Health Topics
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Publication Date: October 1999
Questions and Answers About Spinal Stenosis
This fact sheet contains general information about spinal stenosis.
It describes the condition's causes, symptoms, diagnosis, and treatments.
At the end is a list of additional resources. If you have further questions
after reading this fact sheet, you may wish to discuss them with your
doctor.
What Is Spinal Stenosis?
Spinal stenosis is a narrowing of spaces in the spine
(backbone) that results in pressure on the spinal cord and/or nerve
roots. This disorder usually involves the narrowing of one or more of
three areas of the spine: (1) the canal in the center of the column
of bones (vertebral or spinal column) through which the spinal cord
and nerve roots run, (2) the canals at the base or roots of nerves branching
out from the spinal cord, or (3) the openings between vertebrae (bones
of the spine) through which nerves leave the spine and go to other parts
of the body. The narrowing may involve a small or large area of the
spine. Pressure on the lower part of the spinal cord or on nerve roots
branching out from that area may give rise to pain or numbness in the
legs. Pressure on the upper part of the spinal cord (that is, the neck
area) may produce similar symptoms in the shoulders, or even the legs.
Who Gets Spinal Stenosis?
This disorder is most common in people over 50 years of
age. However, it may occur in younger people who are born with a narrowing
of the spinal canal or who suffer an injury to the spine.
What Structures of the Spine
Are Involved?
The spine is a column of 26 bones that extend in a line
from the base of the skull to the pelvis (see
fig. 1). Twenty-four of the bones are called vertebrae. The bones
of the spine include 7 cervical vertebrae in the neck; 12 thoracic vertebrae
at the back wall of the chest; 5 lumbar vertebrae at the inward curve
(small) of the lower back; the sacrum, composed of 5 fused vertebrae
between the hip bones; and the coccyx, composed of 3 to 5 fused bones
at the lower tip of the vertebral column. The vertebrae link to each
other and are cushioned by shock-absorbing disks that lie between them.
The vertebral column provides the main support for the
upper body, allowing humans to stand upright or bend and twist, and
it protects the spinal cord from injury. Following are structures of
the spine most involved in spinal stenosis.
-
Intervertebral disks--pads of cartilage between
vertebrae that act as shock absorbers.
-
Facet joints--joints located on both sides
and on the top and bottom of each vertebra. They connect the vertebrae
to each other and permit back motion.
-
Intervertebral foramen (also called neural foramen)--an
opening between vertebrae through which nerves leave the spine
and extend to other parts of the body.
-
Lamina--part of the vertebra at the upper
portion of the vertebral arch that forms the roof of the canal
through which the spinal cord and nerve roots pass.
-
Ligaments--elastic bands of tissue that
support the spine by preventing the vertebrae from slipping out
of line as the spine moves. A large ligament often involved in
spinal stenosis is the ligamentum flavum, which runs as a continuous
band from lamina to lamina in the spine.
-
Pedicles--narrow stem-like
structures on the vertebrae that form the walls of the bottom
part of the vertebral arch.
-
Spinal cord/nerve roots--a major part of
the central nervous system that extends from the base of the brain
down to the lower back and that is encased by the vertebral column.
It consists of nerve cells and bundles of nerves. The cord connects
the brain to all parts of the body via 31 pairs of nerves that
branch out from the cord and leave the spine between vertebrae
(see fig. 2).
-
Synovium--a thin membrane that produces fluid
to lubricate the facet joints, allowing them to move easily.
-
Vertebral arch--a circle of bone around the
canal through which the spinal cord passes. It is composed of
a floor at the back of the vertebra, walls (the pedicles), and
a ceiling where two laminae join.
What Causes Spinal Stenosis?
The normal vertebral canal (see
fig. 3) provides adequate room for the spinal cord. Narrowing of
the canal, which occurs in spinal stenosis, may be inherited or acquired.
Some people inherit a small spinal canal (see
fig. 4) or have a curvature of the spine (scoliosis) that produces
pressure on nerves and soft tissue and compresses or stretches ligaments.
