 If you have lower back pain, you're not alone. Nearly everyone, at some point, has back pain that interferes with daily activities. In fact, Americans spend at least $50 billion each year on low back pain, which is the most common cause of job-related disability and a leading contributor to missed work. Back pain is the second most common neurological ailment in the United States — only headache is more common. Fortunately, most occurrences of low back pain go away within a few days. However, some back pain can take much longer to resolve and may lead to more serious conditions.
There are two types of back pain: acute and chronic. Acute, or short-term, low back pain generally lasts from a few days to a few weeks. Most acute back pain is mechanical in nature, which means it is the result of trauma to the lower back or it is due to a disorder such as arthritis.
Pain from trauma may be caused by a sports injury, work around the house or in the garden, or a sudden jolt, such as a car accident. Symptoms may range from a mild muscle ache to shooting or stabbing pain, limited flexibility, or an inability to stand straight. Occasionally, pain felt in one part of the body may "radiate" from a disorder or injury elsewhere in the body. Some acute pain syndromes can become more serious if left untreated.
Chronic back pain is measured by how long it lasts. Generally, pain that persists for more than three months is considered chronic. Chronic back pain is often progressive and the cause for it can be difficult to determine.
So, what can you expect when you visit your physician with a complaint of low back pain?
A thorough medical history and physical exam can usually identify any dangerous conditions or family history that may be associated with the pain. The doctor will ask you to:
- Describe the onset, location, and severity of the pain.
- State how long you've had the symptoms.
- Describe any limitations in movement.
- Share any history of previous episodes or any health conditions that might be related to the pain.
The physician will then examine your back and conduct neurologic tests to determine the cause of pain and appropriate treatment. Blood tests may also be ordered. Imaging tests may be necessary to diagnose tumors or other possible sources of the pain.
There are a variety of diagnostic methods available to confirm the cause of low back pain. We've listed some of the more common methods:
X-ray imaging includes conventional and enhanced methods that can help diagnose the cause and site of back pain. A conventional x-ray, often the first imaging technique used, looks for broken bones or an injured vertebra. Tissue masses (injured muscles and ligaments) and painful conditions (bulging disc) are not visible on conventional x-rays.
 Discography involves injecting a special contrast dye into a spinal disc thought to be causing low back pain. The dye outlines the damaged areas on x-rays taken following the injection. Myelograms also enhance the diagnostic imaging of an x-ray. In this procedure, the contrast dye is injected into the spinal canal, allowing spinal cord and nerve compression caused by herniated discs or fractures to be seen on an x-ray.
Computerized tomography (CT) is a quick and painless process used when disc rupture, spinal stenosis, or damage to vertebrae is suspected as a cause of low back pain.  Magnetic resonance imaging (MRI) is used to evaluate the lumbar region for bone degeneration or injury or disease in tissues and nerves, muscles, ligaments, and blood vessels. MRI scanning equipment creates a magnetic field around the body strong enough to temporarily realign water molecules in the tissues. Radio waves are then passed through the body to detect the "relaxation" of the molecules back to a random alignment and trigger a resonance signal at different angles within the body. A computer processes this resonance into either a three-dimensional picture or a two-dimensional "slice" of the tissue being scanned, and differentiates between bone, soft tissues and fluid-filled spaces by their water content and structural properties. This noninvasive procedure is often used to identify a condition requiring prompt surgical treatment.
 Electrodiagnostic procedures include (EMG), nerve conduction studies, and evoked potential (EP) studies. EMG assesses the electrical activity in a nerve and can detect if muscle weakness results from injury or a problem with the nerves that control the muscles. Very fine needles are inserted in muscles to measure electrical activity transmitted from the brain or spinal cord to a particular area of the body.
With nerve conduction studies the doctor uses two sets of electrodes that are placed on the skin over the muscles. The first set gives the patient a mild shock to stimulate the nerve that runs to a particular muscle. The second set of electrodes is used to make a recording of the nerve's electrical signals, and from this information the doctor can determine if there is nerve damage. EP tests also involve two sets of electrodes — one set to stimulate a sensory nerve and the other set on the scalp to record the speed of nerve signal transmissions to the brain.
Bone scans are used to diagnose and monitor infection, fracture, or disorders in the bone. A small amount of radioactive material is injected into the bloodstream and will collect in the bones, particularly in areas with some abnormality. Scanner-generated images are sent to a computer to identify specific areas of irregular bone metabolism or abnormal blood flow, as well as to measure levels of joint disease.
Thermography involves the use of infrared sensing devices to measure small temperature changes between the two sides of the body or the temperature of a specific organ. Thermography may be used to detect the presence or absence of nerve root compression. Ultrasound imaging, also called ultrasound scanning or sonography, uses high-frequency sound waves to obtain images inside the body. The sound wave echoes are recorded and displayed as a real-time visual image. Ultrasound imaging can show tears in ligaments, muscles, tendons, and other soft tissue masses in the back.
Where can I get more information?
For more information on neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute's Brain Resources and Information Network (BRAIN) at http://www.ninds.nih.gov. You can also contact the National Institute of Arthritis and Musculoskeletal and Skin Diseases Information Clearinghouse at http://www.niams.nih.gov.
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