Over many years, our necks are subjected to repeated stress and minor injury. These injuries may not hurt at the time, but repeated injuries add up and can eventually result in degeneration of the cervical spine causing neck pain. Most neck pain is due to degenerative changes. The overall condition of the cervical spine usually determines how fast you recover from an injury, and whether your neck pain will become a chronic problem.
For chronic neck pain, there may not be a quick fix or a complete cure. For this reason, you should see a healthcare professional about neck pain right away to keep it from progressing. Work with your health care team to address the problem causing pain in order to help slow down the degenerative process. He or she will also try to keep your neck pain from becoming a chronic condition by teaching you how to slow down the degenerative process and prevent further injury.
To help you understand disc degeneration, compare a spinal segment to two vanilla wafers (the “vertebrae”) and a marshmallow (the “disc”). Imagine a fresh marshmallow between the two wafers. When you press the wafers close together, the marshmallow gives or “squishes out.” Suppose you leave the marshmallow out for a week and it starts to dry out. When you press it between the wafers, it is not quite as spongy. If you press hard enough, the outside of the marshmallow may even tear or split. Suppose you left the marshmallow out for a month. It would probably be so dried out it would be hard and very thin and would not have any “shock absorbing” ability.
As we age, the disc loses some of its water content and, as a result, some of its shock absorbing ability. Like the marshmallow, the first changes that occur in the disc are tears in the outer ring of the disc, called the annulus. Tears in the annulus may occur without symptoms. Therefore, you may not notice when they occur or what caused them. These tears heal by forming scar tissue. Scar tissue is weaker than normal tissue. Repeated injuries and tears cause more wear and tear to the disc. As the disc wears, it loses more of its water content. It becomes less and less “spongy,” eventually no longer able to act as a shock absorber.
As the disc continues to wear, it begins to collapse. The space between each vertebra becomes smaller. The collapse also affects the way that the facet joints in the back of the spine “line up.” Like any other joint in the body, the change in the way the bones fit together causes abnormal pressure on the articular cartilage. Articular cartilage is the smooth shiny material that covers the end of the bones in any joint. Over time, this abnormal pressure causes wear and tear arthritis (osteoarthritis) of the facet joints. Bone spurs may form around the disc and facet joints. It is thought that too much motion in a spinal segment causes the bone spurs to form. Eventually, bone spurs can form around the nerves of the spine, causing a condition called spinal stenosis.
Muscle strain of the neck is a common diagnosis given when a person has a stiff neck. In some cases, it may truly be a “muscle strain” or “pulled muscle” involving the muscles around the spine of the neck. However, in some cases the pain may be due to a muscle spasm, which can result when other areas of the neck are injured. Problems that are commonly referred to as a muscle strain may also involve injury of other soft tissues of the neck including the disc, the ligaments around the spinal segment, and the muscles. Injury to any, or all, of these structures may cause similar symptoms.
A chronic neck ache, where the pain stays mainly in the neck, may be the result of degenerative disc disease and/or arthritis of the facet joints of the cervical spine. Doctors sometimes refer to this type of pain as mechanical pain. This term is used because the pain gets worse when we use our neck, and seems to be coming from the parts of the cervical spine – the mechanical parts that allow us to move our head around and up and down.
Mechanical neck pain does not come from pinched or irritated nerves. The pain seems to come from the inflamed facet joints and from the degenerated disc. The disc and facet joints become more inflamed when we use our neck to move our head, and the muscles around the cervical spine begin to spasm. A muscle spasm is like a muscle cramp. Muscles that are cramping eventually cause pain. The spasm is your body’s way of trying to stop the movement in the cervical spine.
When a nerve root leaves the spinal cord and the cervical spine, it travels down into the arm. Along the way, each nerve supplies sensation (feeling) to a part of the skin of the shoulder and arm and sends electrical signals to certain muscles to move part of the arm or hand. When a nerve is irritated or pinched, by either a bone spur or part of the intervertebral disc, it causes the nerve to not work properly. This shows up as weakness in the muscles the nerve goes to, numbness in the skin where the nerve goes, or pain in the area where the nerve travels. This condition is called cervical radiculopathy. There are two causes of cervical radiculopathy: herniated disc, and degeneration and bone spurs.
Pinched Nerve from a Herniated Disc
Bending the neck forward and backward, and twisting left and right, puts pressure on the vertebrae and disc. The disc responds to the pressure by acting as a shock absorber. Bending the neck forward compresses the disc between the vertebrae. This increased pressure on the disc may cause the disc to bulge toward the spinal canal and the nerve roots. Remember the vanilla wafers and marshmallow? Pressing the wafers together on one side would cause the marshmallow to bulge out on the opposite side.
Injury to the disc may occur when neck motion puts too much pressure on the disc. One of the most painful injuries that can occur is a herniated disc. [link to herniated disc] In this injury, the tear in the surface of the disc is so bad that part of the inside of the disc squeezes out. A tear or rupture can occur anywhere around the disc. If it tears on the side next to the spinal canal, then when the inside squeezes out, it can press against the spinal nerves. Pressure on the nerve root from a herniated disc can cause pain, numbness, and weakness along the nerve. Chemicals released from the ruptured disc may also irritate the nerve root, leading to some of the symptoms of a herniated disc, especially pain.
Herniated discs are more common in younger and middle-aged adults. This condition may occur when too much force is put on an otherwise healthy disc: for example, in a car accident where your head snaps forward. The force on the neck may be too much for even a healthy disc to absorb, and injury is the result. A herniated disc may also occur in a disc that has been weakened by degeneration. Once weakened, less force is needed to cause the disc to tear or rupture. However, not everyone with a ruptured disc has degenerative disc disease. Likewise, not everyone with degenerative disc disease will suffer a ruptured disc.
In middle-aged and older people, degenerative disc disease can cause bone spurs to form around the nerve roots. A bone spur is abnormal growth of bone, and usually occurs inside the neural foramen, the opening in the cervical spine between two vertebrae where the nerve root leaves the spine to travel into the arm. If these bone spurs get large enough, they may begin to rub on the nerve root and irritate it. This causes the same symptoms as a herniated disc: pain to run down the arm, numbness to occur in the areas the nerve serves, and weakness in the muscles that the nerve supplies.
Perhaps the most serious of the problems caused by degeneration of the spinal segment in the cervical spine is the condition called spinal stenosis. Spinal stenosis is caused by bone spurs in the late stages of spinal degeneration. As the bone spurs form, the size of the spinal canal becomes smaller. The bone spurs begin to press on the spinal cord or the nerve roots. This pressure can cause numbness, tingling, or pain in the arms, hands, and legs.
Spinal stenosis is sometimes called cervical myelopathy, and is different from the simpler problem where only one nerve root is being pinched by a herniated disc or a bone spur. When there is narrowing of the spinal canal (the bony tube where the spinal cord runs), the whole spinal cord may be affected. This is different than when the bone spurs only narrow one of the neural foramen. The symptoms are also much different. A pinched nerve from either a herniated disc or a bone spur rarely affects the legs. Cervical myelopathy can affect both the arms and the legs.
Source: DePuy Spine, Inc.