The Body's Aging Process
As your spine ages, it goes through some natural changes. In a condition often referred to as the degenerative (or aging) spine, the gelatin-like centers of your discs begin to dry out, causing them to become compressed or flattened (Fig. 5). This, in turn, causes the vertebrae to settle. It's one of the reasons most people actually become shorter as they grow older.
As your discs begin to compress and your vertebrae begin to settle, the openings of the foramen - where spinal nerves branch off of the spinal cord - become smaller and smaller (Figs. 5 above and 6,below). Eventually, the opening can become so small that the nerve is "pinched" against a vertebra. It's similar to placing your hand on a windowsill. As long as the window is open, there is no problem. However, if someone slowly closes the window, there will be a point at which your hand begins to feel the pressure. The more the window is closed, the greater the pressure and the greater the pain you will feel.
The Loss of Your Spine's "Shock Absorbers"
At the same time, your aging discs are drying out and losing their ability to act as effective "shock absorbers." Your vertebrae begin to bounce against one another and this jarring action actually causes the bone matter of the vertebrae to grow. This results in the formation of bone spurs. The jagged edges of this new growth can cause both the spinal canal and the foramen to become even smaller. When this happens, the result is often the pinching of the cauda equina and/or a spinal nerve root.
If aging of the spine is a natural process and happens to everyone, why does one person end up with lateral recess stenosis or lumbar canal stenosis while someone else is seemingly unaffected? The answer is that everyone's spine is unique. Some people are born with discs that are naturally more plump than others. Some have wide foraminal or spinal canal openings, while others have narrow ones. These factors, as well as weight, posture and level of physical activity help determine who will be adversely affected by the aging process.