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). https://www.spineclinicnoida.com/ https://www.youtube.com/watch?v=lY-2XfD0K_Y& t=5s https://www.practo.com/ghaziabad/doctor/pramod-saini