically asymptomatic. These cysts may grow over time to stretch or compress the nerve root. Symptoms of nerve root compression, such as sacral radiculopathy, perineal, hip, or leg pain, and bladder or bowel dysfunction, may be found in up to 20% of patients.
Multiple treatment options exist for symptomatic perineurial cysts larger than 1.5 cm. Peritoneal or percutaneous drainage have provided temporary relief when the shunt is in place; however there is a risk of meningitis in percutaneous drainage. Surgical removal of the cyst with excision of the nerve root and ganglion has also been proposed but the potential for neurological defects limits its acceptance. Decompressive laminectomy has not proven to be a useful approach. Other surgical options include cyst wall resection, cyst fenestration and imbrication, and cyst shrinkage with bipolar cautery.
References:
- Acosta FL Jr, Quinones-Hinojosa A, Schmidt MH, Weinstein PR. Diagnosis and management of sacral Tarlov cysts. Case report and review of the literature. Neurosurg Focus. 2003 Aug 15;15(2:)E15. [Medline]
- Langdown AJ, Grundy JR, Birch NC. The clinical relevance of Tarlov cysts. J Spinal Disord Tech. 2005 Feb;18(1):29-33. [Medline]
- Tarlov IM. Perineural cysts of the spinal root. Arch Neurol Psychiatry. 1938;40:1067-1074.
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