How Disc Bulges & Herniations Injure Nerves

If you have back pain and in particular, if you have leg or arm pain too, you’ve probably had an MRI. MRI’s are useful because they can show damage to discs, nerves and the spine itself. In my mind there are two very common types of diagnosis. One type is related to arthritis and the other, which I will cover in this post, is colloquially referred to as a “slipped disc.”

There are many different terms to describe bulging and herniated discs because historically there was not much consensus regarding taxonomy. Some of the names include disc herniation, prolapse, disc bulge, and nowadays the preferred name is oftentimes spinal stenosis. Unless you are a surgeon, they practically mean the same thing. Namely, part of an intervertebral disc is physically touching a nerve or the spinal cord. This can cause symptoms In the neck or back, or extremities. Most commonly, patients arrive in my office towing an MRI that shows a disc condition involving the last two discs in their low back. Their complaint usually involves back pain and a numbness, paresthesia or pain in their leg and/or foot.


The diagram below shows a normal alignment of the vertebrae and disc. The nerve opening is large enough to transmit the spinal nerve that goes from the back, down the leg to the foot.



The next diagram shows a bulged or herniated disc. As you can see the disc has slipped or bulged backward into the nerve opening. This disc is physically pressing upon the nerve itself as it exits through the opening.

In my experience, many patients don’t fully understand what a disc bulge or disc herniation looks like. MRI’s are difficult to read. Hopefully, these crude illustrations help shows how disc problems injure nerves. More later....