A herniated disk describes the protrusion of the soft, gel-like inner portion of the intervertebral disk, known as the nucleus pulposus. The nucleus pulposus exits from a weakened layer of the outer fibrous band of the intervertebral disk, known as the annulus fibrosus. The herniated disk, if in the lower back, can inflame or compress a nearby spinal nerve, resulting in shooting pain down the leg. This is commonly referred to as sciatica. A herniated disk can also occur in other portions of the spine, including the neck. If the disk herniation occurs in the neck and irritates or compresses a spinal nerve, one may get numbness, tingling and pain in the arm on the side of the herniation.
The are several reasons why a disk can herniate. These include wear and tear on the spine, or degeneration, that weakens the annulus fibrosus. Injury is another common cause. Mechanisms of injury may include motor vehicle accidents, lifting heavy objects and sudden twisting movements. Intervertebral disk herniations may also result from a combination of wear and tear and injury. A disk that has experienced a gradual weakening over time is more susceptible to herniation after a traumatic event.
A herniated disk may produce no symptoms. Symptoms, when present, depend on the location of the herniated disk. A herniated disk in the lower back can cause pain that radiates to the buttocks, legs and the feet. This is commonly referred to as sciatica. There may be tingling or numbness in the legs and feet and muscle weakness.
In the neck, a herniated disk can cause shoulder pain, radiating pain to the arm and occasionally the hands and fingers. Neck pain may be present in the back and sides of the neck. This pain may become worse with bending or turning the neck. Spasm of the neck muscles is also common.
Herniated disks in the middle of the back are not as common as in the neck or lower back. When present, the symptoms include pain in the upper or lower back, abdomen and legs. Weakness and numbness may be present in one or both legs.
The diagnosis of a herniated disk begins with a medical history and physical exam. The physical exam includes an assessment for muscle weakness or loss of sensation. Your physician may ask you to walk on your heels and toes to assess the strength of your lower legs. She or he will check for loss of sensation by asking you if you can feel a light touch on the leg or foot and test your reflexes at the knees and ankles. Reflexes may be diminished or absent if there is a compressed spinal nerve. The physician may ask you to lie on your back as she or he lifts your leg without flexing the knee. This is called the straight leg raise test and is an accurate indicator of a herniated disk for patients less than 35 years of age.
An MRI clearly delineates soft tissues and can accurately pinpoint a herniated disk. It is commonly used to evaluate a patient with a suspected herniated disk and can help determine which, if any, spinal nerves may be affected. A CT scan or CT myelogram can be ordered for patients who cannot tolerate an MRI.
Treatment of herniated disks is largely non-surgical. If symptoms do not resolve with over-the-counter pain medications and rest, injections by an interventional pain specialist along with physical therapy may improve symptoms significantly. The injections often include steroid to decrease inflammation around a potentially affected nerve root. Physical therapy can help reduce pain, swelling and muscle spasms. If the pain is prolonged and unbearable and if there is motor weakness in the arm or leg, or loss of bowel and bladder function in the case of a herniated lumbar disk, then surgery is the next step in management.