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Spinal Stenosis can occur in any one of the three regions of the spine:  cervical, thoracic, and lumbar.  In this article we will be discussing stenosis in the lumbar spine.  The lumbar spine is also known as the lower back.  In the diagram above you will see how the different regions of the spine are in different colors.  It is the green section (lumbar) and part of the blue section (the sacrum) that will be the focus of this article, the lumbrosacral spine.
 

Lumbar Spinal Stenosis is the narrowing of either the spinal canal and/or the spaces between the vertebrae.  People with stenosis are not necessarily symptomatic from it either.  It is usually slow and comes on in an insidious way unlike an acute herniated disc itself.  However stenosis is not a life sentence and there are various ways that it can be treated.  It does not always require surgery if the symptoms are alleviated by conservative measures.  When symptomatic, Spinal Stenosis can cause pain in the back and/or legs.  It can cause sciatica (radicular pain) and numbness in the legs and feet.  There are three different forms of lumbar stenosis:  1) Central Stenosis  2)  Lateral Stenosis  and 3) Foraminal stenosis.  The sufferer may have one or two types of stenosis or all of them.  Stenosis can be congenital or acquired or a combination of the two.

In Lumbar stenosis the most commonly affected levels are start at L3 to S1.  The most common level being L4-L5.  Unlike a lumbar herniated disc alone, Stenosis tends to be at more than one level and can be at multiple levels of the lumbar spine.

Central Stenosis is the narrowing of the spinal canal which the spinal cord runs through.  In the lumbar spine the spinal cord tapers off from the Conus Medullaris to the Cauda Equina (latin word for horse's tail).  Some people are born with a congenital narrowing of the spinal canal while others have degeneration of the lumbar spine with osteophytes secondary to degenerative disc disease.  It also can be caused by a central disc herniation of a significant size.  In fact it is this type of stenosis is the most common in causing Cauda Equina Syndrome, a very uncommon but devastating complication of central stenosis.  Lateral Stenosis is the narrowing of the lateral recess which results in nerve root compression.  Foraminal stenosis is the narrowing of the foramen (the place where the nerve roots exit the vertebrae).
 
 
 

Aging is one of the more common causes of stenosis.  In this type of stenosis, degenerative disc disease and stenosis go hand in hand.  As we get older the height of discs shrink from wear and tear.  The ligamentum flavum will thicken and the joints will enlarge.  Bone spurs will form as the spine tries to compensate and the diameter of the spinal canal and/or lateral recess, and/or foramen will decrease and become "stenoic."  Osteoarthritis and rheumatoid arthritis both are conditions that affect the joints in the spine (and the rest of the body) and can be causes of stenosis.  Osteoarthritis is the more common form of the two and is seen at an older age than rheumatoid arthritis.

Stenosis can also be caused by trauma and slippage of one vertebrae on to the other.  This type of slippage and instability is called spondylolisthesis which starts from a pars fracture in the vertebra called spondylolysis.  Other causes of stenosis include synovial cysts, spinal tumors, infection, post surgical causes, and Paget's disease of the bone.

Spinal Stenosis is rare in people under the age of 50 years old.  It usually hits people in their 60's, 70's, and 80's.  People with congenital narrowing will become symptomatic at an earlier age (i.e.:  their 30's and 40's). People that acquire it through trauma can get it at ANY age.  It is also characterized by the unique feature of neurogenic claudication, especially in its more severe stages.  Often the sufferer will get more relief with sitting than they will with standing or walking.  Sitting opens up the facet joints and in turn makes more room for the nerves while standing will close the joints and often make pain and numbness worse.  With neurogenic claudication, the flexion position (bending forward) will often alleviate pain and the extension position (lordosis) will often trigger pain.  This is one of many reasons why many with stenosis walk in a hunched over position.  This is also the opposite of what happens with people only with herniated discs.  They tend to get relief with extension and flexion makes their symptoms worse.

Notice in the below drawing how there are three figures.  Well the figure in the middle standing straight is in a neutral position and in fact is showing proper posture when standing.  The figure to the left that is leaning backwards is in extension.  The figure to the right is bending down and this is flexion.  It is this position that is usually more comfortable for stenosis patients.

Diagnositic tests that detect stenosis include:

X-Rays:  They are not very conclusive in determining central stenosis but can find things like decreased disc space height in older patients and fractured vertebrae.

CT- Scan (Computerized Tomography):  This gives a very accurate image of the bone features of the spine but is not as accurate as an MRI in looking at soft tissue (i.e. discs, nerve roots, etc.).

