Most commonly, degenerative disorders of the spine are responsible. Degenerative "disease" is the changes associated with spinal wear and tear or age. Though among the most frequent causes of neck pain, it is the sometimes the most difficult to treat.
The focus of this article is a discussion of degenerative disorders of the cervical spine. These affect adult patients of any age, with a tendency for particular disorders to affect certain age groups. Cervical disk herniations are more characteristic in the young (less than 40 years old), while cervical spondylosis and stenosis are typically found in older patients.
As a patient, the first question is obvious. "What is degenerative disease of the spine?"
In all honesty, the academic leaders of the spine world are currently pondering this same question. What we mean is that spine doctors can recognize and treat degenerative disorders of the spine but are often unclear how the disorder actually arises except to attribute it to age.
To date, most theories about how the spine degenerates remain just that—theories. Although these theories are often well thought out and reasonable, it is exceedingly difficult to prove them. Regardless, it is worthwhile trying to understand them, as they are the best explanation we have to explain degenerative disease of the spine at this time.
Degenerative disease of the spine refers to a breakdown of the normal architecture of the various components of the cervical spine.
Normally, the neck is very flexible. As you may demonstrate on yourself, the neck allows the head to rotate from side to side nearly 180°, to flex forward to touch your chin to your chest, and extend backwards to almost touch the back of the head to your upper back, as well as bend your head toward your shoulder (and all ranges in between these basic motions). These motions are afforded by the various joints of the cervical spine.
There are seven cervical bones in the spine. Known as vertebrae, they can be likened to the cars of a passenger train. The cars of the train, by themselves, are stiff with no ability to bend. Each car (ie, vertebra) is joined to its neighbor by a joint. The joint allows motion between the cars.
As in the spine, joining a number of cars together can allow overall motion. The more joints and vertebrae (the plural of vertebra), the more motion is allowed.
In contrast to the joints of the car, the cervical vertebrae are connected by three joints. This gives the spine more stability, while still allowing motion. The extremes of motion must be limited because of the fragile "freight" that the vertebrae hold—the spinal cord. Like the people in the cars of the train, the spinal cord is located in the center of the vertebrae.
At this point, clarification of terms is important. "Spine" refers to the bony parts. These are the vertebrae that were described above. "Spinal cord" is the nerve elements that travel within the spine from the brain down to the rest of the body. The spinal cord transmits signals (bioelectrical and biochemical) that control all the functions (muscles and sensation) below that level. The function of the spine is to protect the spinal cord from injury during motion and activity.
Joints are comprised of two opposing surfaces of bone. Some joints are covered with smooth, glistening cartilage. The slippery properties of cartilage make the two surfaces move easily in relation to each other. The facet joints of the cervical spine have these properties.
In contrast, the main joint between two cervical vertebrae is made up by a large spongy mass, the intervertebral disc. This disc sits between the two broad flat surfaces of the vertebral bodies. The disc is made up of specialized materials that act as a soft "glue" between the bones, while still allowing them to move. The disc is extremely important to spinal stability. However, it is a frequent site of degeneration or breakdown.
In another way, the disc can be considered as a pillow in between two bones. The pillows can softly resist the downward forces placed on the vertebrae from the weight and movement of the head. A good pillow is thick and soft and functions best. It allows some movement between the vertebrae. Because the pillow is well-fixed to both bones, it resists the tendency of the bones to become misaligned. With time and use, the pillow can become flattened.
In this state the disc no longer provides adequate cushioning between the vertebrae. The bones then come closer and closer together. Because the disc is no longer sustaining the forces that it usually does, the other joints of the spine are forced to take on these extra loads. The two smaller sliding joints (facet joints, fah-set) have greater demands placed on them.
Since they were designed to sustain only a small portion of the forces of the spine, the previously glistening, healthy cartilage starts to breakdown. As the cartilage degenerates, the underlying bone becomes exposed and an inflammatory reaction begins. This causes irritation of the joint, which can lead to pain. This sets up a vicious cycle of events. The more the facet joints become degenerated, the less they are able to tolerate the increased demands. Thus, greater demands will then be placed on the intervertebral disc, causing it to further degenerate (or breakdown) as well. The changes in the intervertebral disc and facet joints are not reversible at this time.
