1) Disc Degeneration: Chemical changes associated with aging causes discs to weaken, but without a herniation.

2) Bulge: Inner annulus fibrosus has broken and the outer fibrosus bulged. It will be a round moon shadow on the CT scamming.

3) Prolapse: The form or position of the disc changes with some slight impingement into the spinal canal.

4) Extrusion I: The gel-like nucleus pulposus breaks through the tire-like wall (annulus fibrosus) but remain within the tough ligament.

5) Extrusion II: The gel-like nucleus pulposus breaks through both the tire-like wall (annulus fibrosus) and tough ligament but remains within the disc.

6) Sequestration or Sequestered Disc: the nucleus pulposus breaks through the annulus fibrosus and lies outside the disc in the spinal canal (HNP).

Prolapse; Extrusion; Sequestration or Sequestered.

Central type, Outer back side type, Outer side type, Far-outer side type.