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Spinal Disc – Common Terms


Terminology related to spinal disc disease and injury can be confusing. Shock-absorbing discs between each spinal vertebra may slide, tear, bulge or degenerate to cause back pain. During diagnosis and consultation with your physician, spinal disc terminology can become confusing. Terms such as disc extrusion, disc protrusion, bulging disc, slipped disc treatment or herniated nucleus pulposus may be used during descriptive discussions of your back ailment.

Disc Anatomy

The vertebral bones running down your back protect your spinal cord and its extending nerves. Between each vertebra there is a thick fibrous disc with a central gel-like zone. The discs prevent your vertebra from rubbing against one another and pinching spinal nerves that exit the spinal cord between each vertebra to innervate your body. Also, the discs allow flexibility and act as shock-absorbers during physical activity.

Disc Extrusion

Disc extrusion and ruptured or herniated disc have the same meaning. As you age, your vertebral discs loose water content and become brittle. This predisposes them to cracking and tearing. As tears develop, the disc tissue may extrude, which means to push or thrust, into the spinal canal and compress spinal nerves. At the site of the extrusion, you may experience pain, stiffness, numbness, a prickling feeling or unexpected muscle weakness.

Disc Protrusion

As your vertebral discs age, they lose flexibility and their lack of elasticity may cause a disc to become protruded during compressive exercise. Disc protrusion can irritate or pinch the nerves running between your vertebrae. Protrusion is defined the same as extrusion, to thrust or push out. Therefore, disc extrusion and disc protrusion have the same symptoms and may be used interchangeably.

Bulging Disc

A weakened intervertebral disc wall can result in a bulging disc. A bulge can develop as the result of normal wear and tear or trauma. Bulging means to swell or protrude. The bulging disc may press on nerves to cause pain and weakness. If a bulging disc breaks open, its gel-like contents will leak out and reduce the cushioning effect of the disc. As the disc space becomes compressed intervertebral space may decrease and cause pinched nerves.

Slipped Disc

A slipped disc, bulging disc, disc protrusion and disc extrusion are terms used to describe the same spinal pathology. A slipped disc does not mean an intervertebral disc has actually slipped out of position, but that its outer wall has been forced out of its normal position. The more disc tissue that is forced beyond the edge of the vertebra, the more likely it is that you will experience symptoms such as pain, tingling, numbness or weakness from disc tissue pressing on nerves.

Herniated Nucleus Pulposus

The central gel-like tissue of an intervertebral disc is called the nucleus pulposus, while the outer region is the annulus fibrosus. Herniation means an abnormal protrusion. As disc elasticity and water content decrease with age, herniated nucleus pulposus can occur. It can have a slow or sudden onset, which progresses from protrusion to extrusion and then rupturing. When the gel-like central region of the nucleus pulposus breaks through the annulus fibrosus and the fluid drains onto the spinal cord or spinal nerves, the nerve tissues may become irritated and painful.

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