The authors report on a 56-year-old woman who presented with radicular symptoms and neurogenic claudication caused by far-advanced degenerative spondylolisthesis and concomitant synovial cyst, which forms encircling mass around the traversing nerve root. Spinal magnetic resonance imaging(MRI) demonstrated a far-advanced degenerative spondylolisthesis at the level of L4-5. Axial MRI on T2-weighted images revealed an abnormal signal with double contour that was located along the margin of the right L5 pedicle and appeared to adhere to the dural sac. During surgery, a 1.5cm encircling mass around the right L5 traversing nerve root was identified and complete excision was achieved. Histopathologic examination revealed a synovial cyst.
