Degenerative Disc Disease

Increasingly, degenerative disc disease is viewed differently from the normal process of degeneration associated with aging.

Neck and back pain is strongly associated with degenerative disc disease. The diseased state of disc degeneration is also associated with sciatica and disc herniation. The process of degeneration alters disc height and the mechanics of the rest of the spine and may cause problems with other supporting structures such as muscles and ligaments. The long term consequences are spinal stenosis, which is a major cause of pain and disability. The incidence of degenerative disc disease is rising in the population and is the reason for over 90% of all spinal surgeries.

Studies have found that degenerative changes are noted in people without pain. This would not represent a diseased state and is an incidental finding on many x-rays and MRI's. It may be that the process has not yet progressed to a disease state. Indeed, a 50,000 mile tire would show signs of wear and tear at 40,000 miles, however, at 20,000 miles, signs of the same wear and tear would not be considered "normal".

The disc sits between two spinal bones and consists of a nucleus (yellow) and annulus (blue) in the diagram above. A healthy disc acts like a water bed. There is a high water content in the nucleus and inner portion of the annulus which allows this portion of the disc to act as a fluid. The outermost part of the annulus acts as a skin or the covering of a water bed to restrain the inner portions. This creates hydrostatic pressure to reduce loading forces.

The main function of the disc is mechanical as it transmits load from body weight and muscle activity and provide flexibility, allowing bending (forward, backward and sideways) and rotation.

With increasing age, the water content of the disc decreases, forcing the disc to act more like a solid and resist mechanical loading in a haphazard manner as the hydrostatic pressure is reduced or lost completely. Injuries that affect the annulus or end plate can decompress the nucleus, and the healing process is taken over by severe degenerative changes.

The disc has little blood supply and cannot readily heal from injuries. Nutrition is through a process called diffusion where nutrients travel through the end plate (gray). The end plate is pourous and permeable to allow the transport of nutrients. This permeability and the ability to transport nutrients normally decreases during growth and aging, however, it increases when there is disease due to disc degeneration and following end plate damage. This is one difference between normal aging and degenerative disease process. Additionally, nerve fibers normally only penetrate the outer area of the annulus, however, in degenerative disc disease, the nerves are noted to progress towards the nucleus and is associated with pain and inflammation.

Load placed on a degenerated disc results in rapid loss of disc height and the joints behind the disc (facet joints) must change to bear the load which leads to arthritic changes. These changes result in what is called hypertrophy as there is a buid up around the joints which may result in a facet syndrome and can narrow the spinal canal where the spinal cord runs through as shown in the diagram looking from above - down. The loss of height associated with degenerative disc disease can also reduce the tension on ligaments surrounding the disc causing loss of elasticity and bulging into the spinal canal, further narrowing the space for the spinal cord and leading to stenosis.

As the disc ages it becomes stiffer and weaker. Although degenerative changes can cause the annulus to collapse in some old discs, disc height does not show a major decrease with age. Severe disc degeneration cause a significant decrease in nucleus pressure and collapse of annulus height causing the disc to act like a flat tire. The disc height is important as it keeps the bones from placing pressure on sensitive nerves and loss of disc height can result in 50% of compression forces being transmitted to the joints behind the disc causing osteoarthritis in these joints as mentioned and diagramed previous. The loss of disc height is also associated with similar type of osteoarthritic changes around the bones called osteophytes which attempt to stabilize the area.

Painful discs always show structural disruption and display irregular stress concentrations as the disc become sensitive to mechanical loading. The features most closely associated with pain include disc prolapse or herniation, loss of disc height, radial fissures which are tears in the annulus that can leak fluid outside the disc lowering the pain threshold in surrounding tissues and internal disc disruption. Of these, loss of disc height is most closely related to pain history. Disc bulging and damage to the end plate which decompresses the nucleus are also associated with pain although less than loss of disc height. Disc signal intensity noted on MRI has little relationship to pain.

The highest risk factor for degenerative disc disease is genetic inheritance which accounts for 74% in the lower back and 73% in the neck. The primary factors associated with genetic influence related to degenerative disc disease is disc height and disc bulging. Stronger genetic effects are associated with earlier onset of degenerative disc disease.

Degenerative disc disease causes instability as the disc and surrounding tissues degenerate resulting in structural damage. This instability persists until the latter stages where fusion takes place. The instability causes increased and abnormal motion within the spine, however, movements become more painful, thus restricting overall motion. In the neck, instability may be noted as intolerance to prolonged static postures, fatigue and inability to hold the head up, better with external support, including hands or a collar, frequent need for self-manipulation (cracking your neck), a feeling of instability, shaking or lack of control, frequent episodes of acute attacks and sharp pain, possibly with sudden movements. In the lower back, the instability may present as diffuse, dull ache or a deep burning or sharp pain in the back, a feeling of weakness or an unstable back, pain may radiate to the hips or legs, and sitting intolerance - painful or discomfort when sitting.

Where significant disc height is lost, care should be taken during lifting and when exercising especially at the end range of motions like bending or twisting. Pain may often occur several hours after the actual damage to a disc that already has structural damage from degenerative disc disease. There may be pain free or minor discomfort during these activities, however, it may result in the inability to get out of bed the next morning.

It is structural failure that predominates as an indication of degenerative disc disease. Structural failure impairing disc function does not occur as an inevitable consequence of age and is more closely related to pain. Structural failure is permanent because adult discs are not capable of repairing major defects. Because damage to one part of the disc increases the stress on other areas, the damage is likely to spread. Similar to a collapsed house, a physically disrupted disc can no longer perform it's function even though the basic parts remain.

