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

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."

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."

"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.