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Several different lumbar spine (low back) disorders can cause sciatica. Sciatica is often described as mild to intense pain in the left or right leg. Sciatica
is caused by compression of one or more of the five sets of nerve roots in the
lower back. Sometimes doctors call sciatica a radiculopathy. Radiculopathy is
a medical term used to describe pain, numbness, tingling, and weakness in the
arms or legs caused by a nerve root problem. If the nerve problem is in the
neck, it is called a cervical radiculopathy. However, since sciatica affects
the low back, it is called a lumbar
radiculopathy.
Pathways to Sciatic Nerve Pain
Five sets of paired nerve roots in the lumbar spine combine to create the sciatic
nerve. Starting at the back of the pelvis (sacrum), the sciatic nerve runs from
the back, under the buttock, and downward through the hip area into each leg.
Nerve roots are not 'solitary' structures but are part of the body's entire
nervous system capable of transmitting pain and sensation to other parts of
the body. Radiculopathy occurs when compression of a nerve root from a disc
rupture or bone spur occurs in the lumbar spine prior to it joining the sciatic
nerve.
Sciatic Nerve Compression
Several different types of spinal disorders can cause spinal nerve compression
and sciatica or lumbar radiculopathy. The six most common are:
Each condition is briefly explained below.
Common Sciatica Cause #1: Lumbar Bulging or Herniated Disc
A bulging disc is also known as a contained disc disorder. This means the gel-like
center (nucleus pulposus) remains 'contained' within the tire-like outer wall
(annulus fibrosus) of the disc. A herniated disc occurs when the nucleus breaks
through the annulus. It is called a 'non-contained' disc disorder. Whether a
disc bulges or herniates, disc material can press against an adjacent nerve
root and compress delicate nerve tissue and cause sciatica. The consequences
of a herniated disc are worse. Not only does the herniated nucleus cause direct
compression of the nerve root against the interior of the bony spinal canal,
but the disc material itself also contains an acidic, chemical irritant (hyaluronic
acid) that causes nerve inflammation. In both cases, nerve compression and irritation
cause inflammation and pain, often leading to extremity numbness, tingling,
and muscle weakness.
Common Sciatica Cause #2: Lumbar Spinal Stenosis
Spinal stenosis is a nerve compression disorder most often affecting mature
people. Leg pain similar to sciatica may occur as a result of lumbar spinal
stenosis. The pain is usually positional, often brought on by activities such
as standing or walking and relieved by sitting down. Spinal nerve roots branch
outward from the spinal cord through passageways called neural foramina comprised
of bone and ligaments. Between each set of vertebral bodies, located on the
left and right sides, is a foramen. Nerve roots pass through these openings
and extend outward beyond the spinal column to innervate other parts of the
body. When these passageways become narrow or clogged causing nerve compression,
the term foraminal stenosis is used.
Common Sciatica Cause #3: Spondylolisthesis
Spondylolisthesis is a disorder that most often affects the lumbar spine. It
is characterized by one vertebra slipping forward over an adjacent vertebra.
When a vertebra slips and is displaced, spinal nerve root compression occurs
and often causes sciatic leg pain. Spondylolisthesis is categorized as developmental
(found at birth, develops during childhood) or acquired from spinal degeneration,
trauma or physical stress (i.e. weightlifting).
Common Sciatica Cause #4: Trauma
Sciatica can result from direct nerve compression caused by external forces
to the lumbar or sacral spinal nerve roots. Examples include motor vehicle accidents,
falling down, football and other sports. The impact may injure the nerves or
occasionally fragments of broken bone may compress the nerves.
Common Sciatica Cause #5: Piriformis Syndrome
Piriformis syndrome is named for the piriformis muscle and the pain caused when
the muscle irritates the sciatic nerve. The piriformis muscle is located in
the lower part of the spine, connects to the thighbone, and assists in hip rotation.
The sciatic nerve runs beneath the piriformis muscle. Piriformis syndrome develops
when muscle spasms develop in the piriformis muscle thereby compressing the
sciatic nerve. It may be difficult to diagnose and treat due to the lack of
x-ray or MRI findings.
Common Sciatica Cause #6:Spinal Tumors
Spinal tumors are abnormal growths that are either benign or cancerous (malignant).
Fortunately, spinal tumors are rare. However, when a spinal tumor develops in
the lumbar region, there is a risk for sciatica to develop as a result of nerve
compression.
If you think you may be suffering from sciatica, contact a spine specialist
in your community. The first step toward relieving pain is a proper diagnosis!
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