Sciatica is pain that runs along the large sciatic nerve, which extends from the lower back down through the buttocks and along the back of each leg. It is a relatively common form of back pain.
Sciatica is usually caused by pressure on the sciatic nerve from a herniated disc (also referred to as a bulging disc, ruptured disc, or pinched nerve). The problem is often diagnosed as a “radiculopathy”, meaning that a disc has protruded from its normal position in the vertebral column and is putting pressure on the radicular nerve (nerve root).
For some people, the pain from sciatica can be severe and debilitating. For others, the pain might be infrequent and irritating, but has the potential to get worse. Usually, sciatica only affects one side, and the pain often radiates through the buttock and/or leg.
One or more of the following sensations may occur:
- Pain in the buttocks and/or leg that is worse when sitting
- Burning or tingling down the leg
- Weakness, numbness or difficulty moving the leg or foot
- A constant pain on one side of the buttocks
- A shooting pain that makes it difficult to stand up
While sciatica can be very painful, it is rare that permanent nerve damage (tissue damage) will result. Most pain syndromes result from inflammation and will get better within two weeks to a few months. Also, because the spinal cord is not present in the lower (lumbar) spine, a herniated disc in this area of the anatomy does not present a danger of paralysis.
Symptoms that may constitute a medical emergency include progressive weakness in the legs or bladder/bowel incontinence. Patients with these symptoms may have cauda equina syndrome and should seek immediate medical attention.
Any condition that causes irritation or impingement on the sciatic nerve can cause the pain associated with sciatica. The most common cause is lumbar herniated disc. Other common causes include lumbar spinal stenosis, degenerative disc disease, or isthmic spondylolisthesis.
Nerve pain is caused by a combination of pressure and inflammation on the nerve root, and treatment is centered on relieving both of these conditions. Treatments include:
- Manual treatments (including physical therapy and osteopathic or chiropractic treatments) to help relieve the pressure.
- Medical treatments (such as NSAIDs, oral steroids, or epidural steroid injections) to help relieve the inflammation.
- Surgery (such as microdiscectomy or lumbar laminectomy) to help relieve both the pressure and inflammation may be warranted if the pain is severe and has not been relieved with appropriate manual or medical treatments.
What causes sciatica?
The sciatic nerve is the largest nerve in the body. It starts in the low back at lumbar segment 3 (L3). The nerve roots run through the bony canal, and at each level a pair of nerve roots exits from the spine.
The nerve is named for the upper vertebral body that it runs between (for example, the nerve that exits at L4-L5 is named L4). The nerve passing to the next level runs over a weak spot in the disc space, which is the reason discs tend to herniate (extrude) right under the nerve root and can cause leg pain.
The sciatica symptoms (pain, numbness, tingling, weakness) are different depending on where the pressure on the nerve occurs. For example, a lumbar segment 5 (L5) nerve impingement can cause weakness in extension of the big toe and potentially in the ankle (foot drop).
Common conditions that can cause sciatica, or pain along the sciatic nerve include:
- Lumbar herniated disc
A herniated disc can occur when the soft inner core of the disc (nucleus pulposus) extrudes through the fibrous outer core (annulus) and the bulge places pressure on the contiguous nerve root. In general, it is thought that a sudden twisting motion or injury can lead to an eventual disc herniation. A herniated disc is sometimes referred to as a slipped, ruptured, bulging, or protruding disc, or a pinched nerve.
- Lumbar spinal stenosis
This condition involves a narrowing of the spinal canal. It is more common in adults over age 60, and typically results from enlarged facet joints placing pressure on the nerve roots as they exit the spine.
- Degenerative disc disease
While disc degeneration is a natural process that occurs with aging, in some cases it can also lead to pain along the sciatic nerve. The condition is diagnosed when a weakened disc results in excessive micro-motion at the corresponding vertebral level and inflammatory proteins from inside the disc can become exposed and irritate the area.
- Isthmic spondylolisthesis
Relatively common in adults (approximately 5% to 7% of adults), this condition rarely causes pain. It occurs when a small stress fracture, often at the fifth segment, allows the L5 vertebral body to slip forward on the S1 vertebral body. Caused by a combination of disc space collapse, the fracture, and the vertebral body slipping forward, the L5 nerve can get pinched as it exits the spine.
See also Isthmic spondylosthesis
- Piriformis syndrome
The sciatic nerve can get irritated as it runs under the piriformis muscle in the buttocks, leading to sciatica.
See also Piriformis syndrome – another irritation to the sciatic nerve
- Sacroiliac joint dysfunction
Irritation of the sacroiliac joint can also irritate the L5 nerve, which lies on top of it, and cause sciatica.
How is sciatica treated?
The good news is that if pain along the sciatic nerve is going to get better on its own it will usually do so within a couple of days or weeks. In fact, the vast majority of sciatica episodes usually heal on their own within six to twelve weeks.
- Conservative care:
During an episode of sciatic pain there are a number of conservative care options available to help alleviate the pain and discomfort.
For acute sciatica pain, heat and/or ice packs are most readily available and can help alleviate the pain, especially in the acute phase. Usually ice or heat is applied for approximately 20 minutes, and repeated every two hours. Most people use ice first, but some people find more relief with heat. The two may be alternated.
Over-the-counter or prescription medications may also be helpful in relieving sciatica. Non-steroidal anti-inflammatory drugs (NSAIDs) or oral steroids can be helpful in reducing the inflammation and pain.
- Surgical treatments:
If the pain is severe and has not gotten better within six to twelve weeks, it is reasonable to consider minimally invasive spine surgery (MISS specialist) or traditional open spine surgery. Depending on the cause and the duration of the sciatic pain, one of two surgical procedures may be considered: an arthroscopic microdecompression (microdiscectomy) or an open decompression (lumbar laminectomy).
- Arthroscopic Microdiscectomy (microdecompression)
In cases where the pain is due to a disc herniation, a microdiscectomy may be considered after 4 to 6 weeks if the pain is not relieved by conservative means. Urgent surgery is only necessary if there is progressive weakness in the legs, or sudden loss of bowel of bladder control. A microdiscectomy is typically an elective procedure, and the decision to have surgery is based on the amount of pain and dysfunction the patient is experiencing, and the length of time that the pain persists. Approximately 80% to 95% of patients will experience relief from their pain after this type of surgery.
This procedure can be performed for cervical, thoracic and lumbar disc herniations.
- Lumbar laminectomy (open decompression)
Lumbar spinal stenosis often causes pain that waxes and wanes over many years. Surgery may be offered as an option if the patient’s activity tolerance falls to an unacceptable level. Again, surgery is elective and need only be considered for those patients who have not gotten better after conservative treatments. After a lumbar laminectomy (open decompression), approximately 70% to 80% of patients experience relief from their pain.
Diagram of herniated disc by debivort (Own work) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons