Introduction
Between every bone in the spine (called a 'vertebra') sits a small disc composed of an inner sac, called the 'nucleus pulposus', containing a type of gel, and an outer ring ('annulus') made of a more dense type of cartilage (fibrocartilage). These discs are called 'intervertebral discs' and, much like cartilage in other joints in the body, their role is to be 'shock absorbers' for the spine as the body moves.
A herniated disc develops when there is a small bulge or tear in the outer ring and some of the inner sac pushes out. As you age this becomes more likely, partially due to a buildup of general 'wear and tear' but also because these discs naturally lose some of the inner gel and become harder and flatter – this is called 'degenerative disc disease'.
Sometimes a herniated disc has no symptoms at all, but it can cause pain and restriction of motion.
Herniated discs are often also referred to by the terms 'slipped disc', 'ruptured disc', and 'prolapsed disc'.
Causes
As described above, the most common cause of a herniated disc is age-related 'wear and tear' as the intervertebral discs become less flexible, although traumatic injury to the back may also cause disc herniation. There are a number of risk factors for developing one or more herniated discs…
- Being male – men develop herniated discs more than women (by a factor of 2:1).
- Age – most herniated discs occur in people aged 35-50.
- Being overweight/obese – this puts considerably more strain on the discs in the lower back and often results in the same disc herniating again (called 'recurrent disc herniation').
- Physically demanding work – work where there is a lot of heavy lifting, twisting, bending, pushing and pulling puts greater strain on the discs.
- Family history – inherited anatomical traits can make you more prone to developing herniated discs.
- Smoking – nicotine may decrease the amount of oxygen in the blood getting to the discs, which may accelerate the ageing process.
Symptoms
It is perfectly possible to have a herniated disc and have no symptoms at all. Where symptoms do occur, they are generally…
- Back pain (generally affecting the lower back) .
- Pain in the buttocks.
- Leg pain – often worse than pain in the lower back.
- Pain in the arms or shoulders – although most herniated discs affect the lumbar region (the lower back), causing pain in the legs, a herniated disc in the cervical (upper) section of the spine may cause pain in one or both arms.
- Numbness, weakness or 'pins and needles' in the affected limb/s.
- Pain with movement or specific movements.
- Stiffness and reduction in range of movement without pain.
- Pain when shifting from prolonged standing or sitting or lying down.
- Pain when sneezing or laughing.
- Problems when walking, specifically where the heel to toe motion is impaired (this is known as 'foot drop') .
Often symptoms only affect one side of the body.
Tests / Diagnosis
The diagnostic process for a herniated disc involves a physical examination and a review of medical history. The doctor will check where exactly any pain or tenderness is and may ask you to lie down and move your legs into different positions. They may also conduct a series of tests to check your reflexes, ability to walk, strength of muscles and your ability to sense various thing like a light touch, a pin prick or a small vibration.
If disc herniation is suspected, advanced imaging may be ordered.
In some cases you may be recommended to undergo imaging test. Although an X-ray will not show a herniated disc, it may show other possible causes for the symptoms (e.g. broken bone, misalignment of the spine, infection or tumour).
Other imaging tests such as a CT scan or MRI scan may be recommended. In some cases, nerve conduction studies may be recommended to test any electrical dysfunction in the nerves.