Clinical Presentation

A 58-year-old man with left lumbar radiculopathy.

Further Work-up

(A) Lateral radiograph of the lumbar spine demonstrates anterior slippage of L5 on S1. There is a gap between the superior (black arrow) and inferior (white arrow) facets of L5. (B) Sagittal T1-weighted image (WI) confirms anterior displacement of L5 with respect to S1, with a fat-filled gap between the superior and inferior facets of L5 (asterisk). (C) Axial T1WI shows elongation of the anteroposterior diameter of the spinal canal secondary to anterolisthesis (arrows).

Differential Diagnosis

• Spondylolysis with spondylolisthesis: This is a focal interruption of the pars interarticularis. This interruption causes forward slippage of the superior vertebral body (spondylolisthesis). If significant anterolisthesis of the vertebral body is present, a fat-filled gap between the pars fragments can sometimes be appreciated.

• Degenerative lumbar spondylolisthesis: