Disc Disease and Radiology
Wessam Bou-Assaly, MD
The intervertebral discs are spongy cushions elements, formed by strong connective tissues that separate the vertebral bodies of the spine. These have many important functions including shock absorption, stability of the vertebral column and giving the vertebrae pivot points for its movement.
A disc is made of two parts: the annulus fibrosis, an elastic outer shell and nucleus pulposus, a jelly-like central content.
With age and with certain types of pressure the annulus fibrosis can be damaged and the nucleus bulge through it.
Some people are more susceptible to disc problems than others. Risk factors include:
-Poor muscle tone
-Lack of exercise.
-Incorrect lifting techniques.
But often, there is no recognizable risk factor present.
The symptoms of disc problems vary according to its location, its severity and its compression on the adjacent structure, mainly the spinal cord or nerve roots. Many people with disc herniation on MRI have no symptoms.
Symptomatologic disc problem complains may include:
-Back pain with or without radiation down the legs.
-Worsening pain associated with bending over or sitting down for a long time.
-Pain associated with activities like coughing or sneezing.
-Numbness or pins-and-needles in an arm or leg.
-Loss of bladder or bowel control.
Diagnosis is of course suspected during taking medical history and when performing physical examination.
Radiology plays crucial role in diagnosing disc problem. The X-ray, even though limited in visualizing and evaluating the intervertebral disc, can shows signs of degenerative changes in the spine, which can be associated with underlying disc disease.
Signs of degenerative changes on X-Ray includes disc space narrowing, endplates sclerosis and presence of osteophytes.
MRI is the modality of choice in diagnosis disc degeneration and its effect on adjacent structure such as spinal cord and nerve roots.
MRI can precisely evaluate the type of herniated is material.
1- Diffuse disc bulge: Herniated disc tissue "circumferentially" (50–100%) beyond the edges of the vertebra. It is not considered a form of herniation.
It could be Symmetrical:
2- Broad based disc herniation: Herniation between 25% and 50% (90 –180°) of the disc circumference.
3- Focal herniation: Involves less than 25% or 90° of the disc circumference.
Focal disc herniation versus Broad base:
Focal disc herniation can also be classified as protrusion or extrusion, based on the
shape of the displaced material.
Protrusion is present if the greatest distance, in any plane, between the edges of the herniated disc material beyond the disc space is less than the distance between the edges of the base, in the same plane.
Extrusion is present when, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base, or when no continuity exists between the disc material beyond the disc space and that within the disc space.
A sequestration is present when there is discontinuity between the herniated disc material and the parent disc
Wessam Bou-Assaly, MD is a Neuroradiologist. He has many years in experience in medical Imaging fields.