Lumbar Synovial Cysts: Experience With Nine Cases

Abstract

Nine patients treated surgically for lumbar spinal synovial cyst were reviewed. Four patients had synovial, two had ganglion, one had posterior longitudinal ligament, and two had ligamentum flavum cyst. Synovial cysts had a single layer of epithelial cells in the inner layer of the cyst with continuity with the facet joint. Ganglion cyst had no continuity with the facet joint and epithelial lining was present in one and absent in one case. Posterior longitudinal ligament and ligamentum flavum cysts had no continuity with the facet joint and no epithelial lining. Magnetic resonance imaging showed the cysts better than computed tomography. All patients treated for nerve root compression or lumbar spinal canal narrowing. One patient suffered recurrence 1 year later and was reoperated. Operative results were excellent in six and good in three patients. Lumbar spinal synovial cysts should be considered in differential diagnosis of lumbar radiculopathy/neurogenic claudication and is surgically treatable.

Intradural Invasion of Lumbar Synovial Cyst

“…Lumbar synovial cyst is now reported with increasing frequency owing to the availability of MR imaging and CT. The incidence is 0.65-2.3% 2,8) in the general population. The incidence of lumbar synovial cyst was 1% in 2898 lumbar MR images.…”

“…9,16,19) The most frequent location of lumbar synovial cyst is at the L4-5 level, which is the most mobile segment in the lumbar spine. 2,4,20,26) The clinical symptoms and signs of synovial cyst are various, and depend on its size, site, and relationship with adjacent structures. 4) Patients usually suffer insidious onset of pain that persists for months or even years, that does not improve with exercise, steroid injection, or hot packs, and shows no radiological signs, but causes definite restriction of movement.…”

“…Acute onset of symptoms tends to be associated with intracystic hemorrhage, which occurred in 9% of reported cases. 2,17,19) The most common presenting symptoms are radiculopathy, neurogenic claudication, or cauda equina syndrome, with associated sensory loss and motor weakness, whereas back pain usually precedes radiculopathy. 4,6,14,16,17,19,20,27) Neuroimaging investigations such as MR imaging have been advocated to accurately identify synovial cyst.…”

“…27) The MR imaging findings of synovial cyst are usually low signal intensity on T 1 -weighted images and high signal intensity on T 2 -weighted images, with enhancement of the cyst wall after gadolinium injection, which can vary depending on the changes in protein concentration or the presence of hemorrhage. 2,4,12,19,27) The differential diagnosis of synovial cyst in the lumbar spine includes migrated herniated disk, schwannoma, cystic neurofibroma, extradural arachnoid cyst, perineural cyst, meningioma, ganglion cyst, and ligamentum flavum cyst, among others. 3,7,12,17,27) In the present case, we could not definitely confirm that synovial cyst was the causative pathology based only on the findings of MR imaging and CT. CT showed a small amount of gas in the mass.…”

“…Synovial cyst is usually monoarthritic and is characterized by protrusion of the synovial membrane through defects of the joint capsule due to degeneration, resulting in the formation of a para-articular cavity with synovial fluid collection and a demonstrable communication to a synovial sheath. 2,6,13) Cases of lumbar synovial cysts have been reported, but not involving invasion of the dura mater and mimicking an intradural extramedullary tumor. Indeed, relatively few cases of synovial cyst in the lumbar or cervical spine have been reported.…”