MRI (Magnetic Resonance Imaging):  This is the best diagnostic tool for looking at soft tissue and detecting things such as degenerative disc disease and herniated discs.  It also shows things like the thecal sac, ligaments, and visualisation of the spinal cord, etc.

Discogram:  This procedure is done to find torn discs.  MRIs and CT Scans are able to detect herniated and degenerative discs but don't always detect torn discs.  Torn discs in themselves can cause a lot of damage as the goop that leaks out of them is toxic to nerves with an acidic p.h. of 6.8.

Myelograms are rarely ever used anymore and have been pretty much replaced by the MRI.  The dyes are toxic to the spine and can also cause uncurable conditions such as adhesive arachnoiditis.

EMG/NCV (Electromyography/Nerve Conduction Velocity Tests):  These tests can help determine if there is ongoing nerve damage and/or muscle damage.

Spinal Stenosis can be managed with conservative treatment in most cases such as physiotherapy, NSAIDs, braces, accupuncture, TENS, nerve block injections, etc.  These treatments do nothing to change the mechanics in the spine, hence the stenosis is still there but the pain can normally be managed by conservative measures in the short term.  If the pain is not manageable by conservative measures often diagnositc tests (CT or MRI) should be requested by your physician within six weeks.  An EMG/NVC is usually requested as well in order to look for pinched or damaged nerves/muscles.  Surgery is sometimes necessary, especially in severe cases that do not respond to conservative measures where the patient has been affected neurologically in which the mobility and quality of life of the sufferer is very diminished.  The common surgery done for stenosis is a decompressive laminectomy which may or may not be accompanied by a discectomy or microdisectomy.  Sometimes a fusion may need to be done with the laminectomy all depending on the particular case and type of stenosis.  The effects of surgery last around 5 years and after that the stenosis may come back.
 

Possible Complications of Spinal Stenosis include Cauda Equina Syndrome (CES) which is most commonly caused by a massive central disc herniation but can be caused by other forms of central stenosis among other things.  Cauda Equina Syndrome is what occurs when the nerves supplying the legs, bladder, bowels, and sexual functions are impaired.  Although it is not a common phenomenon, it is a lot more common than the medical community will admit.  Doctors almost never tell us about this complication.  There are certain "red flags" as the medical community calls it that point to the possibility of CES.

-Bilateral leg weakness, pain, and numbness often accompanied by severe lower back pain.  Although this is not always the case with CES.  You may have unilateral pain/numbness.

-Urinary retention and/or incontinence.  You do not have to be a diaper case to have CES.  If it comes on gradually then it may start from Urinary retention where the sufferer is unable to pass urine.

-Stool retention and/or incontience.  The same applies here in that you do not have to be a diaper case to have CES if it comes on gradually.

-Loss of sphincter tone, loss of ejaculation/orgasm, genital, groin and tailbone pain and/or saddle anethesia (tail bone numbness, genital numbness, rectal numbness and perianal numbness as well as numbness of the groin region).

If you have any of these symptoms don't walk, run to the nearest Emergency room.  This requires immediate surgery.  Surgery is supposed to be done within 48 hours.  I also suggest that you get in touch with the Cauda Equina Syndrome Support Group (CESSG) at http://www.caudaequina.org


 
Sources:

What is Spinal Stenosis?.
Spinal Stenosis.org
 <http://www.spinalstenosis.org/ss1.html>

Q & A about spinal stenosis.  October 1999
National Institute of Arthritis and Musculoskeletal and Skin Diseases.
http://www.niams.nih.gov/hi/topics/spinalstenosis/spinal_sten.htm

Spinal Stenosis.
<http://www.orthoteers.co.uk/Nrujp~ij33lm/Orthspinestenosis.htm>.

Cauda Equina and Conus Medullaris Syndromes.  Ed.  Dr. Segun T Dawodu.  February 14, 2004.
eMedicine.com
<http://www.emedicine.com/neuro/topic667.htm>

The Tale of the Horse's Tail.  Ed.  Dr. Sarah Smith.  August 2000.
The Cauda Equina Syndrome Support Group
<http://www.caudaequina.org/definition.html>.

What is CES.  Ed.  Vickie Wolfe
The Cauda Equina Syndrome Support Group
<http://www.caudaequina.org/whatisces.html>.

AAOS Online Service Fact Sheet Spondylolysis and Spondylolisthesis.
<http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID=155&topcategory=Spine>.
 
 
 

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