In an inherited condition called achondroplasia, defective bone formation
results in abnormally short and thickened pedicles that reduce the diameter
of (distance across) the spinal canal.
Acquired conditions that can cause spinal stenosis are
explained in more detail in the sections that follow.
Degenerative (Aging) Conditions, Including Osteoarthritis
Spinal stenosis most often results from a gradual, degenerative
aging process. Either structural changes or inflammation can begin the
process. As people age, the ligaments of the spine may thicken and calcify
(harden from deposits of calcium salts). Bones and joints may also enlarge,
and osteophytes (bone spurs) may form. When the health of one part of
the spine fails, it usually places increased stress on other parts of
the spine. For example, a degenerative condition affecting the facet
joints may eventually cause secondary changes, such as a herniated (bulging)
disk that places pressure on the spinal cord or nerve root (see
fig. 5). When a segment of the spine becomes too mobile, the capsules
(enclosing membranes) of the facet joints thicken in an effort to stabilize
the segment, and bone spurs may occur. This decreases the
space (neural foramen) available for nerve roots leaving the spinal
cord.
Aging with secondary changes is the most common cause
of spinal stenosis. Two forms of arthritis that may affect the spine
are osteoarthritis and rheumatoid arthritis.¹
Osteoarthritis is the most common form of arthritis and is more likely
to occur in middle-aged and older people. It is a chronic, degenerative
process that may involve multiple joints of the body. It wears away
the surface cartilage layer of joints, and is often accompanied by overgrowth
of bone, formation of bone spurs, and impaired function. If the degenerative
change affects the facet joint(s) and the disk, the condition is sometimes
referred to as spondylosis. This condition may be accompanied by disk
degeneration, and an enlargement or overgrowth of bone that narrows
the central and root canals.
Spondylolysthesis, a condition in which one vertebra slips
forward on another, may result from a degenerative condition
or an accident, or may be acquired at birth. Poor alignment of the spinal
column when a vertebra slips forward onto the one below it can place
pressure on the spinal cord or nerve roots at that place.
¹The National Institute of Arthritis and
Musculoskeletal and Skin Diseases Information Clearinghouse has separate
information packages on osteoarthritis and rheumatoid arthritis. Single
copies are free.
Rheumatoid Arthritis
Rheumatoid arthritis usually affects people at an earlier
age than osteoarthritis does and is associated with inflammation and
enlargement of the soft tissues of the joints. Although not a common
cause of spinal stenosis, damage to ligaments, bones, and joints that
begins as synovitis (inflammation of the synovial membrane) has a severe
and disrupting effect on joint function. The portions of the vertebral
column with the greatest mobility (for example, the neck area) are often
the ones most affected in people with rheumatoid arthritis.
Nonarthritic Acquired Spinal Stenosis
The following conditions that are not related to arthritis
or degenerative disease are causes of acquired spinal stenosis:
-
Tumors of the spine are abnormal growths of
soft tissue that may affect the spinal canal directly by inflammation
or by growth of tissue into the canal. Tissue growth may lead to
bone resorption (bone loss due to overactivity of certain bone cells)
or displacement of bone and the eventual collapse of the supporting
framework of the vertebral column.
-
Trauma (accidents) may either dislocate the
spine and the spinal canal or cause burst fractures that produce
fragments of bone that penetrate the canal.
-
Although surgery that involves fusion (union) of
vertebrae may be skillfully performed, tissue swelling after
surgery may place pressure on the spinal cord.
-
Paget's disease of bone is a chronic (long-term)
disorder that typically results in enlarged and deformed bones.
Excessive bone breakdown and formation cause thick and fragile bone.
As a result, bone pain, arthritis, noticeable deformities, and fractures
can occur. The disease can affect any bone of the body, but is often
found in the spine. The blood supply that feeds healthy nerve tissue
may be diverted to the area of involved bone. Also, structural deformities
of the involved vertebrae can cause narrowing of the spinal canal,
producing a variety of neurological symptoms.
