51-year-old male with a sacral lesion. There is a 7 mm small focus with lobulated margins within the posterior aspect of the S4 vertebral body which is low signal intensity in T1-weighted images and high signal intensity on T2-weighted images. There is minimal if any enhancement following contrast administration. This may represent a benign notochordal remnant or perhaps a small cartilaginous rest based on its lobulated contours. There is also low signal intensity within the right sacral wing adjacent to the sacroiliac joint that shows enhancement following gadolinium administration. We suspect that this is degenerative in etiology, based on its proximity to the sacroiliac joint. There also appears to be low signal intensity along the iliac margin of the joint compatible with sclerosis. There is an additional small focus of signal abnormality and enhancement more posteriorly within the ilium, along the sacroiliac joint, which is also likely degenerative in etiology. Facet joint osteoarthritis affects the lower lumbar spine. Degenerative disc disease affects the lower lumbar spine.
1. Small lobulated focus of signal abnormality in the S4 vertebral body may represent a benign notochordal remnant or a small cartilaginous rest.2. Foci of signal abnormality along the right sacroiliac joint are likely degenerative in etiology.3. Degenerative disc disease and facet joint osteoarthritis of the lower lumbar spine.