Introduction to Pathologic Intervertebral Disc:
There are three different types of pathologic disc (intervertebral disc) conditions: degenerated disc, bulging disc, and herniated disc. A degenerated disc occurs when the height of the disc thins due to wear and tear. A bulging disc is characterized by bulging of the annulus fibrosus due to a weakness in its fibers. A herniated disc, also known as a ruptured disc or prolapsed disc, is characterized by a rupture of the fibers of the annulus fibrosus, with a subsequent herniation of the nucleus pulposus through the annulus. Note: If the nucleus pulposus of a herniated disc becomes fragmented and a piece or multiple pieces of it separate from the main body of the nucleus, it is often referred to as a sequestered disc.
The term “slipped disc” is a lay term that has no true meaning. It is generally used to describe an unhealthy disc.
The unhealthy annular fibers of a degenerated disc are often the precursor to a broader weakness that can lead to a bulging disc. Similarly, the weakened annular fibers of a bulging disc are often a precursor to a disc herniation. In other words, a degenerated disc is often the early stage of a bulging disc, which is often the precursor to a herniated disc.
The most serious aspect of a pathologic disc is not the pathologic disc itself, but whether it results in compression of nearby neural tissues. Directly posterior to the disc is the spinal cord (or cauda equina in the lower lumbar spine); and directly posterolateral to the disc on either side is the spinal nerve traveling in the intervertebral foramen (IVF). If a bulging or herniated pathologic disc is large enough, it can compress the spinal nerve or spinal cord, resulting in what is commonly referred to as a pinched nerve. A degenerated pathologic disc is usually not as serious a condition as a pathologic bulging or herniated disc because it results in neural compression far less often. However, a pathologic degenerated disc does decrease the size of the IVF, which can contribute to compression of the spinal nerve that runs through it.
A pathologic disc in the cervical spine is likely to cause neck pain and/or referral of sensory or motor symptoms into the upper extremity; whereas a pathologic disc in the lumbosacral spine is likely to cause low back pain and/or referral of sensory or motor symptoms into the lower extremity. If compression of lumbosacral nerve roots that contribute to the sciatic nerve occurs, it can cause the condition of sciatica. A pathologic disc in the thoracic spine is fairly rare because the presence of the rib cage limits the amount of motion possible in this region. The thoracic spine is also not as affected by weight bearing stress as is the lumbar spine.