Ligamentum flavum cyst

Case contributed by Dr Digvijay Rane


Back pain with numbness in left leg since 4 years

Patient Data

Age: 48
Gender: Female

Small altered signal intensity extradural lesion is noted at L4 vertebral body level along left-posterior aspect moderately displacing cauda equine roots and thecal sac to right side.

It appears hypointense on T1WI and hyperintense on T2WI images and shows suppression on FS study.

Severe ligamentum flavum hypertrophy (6.5mm) as well as with mild spinal canal compromise is noted at this level.

Grade I anterolisthesis of L4 over L5 vertebrae.

Case Discussion

Ligamentum flavum cysts are rare lesions, most commonly occurring in the lower lumbar region than cervical region 1. The exact cause is not known, however, they generally tend to occur secondary to degenerative changes. These cysts may cause neuralgic sign due to spinal canal stenosis or lumbar root compression. Pathologically these cysts occur due to fibrocollagenous tissue degeneration and hypermobility of the spinal segment 2. After surgical removal, excellent postoperative results are reported.

Imaging features:

  • on myelography, it is seen as intraspinal extradural mass 3
  • on CT, it appears as a subtle cyst seen adjacent to the ligamentum flavum
  • MRI is choice of investigation. It appears as epidural cystic lesion which is of variable intensity on T1WI 4 and hyperintense on T2WI; it may show peripheral enhancement

Differential diagnosis are synovial cysts. These cysts tend to originate from synovial joint and appear as protrusion of synovial membrane into spinal canal.

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Case information

rID: 38740
Published: 2nd Aug 2015
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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