Yoss RE, Corbin KB, MacCarty CS, Love JG: Significance of symptoms and signs in localization of involved root in cervical disc protrusion. Neurology 7:673, 1957.
Figure 10-1. A. The lumbar vertebrae viewed from above B. from the side and C. mid-sagittally. A and B show the bony structures and their relationships to the disc space, facet joints and intervertebral foramina. C demonstrates in a cutaway mid-sagittal view, the main ligamentous structures of the spine in relation to the bones and discs. The ligaments and articulations are critical to the mechanical integrity of the spinal column.
Figure 10-2. (1) Costovertebral angle. (2) Spinous process and interspinous ligament. (3) Region of articular facet (fifth lumbar to first sacral). (4) Dorsum of sacrum. (5) Region of iliac crest. (6) Iliolumbar angle. (7) Spinous processes of fifth lumbar and first sacral vertebrae (tenderness = faulty posture or occasionally spina bifida occulta). (8) Region between posterior superior and posteroinferior spines. Sacroiliac ligaments (tenderness = sacroiliac sprain, often tender, with fifth lumbar or first sacral disc). (9) Sacrococcygeal junction (tenderness = sacrococcygeal injury; i.e., sprain or fracture). (10) Region of sacrosciatic notch (tenderness = fourth or fifth lumbar disc rupture and sacroiliac sprain). (11) Sciatic nerve trunk (tenderness = ruptured lumbar disc or sciatic nerve lesion).
Figure 10-3. Mechanisms of compression of the fifth lumbar and first sacral roots. A lateral disc protrusion at the L4-L5 level usually involves the fifth lumbar root and spares the fourth; a protrusion at L5-S1 involves the first sacral root and spares the fifth lumbar root. Note that a more medially placed disc protrusion at the L4-L5 level (cross-hatched) may involve the fifth lumbar root as well as the first (or second and third) sacral root.
Figure 10-4. Lumbar disc herniation as shown by T2-weighted MRI. A. Sagittal view of a large herniated nucleus pulposus at L5-S1. The posteriorly protruding disc material indents and elevates the anterior thecal sac and narrows the spinal canal. The extruded material has the same signal characteristics of the parent disc. The disc space at this level is narrowed and the disc is less hyperintense than normal because of desiccation and the extruded component. B. Axial view showing the focal right paracentral posterior disc herniation (large arrow) protruding into the canal and compressing the traversing nerve root (the right S1 nerve root) at this level. The exiting L5 roots above are not affected and can be seen laterally to the disc (small arrows).
Figure 10-5. Lumbosacral MRI of a patient with lymphoma, with radiation-induced arachnoiditis causing severe back pain and leg weakness. A. Sagittal T2-weighted MRI showing clumping of the nerve roots of the cauda equina. B. Axial T2-weighted image at the L3 vertebral level showing clumping of the nerve roots. C. Axial T2-weighted image at the L5 vertebral level showing lateral displacement of nerve roots by acquired arachnoid cysts. There are bilateral metallic pedicle screws.