Back Pain and Sciatica

Description

Alternative Names

Diagnosis

Because nearly all cases of low back pain clear up in a short time and are not due to serious problems, a medical history and a brief physical examination are almost always sufficient.

Still, with very severe or chronic back pain, it is important that any serious medical causes as well as cauda equina syndrome and progressive nerve damage be ruled out first. If the physician suspects a serious underlying cause, the approach to determining the origin of back pain involves answering three questions:

• Is some general medical disorder present that could be causing the pain?
• Are there social or emotional factors that might be intensifying the pain?
• Are the nerves in the spine involved in the pain (such as in sciatica)?

Such questions can usually be answered with a medical history and physical examination.

Medical History

A medical and family history should include heart problems, cancer, arthritis, and any other serious conditions. The patient should report the following:

• Previous episodes of back pain.
• Any history of injuries or accidents involving the neck, back, or hips.
• Any indications of a serious underlying disease (e.g., history of cancer, unexplained weight loss, chronic infection).
• The frequency, duration, and nature of the pain (e.g., whether it is dull, piercing, throbbing, or burning).
• The timing of back pain (whether it occurs at night or during the day).
• Events surrounding the onset and whether the pain was triggered by an event, such as lifting a heavy object. (Often, the patient cannot describe an event that produced the pain.)
• Any condition that worsens the pain (for example, coughing, exercise, straining during bowel movements, walking).
• Any situation that relieves the pain (lying down, exercise).
• Problems with urination or defecation (symptom of cauda equina syndrome).
• Other relevant symptoms (e.g., morning stiffness, weakness or numbness in the legs).

Physical Examination

The main objectives of a physical examination are to attempt to locate the specific location of the pain source and to determine limits of movement:

• Patients are asked to sit, stand, and walk in different ways (flat-footed, on the toes, and on their heels).
• In some cases they are asked to walk on a treadmill to test for weakness in toe or heel walking (which may indicate stenosis).
• Patients will be requested to bend forward, backward, and sideways and to twist.
• Patients will be asked to lift their leg straight up while lying down. The physician will also move the patient's legs in different positions and bend and straighten the knees. (Pain caused by sciatica can be intensified by lifting the affected leg straight in the air. It is usually sharp, localized, and accompanied by numbness or tingling. Pain caused by inflammation is duller and more generalized and not affected by lifting a straight leg.)
• The physician may measure the circumference of the calves and thighs to look for muscle deterioration.
• To test nerve function and reflexes, physicians will tap the knees and ankles with a rubber hammer. The physician may also touch parts of the body lightly with a pin, cotton swab, or feather to test for numbness and nerve sensitivity.

Imaging Techniques

Because most patients with back pain are on the mend or completely recovered within six weeks, imaging techniques such as x-rays or scans are rarely recommended in the first month unless a tumor, fracture, infection, cauda equina syndrome, or progressive neurologic disease is suspected.

Symptoms that may indicate the need for imaging studies include the following:

• Pain that lasts more than a month.
• Very severe or progressive pain, numbness.
• Muscle weakness.
• A previous accident or injury that might have affected the back.
• A history of cancer or other indications of an underlying disease, such as fever or unexplained weight loss.
• Pain that occurs in older patients (over 65 years of age).

If these conditions exist, usually an x-ray is used first. If results are inconclusive, either computed tomography (CT) or magnetic resonance imaging (MRI) may be performed. (Ultrasound is not useful.)

X-Rays Although many patients with acute and uncomplicated low back pain believe that plain x-rays of the spinal column are important in a diagnosis, they are not very helpful in most patients except for reducing anxiety. If pain persists after six to eight weeks, then x-rays are usually warranted. In such cases, x-rays may reveal signs of injury, infection, tumors, stenosis, or changes in the vertebrae that may be causing inflammation or compression on the nerve. Types of x-rays for the spine include the following:

• A discography is an x-ray of the disc. It requires injections into discs suspected of being the source of pain and discs nearby. It can be painful and is generally only used for patients who are undergoing back surgery to identify the location of the injured disc.
• An x-ray myelogram is an x-ray of the spine that requires a spinal injection of a special dye and the need to lie still for several hours to avoid a very painful headache. It has value only for select patients with pain on moving and standing. It has largely been replaced by CT and MRI scans.

CT stands for computerized tomography. In this procedure, a thin X-ray beam is rotated around the area of the body to be visualized. Using very complicated mathematical processes called algorithms, the computer is able to generate a 3-D image of a section through the body. CT scans are very detailed and provide excellent information for the physician.

Magnetic Resonance Imaging (MRI). Magnetic resonance imaging (MRI) is not painful and can provide very well-defined images of soft tissue and bone. MRIs are able to detect annular tears or disc fragments and can detect non-spinal causes of back pain, including infection and cancer. MRIs are no more effective than x-rays in identifying bone problems, however, and they are more expensive. Furthermore, evidence suggests that relying on MRI images of disc abnormalities to determine treatment has resulted in many unnecessary surgeries. At least 40% of all adults have bulging or protruding vertebral discs, and most have no back pain. The degree of disc abnormalities revealed by MRIs, therefore, have very little to do with the severity of the pain or the need for surgery. Disc abnormalities in people who have back pain may simply be a coincidence rather than an indication for treatment.

Click the icon to see an image of a MRI machine.

Advanced imaging techniques should be used only when underlying infection, cancer, or nerve involvement are suspected.

Bone Scintigraphy and SPECT Imaging. In rare cases, doctors may use bone scintigraphy to determine abnormalities in the bones. In this technique, a small amount of radioactive material is injected into a vein, circulates through the body, and is taken up by the bones. The bones can then be visualized using x-rays or, in specialty cases, nuclear scanning techniques such as a single photon emission computed tomography (SPECT). Bone scintigraphy may be useful for early detection when bone abnormalities are suspected from such conditions as spinal fracture, cancer that has spread to the bone, or osteoarthritis.

Electrodiagnostic Tests

Electrodiagnostic tests that analyze the electric waveforms of nerves and muscles may be useful for detecting nerve abnormalities that may be causing back pain and identifying possible injuries. They are also useful to determine if any abnormal structural findings on an MRI or other imaging test have real significance as a cause of the back pain. It should be noted that any nerve injuries that affect these tests may not be present for two to four weeks after symptoms begin.

Nerve conduction studies and electromyography are the electrodiagnostic tests most commonly performed.

• Nerve Conduction Studies. To perform nerve conduction studies, surface electrodes are attached to the skin. Small electric shocks are then applied to measure the speed of nerve conduction.
• Electromyography. To perform electromyography, a fine, sterile, wire electrode is inserted briefly into a muscle and the electrical activity is displayed on a viewing screen. Electromyography can be quite painful, and some experts question, in fact, whether it adds any valuable diagnostic information. They suggest it be limited to unusual cases or when other tests indicate that the condition is aggressive and may increase the risk for rapid, significant injury.

Other Tests

Blood and urine samples may be used to test for infections, arthritis, or other conditions. Injecting a drug that blocks pain into the nerves in the back helps locate the level in the spine where problems occur. A procedure called a facet block is also useful in locating areas of specific damage. Provocative discometry is a test that uses an injection of saline solution into the suspected disc to reproduce the pain, which is then followed by injection of an anesthetic to dull the pain.