Herniated Disc

Overview

The term herniated disc describes the condition when the intervertebral disc is injured, and its contents are bulging or protruding into the spinal canal. The terms slipped disc, ruptured disc, bulging disc, disc protrusion, and extruded disc, among others, all mean herniated nucleus pulposus (herniated disc), which is the proper medical term. Although disc injuries and degenerative changes (wear and tear changes as part of the aging process) occur almost equally in both the cervical and lumbar spine, cervical injuries are much less likely to require surgical treatment. However, patients with a severe cervical herniated nucleus pulposus are at risk for injury to the spinal cord, and require careful management.

Causes

The most common cause of a cervical herniated nucleus pulposus is gradual degeneration of the disc, attenuation (weakening) of the posterior annulus fibrosis, and subsequent protrusion of the nucleus pulposus into the spinal canal causing compression of the nerve root. Sometimes the disc injury occurs suddenly because of an accident or trauma. Most often, however, a cervical disc herniation occurs over time, and patients finally take notice when the neck pain symptoms and/or radiculopathy (radiating arm pain, numbness, and/or weakness) become significant. Although there is an extensive list of risk factors for the development of neck pain (and disc problems), a disc injury can occur in almost any person. A cervical disc injury occurs most frequently in people over the age of 40 years old, and affects men and women equally. The specific cause of a cervical herniated disc injury can often be identified if someone develops severe neck pain and radiculopathy immediately after an accident or injury. However, most people presenting with a disc injury do not recall a specific event that provoked their pain, and the actual cause is indeterminate. People who perform heavy labor (and utilize proper lifting techniques) or participate in sports have nearly the same rate of injury as people who do not.

Symptoms

Patients may present with isolated neck pain or arm pain, but it is usually both when the disc injury is significant. The radiculopathy (arm pain, numbness, and/or weakness) is typically present in one arm only, but occasionally in both. The arm symptoms may manifest as a shooting electricity pain through the shoulder, arm, and into the hand and fingers. The radicular pain may also have a component of numbness, tingling (parasthesia), and/or weakness. Patients may have difficulty turning their head and bending their neck, as it may provoke the radicular pain symptoms. Occasionally, patients will only have significant arm weakness and numbness, but not have any neck or arm pain. In rare instances, a very large herniated disc can cause paraplegia and/or bowel/bladder incontinence, and is considered to be a surgical emergency.

Physical Findings

The physical findings for patients with a cervical herniated disc often include neck tenderness and spasm, in addition to decreased cervical range-of motion. Patients are generally in greater pain if the neck is flexed down and toward the side of the disc herniation. If the spinal nerve compression is severe, it may cause significant numbness (loss of sensation) in the arm and hand and some of the arm and/or hand muscles to be weak. Patients with longstanding nerve compression and muscle weakness may demonstrate atrophy (decreased size) of the affected muscle(s), and this may be quite noticeable when comparing it with the opposite arm. Deep tendon reflexes may be diminished or absent for the particular spinal nerve that is affected.

Imaging Studies

Plain x-rays of the spine will not show a herniated disc because an x-ray only shows bone structures, not the cartilage disc or spinal nerves. A magnetic resonance imaging test (MRI) of the cervical spine is necessary to clearly define the disc injury, and is noninvasive (no needles or dye injection). Before MRI was invented, patients were required to have a CT, myelogram, or CT-myelogram in order to confirm the diagnosis of herniated nucleus pulposus. MRI is now much easier to perform and generally provides better visualization of the disc injury. However, some patients are not able to have an MRI, such as those patients with a cardiac pacemaker, and must have one of the other described imaging tests.

Laboratory Tests

There are no laboratory tests used to diagnose a cervical herniated disc. Occasionally, specific tests are ordered to rule out infection or other causes or neck pain and/or radiculopathy.

Special Tests

Electromyography and nerve conduction velocity (EMG/NCV) tests are useful to determine which nerve is affected, and how severely it is damaged or irritated. The test will often clarify where a nerve is actually being compressed - whether it is in the neck, shoulder, elbow, or wrist. For instance, it can differentiate whether hand and finger numbness is caused by a disc injury in the neck or carpal tunnel syndrome (compression of the median nerve in the wrist).

Diagnosis

The diagnosis of a cervical herniated nucleus pulposus is fairly straight-forward in most patients. It can be complicated when the symptoms or physical findings are atypical. Patients with isolated neck pain may be erroneously diagnosed with a simple neck strain or sprain. Some patients will complain of isolated shoulder pain, arm pain, or hand numbness, and be evaluated and treated for an extremity problem rather than a neck problem. It is important for the clinician to conduct a thorough history and clinical examination prior to formulating a diagnosis so as not to misdiagnosis this condition. Imaging studies (and occasionally laboratory tests) must be used to clarify the diagnosis.

Treatment Options

The treatment for a cervical herniated disc almost always begins with a trial of conservative treatment, which is frequently effective. The primary reason to consider early or immediate operative treatment is when a patient demonstrates profound spinal cord compression from a large herniated disc and has clinical signs of myelopathy and/or spinal cord injury. The natural history of a cervical herniated disc is quite favorable, meaning that the majority of patients improve and do not require surgery. In 1996, Saal published a research study that demonstrated nearly 90% of patients with a cervical disc herniation improved remarkably with nonoperative treatment. Conservative treatments available include rest, ice, heat, chiropractic or physical therapy, medications, neck brace or soft collar, cervical traction, and acupuncture. The most commonly prescribed medications are oral anti-inflammatory medications and pain medications. Muscle relaxant medications should be used for severe pain and muscle spasms, and only for short duration in elderly patients. Complications secondary to medications are more common in the elderly, and all medications should be closely monitored by the prescribing physician. Physical therapy and modalities may also be utilized, primarily to improve a patient's strength, endurance, and level of function. Manipulation and chiropractic adjustments should be utilized with caution, and may be contraindicated in patients with large disc injuries. Epidural steroid injections and nerve blocks may provide short-term improvement of pain symptoms. Spinal injections are considered immediately for patients with severe, incapacitating pain or patients who have reached a plateau with conservative treatments yet continue to have moderate or severe pain. Surgical intervention is considered when a patient with a cervical herniated nucleus pulposus continues to have pain, weakness, and/or numbness, and has failed conservative modalities. The goal of surgery is to remove the compression from the spinal cord and/or spinal nerves and to improve a patient's pain and level of function. The preferred surgical treatment is an anterior (front of the neck) cervical discectomy (removal of the disc) and fusion (mending the spine bones together). Generally, a cervical spinal fusion will always be required and recommended in addition to the decompression component, because almost all of the disc will be removed during this procedure. A small bone graft is usually placed between the two spine bones where the disc was removed, so as to restore the normal disc space height and promote fusion. Spinal instrumentation (small metal plate with screws) may also be utilized to impart immediate stability and increase the fusion (bone healing and mending together) rate. In some instances, patients may be candidates for a microscopic posterior (back of the neck) cervical foraminotomy procedure, which can be done using a minimally invasive technique and does not require the spine bones to be fused. This is typically done if the disc injury is small and the nerve compression is primarily due to foraminal stenosis. Regardless of the surgical technique, the outcome is generally excellent with a short recovery period. Patients often have rapid relief of symptoms following surgery and return to work and normal activities within one to three weeks.

Selected Bibliography

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