Full endoscopic treatment of unusual spontaneous degenerative epidural cyst: A case report

BACKGROUND: Extensive studies have been performed about the synovial cyst and intraspinal extradural ganglion cyst. Here, we describe a new type of the cyst with entirely different histological characteristics, which we are now calling a “Spontaneous Degenerative Epidural Cyst.” CASE DESCRIPTION: A 74-year-old male presented with low back pain, bilateral lower extremity radiculopathy, and a cauda equina syndrome. He exhibited a partial left foot drop (Grade 3/5) and hypoesthesia in the sacral region. The magnetic resonance imaging (MRI) showed two cysts at the L4–L5 level; Cyst I was in the left foramen and Cyst II was within the epidural space between the dura and ligamentum flavum. Cyst I was removed through an endoscopic transforaminal approach; it originated from the left facet joint and with synovial lining was confirmed to be a synovial cyst. Cyst II required an endoscopic interlaminar approach, and pathology revealed granulation tissue with micro-calcification, woven bone formation, hemosiderin pigment, and focal cystic change consistent with our designation “Spontaneous Degenerative Epidural Cyst.” CONCLUSION: “Spontaneous Degenerative Epidural cyst” should be considered among the differential diagnostic consideration for the different lumbar cysts. High-resolution MRI is the most useful in diagnosing these lesions, while full endoscopic treatment provides for adequate resection of these lesions.