What is a lumbar herniated disc?
The lumbar spine, more commonly known as the lower back, is composed of five bones called vertebra. Two adjacent vertebral bodies are each separated a ring of cartilage, called a disc, forming a joint where motion can occur. The disc is made of a tough outer fibrous ring (annulus fibrosus) that encases a soft gelatinous core (nucleus pulposus). Normal wear and tear can weaken annulus fibrosus allowing the gelatinous core, or nucleus pulposus, to squeeze (herniate) out into the spinal canal. Once in the spinal canal the disc herniation may put pressure in the nerves resulting in severe pain, occasional weakness, and in severe cases loss of bowel and bladder function.
What causes a lumbar herniated disc?
Like any joint in the body, the lumbar discs are the subject of tremendous wear and tear. Over time the ligaments and cartilage can weaken permitting the soft nucleus pulposus to herniate.
How is a lumbar herniated disc diagnosed?
The diagnosis of a herniated lumbar disc is confirmed with an imaging study such as an MRI or a CT scan which can clearly demonstrate the herniated disc and the nerve roots that it compresses. Occasionally an electromyogram (EMG), which tests how signals are conducted along the nerves, may provide information used to differentiate pain due to a herniated disc from pain arising from another disease process affecting the nerve.
How is a lumbar herniated disc treated?
The pain associated with acute lumbar disc herniations frequently improves over a period of four to six weeks without surgery. During this time the pain is managed with medication. Surgery is reserved for the following select group of patients:
- Patients with severe pain that does not respond to medication
- Patients who have symptoms that persist beyond a period of four to six weeks
- Patients who experience sudden weakness in the legs or difficulties with bowel and bladder function. In this last group of patients surgery is usually performed promptly to prevent lasting neurological injury.
Surgery involves making a small incision in the back and moving the muscles aside to reveal the bone over the spinal canal. A small window of bone is then removed, permitting careful inspection of the spinal canal and nerve roots. In this way the herniated portion of the disc is identified and removed.
Patients who either are not healthy enough for surgery or do not wish to undergo surgery may be candidates for epidural steroid injections. Epidural steroid injections may provide temporary pain relief. During an epidural steroid injection a needle is passed through the skin into the spinal canal using x-ray guidance. Once in the proper location a mixture of steroid (a strong anti-inflammatory medication) and local anesthetic is administered.
Axial T2 weighted MRI of the lumbar spine demonstrating a herniated disc in the spinal canal compressing a nerve root.