Degenerative Disc Disease | An Overview

“What is degenerative disc disease” is a common question that arises for those experiencing back pain. Degenerative disc disease refers to age-related wear and tear that can occur in the discs of the spine, potentially leading to symptoms like chronic back pain or numbness/tingling. It’s estimated that about 30% of adults over 50 show some signs of degenerative changes in their spine discs. Understanding the anatomy of the discs and how degeneration manifests can help address this widespread condition.

Anatomy of Interverterbral Discs

The spine contains bones called vertebrae that are cushioned by round, gel-filled discs. These intervertebral discs absorb shock and facilitate movement of the spinal column. Their anatomy includes:

Nucleus Pulposus

This soft, jellylike inner core contains proteins and functions as a shock absorber between vertebrae.

Annulus Fibrosis

The tough exterior wall made of fibrous cartilage surrounds and contains the nucleus pulposus.

Cartilaginous Endplates

These allow the diffusion of nutrients and metabolites to the avascular discs.

In children, the discs consist of around 85% water. However, as part of the natural aging process, they lose hydration over time. By age 70, the water content may drop to 70%. This causes them to become less flexible and prone to damage. It’s estimated that about half of adults show some disc degeneration on MRI by their early 20s.

This degenerative process happens in stages over many years:

Stage 1: Disc experiences acute injury, tears, or nucleus leakage causing sudden pain and instability

Stage 2: The damaged disc leads to episodic pain that gradually improves as the body attempts to stabilize

Stage 3: Disc stabilizes but demonstrates permanent structural changes like collapse, spurring, and nerve compression

While nearly everyone exhibits disc degeneration by age 60, not all experience painful symptoms. When present, typical signs and symptoms relate to the location, nerves affected, and degree of structural deterioration.

Signs and Symptoms

The location of disc involvement and degree of degeneration influences associated signs and symptoms, which may come and go. Common issues stem from neurologic compression, inflammation, and biomechanical instability.

Back Pain

Back pain is the most common symptom of degenerative disc disease. As the cushioning discs between the vertebrae wear down, it can cause chronic aching or stiffness in the back. This is often described as a dull, constant pain rather than sharp or stabbing. The back pain tends to get worse when sitting or standing for longer periods of time, such as when working at a desk or standing in line. Bending forward, lifting objects, or twisting can also increase pain. Many people experience flare ups where the pain intensifies for days or weeks before settling down again. The location of back pain depends on which discs are affected, but it typically centers lower in the spine for age-related disc degeneration. When severe, this can greatly limit mobility and quality of life without relief.

Radiating Pain

In some cases, degenerative disc disease causes radiating pain into the arms and legs rather than isolated back pain. This happens when the damaged discs press against or damage the nerve roots exiting the spine. As they leave the spinal column, these nerve roots become pinched or inflamed. This sends sharp pain signals down the path of the nerve into the limb it controls. Radiating pain most often extends into the back of the thigh and legs from the lower back discs or into the shoulder and arm from cervical spine disc degeneration. The shooting, electric pain sensation can be mild or intensely debilitating. It may be triggered by certain neck/back movements or posture.

Numbness and Tingling

When inflamed, irritated, or compressed spinal nerves cannot properly transmit signals, it leads to abnormal sensations in the areas they supply. Degenerative disc disease can cause nerves exiting the spine to become impinged, resulting in symptoms like numbness, pins and needles tingling, burning, or prickling. These sensory changes start intermittently but often worsen and spread as nerve damage progresses. Numb, deadened areas usually result from sustained compression, while tingling indicates inflamed nerves. Most commonly this manifests in the arms and legs, reflecting cervical or lumbar disc issues impacting the nerve roots.

Muscle Weakness

In advanced degenerative disc disease, severe nerve compression can lead to muscle weakness or impaired reflex responses. Nerve signaling disruption from the sites of disc protrusions/herniations causes corresponding muscles to partially waste away over time. Due to slower reflex arcs, the neurological input reducing muscle contraction strength, people note feeling clumsy, easily fatigued, and lacking coordination of the arms or legs. The pattern relates to specific cervical or lumbar nerve distribution. Significant long-term weakness makes movement challenging without treatment to halt nerve damage.

Bowel and Bladder Control Loss

The worst case scenario involves such extensive spinal nerve damage that even bowel/bladder function becomes compromised – though fortunately very rare. When degenerative issues in the lower spine impact the cauda equina nerve bundle, sacral nerve signaling to these organs gets interrupted. If severe nerve impingement persists untreated, it can contribute to fecal or urinary retention/incontinence issues. However this generally only occurs in extreme circumstances with severe trauma or delayed intervention after the onset of progressive neurological deficits. Still, any bladder or bowel control changes warrant prompt medical investigation.

Diagnosis and Testing

Since most people demonstrate some structural disc degeneration on imaging, the diagnosis relies more on clinical correlation between such findings and symptom onset/severity. Helpful tests include:

Medical History & Exam: Thorough review of symptoms, aggravating factors, pain distribution, trauma history and neurological deficits on physical exam

Imaging Studies: X-ray, CT, or MRI to assess degree of disc collapse, vertebral endplate changes, bone spur formation and nerve/spinal cord impingement

Electromyography: Measures electrical activity of muscles and peripheral nerve insult from disc herniations or neuroforaminal stenosis

Prognosis and Outlook

The course of degenerative disc disease varies substantially between individuals. Many lead functional, productive lives despite age-related structural spine changes apparent on imaging. Most experience gradual normalization and stabilization of symptoms by 1 year even without surgery. However, some unfortunate patients suffer chronic disability from persistent pain, neurological deficits, and cumulative functional loss over time. Appropriate early evaluation and management can halt disease progression to help prevent long-term implications. Remaining cognizant of modifiable risk factors, engaging in proper spine hygiene, and promptly reporting new/worsening neurological symptoms facilitates the best outcomes.

Conclusion

In summary, degenerative disc disease is a common age-related process involving gradual changes to the discs leading to structural weakness and potential symptoms. If you’re experiencing symptoms of DDD it may be best to explore treatment options for degenerative disc disease and consult your doctor immediately. While not everyone with imaging evidence of disc degeneration develops pain, understanding the typical manifestations helps sufferers identify and address this issue to improve comfort and quality of life.