Clinical Aspects

As in the lumbar and thoracic spine, herniation of the contents of an intervertebral disc may occur when a tear occurs in the annulus fibrosus. However, whereas in the lumbar spinal canal only nerve roots are present, in the cervical canal the spinal cord may be compressed. The symptoms and signs produced are the result of nerve root compression, spinal cord compression, or both.

The most common complaint is neck pain which limits motion and is aggravated by neck extension. Pain also may radiate into one arm, in a pattern characteristic of the particular root involved (see below). Patients often hold the arm elevated and behind the head, presumably because this maneuver reduces the tension on the nerve root and thus lessens the pain. In most cases, the onset of pain is upon awakening, without identifiable trauma or other precipitating event.

Table 1. The most common clinical manifestations of cervical disc herniation.

Table 1 shows the usual cervical root syndromes (radiculopathy). Note that the C6-7 disc is the most frequently herniated, about 2/3 of cervical herniations. The C5-6 disc is involved about 20% of the time, the C7-T1 about 10%, and the C4-5 about 2%.

If the disc herniation compresses the spinal cord, certain deficits may result (myelopathy). Weakness in the hands and arms may be more generalized or bilateral, rather than confined to a root distribution. In addition, there may be leg weakness, usually manifested initially by a feeling of heaviness in the legs and noticable difficulty in walking usual distances or up stairs. Examination may show hyperactive reflexes, pathological reflexes, and a spastic gait. Finally, sphincter and sexual function may be compromised, usually later in the progression of myelopathy. Cervical spondylotic myelopathy is discussed in the following section.

Lhermitte's sign refers to a sudden electrical sensation down the neck and back triggered by neck flexion. This was originally described in a patient with multiple sclerosis and dorsal column dysfunction. The conditions which can produce a Lhermitt's sign are:

1. multiple sclerosis
2. cervical spondylosis
3. cervical disc herniation
4. cervical spinal cord tumor
5. Chiari I malformation
6. radiation myelopathy
7. subacute combined degeneration (caused by vitamin B12 deficiency)

Other signs may help in aiding the physical diagnosis. These are very suggestive of cervical disc herniation when present, but are frequently absent in the presence of the disease (that is, they are specific but not sensitive). Spurling's sign refers to the reproduction or exacerbation of pain upon pushing down on the head and bending it toward the involved side. The reduction of pain when axial traction is applied to the head is also suggestive of a disc. Finally, in the shoulder abduction test raising the affected arm above the head reduces the pain.

Radiographic Studies

The radiographic evaluation of a suspected spine disorder begins with plain X-rays. A herniated disc, being composed of soft tissue rather than bone, will not be seen on X-ray, however other associated changes may be seen, such as the characteristic bony ridges of cervical spondylosis. In addition, the alignment can be accurately assessed.

MRI has in most cases become the study of choice in cervical disc herniation. Its superior resolution of soft tissues gives good definition of disc material, cord compression, and root compression. When bony detail is required, a myelogram/CT should be obtained. This is more invasive than MRI and may produce effects such as headache, but in some cases may be essential in defining the anatomy.

Treatment

With bedrest and nonsteroidal medications, many patients with acute cervical radiculopathy from disc herniation will experience improvement or resolution of pain. Surgery is indicated when symptoms worsen or fail to improve. Surgery should also be considered when there is significant compression of the spinal cord with signs of cord dysfunction.

Surgical treatment is usually anterior cervical decompression and fusion (ACDF). An incision is made in the neck, usually to the right of the midline. A plane between the muscles of the neck is taken to the cervical spine. The disc material is removed, and the level is usually fused with bone from the patient's hip or banked bone (allograft). Postoperatively, patients may be up walking the same evening or the next morning. Discomfort in swallowing, from retracting the esophagus, occurs commonly and is usually mild and transient. Patients are usually discharged home in 3 to 5 days.

Serious neurologic complications are very rare with modern techniques, probably around 2%. Improvement in symptoms of neck and arm pain is seen in about 90%, while improvement in leg weakness occurs in about 80%.

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