[Juxta-facet cysts: magnetic resonance tomography diagnosis]

The term juxta-facet cyst summarizes synovial cysts, arising from degenerated facet joints and ganglion cysts, developing from mucinous degeneration of periarticular connective tissue. Most juxta-facet cysts are observed at the L4/5 level, which generally has the most motion within the lumbar spine. In this retrospective study 31 juxta-facet cysts in 28 patients were detected within 2898 lumbar MRI studies over a 2-year period (frequency 1%). 24 patients complained of back and lower extremity pain, the other 4 patients had unilateral back pain. In 7 cases radicular symptoms were observed, in 6 patients a neurogenic claudication. In 78% of the patients juxta-facet cysts were responsible for clinical symptoms. MRI is the diagnostic imaging technique of choice due to a high sensitivity. The juxta-facet cysts were located extradural, laterally to the thecal sack and adjacent to a degenerated facet joint. In all but one cases the cysts showed a signal intensity equivalent to cerebrospinal fluid. T2-weighted pulse sequences in sagittal orientation were very useful in delineating the hypointense cyst wall. In 1 patient with acute radicular pain MRI demonstrated a subacute hemorrhage within a juxta-facet cyst. Calcifications and gas-filled cysts can be missed with MRI, but will be demonstrated by computed tomography. 45% of the juxta-facet cysts showed an enhancement of the cyst wall after injection of Gd-DTPA. Spontaneous reduction or resolution of the cyst may occur during rest. Injection of corticosteroids into the corresponding facet joint may reduce the inflammatory process and resolve the symptoms in up to 70%. Surgical resection of the cyst is indicated in case of intractable pain and significant neurologic deficit and generally produces good relief from radicular symptoms.