Lumbar Synovial Cysts

Abstract & Commentary

Synopsis: Those patients undergoing decompression alone may postoperatively develop progression or the new appearance of olisthy, while those primarily fused rarely show further increase or a new onset of slip.

Source: Epstein NE. Lumbar Synovial Cysts. A Review of Diagnosis, Surgical Management, and Outcome Assessment. J Spinal Disord Tech. 2004;17:321-325.

Typically located at l4-5 or l5-s1, less often at L3-4 or L2-3, lumbar synovial cysts originate from facet joint arthrosis, and are present in 0.6% of computerized tomography (CT) or magnetic resonance imaging (MRI) studies of the lumbar spine. Cervical and thoracic synovial cysts occur much less frequently, approximately 50-fold. Men are affected twice as often as women. The average age of patients being 65 years, spanning a range from 28-94 years.

Radiculopathy is the typical mode of presentation in 55-97% of cases, with neurogenic claudication due to spinal stenosis affecting 25-44%. However, clinical signs are only seen in 18%, and include motor or sensory deficits (approximately 40% each), deep tendon reflex alteration (57%), or cauda equina syndrome (13%). Diagnosis is made by imaging where cysts may be seen to be peri-articular, posterolateral, or epidural in location. Facet joint deterioration is seen in up to 90%, with spondylolisthesis in 32%. Cysts are hypo- or iso-intense on T1-weighted MRI scans, hyperintense centrally on T2 images, and demonstrate capsular enhancement around their periphery with gadolinium. MRI is more sensitive than CT study in diagnosing synovial cysts, 77% vs 56%, respectively. Myelography will reveal the cyst in only 42%.

Steroid facet-joint injection will benefit one third of patients, whereas the need for decompressive laminectomy surgery, with or without cyst resection, will be determined by the degree of spondylostenosis. Overall, surgical series report good/excellent response in 91%, and fair/poor outcome in 9%, with postoperative complications including cerebrospinal fluid fistula, discitis, epidural hematoma, phlebitis, and death. Combining primary fusion with laminectomy does not improve outcome.

Commentary

Microsurgical resection of lumbar synovial cysts appears equally efficacious (Neurosurgery. 2004;54;107-111). Among 17 patients with magnetic resonance imaging (MRI) evidence of synovial cysts, 47% of whom demonstrated grade 1 spondylolisthesis, microsurgical resection resulted in good/excellent results in 94%, with a mean operating time of only 97 minutes, and an average blood loss of only 35 cc. One patient experienced a dural tear, but this did not involve the arachnoid membrane, and no treatment was necessary. Endoscopic or microscopic synovial cyst resection is safe and effective, and absent laminectomy, minimizes the need for fusion. — Michael Rubin, MD

Dr. Rubin, Professor of Clinical Neurology, New York Presbyterian Hospital-Cornell Campus, is Assistant Editor of Neurology Alert.