The bones (vertebrae) that form the spine in the back are cushioned by discs. These discs are round, like small pillows, with a tough, outer layer (annulus) that surrounds the nucleus. Located between each of the vertebra in the spinal column, discs act as shock absorbers for the spinal bones.
A herniated disc (also called bulged, slipped or ruptured) is a fragment of the disc nucleus that is pushed out of the annulus, into the spinal canal through a tear or rupture in the annulus. Discs that become herniated usually are 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 pain is experienced depends on what part of the spine is affected.
A single excessive strain or injury may cause a herniated disc. However, disc material degenerates naturally as one ages, 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.
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, the patient 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/Radiculopathy 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. Straightening the leg on the affected side can often make the pain worse. Along with leg pain, one may experience low back pain; however, for acute sciatica the pain in the leg is often worse than the pain in the low back.
Cervical spine (neck): Cervical radiculopathy is the symptoms of nerve compression in the neck, which 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.
Diagnosis & Imaging
Testing modalities are listed below. The most common imaging for this condition is MRI. Plain x-rays of the affected region are often added to complete the evaluation of the vertebra. Please note, a disc herniation cannot be seen on plain x-rays. CT scan and myelogram were more commonly used before MRI, but now are infrequently ordered as the initial diagnostic imaging, unless special circumstances exist that warrant their use. An electromyogram is infrequently used.
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 3D 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.
Myelogram: 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. This test is infrequently ordered.