International Journal of Medical Sciences (IJMS)

The nucleus pulposus is the soft, gelatinous central portion of the intervertebral disk. The nucleus pulposus affords disk mobility and its ability to absorb mechanical energy under compressive loading. Intervertebral disk moves within the disk with changes in posture [1]. In the normal disk, the nucleus pulposus moves anteriorly with lumbar extension and frequently communicates with the epidural space and surrounding structures. In a study of methylene blue injection into the nucleus, 14% of 105 disks showed leaks, with 93% of the leaks located in the posterolateral region lateral to the posterior longitudinal ligament (PLL). Injected dye showed contact with the adjacent root in 27% of the leaks