Proximal lumbar spinal nerves in axial MR imaging, CT, and anatomic sections.

The proximal lumbar spinal nerve is composed of a group of small fascicles interspersed with fat. These fascicles converge into the ventral ramus. The authors studied the appearance of this portion of the spinal nerve through analysis of magnetic resonance (MR) images, computed tomographic (CT) scans, and exactly corresponding anatomic sections in cadavers. The fascicles can be identified at MR imaging or CT as poorly defined structures surrounded by the fat lateral to the neural foramen. The ventral ramus appears as a pair of oval, contiguous, small homogeneous structures. The evaluation of nerve compression may be aided by identification of the fascicles and ventral rami on CT and MR images.