-
Fluorosis is an excessive level of fluoride
in the body. It may result from chronic inhalation of industrial
dusts or gases contaminated with fluorides, prolonged ingestion
of water containing large amounts of fluorides, or accidental ingestion
of fluoride-containing insecticides. The condition may lead to calcified
spinal ligaments or softened bones and to degenerative conditions
like spinal stenosis.
What Are the Symptoms of Spinal
Stenosis?
Spaces within the spine can narrow without producing any
symptoms. However, if narrowing places pressure on the spinal cord or
nerve roots, there may be a slow onset and progression of symptoms.
The back itself may or may not hurt. More often, people experience numbness,
weakness, cramping, or general pain in the legs that occurs during flexing
the lower back while sitting. (The flex position "opens up"
the spinal column, enlarging the spaces between vertebrae at the back
of the spine.) If a disk between vertebrae is compressed, people may
feel pain radiating down the leg (sciatica).
People with more severe stenosis may experience abnormal
bowel and bladder function and foot disorders. For example, cauda equina
syndrome is a partial or complete loss of control of the bowel or bladder
and sometimes sexual function; it is due to compression of the collection
of spinal roots that descend from the lower part of the spinal cord
and occupy the vertebral canal below the cord. In very rare instances,
compression above the area where the lumbar vertebrae and sacrum meet
results in partial or complete paralysis of the legs.
How Is Spinal Stenosis Diagnosed?
The doctor may use a variety of approaches to diagnose
spinal stenosis and rule out other conditions.
-
Medical history--the patient tells the doctor
details about symptoms and about any injury, condition, or general
health problem that might be causing the symptoms.
-
Physical examination--the doctor (1) examines
the patient to determine the extent of limitation of movement; (2)
checks for pain or symptoms when the patient hyperextends the spine
(bends backwards); and (3) looks for the loss of extremity reflexes,
which may be related to numbness or weakness in the arms or legs.
-
X ray--an x-ray beam is passed through the
back to produce a two-dimensional picture. An x ray may be done
before other tests to look for signs of an injury, tumor, or inherited
abnormality. This test can show the structure of the vertebrae and
the outlines of joints, and can detect calcification.
-
MRI (magnetic resonance imaging)--energy from
a powerful magnet (rather than x rays) produces signals that are
detected by a scanner and analyzed by computer. This produces a
series of cross-sectional images ("slices") and/or a three-dimensional
view of parts of the back. An MRI is particularly sensitive for
detecting damage or disease of soft tissues, such as the disks between
vertebrae or ligaments. It shows the spinal cord, nerve roots, and
surrounding spaces, as well as enlargement, degeneration, or tumors.
-
Computerized axial tomography (CAT)--x rays
are passed through the back at different angles, detected by a scanner,
and analyzed by a computer. This produces a series of cross-sectional
images and/or three-dimensional views of the parts of the back.
The scan shows the shape and size of the spinal canal, its contents,
and structures surrounding it.
-
Myelogram--a liquid dye that x rays cannot
penetrate is injected into the spinal column. The dye circulates
around the spinal cord and spinal nerves, which appear as white
objects against bone on an x-ray film. A myelogram can show pressure
on the spinal cord or nerves from herniated disks, bone spurs, or
tumors.
-
Bone scan--an injected radioactive material
attaches itself to bone, especially in areas where bone is actively
breaking down or being formed. The test can detect fractures, tumors,
infections, and arthritis, but may not tell one disorder from another.
Therefore, a bone scan is usually performed along with other tests.
Who Treats Spinal Stenosis?
Nonsurgical treatment of spinal stenosis may be provided
by internists or general practitioners. The disorder is also treated
by specialists such as rheumatologists, who treat arthritis and related
disorders; and neurologists, who treat nerve diseases. Orthopaedic surgeons
and neurosurgeons also provide nonsurgical treatment and perform spinal
surgery if it is required. Allied health professionals such as physical
therapists may also help treat patients.
