The four stages to a herniated disc include:
1. Disc Degeneration - chemical changes associated with aging causes discs to weaken, but without a herniation.
2. Prolapse- the form or position of the disc changes with some slight impingement into the spinal canal. Also called a bulge or protrusion.
3. Extrusion - the gel-like nucleus pulposus breaks through the tire-like wall (annulus fibrosus) but remains within the disc.
4. Sequestration or Sequestered Disc - the nucleus pulposus breaks through the annulus fibrosus and lies outside the disc in the spinal canal (HNP).