Ligamentum flavum cyst

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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