What Are Some Nonsurgical
Treatments for Spinal Stenosis?
In the absence of severe or progressive nerve involvement,
a doctor may prescribe one or more of the following conservative treatments:
-
Nonsteroidal anti-inflammatory drugs, such as aspirin,
naproxen (Naprosyn),²
ibuprofen (Motrin, Nuprin, Advil), or indomethacin (Indocin), to
reduce inflammation and relieve pain.
-
Analgesics, such as acetaminophen (Tylenol), to relieve
pain.
-
Corticosteroid injections into the outermost of the
membranes covering the spinal cord and nerve roots to reduce inflammation
and treat acute pain that radiates to the hips or down a leg.
-
Restricted activity (varies depending on extent of
nerve involvement).
-
Physical therapy and/or prescribed exercises to maintain
motion of the spine and build endurance, which help stabilize the
spine.
-
A lumbar brace or corset to provide some support and
help the patient regain mobility. This approach is sometimes used
for patients with weak abdominal muscles
or older patients with degeneration at several levels of the spine.
²Brand names included in this fact sheet
are provided as examples only. Their inclusion does not mean that these
products are endorsed by the National Institutes of Health or another
Government agency. Also, if a particular brand name is not mentioned,
this does not mean or imply that the product is unsatisfactory.
When Should Surgery Be Considered
and What Is Involved?
In many cases, the conditions causing spinal stenosis
cannot be permanently altered by nonsurgical treatment, even though
these measures may relieve pain for a time. To determine the extent
to which nonsurgical treatment will help, a doctor seldom recommends
surgery during the first 3 months of treatment. However, surgery might
be considered within the 3-month period if a patient experiences numbness
or weakness that interferes with walking, impaired bowel or bladder
function, or other neurological involvement.
The purpose of surgery is to relieve pressure on the spinal
cord or nerves and restore and maintain alignment and strength of the
spine. This can be done by removing, trimming, or adjusting diseased
parts that are causing the pressure or loss of alignment. The most common
surgery is called decompressive laminectomy: removal of the lamina (roof)
of one or more vertebrae to create more space for the nerves. A surgeon
may perform a laminectomy with or without fusing vertebrae or removing
part of a disk. Various devices may be used to enhance fusion and strengthen
unstable segments of the spine following decompression surgery.
Patients with spinal stenosis caused by spinal trauma
or achondroplasia may need surgery at a young age. When surgery is required
in patients with achondroplasia, laminectomy (removal of the roof) without
fusion is usually sufficient.
What Are the Major Risks of
Surgery?
All surgery, particularly that involving general anesthesia
and older patients, carries risks. The most common complications of
surgery for spinal stenosis are a tear in the membrane covering the
spinal cord at the site of the operation, infection, or a blood clot
that forms in the veins. These conditions can be treated but may prolong
recovery.
What Are the Long-Term Outcomes
of Surgical Treatment for Spinal Stenosis?
Removal of the obstruction that has caused the symptoms
usually gives patients some relief; most patients have less leg pain
and are able to walk better following surgery. However, if nerves were
badly damaged prior to surgery, there may be some remaining pain or
numbness or no improvement. Also, the degenerative process will likely
continue, and pain or limitation of activity may reappear 5 or more
years after surgery.
What Research on Spinal Stenosis Is Being Supported by the NIAMS?
The National Institute of Arthritis and Musculoskeletal
and Skin Diseases (NIAMS) is supporting several research projects on
spinal stenosis. For example, at the Multipurpose Arthritis and Musculoskeletal
Disease Center at the Hospital for Special Surgery in New York City,
doctors are comparing the effectiveness of injecting a steroid (cortisone-like)
medicine with that of injecting an analgesic medicine into the epidura
(outermost membrane covering the spinal cord) for relief of pain and
disability due to spinal stenosis. In another NIAMS-funded study involving
11 different medical centers, researchers are comparing surgical vs.
nonsurgical treatment of spinal stenosis and two other conditions that
cause back pain.
