Back Pain

Overview

After the common cold, back pain is the most frequent problem that brings people to a doctor's office. It is often difficult to pinpoint the exact cause of back pain because so many different structures can be affected.

This section includes information on:

• Questions your doctor may ask
• Physical examination
• Imaging studies
• Electrical tests

Routine blood tests help determine the cause of back problems in a few situations.

Questions your doctor may ask

Obtaining an accurate history and description of the back pain is a doctor's primary method of tracking down its cause and determining whether treatment is necessary. Questions include:

• Where is the pain located? Is it confined to the lower back, or does it radiate to the buttocks and legs? (These questions check for sciatica.)
• How severe is the pain? (A good description of pain intensity can help the doctor determine its cause.)
• When the did the pain begin? (If the pain follows an injury, it is less likely to be due to a slowly progressing condition, such as spinal stenosis.)
• What makes the back feel better or worse? (The pattern of pain may indicate whether a nerve is involved, possibly because of a disk herniation.)
• Has there been a prior episode of back pain? If so, how was it treated, and how effective was the treatment? (The condition may have recurred.)
• Are there any other health problems? (Weight loss and poor appetite, for example, raise the concern that cancer has spread to the vertebrae.)
• Are any medications being taken, such as corticosteroids or anticonvulsants? (These can affect spinal bone mass.)
• What is the person's profession, and what kinds of exercise or activities are being performed? (Muscle injury is frequently related to a particular activity.)

Physical examination

A physical examination typically focuses on the back, legs, and feet. The doctor will look at a patient's posture and curvature of the spine; a hands-on examination of tender areas in the back may provide clues to the origin of the pain.

A neurological exam, including tests of sensation, strength, and reflexes, will be conducted as well. These tests are important in the case of disorders such as disk herniation and spinal stenosis, since the nerves issuing from each level of the spine are responsible for sensation and muscle strength in specific parts of the body.

A rectal examination may be done to assess nerve function of the anus, because its nerves also arise from the lower lumbar spine.

Imaging studies

Imaging studies provide a view of the bones and the soft tissues, which comprise muscles, ligaments, cartilage, tendons, and blood vessels. These studies are needed mainly for potential candidates for surgery.

X-rays should be the first imaging study for chronic pain and for new-onset back pain lasting longer than four to six weeks. They are especially useful for detecting fractures and invasion of bone by multiple myeloma. People should not be concerned about the possible risks of modern X-rays; the radiation doses are low and there is no evidence of harm even from repeated X-rays. Conventional X-rays are available almost anywhere and are relatively low in cost ($150 to $200).

A CT scan, also called a computerized axial tomography (CAT) scan, involves a series of X-rays that are taken as a special detector rotates 360° around the patient. A computer combines all the information into a cross-sectional picture. CT scans are 10 to 20 times more sensitive than X-rays; they provide better soft-tissue detail and good detail of the vertebrae. CT scans are considerably more expensive and deliver more radiation than conventional X-rays. The cost is about $550.

A CT myelogram involves a CT scan after the injection of a contrast material into the spinal canal. The injection carries the risk of infection and such side effects as nausea, headaches, and pain or discomfort at the site of the injection, and people are required to sit or lie with their head elevated for six to eight hours afterward. These scans offer the best detail of bone and soft tissue. CT myelograms are usually performed only prior to surgery or after failed surgery. The cost is about $600.

In MRI, the most sensitive imaging technique, the patient is surrounded with a powerful magnet while radio waves are passed through the body. No X-rays are involved. This test provides the best images of soft tissues and is completely safe. However, MRI may not give a useful image of the bones in the spine. MRI is not recommended for early diagnosis of back pain unless the doctor suspects a serious condition, such as cauda equina syndrome. Despite their sensitivity, studies have shown that MRIs should be reserved for preoperative evaluation or for people with a suspected herniated disk whose back symptoms do not respond to conservative treatment after four to six weeks. Because people must lie perfectly still for between 30 minutes and two hours in a relatively small space, MRIs may be uncomfortable and poorly tolerated by those who are claustrophobic. The cost is about $1,000.

Bone scans measure the amount of radioactivity emitted from bone after the injection of a bone-seeking compound that contains technetium, a radioactive metal. An area of bone that displays an increased uptake of technetium has a higher rate of bone turnover, which can be the result of a fracture not identified on an X-ray as well as metastatic cancer, Paget's disease, or osteomyelitis (a bacterial infection of the spine). The amount of radiation delivered is similar to that of a CT scan. This technique can be used to identify fractures in both the central and peripheral areas of the body. The cost is about $500.

Electrical tests

Three basic types of electrical tests may be employed in difficult cases involving leg pain lasting more than a month. They may help the doctor localize the source of pain or numbness or suggest the cause of the pain (for example, whether it is due to disk herniation or nerve damage from an unrelated disorder, such as diabetes).

In one such test, called electromyography, electrodes are used to measure muscle abnormalities. The two other tests--nerve conduction and sensory-evoked potentials--examine nerve function by measuring how fast the nerves conduct impulses. These three tests are used only if the diagnosis is in doubt, since there is still some debate over their usefulness.