Diagnosis

During the physical exam, your doctor will check your back for tenderness. You might be asked to lie flat and move your legs into various positions to help determine the cause of your pain.

Your doctor may also perform a neurological exam to check your:

• Reflexes
• Muscle strength
• Walking ability
• Ability to feel light touches, pinpricks or vibration

In most cases of herniated disk, a physical exam and a medical history are all that's needed for a diagnosis. If your doctor suspects another condition or needs to see which nerves are affected, he or she may order one or more of the following tests.

Imaging tests

• X-rays. Plain X-rays don't detect herniated disks, but they can rule out other causes of back pain, such as an infection, tumor, spinal alignment issues or a broken bone.
• CT scan. A CT scanner takes a series of X-rays from different directions and then combines them to create cross-sectional images of your spinal column and the structures around it.
• MRI. Radio waves and a strong magnetic field are used to create images of your body's internal structures. This test can be used to confirm the location of the herniated disk and to see which nerves are affected.
• Myelogram. A dye is injected into the spinal fluid before X-rays are taken. This test can show pressure on your spinal cord or nerves due to multiple herniated disks or other conditions.

Nerve tests

Electromyograms and nerve conduction studies measure how well electrical impulses are moving along nerve tissue. This can help pinpoint the location of nerve damage.

• Nerve conduction study. This test measures electrical nerve impulses and functioning in your muscles and nerves through electrodes placed on your skin. The study measures the electrical impulses in your nerve signals when a small current passes through the nerve.
• Electromyography (EMG). During an EMG, your doctor inserts a needle electrode through your skin into various muscles. The test evaluates the electrical activity of your muscles when they contract and when they're at rest.