Sciatica

Sciatica is a set of symptoms including pain, weakness, numbness, or tingling in the legs, caused by injury or pressure on the sciatic nerve.

Sciatica is not a medical condition on its own, but a symptom of another medical problem.  This is an important point to note before deciding how to treat it.

Incidence; Causes and Development

Sciatica most often occurs in middle age.  It is rare before age 20; incidence in the 50s and then declines.

The sciatic nerve starts in the lower spine and runs down the backs of the legs.  It controls muscles from the back of the knee to the lower leg, and transmits sensation from the back of the thigh, part of the lower leg, and the sole of the foot.  Anything that puts pressure on the sciatic nerve, or causes damage, can lead to sciatica.  Common causes include:

• Slipped disc (spinal disc herniation)
• Spinal disc degeneration
• Pelvic injury or fracture
• Tumors causing pressure on the spinal cord or nerve roots: Severe back pain extending to the hips and feet, loss of bladder or bowel control, or muscle weakness, may result from spinal tumors.
• Spinal stenosis
• Spinal trauma, e.g. car accident
• Piriformis syndrome.  In about 15% of people, the sciatic nerve runs through the piriformis muscle rather than under it.  Trauma or overuse can cause it to shorten or spasm, compressing the sciatic nerve.
• Pregnancy – the fetus may press against the sciatic nerve

Signs and Symptoms

The pain of sciatica is felt in the lower back, buttock, or various parts of the leg and foot and can range from a mild tingling, pins and needles, or dull ache, to a burning sensation, to severe pain that makes a person unable to stand up or walk.  It can vary from infrequent and irritating to constant and incapacitating.  It usually occurs on one side and in one area, such as the buttock, hip, the upper or lower leg, or sole of the foot, and is often accompanied by weakness, lack of muscle control, and/or numbness, often in a different area.

The pain may be slight at first, but worsen after standing, sitting, sneezing, coughing, laughing, bending backwards, walking, or at night.  Pain is made worse by prolonged exposure to cold weather.

Diagnosis and Tests

A physical exam will be carried out in order to determine whether there is knee or foot weakness, difficulty moving the foot, abnormal reflexes, loss of sensation, pain when lifting the leg.

If sciatica is suspected, further testing may include blood tests, X-rays, CT scan or an MRI.  MR neurography can diagnose 95% of severe sciatica patients.

Treatment and Prevention

The underlying cause of sciatica needs to be identified and treated.

Applying ice and heat often helps with the pain, as do pain relievers.  Physical activity should be reduced, and patients should avoid heavy lifting and twisting their back.  Physical therapy can help, as well as slowly-increasing amounts of exercise.  However, studies have shown little difference in the outcomes from staying active and bed rest.

Surgery to remove the underlying cause (disk herniation) can be beneficial in cases of one-sided sciatica, but benefits become marginal after a few years.

There is evidence that spinal manipulation is safe and effective for the treatment of acute sciatica, but not chronic sciatica.

Prognosis

Most people (about 90%) with sciatica get better within a few weeks or months without surgical treatment, so a period of 'watchful waiting' is generally recommended.  However, sciatica often returns later.  While symptoms can be very painful, it is rare that permanent sciatic nerve damage will result.