Disc Herniation Explained
What is spinal disc herniation? There are five lumbar discs in the lower portion of your spine. These discs help cushion the spine from loads placed on it by gravity and physical activity.
The discs have an outer ring called the anulus. This is made of multiple layers of fibrous tissue, similar to an automotive tire.
Within this ‘tire’ is a central space filled with softer material called the nucleus.
A spinal disc herniation occurs when a partial or full tear in the anulus allows a portion of nucleus to either bulge out or rupture. This can place pressure on nerves, causing pain.
Three types of disc herniation
Spinal disc herniations are a common problem, resulting in more than one million surgeries each year.
What are symptoms of a herniated disc?
The symptoms of a herniated disc depend on the exact level of the spine where the disc herniation occurs and whether or not nerve tissue is being irritated. A disc herniation may not cause any symptoms. However, disc herniation can cause local pain at the level of the spine affected.The most common symptom from lumbar disc herniation is called sciatica and is a characteristic type of leg pain. Lower back pain can sometimes also be present with sciatica.
If the disc herniation is large enough, the disc tissue can press on the adjacent spinal nerves that exit the spine at the level of the disc herniation. This can cause shooting pain in the distribution of that nerve and usually occurs on one side of the body. For example, a disc herniation at the level between the fourth and fifth lumbar vertebrae of the low back can cause a shooting pain down the buttock into the back of the thigh and down the leg. Sometimes this is associated with numbness and tingling in the leg. The pain often is worsened upon standing and decreases with lying down.
If the disc herniation is extremely large, it can press on spinal nerves on both sides of the body. This can result in severe pain down both lower extremities. There can be marked weakness of the lower extremities and even incontinence of bowel and bladder. This is medically referred to as cauda equina syndrome.
How is spinal disc herniation diagnosed?
The physician will suspect a herniated disc when symptoms described above are present. The neurologic examination can reveal abnormal reflexes. Often pain can be elicited when the straight leg is raised when lying or sitting. This is referred to as a "positive straight leg raising test." There can be abnormal sensation in the foot or leg.
A variety of blood tests are frequently done to determine if there are signs of inflammation or infection.
Plain film X-rays can indicate "wear and tear" (degeneration) of the spine. They do not, however, demonstrate the status of discs. In order to determine whether or not a disc is herniated, an MRI scan is performed for diagnosis.
An electromyogram (EMG) can be used to document precisely which nerves are being irritated by a disc herniation.