What is Sciatica?
There are a Number of Causes of this Type of Leg Pain
Sciatica occurs mainly on one side only, and is normally associated with low back pain. If the pain is going down both legs at the same time it’s not a straightforward sciatica but likely to be something more serious.
- Pain: this is the usual symptom. The site of the pain varies, sometimes it’s just in the foot but more often than not pain is present down most of the leg –usually at the back or down the side.
- Numbness: another common feature, normally in the toes or foot. Sometimes rather than numbness, pins and needles is experienced and occasionally a burning sensation.
- Muscle weakness: this is a more serious feature, most likely to occur if the sciatica goes on for any length of time. In extreme cases, the foot can drop as the muscle on the front of the lower leg becomes weak.
Anatomy of the Sciatic Nerve
The largest nerve in the body, it arises from either side of the spine as several roots. After it leaves the spinal column the roots join to form the nerve. It’s really a cable of many of nerves rather than a single nerve and it’s about as thick as a little finger.
It extends down the leg as far as the foot with numerous branches leaving on the way. Some nerves carry sensation away from the leg and foot: if you stepped on a tack the pain would reach your spinal cord and brain via the sciatic nerve. Impulses also flow the other way, from the cord and brain to the leg. These signals control the muscles, veins and arteries.
Causes of Sciatica
Nearly always due to pressure on the nerve or its roots; this can have a number of causes. Frequently this pressure on the nerve roots happens in or near the small gap between the vertebrae (intervertebral foramen) where the nerve roots exit. There’s very little room in this area so any disc protrusion or swelling is likely to impinge on the nerve roots.
- ‘Slipped’ disc: the intervertebral disc doesn’t really slip but it can bulge or its jelly-like centre can leak. Either of these can irritate the sciatic nerve roots.
- Arthritis: most people from middle-age onwards have arthritis in the spine and it doesn’t generally cause any problems other than a bit of aching or stiffness. However sometimes it can cause swelling in the joints near the intervertebral foramen and put pressure on the sciatic nerve roots. The bony outgrowths that occur with arthritis in the spine can also impinge on the nerve roots.
- Vertebral collapse: in osteoporosis the vertebrae may collapse and trap the nerve roots.
- Muscle spasm: muscle spasm caused by back strain may trap part of the sciatic nerve that runs through the strained muscle. This may occur within the muscles that run close to the spinal column or in the deep muscles of the buttock.
- Pelvic disease: rarely, tumours or inflammation in the pelvic cavity can cause sciatica.
- Damaged or deformed vertebrae: anything that results in the intervertebral foramen becoming narrower can lead to sciatica.
Simple management is often effective. Exercises, massage and gentle manipulation are all worth trying as are your usual pain killers.
In cases that don’t resolve interventions may include spinal injections and surgery depending on the cause.
Sciatica is not a disease: it’s a symptom of something else so if you have sciatic pain you should consult the appropriate health professional.
