Diseases And Conditions
Cervical disc herniation
The human spine is composed of 7 cervical, or neck, vertebrae, 12 thoracic, or upper back vertebrae and 5 lumbar, or low back vertebrae. The vertebrae are the bones that make up the spine. Between the bones are the intervertebral discs, or just discs, for short. The discs have an important function in stabilizing the spine. The discs allow rotation, flexion and extension of the spine without undue stress. The discs also absorb much of the axial load to the spine. Axial load refers to the compression felt by the spine during everyday activities like sitting, walking or standing. Certain activities, like jumping, exercising or carrying heavy objects increase the compression felt by the spine.
Discs are named based on whether they are cervical (C), thoracic (T) or lumbar (L) and the two vertebral levels that they lie between. For example, the disc between the 4th cervical vertebra and the 5th cervical vertebra is called C4/5.
The disc is composed of two layers, an outer fibrous layer (annulus fibrosis) and an inner gelatinous layer (nucleus pulposus). An injury to the disc will likely tear the outer fibrous layer, called an annular tear, causing pain across the region of the disc. If the tear to the outer fibrous layer is large enough, the inner gelatinous layer may pass through the tear. This is a condition called disc herniation. When the herniated disc pushes or irritates the passing nerves of the spine, there is nerve pain. There are various degrees of herniation. In the mildest form, a partial tear of the outer layer causes the disc to bulge. If the bulge involves less than half of the disc circumference it’s called a broad based herniation. If the herniation involves less than 25% of the disc circumference, it’s called a focal herniation. Focal herniations are called protrusions, if they have a broad base of attachment to the disc, or extrusions if the size of displaced disc material is larger than the attachment to the disc. Sometimes the herniated disc will completely detach from the parent disc. This is called sequestration.
Cervical (or neck) intervertebral disc herniation is most common at the C4/5 and C5/6 discs. When there is injury or tearing of the disc, the pain is axial, or felt along the neck. Sometimes this pain can refer to other parts of the body, usually the low neck, shoulder, or between the shoulders. When an upper cervical disc is injured, the referred pain can cause pain in the back of the head, or headache. This is called cervicogenic headache.
When a disc herniation occurs in the neck, the herniated disc material may extend to the side, compressing a nerve exiting the neck and traveling to the arm. If mild, the nerve compression may only cause a burning pain. This nerve pain is called radiculopathy. If worse, the herniated disc may cause arm or hand weakness, depending on the function of the compressed nerve. Occasionally the disc herniation may extend directly posteriorly. This may actually push against the spinal cord. When herniated disc compresses and hurts the spinal cord it’s called myelopathy. The symptoms of myelopathy reflect the level in the spine that the compression takes place. When the spinal cord compression is in the neck, one can develop weakness in the arms and legs, lose sensation in the body and develop bowel or bladder incontinence.
The diagnosis of cervical or neck disc herniation is usually made by MRI. In cases where an MRI cannot be performed, usually in patients with a pacemaker, surgical implants or severe claustrophobia, a procedure called a myelogram can be performed. This involves injecting dye into the spine via a spinal tap. In cases where there has been previous spine surgery with screws and plates MRI may be difficult to interpret. Myelogram may be helpful in these cases as well.