In the above diagram you can see the effects of degeneration. A herniated disc can start the process; loss of disc pressure and height place excessive loads on the joints located towards the back. Increased load on the facet joints behind the spinal cord may cause hypertrophy or outgrowths of bone leading to a facet syndrome and/or joints in the back and side of the disc and in front of the spinal cord, which are called uncovertebral joints, may undergo the same degenerative process. Both of these, including herniations of the disc can lead to a piched nerve or radiculopathy.

Excessive mechanical loading or damage to the disc causes degeneration by disrupting its structure which causes a progressive and irriversible process resulting in further disruption. The combination of genetic inheritance and injury through too much or abnormal mechanical loading (or not enough) can weaken some discs to the point that physical disruption may follow a minor incident, such as a herniation following a cough or sneeze. Similarly, a tire made of inferior materials may rupture after hitting a small pothole in the road. As the foundation of a house weakens from deterioration, winds from a storm may cause failure or collapse. A recent article in Spine: 1 April 2009 - Volume 34 - Issue 7 - pp 706-712 indicates; "Patients who developed clinical symptoms during 10 years, including neck pain, stiff shoulder, and numbness in the upper extremities, demonstrated significantly more frequent progression of disc degeneration on MRI than those without the clinical symptoms."

A study in the Journal of Spinal Disorders and Techniques. 2009 May;22(3):214-8, indicates the normal response to loading of the disc is lost with degenerative disc disease, further supporting that structural damage leads to loss of function. The ability for a degenerated disc to resist normal loads and protect the sensitive structures of the spine is lost.

According to a recent article in Spine. 2009 Mar 1;34(5):E178-82, "The painful degenerative disc is significantly different from the asymptomatic degenerative disc with regard to histopathological findings". The study indicated a strong expression of connective tissue growth factor expression in the painful disc related to disc fibrosis and degeneration. Painful discs showed chronic inflammatory reaction with blood vessel infiltration in varying degrees. The anulus fibrosus had lost its normal architecture, and instead, disorganization, disruption, and crossed fusion were observed. The study further noted, "In other tissues, injury healing proceeds from the inside to the outside. On the contrary, healing in disc tissues proceeds from the outside to inside, since only the outer anulus fibrosus and longitudinal ligaments of discs possess vascular distribution. When the anulus fibrosus is lacerated or injured, vascular tissues can only gradually develop from the outer to the inner anulus fibrosus".

There is a certain type of degeneration which involves changes visible on MRI called Modic Type 1 changes, which have responded to antibiotics for back pain relief.

The degenerative process can also produce sympathetic symptoms related to the neck which may include; headaches, vertigo, disequilibrium, tinnitus, scotomata, decreased vision, dysphagia, dysphonia, cough and anxiety. This is a condition known as posterior cervical sympathetic syndrome or Barre-Lieou Syndrome. It is a condition that is characterized by a host of cranial symptoms, such as headaches, abnormal functions of the eyes and the ears, and psychological and mental disorders.

There has been a common belief among many health care providers that degenerative disc disease is just a part of normal aging and not relevant to any pain or disability that a patient is experiencing. This belief has led many to tell patients without any clear, traditional form of pathology to "learn to live with it". This policy of nonintervention has not minimized the disability of neck or back pain and, in fact, perpetuates the very problems they desire to avoid. With a history of treatment drugs which have proven fatal and the high incidence of spinal surgeries performed for degenerative disc disease, it would seem unreasonable to suggest that chiropractic care, which has addressed this condition for many years, is not appropriate. Although new biological and genetic research is promising in this area, it is still many years in the future as of this writing. Mobilization, manipulation, massage, exercise, traction and posture modification are all reasonable therapies. Recently, TENS Unit Therapy has been shown to provide relief for degenerative disc disease. The major concern is for the neck is progression with myelopathy.

You must remember that attitude is important. I remember while in Kung-Fu class many years ago, explaining to another student (a Lawyer) that the disc in my lower back was 75% gone - at that time, more now. He asked, how are you still walking? My response was, I am trying to control the way that it degenerates so that when it fuses there will be minimal damage to the nerves. Well, I dont know how reasonable that is, an unrelated surgery ended my studies a year prior to my Sifu (teacher) retiring, however it shows an attitude that is important. I believe that my condition may eventually require sugery, and that is just half of it - I have the same condition going on in my neck, but I am not going to feel helpless.

One must use reasonable means to break the chronic pain cycle as much as possible. You should not be afraid to perform reasonable activities and be comfortable within your limitations. Keep in mind that no two cases are the same and small things you can do can make a difference - you are not doomed to a life of severe, debilitating pain.

Some people will tell you your pain is psychological or due to depression. It is true that chronic pain is associated with depression, however, it seems reasonable to assume that a condition which does not improve and causes some degree of pain and/or disability would be a cause for depression. However, this depression is not helpful and needs to be dealt with in coping with neck pain. Further disturbing is the effects chronic pain present to you or a loved one's life. In General Hospital Psychiatry. 2008 Nov-Dec;30(6):521-7, a study concluded; "These findings highlight the importance of pain as a potentially independent risk factor for suicide, particularly among those with head pain or multiple forms of co-occurring pain. Individuals suffering from chronic pain may be particularly appropriate for suicide screening and intervention efforts."

There are books, speakers and professional help is certainly warranted if other methods fail or concern is great enough. Support of family and friends can help, however, you should not feel sorry for yourself or have other people feel sorry for you. One particular source that has greatly influenced me is from a wonderful author/speaker Andy Andrews who is a New York Times bestselling author and inspirational speaker, best known for his book The Traveler's Gift.