HOW IS LOW BACK PAIN OR SCIATICA DIAGNOSED?

Medical History and Physical Examination

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. The physician should check for any medical conditions that might be causing low back pain.

Medical History. A medical and family history should include heart problems, cancer, arthritis, and any other serious conditions. The patient should report previous episodes of back pain as well as any history of injuries or accidents involving the neck, back, or hips. The physician will generally ask about frequency, duration, and the nature of the pain (eg, whether it is dull, piercing, throbbing, or burning). The patient should describe its onset, if possible, 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.) The physician will need to know what worsens the pain (for example, coughing, exercise, straining during bowel movements, walking) and what relieves the pain (lying down, exercise). Other important symptoms may include morning stiffness, problems with urination or defecation, and weakness or numbness in the legs.

Physical Examination. Most patients with low back pain find that it gets worse during movement and prolonged sitting or standing. The main objective of a physical examination is to locate the specific source of the pain:

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 indicated 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 is usually sharp, localized, and accompanied by numbness or tingling. It can be intensified by lifting the affected leg straight in the air. Pain caused by inflammation is duller and more generalized and not affected by lifting a straight leg.)
The circumference of the calves and thighs may be measured 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

Imaging techniques such as x-rays or scans are rarely used except under certain circumstances that may include the following:

Pain that lasts more than a month.
Very severe pain, numbness.
Muscle weakness.
Accidents that might involve the vertebrae.
A history of cancer.
The presence of fever.

If these conditions exist, usually an x-ray is used first, and then, if results are inconclusive, either a computed tomography (CT) or magnetic resonance imaging (MRI) scan. (Ultrasound is not useful.)

X-Rays. A plain x-ray is usually not very helpful, but it can aid in ruling out infection, injuries, or tumors. It may also reveal signs of stenosis and changes in the spine due to aging.

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 used for patients who are undergoing back surgery to identify the location of the injured disc. Some experts believe that discography is not at all useful in identifying the source of pain because it requires expert execution and analysis for any degree of accuracy. Others argue that it is the only procedure that can reveal the shape of the disc and identify nerve structures in the disc, which may play a role in some cases of sciatica.

A myelogram is an x-ray of the spine that requires a spinal injection and the need to lie still for several hours to avoid a very painful headache. It has largely been replaced by CT and MRI scans.

CT and MRI Scans. MRI and CT scans are often used for identifying disc abnormalities. MRIs are more accurate than CTs and provide very well-defined images of soft tissue and bone. MRIs are able to detect annular tears or disc fragments and can detect nonspinal causes of back pain, including infection and cancer. Still, studies have reported that MRIs miss between 6% and 23% of damaged discs that were revealed during surgery. Spinal abnormalities identified by MRIs also predict long-term problems. Three-dimensional CT scans and MRI refinements may soon make diagnosis more accurate.

These techniques are not painful, but they are very expensive. Furthermore, evidence now strongly suggests that an image of an abnormal disc is not necessarily an indication for surgery. For example studies indicate at least 40% of all adults have bulging or protruding vertebrae discs. And most have no back pain at all. Discs abnormalities in people who have back pain, then, may simply be a coincidence rather than an indication for treatment. Many experts now believe that relying on images of disc abnormalities to determine treatment has resulted in many unnecessary surgeries.

Bone Scans and SPECT Imaging. Bone scintigraphy and single photon emission computed tomography (SPECT) may also be used, especially if bone abnormalities are suspected from conditions that include spinal fracture, cancer that has spread to the bone, or osteoarthritis.

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.