Isthmic spondylolysis of L5 in a 29–year–old woman who had been completely asymptomatic. This axial section is carried a few millimeters caudal to the level of Slide 13 through the lower portion of the L5 body. Characteristic of L5 are the sharp ridges at the lateral aspect of the bodies from which the corporo–transverse ligaments arise. A large and broad–based right–sided paramedian and foraminal herniation of the L5–S1 disc has tracked upward behind the L5 body. The herniation, although it is not clearly contained by any restraining structures, does not have the appearance of a typical free sequester. The herniation displaces the L5 dorsal root ganglion laterally and slightly superiorly and flattens the medial border of the ganglion. Note the immediate contact of the herniated disc material with the ganglion. Between the radicular artery and the L4 nerve corporo–transverse and foraminal ligaments are seen