Most changes in the spinal cord are age-related, and they occur when the spinal discs break down or degenerate. This may be due to the loss of fluids in the spinal discs, which reduces the disc's ability to absorb shock or act as a cushion. Loss of fluid makes the spinal discs thinner and narrows the amount of space in between the vertebrae. It also causes inflexibility in the spine. Degenerative disc disease may also be due to tiny cracks or tears in the outer layer of the disc, which may cause the disc to break into fragments or bulge.