What causes sciatica?
Sciatic pain is often caused by a trapped nerve from a bulging, herniated or prolapsed disc (“slipped disc”). The lowest discs in the spine are the most vulnerable as they lie at a greater angle, carry the most weight and one of the important spinal ligaments is narrow here. The transition between the highly mobile lumbar spine and the immobile pelvis puts more mechanical stress at this level.
The illustration shows the close relationship between the disc (dark brown) and the nerve (yellow). The vertebral boney structures show advancing signs of degenerative (arthritic) change.
In sciatica the one thing to be most concerned about is not the pain itself, but numbness and weakness. When the nerve roots that leave the spine, such as those that lead into the sciatic nerve, get trapped the first sign is pain as the nerve itself gets inflamed.
The illustration shows chiropractor Michael Copland-Griffiths using a pin wheel passed lightly over the skin surface to determine changes in skin sensitivity, such as numbness, which may occur with nerve root entrapment.
If nerve root compression continues then tingling, pins and needles follow, eventually leading to numbness and paralysis of muscles in the leg. Sometimes these symptoms can progress in the absence of a sore back. If the compression is not relieved urgently, there may be permanent problems. Should you develop loss of bladder or bowel control it must be treated as a medical emergency. However, all too often “sciatica” and “disc bulges” are misdiagnosed so it is essential to get an accurate diagnosis. The treatments you may be receiving for your medical condition could, if you have not been correctly diagnosed, be quite different from what you actually need to secure a lasting recovery.
In a study a while ago it was found that 40% of normal middle aged adults had a disc bulge showing on their MRI scans and yet they were not suffering any adverse symptoms. Many people who go to the GP with low back pain and sciatica from a lumbar joint problem will have an MRI that shows a bulging disc that is completely un-related to their pain. This factor may account for failures to resolve the symptoms after lumbar spine surgery. Although the offending disc bulge has been removed the patient soon finds out that the lumbar spine joint problem remains.
Sciatica pain can start in the back and travels into the buttock, the back of the thigh, into the back or outside of the calf, and finally into the outside or underneath of the foot and toes. The pain may skip some areas of the sciatic nerve pathway altogether. If the pain does not go beyond the knee it may not be sciatica but simply a referred pain from a back muscle or joint. If the pain is in the front of the thigh it is unlikely to be sciatica and may be arising from irritation to the femoral nerve.
Many cases of sciatic nerve irritation are not caused by compression of the nerve at all. New research has shown that the damage around the nerve root may be due inflammatory changes. These changes may be caused by an auto-immune response or other chemical changes initiated by the body due to leakage of the jelly like interior of the disc into the spinal canal. If this is true, new drug treatment options may be coming along in the future. In the meantime, we are stuck with traditional methods of treatment and chiropractic care may help.
It is well documented that that emotional stress (“psychosocial factors”) can play a role in some people’s pain. Back pain research shows that stress and levels of happiness influence symptoms and the same may be true for sciatica. Perhaps the stress hormones are the key here as they can have a pro-inflammatory effect which would be like pouring petrol on the embers of inflammation from a disc bulge.
GP’s will often prescribe anti-inflammatory medication and pain-killers which can help. If things are not settling down within a few days more active treatment may be needed.
Most chiropractors will use low back manipulation (“adjustment”) which frees up stiff joints, reduces adhesions and raises the pain threshold. The illustration shows Michael Copland-Griffiths delivering an adjustment to free the right sacroiliac joint.
Some encouraging studies have shown a reduction in the size of the disc bulge after manipulation. A recent review of all forms of manual therapy found that there is moderately positive evidence that manipulation is helpful for sciatica.
The most important thing for a quick and complete recovery is to stay as active as you can manage and to do the exercises that you are prescribed. Exercises are prescribed to strengthen the core stability trunk muscles and the tiny muscles between the vertebrae themselves. Strengthening these muscles reduces the mechanical strain on the discs and joints and not only helps with recovery but may help to prevent it happening again.