Joseph Z. Levinson, MD
Resident Physician
University of Virginia, Department of Physical Medicine and Rehabilitation
Charlottesville, Virginia, United States
Kevin Mesina, MD
Resident Physician
University of Virginia Health System - - Charlottesville, VA
Charlottesville, Virginia, United States
Joseph Amalfitano, DO
Assistant Professor
University of Virginia, Department of Physical Medicine and Rehabilitation
Charlottesville, Virginia, United States
Atypical facet cyst causing active S1 radiculopathy, not well demonstrated on MRI, and better characterized on subsequent CT.
Case Description:
An 83-year-old female presented with right gluteal pain and paresthesias radiating to the foot, without known inciting event. She underwent right piriformis corticosteroid injection and trigger point injections with minimal relief. MRI lumbar spine demonstrated multilevel degenerative disc disease without severe stenosis of central canal, lateral recess, or neural foramen. Electrodiagnostic testing noted an active right S1 radiculopathy. She underwent two L5-S1 epidural steroid injections without substantial relief. The physiatrist noted a possible perineural versus facet cystic structure at the L5-S1 facet joint with S1 nerve compression on the MRI. Upon coordination with radiology, the patient was referred to neurosurgery who ordered a CT lumbar spine. CT demonstrated a hyperdense synovial cyst with high-grade lateral recess effacement and nerve root compression at L5-S1. Neurosurgery offered an L5-S1 hemilaminotomy and cyst resection. She elected to undergo L5-S1 facet joint steroid injection and facet cyst rupture, and reported complete resolution of pain.
Discussions: Synovial facet cysts may form due to degenerative disc disease with subsequent increased stress to facet joints. The presentation may include radiculopathy, low back pain, paresis, and sensory deficits. MRI typically characterizes cysts better than CT, demonstrating hyperintensity on T2 and STIR images. CT interpretation is often difficult, as cysts may be a similar density to cerebrospinal fluid. Synovial facet cysts are more readily identifiable on CT when they are hyperdense due to intracystic hemorrhage or calcification, or hypodense due to intracystic gas.
Conclusions: While MRI typically demonstrates synovial facet cysts, in patients with persistent symptoms and an equivocal MRI, CT should be considered.
