So you have a disc bulge …., but what does that really mean?

So you have a disc bulge…., what does it mean for you?

If you have had back pain for a while, it likely that you have a CT or MRI scan. Typically, the report will identify one or more lumbar discs with a ‘bulge”. Perhaps a clinician has told you that you have a bulging disc, and now you are concerned with what this might mean for you. So, read on….., this primer will provide an overview on understanding disc injuries. (There are also supporting research-based references at the end of this bolg if you really want to dig deeper). 

INSIGHT: A major consideration in the discussion of disc injuries, is to ask why your back pain is present (or ‘why’ do I have a disc injury), not just where does the pain come from. Identifying the disc injury is only part of the process of understanding why you have back or neck pain. Identifying the things that likely contributed to the injury such as movement, posture, strength and ‘overloading’ issues are important in choosing treatment strategies and directing efficient recovery.

Firstly, lets start with the ‘language’ of disc injuries. Terms like disc herniation and disc prolapse are generic terms that cover all disc injuries. A more exact method of describing disc injuries is to classify them into three types; (1) disc bulges, (2) disc protrusion and (3) disc extrusions. Each type of disc injury has a wide range of clinical implications that vary all the way from ‘no effect on you’ to the need for surgery. I’ll describe each type of disc injury below. But firstly, understanding the basic anatomy is helpful. The image below will show you the basic structure and terminology.

Disc bulges

Disc bulges are the most common finding seen on imaging. They are are commonly found in people with and without back pain. Some people who are known to have disc bulges have never experienced back pain. A disc bulge might be associated with pain but this will depend a number of things such as if a sudden tear has occurred, if there is inflammation, if the bulge combines with other components to narrow spaces for nerves, if there is damage to the ‘endplates’ that are on the top and bottom of the disc etc. It’s important to understand that pain intensity does not directly relate to the size of the bulge. This means that you could have strong pain with only a minor disc bulge. 

This image illustrates a typical disc bulge, that is broad-based and usually does not cause nerve compression.

Annular tears

Small disruptions to the outer fibrous ring of the intervertebral disc (known as the the annulus fibrous) can occur and these are called ‘annular tears’. They can be present with or without pain and do not require surgical intervention. Annular tears may be associated with pain and annecdotally, seem to take several weeks to settle. During the recovery time it is not uncommon to have flare-ups of pain followed by further recovery.

Disc protrusions

Disc protrusions are asymmetrical disc bulges that usually affect one side of the disc, with the possibility (but not always) of compressing nerve tissue. People often describe their pain as a “pinched nerve” but true symptoms of nerve compression are those of sensory changes such as ‘pins and needles’ (paraesthesia) or numbness (anaesthesia), loss of strength and reduced reflexes. Pain associated with nerve compression is often described as sharp, electric, shooting, swirling pain.But pain itself is not a reliable indicator of nerve compression or nerve entrapement.

This image and the line drawing illustrate a disc protrusion when looking from side on (sagittal view) or from above or underneath (axial view).

Disc extrusions

A disc extrusion is just another from of tear with material emerging from the disc, similar to a disc protrusion but with disc material extending past the upper or lower endplate of the vertebrae. Extrusions may extend in any direction, but are more commonly seen in the either side of midline towards the space where the spinal nerve exits (lateral recess) in the lateral aspect of the spinal canal. In recent studies, extrusions were more commonly associated with signs of nerve root compression (often know as a radiculopathy). However, disc extrusions are an example of size not meaning everything.  A number of studies have shown that large disc extrusions can shrink over time. Some disc injuries, including protruded and extruded discs may do better with surgical decompression, but the natural history of recovery will mean that many people with significant disc injuries do not need surgery. As a general rule, recovery strategies will include activity and movement while respecting nerve sensitivity. Typically, many people will show spontaneous recovery over a three month period, although the extent of nerve damage, higher pain intensity and/or slow recovery may mean earlier surgical intervention for some people. Physiotherapy, exercise and gradual return to activity are usual first line strategies of management.

Disc extrusions can ascend or descend as shown in this image.

References for further reading:

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