A herniated (also called a slipped or ruptured) disc is a fragment of the disc nucleus which is pushed out of the annulus, into the spinal canal through a tear or rupture. Discs that become herniated are usually in an early stage of degeneration. The spinal canal has limited space which is inadequate for the spinal nerve and the displaced herniated disc fragment. Due to this displacement, the disc presses on spinal nerves, often producing pain, which may be severe.

Herniated discs can occur in any part of the spine. Herniated discs are more common in the lower back (lumbar spine), but also occur in the neck (cervical spine). The area in which you experience pain depends on what part of the spine is affected.

Causes
A single excessive strain or injury may cause a herniated disc. However, disc material degenerates naturally as you age, and the ligaments that hold it in place begin to weaken. As this degeneration progresses, a relatively minor strain or twisting movement can cause a disc to rupture.

Certain individuals may be more vulnerable to disc problems, and as a result may suffer herniated discs in several places along the spine. Research has shown that a predisposition for herniated discs may exist in families, with several members affected.

Herniated Disc Symptoms
Symptoms vary greatly depending on the position of the herniated disc and the size of the herniation. If the herniated disc is not pressing on a nerve, you may experience a low backache or no pain at all. If it is pressing on a nerve, there may be pain, numbness, or weakness in the area of the body to which the nerve travels. Typically, a herniated disc is preceded by an episode of low back pain or a long history of intermittent episodes of low back pain.

Lumbar spine (lower back): Sciatica frequently results from a herniated disc in the lower back. Pressure on one or several nerves that contribute to the sciatic nerve can cause pain, burning, tingling, and numbness that radiates from the buttock into the leg and sometimes into the foot. Usually one side (left or right) is affected. This pain often is described as sharp and electric shock-like. It may be more severe with standing, walking or sitting. Along with leg pain, you may experience low back pain.

Cervical spine (neck): Symptoms may include dull or sharp pain in the neck or between the shoulder blades, pain that radiates down the arm to the hand or fingers, or numbness or tingling in the shoulder or arm. The pain may increase with certain positions or movements of the neck.

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Diagnosis
Diagnosis is made based on your history, symptoms, a physical examination, and results of tests, including the following:

X-ray: Application of radiation to produce a film or picture of a part of the body can show the structure of the vertebrae and the outline of the joints. X-rays of the spine are obtained to search for other potential causes of pain, i.e. tumors, infections, fractures, etc.

Computed tomography scan (CT or CAT scan): A diagnostic image created after a computer reads x-rays; can show the shape and size of the spinal canal, its contents, and the structures around it.

Magnetic resonance imaging (MRI): A diagnostic test that produces three-dimensional images of body structures using powerful magnets and computer technology; can show the spinal cord, nerve roots, and surrounding areas, as well as enlargement, degeneration, and tumors.

Myleogram: An x-ray of the spinal canal following injection of a contrast material into the surrounding cerebrospinal fluid spaces; can show pressure on the spinal cord or nerves due to herniated discs, bone spurs or tumors.

Electromyogram and Nerve Conduction Studies (EMG/NCS): These tests measure the electrical impulse along nerve roots, peripheral nerves, and muscle tissue. This will indicate whether there is ongoing nerve damage, if the nerves are in a state of healing from a past injury, or whether there is another site of nerve compression.