Spinal Disc Disease

Between each vertebra is a fibrous disc with a jelly-like core. These cushions of cartilage allow the body to accept and dissipate load across multiple levels in the spine and still allow for the flexibility required for performing normal activities of daily living. As the body twists, bends, flexes and extends, the intervertebral discs are constantly changing their shape.

Causes

When discs degenerate, becoming less supple due to age or back strain, the disc may prolapse — squeezing out some of the soft core. This loss of cushioning may cause pressure on nerves rootsand cause back or neck pain, numbness or tingling in the arms, or searing pain down one or both legs. If the prolapse becomes severe, it can damage the spinal cord.As a part of the aging process, the discs begin to lose their high water content, their ability to cushion the vertebrae, and to dissipate force as efficiently. This is called degenerative disc disease. As the discs deteriorate, the spine can initially become less stable. Bony spurs can develop as a result of this instability and can cause pressure on nearby nerves leading to leg or arm pain. Narrowing of the neural canal by these bony spurs is known as degenerative spinal stenosis.

By the age of 35, approximately 30% of people will show evidence of disc degeneration at one or more levels. By the age of 60, greater than 90% of people will show evidence of disc degeneration at one or more levels on MRI. In some patients, this disc degeneration can be nearly asymptomatic; in others, disc degeneration can lead to intractable back pain.

The outer layer of the discs themselves can also tear. When this occurs, the inner, gelatinous layer can herniate out (a “herniated” or “ruptured” disc) and also cause pressure on an adjacent nerve. If the herniation occurs in the neck and causes pressure there, it can cause pain that radiates into the shoulder and arm; if it occurs in the lower back, the pain produced can radiate down into the hip and leg.

Symptoms

Patients with disc disease in the cervical, thoracic, or lumbar spine can experience:

• Neck pain
• Back pain
• Arm pain
• Leg pain or
• Any combination of the above

In rare cases, patients with large disc herniations may experience weakness in an extremity or signs of spinal cord compression such as difficulty with gait, incoordination, or loss of bowel/bladder control.

Diagnosis

• Cervical spine x-rays are commonly taken after a neck injury in order to rule out a fracture, dislocation or instability. If the x-rays show degenerative changes right after the injury, then we assume they were present prior to the injury. Cervical spine x-rays may reveal congenital narrowing of the cervical spinal canal when present.
• CT scan of the cervical spine is most valuable in assessing bone injury, such as fracture and/or dislocation. Bulging or herniated discs may or may not be visible on CT scan, and may or may not be related to the patient’s symptoms. CT scan is most useful in showing bone structures, and is not as good as MRI in showing spinal cord, nerve roots or discs. CT scan does not show torn ligaments or minor tears of discs.
• MR scanning (MRI) of the cervical spine is the best method of imaging the spinal cord and nerve roots, the intervertebral discs, and the ligaments. However, MRI findings can only be of value when they are interpreted together with and in the light of the entire clinical picture, and exactly match the clinical findings.
• Cervical myelography consists of neck x-rays taken after the injection of radio-opaque contrast material into the spinal fluid via a lumbar puncture, and is followed by post-myelogram CT scan of the cervical spine (myelo-CT). It may provide useful images of the interior of the spinal canal, and can reveal indentations of the spinal fluid sac caused by bulging or herniated discs or bone spurs that might be pressing on the spinal cord or nerves. MRI provides superior images of the spinal cord, nerve roots and discs.
• Electrodiagnostic studies(EMG and nerve-conduction velocities) are useful in evaluating weakness of hand and arm muscles, and can indicate whether the weakness is due to abnormality or compression of a cervical nerve root, or to some other cause.

Treatment

Treatment for disc disorders must be closely tailored to the patient, based on:

• The history and severity of their pain
• Whether or not they have had prior treatments for this problem and how effective they have been and
• Whether or not there is any evidence of neurologic damage such as weakness of an extremity or the loss of reflexes

Some of the non-surgical treatments used include

• Physical therapy
• Anti-inflammatory medication
• Braces
• Chiropractic manipulation
• Epidural steroid injections, or
• Modalities such as heat, ultrasound, electrical stimulation and massage

Surgery for patients with disc disorders of the spine is usually reserved for those who have failed exhaustive attempts at conservative treatment. An exception to this is the patient with a neurologic deficit; in this patient, it is wise to consider early surgical decompression to maximize the likelihood of neurologic recovery.