Cervical Spinal Stenosis
An important feature of disc degeneration is the reaction that the bone undergoes. Because the normal relationships of the bones are lost, there is a condition of instability. This refers to one vertebra moving in an abnormal manner in relation to the next vertebra.
To attempt to stabilize this excess motion, bone grows outward. These outward growths are called osteophytes. Osteophytes can be found near the disc spaces and around the facet joints. Osteophytes take up space. If they grow in areas where nerves or the spinal cord are nearby, they can impinge or compress these structures. This can cause pain, numbness, tingling, or weakness to varying degrees. This is known as cervical stenosis.
Cervical Disc Herniation
Disc degeneration can sometimes follow a slightly different course. In the process of sustaining increased mechanical loads, the outer aspect of the disc, known as the anulus fibrosus, can become stressed. With time, small tears can form in the anulus.
This outer ring normally keeps the soft, gel-like center of the disc contained. The gel center, known as the nucleus, can be ejected from the disc through an anular tear. This is called a disc herniation. If the disc herniates in the direction of the spinal cord or nerve root, it can cause neurologic compromise. Disc herniations in the cervical spine can be serious. If significant enough, they can cause paralysis of both the upper and lower extremities, though this is extremely rare.
In most cases, a patient complains of neck pain associated with radiating pain to one arm. This is caused by compression of a nerve root, rather than the spinal cord itself. With time, some herniated discs resolve or shrink by themselves. Sometimes, disc herniations can persist, causing prolonged symptoms and neurologic problems, which may lead to surgical considerations.
This rather elaborate sounding word is really nothing more than a description of what happens to the vast majority of our cervical spines as we get older. The term spondylosis refers to the bony overgrowths associated with aging of the spine.
Though it is hypothesized, as discussed, that osteophytes form because of micro-instability and disc degeneration, this is not certain. It is known that a high percentage of patients without any neck pain or other symptoms have spondylosis of the spine.
In some people, however, spondylosis may be associated with neck pain. Spondylosis is likely the end result of disc degeneration that has been present for a very long time.
What else can be causing my neck pain?
Diagnosing degenerative disorders of the spine starts with a good history and physical examination. Typically, patients have neck pain. This is a common complaint that bring them in to the doctor's office. Unfortunately, neck pain is a common complaint in the vast majority of people who have nothing more than a stiff neck. It is important to differentiate neck pain related to degenerative spinal disorders from other more serious ailments.
Muscle strains can cause mild pain. This can vary from the occasional "stiff neck" (from keeping your neck in one position too long, such as during sleep) to neck soreness associated with a low-speed motor vehicle collision (whiplash)
The pain and tenderness is not deep and is usually limited to the surrounding muscles around the neck. Often, one side is more symptomatic than the other. Muscle strains are differentiated from degenerative disorders by their self-limited course. Muscle strains usually resolve, or at least dramatically improve, within a couple of days to weeks. Pain that continues for more than 3 weeks without improving may not be a muscle strain and other diagnoses should be considered.
Patients with rheumatoid arthritis can have neck pain. It is important to recognize this. Any patient with rheumatoid arthritis should have neck x-rays taken. These patients can develop instability in the upper cervical spine that can endanger the spinal cord. This is easily recognized on plain x-rays.
Neck pain can be a presenting symptom of meningitis, an infection of the brain and spinal cord linings. Meningitis can have many causes and may be contagious.
Although neck pain is probably the most common symptom, it is important to recognize the others signs. Patients often are extremely sensitive to light, irritable, have high fevers, and actually tolerate very little movement of the neck. Though it is rare, this diagnosis is very serious and should prompt an individual to seek urgent medical care.
Other types of infection can also occur in the neck. Infection can occur in the bone or intervertebral disc. This is more common in older patients who may have a weak immune system. Again, as with meningitis a history of fever could be important, but there is not hypersensitivity to bright light.
Tumors can also cause neck pain. One way to clinically differentiate tumor from degenerative disorders is the presence of generalized, or constitutional, symptoms. Unintentional weight loss, feeling of extreme lethargy, persistent low grade fevers, and night sweats are typical constitutional symptoms. A history of cancer elsewhere is also a clue, as the majority of neck tumors are metastases (or spread) from a cancer in the lung, prostate, kidney or breast.
Only a doctor can tell you for sure what is causing your neck pain. He or she will pinpoint the spinal condition leading to your pain, so if you have persistant pain, make an appointment to see your doctor.