Intervertebral discs are composed of an outer layer called the annulus fibrosis and an inner layer, the nucleus pulposus. The annulus is a more fibrous substance that encircles the nucleus, a more jelly like substance. The nucleus should be contained by the annulus, though with excessive or repetitive pressure and strain the nucleus can deform the annulus or exit the annulus.
There are several terms that describe these happenings in the cervical, thoracic, and lumbar spine. During your research involving the spine and back and neck pain, terms such as ‘protrusion,’ ‘bulge,’ ‘herniation,’ and ‘extrusion’ arise. These are the scientific terms that are used to describe the nature of disc changes, some that may cause back pain, and some that are not pain generating changes. Here is a quick explanation of terms you may be introduced to on the internet, or in your MRI report, or through your physician or physical therapist.
Disc Bulge: Tissue of the annulus, the outer layer of the disc, projects outward beyond the border of a comparable disc (usually the adjacent disc). Think of what happens when you sit on a couch in the same place every day, the couch cushion begins to change its shape in response.
Disc Protrusion: Movement of the nucleus of the disc causing a more pronounced bulge in the disc that extends past the border of the nearby vertebrae. This creates a dome like shape. Think of the same couch cushion example, the sides of the couch cushion begin to ‘protrude’ in response to the pressure on the top of the cushion.
Disc Extrusion: Movement of the nucleus of the disc further from the central containment of the annulus creating more of a bubble shape outside of the annulus, though the disc maintains it continuity. You’re starting to lose some of the cushion’s filling, but the cotton filling is still intact.
Disc Sequestration: This the characterization of a disc extrusion that loses its continuity with the disc. This is some of the cushion’s filling falling out of the cushion.
Let’s look a little deeper into the couch cushion analogy and how that relates to daily function of the spine. We all have a favorite spot we like to sit in right? The special spot on the couch where everything is at your fingertips while your favorite movie plays. Over time that spot in the couch becomes noticeable as the cushion’s filling begins to shift away from the spot that is used more often. This same process happens in the intervertebral discs of the spine. We all have a daily routine that involves repetition and prolonged positioning and it just so happens that most of these activities involve bending forward. Bending to sit, sitting for a prolonged period at work, driving in the same bent position, bending to put on pants, socks, and shoes, among others. These repetitious and prolonged activities cause the inner substance of the disc to push toward the back portion of the discs borders, leading to the above mentioned structural changes.
Now think about how it feels when you ‘miss’ the favorite spot in the couch and sit just off target. The stimulus from the couch feels a little odd and a little different until you can settle back into the favorite spot. This also happens in the spine when we introduce a new stimulus to our day, however the stimulus is often perceived as pain. This leads to a common presentation of low back pain which if left untreated can lead to a more severe low back pain and involve pain in the leg, often times termed ‘sciatica.’
However if we introduce that stimulus in a safe manner and with enough repetition to compete with our daily tasks we can return the structure of the disc to a more normal presentation and alleviate low back pain. If we introduce this new stimulus in a safe manner we can reorganize the couch cushion’s filling.
At SCORE Performance Medicine part of our evaluative procedures attempt to identify the patterns in daily activity that cause changes in the intervertebral disc structure and use functional examination procedures to reach the solution that will lead to a return in the proper structure of the disc, or better yet reach pain free activities of daily living regardless of the structure of the disc!
Dr. Nicholas Smith