Other researchers are exploring why spinal cord changes
lead to a decreased pain threshold or an increased sensitivity to pain,
and how fractures of the spine and their repair affect the spinal canal
and intervertebral foramen.
What Are Other Sources of
Information on Spinal Stenosis?
- American Academy of Orthopaedic Surgeons
P.O. Box 2058
Des Plaines, IL 60017
Phone: 800-824-BONE (2663) (free of charge)
World Wide Web address: http://www.aaos.org/
The academy provides education and practice management services for orthopaedic surgeons and allied health professionals. It also serves as an advocate for improved patient care and informs the public about the science of orthopaedics. The orthopaedist's scope of practice includes disorders of the body's bones, joints, ligaments, muscles, and tendons. For a single copy of an AAOS brochure, send a self-addressed stamped envelope to the address above or visit the AAOS Web site.
- North American Spine Society
22 Calendar Ct., 2nd floor
LaGrange, IL 60525
Toll Free Phone: (877) 77463 37 (SpineDr)
Phone: (708) 588-8080
Fax: (708) 588-1080
World Wide Web address: http://www.spine.org/
This professional association can identify specialists
throughout the country who treat disorders of the spine.
- American College of Rheumatology/Association of Rheumatology
Health Professionals
1800 Century Place, Suite 250
Atlanta, GA 30345
404/633-3777
Fax: 404/633-1870
E-mail: acr@rheumatology.org
World Wide Web address: http://www.rheumatology.org/
This national professional organization can provide
referrals to rheumatologists and allied health professionals, such
as physical therapists. One-page fact sheets are available on various
forms of arthritis. Lists of specialists by geographic area and fact
sheets are also available on the American College of Rheumatology's
Web site.
- Arthritis Foundation
1330 West Peachtree Street
Atlanta, GA 30309
404/872-7100
800/283-7800
or your local chapter listed in your local telephone directory
Fax: 404/872-9959
E-mail: helpdesk@arthritis.org
World Wide Web address: http://www.arthritis.org/
The foundation has a free brochure on back pain and
several free brochures about coping with arthritis, taking nonsteroid
and steroid medicines, and exercise. The foundation also provides
referrals to doctors treating various forms of arthritis.
- Spondylitis Association of America
P.O. Box 5872
Sherman Oaks, CA 91413
818/981-1616
800/777-8189
Fax: 818/981-9826
E-mail: info@spondylitis.org
World Wide Web address: http://www.spondylitis.org/
This association provides physician referrals and information on spondylitis.
- National Institute of Arthritis and Musculoskeletal
and Skin Diseases Information Clearinghouse
National Institutes of Health
1 AMS Circle
Bethesda, MD 20892-3675
301/495-4484
Fax: 301/718-6366
TTY: 301/565-2966
World Wide Web address: http://www.niams.nih.gov/
The clearinghouse has additional information about some
back problems and about arthritis. Single copies of fact sheets and
information packages are available free upon request.
Acknowledgments
The NIAMS gratefully acknowledges the assistance of James
S. Panagis, M.D., M.P.H., NIAMS; David G. Borenstein, M.D., Arthritis
and Rheumatism Associates, Washington, DC; and James H. Weinstein, M.D.,
Dartmouth Medical School, Hanover, NH, in the preparation and review
of this fact sheet.
The National Institute of Arthritis and Musculoskeletal
and Skin Diseases (NIAMS), a part of the National
Institutes of Health (NIH), leads the Federal medical research
effort in arthritis and musculoskeletal and skin diseases. The
NIAMS supports research and research training throughout the United
States, as well as on the NIH campus in Bethesda, MD, and disseminates
health and research information. The National Arthritis and Musculoskeletal
and Skin Diseases Information Clearinghouse (NAMSIC) is a public
service sponsored by the NIAMS that provides health information
and information sources.