Imaging of degenerative spondylolisthesis in a 65-year-old woman. (A) Lateral radiography reveals degenerative spondylolisthesis at L4-5 and decreased disc height at the L5-S1 level. (B) T2-weighted right parasagittal magnetic resonance imaging (MRI) of the lumbar spine reveals spondylolisthesis at the L4-5 level and right foraminal stenosis (white arrow) of L5-S1. (C) MRI reveals aggravation of the foraminal stenosis (black arrow) of L5-S1 after anterior lumbar interbody fusion of L4-5 (10 years after surgery). (D) MRI reveals widening of the L5-S1 foramen (white circle) after decompression via the intermuscular approach at L5-S1.