Spontaneous remission of lumbar synovial cysts. Case series and literature review

Synovial cysts of the lumbar spine are extradural herniations of the synovial membrane at the facet joint, which extend into an intraspinal, foraminal or paravertebral location, presenting symptoms such as low back pain or radiculopathy. Its pathogenesis is due to the presence of degenerative phenomena affecting the facet joints, repeated chronic microtraumas and spinal instability with the generation of spondylolisthesis that promotes greater mobility of the apophyseal joints developing capsular weakness. Synovial cysts show typical characteristics and signal intensity on magnetic resonance imaging (MRI), those can be modified by the presence of calcium or hemorrhage. There are few reported cases of spontaneous resolution of synovial cysts. The hypotheses that were handled regarding this event are leakage of the content due to rupture of the cyst, decreased intra-articular pressure due to compensatory facet hypertrophy with disc collapse, and the effect of non-steroidal anti-inflammatory drugs and corticosteroids by inhibiting the inflammatory process. The objective of our work is to do a global review of synovial cysts and show four cases of patients with synovial cysts located within the vertebral canal that remitted spontaneously, evaluated through MRI in 1.5 T scanners, showing the radiological images that led to the diagnosis.