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Degenerative Disc Disease and Sciatica

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Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Medical Editor:

Catherine Burt Driver, MD

Catherine Burt Driver, MD

Catherine Burt Driver, MD, is board certified in internal medicine and rheumatology by the American Board of Internal Medicine. Dr. Driver is a member of the American College of Rheumatology. She currently is in active practice in the field of rheumatology in Mission Viejo, Calif., where she is a partner in Mission Internal Medical Group.

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Degenerative disc disease & sciatica facts

• The discs of the spine serve as "cushions" between each vertebral segment.
• The discs are designed somewhat like a jelly donut.
• Degeneration (deterioration) of the disc makes the disc more susceptible to herniation (rupture), which can lead to localized or radiating pain.
• Sciatica can result from disc herniation when nerves in the low back are irritated.

How is the spine designed?

The vertebrae are the bony building blocks of the spine. Between each of the largest part of the vertebrae are the discs. Ligaments are situated around the spine and discs. The spine has seven vertebrae in the neck (cervical vertebrae), 12 vertebrae in the mid-back (thoracic vertebrae), and five vertebrae in the low back (lumbar vertebrae). In addition, in the mid-buttock beneath the fifth lumbar vertebra, are five sacral vertebrae -- usually fused as the sacrum bone followed by the tailbone (coccyx).

What is the purpose of the spine and its discs?

The bony spine is designed so that vertebrae "stacked" together can provide a movable support structure. The spine also protects the spinal cord (nervous tissue that extends down the spinal column from the brain) from injury. Each vertebra has a spinous process, which is a bony prominence behind the spinal cord that shields the cord's nerve tissue. The vertebrae also have a strong bony "body" in front of the spinal cord to provide a platform suitable for weight-bearing.

The discs are pads that serve as "cushions" between each vertebral body that serve to minimize the impact of movement on the spinal column. Each disc is designed like a jelly donut with a central softer component (nucleus pulposus). With injury or degeneration, this softer component can sometimes rupture (herniate) through the surrounding outer ring (annulus fibrosus) and irritate adjacent nervous tissue. Ligaments are strong fibrous soft tissues that firmly attach bones to bones. Ligaments attach each of the vertebrae and surround each of the discs. When ligaments are injured as the disc degenerates, localized pain in the area affected can result.

Picture of herniated disc between L4 and L5

Cross-section picture of herniated disc between L4 and L5