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5b - Answer: Back pain. Status post lumbar decompression.

David Yousem MBA, MD
David M Yousem, MBA, MD
Professor of Radiology, Vice Chairman and Associate Dean
Includes DICOM files

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Case Report

HISTORY: Back pain. Status post lumbar decompression.


Bilateral L5 laminectomies have been performed. The thecal sac is patulous at the posterior decompression site, protruding slightly posteriorly. Conus medullaris terminates at L1. Small amount of smooth enhancement is present along a few cauda equina nerve roots, best seen on slice 7 (series 7) . This finding is most evidence along a left exiting S1 nerve root and may represent inflammation of the nerve. The appearance of the cauda equina is otherwise normal.

No evidence of fracture. Alignment of the vertebral bodies and facets is normal. Bilateral sacroiliac osteoarthritis. Hemangiomata are noted within the T12 vertebral body and right iliac wing.

There are multiple Tarlov cysts. Specifically, ovoid perineural root sleeve cysts are noted along the L5 nerve roots, left slightly larger than right. At S1, multiple nerve roots are surrounded by cysts with the largest bulging out of the at the S2 foramen, left larger than right. The right-sided Tarlov cysts measures 14 x 16 x 22 mm and the exiting nerve root is not visible. A tiny perineural root sleeve cyst at T11-T12 on the left is also noted without significant mass effect on the nerve.

There are multilevel degenerative changes, described level by level below.

T12-L1: Mild disc degeneration without neuroforaminal narrowing or spinal stenosis.

L1-L2: Mild disc degeneration without neuroforaminal narrowing or spinal stenosis. Mild bilateral facet arthropathy.

L2-L3: Disc degeneration and mild bilateral facet arthropathy. No neuroforaminal narrowing or spinal stenosis.

L3-L4: A central disc protrusion is present with linear T2 hyperintense signal which may represent a small annular fissure. Thickening of ligamentum flavum. No spinal stenosis or neuroforaminal narrowing. Mild bilateral facet arthropathy with small facet effusions.

L4-L5: A right paracentral inferiorly directed disc extrusion effaces the right lateral recess/subforaminal zone, although transiting nerve roots do not appear to be deviated. Mild bilateral facet arthropathy. No spinal stenosis or neuroforaminal narrowing.

L5-S1: A superolaterally directed right paracentral disc protrusion is separated from the exiting right L5 nerve root by a Tarlov cyst. No spinal stenosis or neuroforaminal narrowing. Moderate bilateral facet arthropathy.


  1. Smooth enhancement along the left S1 nerve root may represent venous enhancement or possibly inflammation. Please correlate clinically and consider dedicated high resolution for clarification if clinically.
  2. A likely Tarlov cyst at the foramen is present, although smaller than other levels.
  3. Status post L5 posterior decompression. Degenerative disc disease, worst at L4-L5 and L5-S1 where a disc extrusion are present, but do not result in significant nerve root impingement, spinal stenosis, or foraminal compromise.
  4. Multiple Tarlov cysts largest at the right S2 nerve root. Other smaller lesions as described above. (Nabor Classification Type 2)

Nabors et al classified these cysts into three types : extradural meningeal cysts without spinal nerve root fibers (Type I); spinal extradural meningeal cysts with spinal nerve root fibers (Type II, Tarlov cyst); and spinal intradural meningeal cysts (Type III)16). Type I is further divided into extradural arachnoid cysts (Type IA) and sacral meningoceles (Type IB). In most of the reported cases of Type IA SEMC, there was a communication of the CSF with intradural subarachnoid space through dural defect.


Case Challenge: Spine MRI Cases - I-MED Study

Content reviewed: May 12, 2022