Degenerative Disc Disease – Normal Aging Or Disease Condition?
Increasingly, degenerative disc disease is viewed differently from the normal process of degeneration associated with aging.
Details Of A Normal Disc
Is Degenerative Disc Disease Painful?
Neck and back pain is strongly associated with degenerative disc disease. The diseased state of disc degeneration is also associated with sciatica and neck disc herniation and back 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 (narrowing of openings that can place pressure on nerves and the spinal cord), 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 Process Of Degenerative Disc Disease
The disc sits between two spinal bones and consists of a soft nucleus (yellow) and firm 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. Spinal discs have been described as shock absorbers, however, they are too stiff to perform this function and act to allow proper motion between spinal bones during movement.
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 porous 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. Back pain from the disc is usually started by physical disruption, and made worse or very painful by inflammation and disc infection.
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 build 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 well as painful bending.
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.
Risk Factors For Degenerative Disc Disease
One of the highest risk factors for degenerative disc disease is genetic inheritance, accounting for in some estimates, over 70% in the lower back as well as 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.
A 2014 study in the Journal of Occupational Rehabilitation noted that disc degeneration of the lumbar spine starts early in life and contributes to back pain development. The authors indicate significant risk factors for disc degeneration as: family history of degeneration, high level of sitting, back injury, bending/twisting, smoking, lifting,, high physical workload, whole body vibration, and susceptibility genes (allele 5A of MMP-3 and allele T of VDR). They additionally noted that the genetic risk factors were also associated with the severity of disc degeneration.
Characteristics Of Degenerative Disc Disease
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 through a reactive process which allows blood vessels and nerves to grow into the disc, which is very painful.
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. If there are modic changes, activity can be painful and treatment resistant. Exercising, with modic degenerative changes, despite being commonly prescribed for back pain, can be harmful.
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.
Degeneration originates from the latin word degeneratus, meaning no longer of its kind. The authors of a study in a 2008 European Spine Journal study indicated a healthy disc is intact structurally and has normal function and height, regardless of age. An ageing disc is intact structurally intact, has reduced function related to stiffening from the ageing process, but has normal height relative to age. A degenerated disc has structural failure and abnormal function, regardless of age. A disc that is completely degenerated has no signs of being normal. They further relate structural failure to the endplates.
In a 2010 study in the journal Spine, the authors of this study indicate narrowing of disc space was more linked to back pain than osteophytes, and that narrowing of the disc space at 2 or more disc levels is more painful than narrowing at just 1 level.
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 pinched nerve or spinal radiculopathy.
Excessive mechanical loading or damage to the disc causes degeneration by disrupting its structure which causes a progressive and irreversible 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. An 2009 study in the journal Spine 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 2009 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 2009 study in the Jounal Spine, “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 annulus 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 annulus fibrosus and longitudinal ligaments of discs possess vascular distribution. When the annulus fibrosus is lacerated or injured, vascular tissues can only gradually develop from the outer to the inner annulus fibrosus”.
Problems With Degenerative Disc Disease
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, as well as other therapies. This type of degeneration produces a deep type of pain that, may change in intensity, but is always there. It is usually most painful in the morning, better in mid afternoon, worse in late afternoon and worse at night. Pain on bending forward is problematic and it is not responsive to normal types of treatment, such as exercise. This may be related to an infection in the disc.
A study in the 2013 American Journal of Orthopedics indicates that disc degeneration of the lower back is found prior to hip joint degeneration and may actually help to cause osteoarthritis of the hip. In a related study in a 2013 edition of the European Spine Journal, a relationship was noted between loss of disc space at the L1/L2 and L2/L3 levels and hip pain.
As the spine undergoes the degenerative process in the discs and joints, the bones become remodeled and there is a weakening of the muscles, allowing a loss of the normal supportive curves. In the picture, you can see how degenerative changes cause an imbalance of the spine, resulting in a forward placement of gravity towards the hips (red circles). This could help explain the progression to hip arthritis with disc degeneration, as the entire body tries to compensate for spinal stiffens and muscle weakness. These mechanisms are outlined in detail in a 2013 issue of the European Spine Journal.
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. These are some of the symptoms usually not thought to be associated with neck conditions.
Disc degeneration weakens spinal structures; mainly the discs, facet joints, vertebral endplates and even the bone itself. A 2015 study in the Journal of the Mechanical Behavior of Biomedical Materials outlined a study where the authors found that vertebral bones with osteoporosis are at increased risk for damage from compression where higher levels of disc degeneration is present.
Dealing With Degenerative Disc Disease
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” or “its all in your head”. 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 progression of the disease to myelopathy.
If many methods have failed, you may look into Modic Antibiotic Spinal Therapy. If you visit this page, there is a questionnaire that may provide some insight as to if you might have modic changes. While this is for back pain, because the studies have been focused on this, there is no reason to assume it does not produce similar findings in the neck.
You must remember that attitude is important. There is promising research being undertaken and things like antibiotic therapy, biological and genetic therapies are promising.
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 like degenerative disc disease, 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. Chronic pain can form pathways in the brain that can continue pain sensation even when the pain generator is gone. This is called centralization and is being addressed through medications, however; lets make sure there is no pain generator before we write these patients off. Conditions like Modic 1 spinal degeneration are frequently written off as inconsequential, despite research indicating they are the degenerative finding on MRI most associated with pain, not responsive to traditional therapies, and made worse with exercise.
In a 2014 study in the journal of Orthopaedic Surgery, they noted that there may be a significant relationship between metabolic syndrome and more severe cases of this osteoarthritic degeneration. Metabolic syndrome features central obesity (excess fat in the stomach area – apple shape), diabetes or high blood sugar problems, high blood pressure, and dyslipidemia (low HDL cholesterol or low levels of the “good cholesterol”).
Remember that having a disc injury does not have to mean you had trauma like a fall or accident. we mentioned that the disc can get weak so that a sneeze can injure it. But injury to a disc means that it has been physically disrupted. This can happen from being weak, or from being overloaded as in lifting or from repeated small loadings that can become fatigued as the damage accumulates. If unexpected or sudden movement happen, internal muscle forces can cause injury, just like weakened and old spinal bones can fracture when just trying to open a window.
Professional help is certainly warranted if other methods fail or concern is great enough. Many drugs used today treat symptoms of chronic pain instead of specific pain generators. This is based partially on the fact that chronic pain can effect the brain, so if there is no pain generator that can be identified, the pain is still felt. This is like the phantom limb experience where there is no limb, but pain is still felt as if there were. Another reason is that there is no belief that there is a pain generator. This is often seen with Modic changes which were long thought to be a normal part of the process of degenerative disc disease, but are now known to be highly associated with pain and disability. Modic Antibiotic Spinal Therapy is providing hope for this condition. Support of family and friends can help, however, you should not feel sorry for yourself or have other people feel sorry for you.
Try to minimize drug dependency as much as possible. Be aware that fear of motion and activity is going to be a part of it. Similarly, depression and anxiety go hand in hand with chronic pain, especially when it limits your ability to function. A good doctor or therapist can help you and your family members understand and deal with this as best as possible. New discoveries are happening all the time. Old ideas regarding disc degeneration are changing. Try to keep hope, but get help if you need.
Research into new therapies for treating degenerative disc disease is happening at a fast pace. Tissue engineering, genetics, biological treatment strategies, new drugs and surgical procedures are undergoing scientific trials. Sometimes, one is able to participate in these studies for new therapies. You can find out more at the clinical trials for disc degeneration.