Sciatica is a
severe pain in the leg caused by compression,
irritation, or inflammation of the sciatic nerve.
The discomfort can
range from mild to incapacitating, and may be
accompanied by tingling, numbness or muscle
weakness. Rather than a disorder in and of itself
sciatica is a symptom of another problem, such as a
herniated disk, that puts pressure on the nerve.
Sciatic pain usually goes away on its own in six
weeks or so. In the meantime, hot and cold packs,
over-the-counter pain relievers, and exercise or
physical therapy can help ease discomfort and speed
recovery. Surgery to relieve pressure on the nerve
may be an option when symptoms don't respond to
conservative treatment and pain is chronic or
disabling.
Signs and symptoms
Pain that radiates from your lower (lumbar) spine to your buttock and
down the back of your leg is the hallmark of sciatica. You may feel the
discomfort almost anywhere along the nerve pathway, but it's especially
likely to follow one of these routes:
-
From
your lower back to your knee
-
From
the midbuttock to the outside of your calf, the top of your foot and
into the space between your last two toes
-
From the inside of
your calf to your inner ankle and sole
The pain can vary widely, from a mild ache to a sharp, burning sensation
or excruciating discomfort. Sometimes it may feel like a jolt or
electric shock. Sciatic pain often starts gradually and intensifies over
time. It's likely to be worse when you sit, cough or sneeze. Usually
only one lower extremity is affected.
In addition to pain, you may also experience:
-
Numbness or
muscle weakness along the nerve pathway in your leg or foot.
In some cases, you may have pain in one part of your leg and
numbness in another.
-
Tingling or a
pins-and-needles feeling.
This occurs most commonly in your toes or part of your foot.
-
A loss of
bladder or bowel control.
This is a sign of cauda equina syndrome, a rare but serious
condition that requires emergency care. If you experience either of
these symptoms, seek medical help immediately.
Causes
Sciatica usually results from compression of a nerve root in your lower
(lumbar) spine — a condition called a radiculopathy. By far the most
common cause of this compression is a herniated disk in your lower back.
Disks are pads of cartilage that separate the bones (vertebrae) in your
spine. Each disk consists of a ring of tough fibrous tissue (annulus
fibrosis) surrounding a jelly-like center (nucleus pulposus). Healthy
disks keep your spine flexible and act as shock absorbers to cushion the
vertebrae when you move.
Between each vertebra is an elastic pad of cartilage called an
intervertebral disk. The disks consist of a tough, fibrous outer
covering (annulus fibrosus) and a jelly-like center (nucleus pulposus).
But as you grow older, the disks may start to deteriorate, becoming
drier, flatter and more brittle. Eventually, the tough, fibrous outer
covering of the disk may develop tiny tears, causing the jelly-like
substance in the disk's center to seep out (herniation or rupture). The
herniated disk then often presses on a nerve root, causing pain — which
can be excruciating — in your back, leg or both. If the damaged disk is
in the middle or lower part of your back, you also may experience
numbness, tingling or weakness in your buttock, leg or foot.
Other conditions that may put pressure on the sciatic nerve include:
-
Lumbar spinal
stenosis.
Your spinal cord is a bundle of nerves that extends the length of
your spine. It's housed inside a channel (spinal canal) within the
vertebrae. Thirty-one pairs of nerves branch off from the spinal
cord, providing communication between your brain and the rest of
your body. In spinal stenosis, one or more areas in the spinal canal
narrow, putting pressure on the spinal cord or on the roots of these
branching nerves. When the narrowing occurs in the lower spine, the
lumbar and sacral nerve roots may be affected.
-
Spondylolisthesis.
This condition, often the result of degenerative disk disease,
occurs when one vertebra slips slightly forward over another
vertebra. The displaced bone may pinch the sciatic nerve where it
leaves the spine.
-
Piriformis
syndrome.
Running directly above the sciatic nerve, the piriformis muscle
starts at your lower spine and connects to each thighbone (femur).
Piriformis syndrome occurs when the muscle becomes tight or goes
into spasms, putting pressure on the sciatic nerve. Active women —
runners and serious walkers, for example — are especially likely to
develop the condition. Prolonged sitting, car accidents and falls
also may contribute to piriformis syndrome.
-
Spinal tumors.
A tumor is a mass of abnormal cells. In the spine, these growths may
occur inside the spinal cord, within the membranes (meninges) that
cover the spinal, or in the space between the spinal cord and the
vertebrae — the most common site. As it grows, a tumor compresses
the cord itself or the nerve roots. This can cause severe back pain
that may extend to your hips, legs or feet; muscle weakness and a
loss of sensation — especially in your legs; difficulty walking; and
sometimes loss of bladder or bowel function.
-
Trauma.
A car accident, fall or blow to the spine can injure the lumbar or
sacral nerve roots.
-
Sciatic nerve
tumor or injury.
Although uncommon, the sciatic nerve itself may be affected by a
tumor or injury, leading to sciatic pain.
-
Other causes.
In some cases, your doctor may not be able to find a cause for your
sciatica. A number of problems can affect the bones, joints and
muscles, all of which could potentially result in sciatic pain.
Risk factors
Risk factors are health problems, lifestyle choices and inherent
qualities, such as age or race that make it more likely you'll develop a
particular condition. Major risk factors for sciatica include:
-
Age.
Age-related changes in the spine are the most common cause of
sciatica. You're likely to have some deterioration in the disks in
your back by the time you're 30, and most people who develop
herniated disks are in their 30s and 40s. Spinal stenosis, another
leading cause of sciatica, primarily strikes people in their 50s and
beyond.
-
Occupation.
A job that requires you to twist your back, carry heavy loads or
drive a motor vehicle for long periods makes you more prone to
develop sciatica.
-
Physical
activity.
Although walking and jogging have been associated with an increased
risk of sciatica, exercise in general has not. In fact, people who
sit for prolonged periods or have a sedentary lifestyle are more
likely to develop sciatica than active people are.
-
Genetic
factors.
Researchers have identified two genes that may predispose some
people to disk problems.
-
Diabetes.
Having this condition, which affects the way your body uses blood
sugar, makes you more likely to develop nerve damage.
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