Lumbar Spinal Stenosis - Causes Symptoms and Treatment

What is Lumbar Spinal Stenosis?

Lumbar spinal stenosis is caused by a narrowing and loss of space either in the central canal where the spinal cord sits or where the nerve roots exit from between the vertebrae.

Symptoms will vary depending on which of these two problems you have. It is a relatively common condition – many of us have a degree of stenosis and are completely unaware that we have these changes as they are asymptomatic much of the time. Generally the narrowing is caused by progressive changes to the spine as it ages.

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To understand lets take a look at some anatomy so you can see what I mean.

The spine is made up of vertebrae which form a bony tunnel running down the whole length of the spine, this channel is called the spinal canal. The tunnel is made up of bone and the ligaments that support the vertebrae, including the anterior longitudinal ligament which runs along the whole length of the spinal canal. The spinal cord normally sits here safely protected in its bony tunnel.

spinal stenosis
Vertebra from the top down showing the
spinal canal space in a normal spine.

At each vertebrae a pair of nerve roots leave the spine and form the peripheral nerves, these are the nerves that run down your legs. There are two major nerves in your legs:

  • the sciatic nerve at the back of your leg
  • the femoral nerve at the front

The nerve roots leave the spinal column through a gap between the vertebrae which is called the foramen.

spinal canal diagram
The spinal canal - this sometimes narrows and
can squeeze the spinal cord

As we get older our spine changes and alters in response to the stresses of a lifetime. These changes are most commonly seen in the facet joints (facet joint arthropathy) or the discs (degenerative disc disease).

  • The discs may bulge backwards into the canal and their height also reduces which increases stress through the facet joints.

  • The facet joints often respond to this pressure by growing some more bone.

  • These small bony outcrops are called osteophytes - very often they just sit there and don’t cause any problems.

  • The ligaments in the spine also thicken and become stiffer and less flexible, especially the posterior longitudinal ligament (the one at the back).

As this process creeps up on us, gradually the changes may intrude into the spaces that the spinal cord and nerve roots need.

Lumbar spinal stenosis symptoms only arise when the space becomes small enough to compress the spinal cord or the nerve roots.

  • When you lose space in the middle, the spinal canal, it is called spinal canal stenosis

  • A loss of space in the gap where the nerve leaves the spine is called foraminal stenosis

x-ray showing a umbar spinal canal stenosis.
X-Ray showing spinal stenosis

 

 

 

In this little image note the discs bulging backward and squashing the spinal cord in addition to changes at the back of the canal causing compression. Image courtesy Wikimedia

 

 

 

 

 

Another common cause of spinal canal stenosis is lumbar spondylolisthesis, usually as a result of aging and degenerative changes in the lower back. A spondylolisthesis is where one vertebrae moves in relation to the one below.

degenerative lumbar spinal canal stenosis caused by spondylolisthesis
Lumbar spondylolisthesis

All these changes have one thing in common – they cause a compression of your nervous tissue which may eventually cause a mixture of symptoms of pain, weakness, tingling and numbness in the feet and legs.

Lumbar Spinal Stenosis Symptoms

  • If the main problem is foraminal stenosis then the symptoms will be very similar to a normal nerve root irritation called a radiculopathy.

  • In younger people this is most usually caused by a bulging or prolapsed spinal disc and is called sciatica, as it is normally the sciatic nerve which is irritated.

  • Symptoms can include pain, usually in a distinct pattern or dermatome, depending on the level affected.

  • Numbness and weakness is also usually in a predictable pattern and commonly the symptoms will be on one side only

  • If the problem is a central spinal canal stenosis then the symptoms are often much more confusing. One of the classic things that alerts me to this condition when I see someone that I suspect may have this is the lack of a pattern.

  • The symptoms may affect one or both legs, they may be in the top of the thighs or just in the lower legs and feet.

  • They tend not to follow a nerve root (dermatomal) pattern but to be more diffuse and mixed.

  • Numbness, tingling and sometimes weakness are not uncommon in both or one leg.

  • One of the more common findings is a dislike of extension or standing tall activities.

  • Walking, especially uphill, can bring on the symptoms, whereas flexion or bending activities tends to ease it.

Therefore things that make it feel worse tend to be:

Things that make it feel better tend to be:

  • Bending forward
  • Sitting in a soft chair
  • Lying curled up or on a softer mattress

I have met many older patients who set off walking, develop symptoms, perch or sit for a while on a wall or something, or lean forward. The symptoms ease and they can go on a bit further until it happens again. This stop-start behaviour is very common with this problem.

Case example


Mr Smith was a 75 year old man who came to see me with pains in both legs and feelings of numbness in his feet. The pain in his legs did not follow the pattern you would see with a 'pinched' nerve, the symptoms were more spread out and patchy.

These symptoms had come on gradually over the last two years and had become worse recently. He felt at his worst when he was walking and they were especially bad every morning when he took his dog for a walk. 

Most mornings he would be able to walk for about 500 yards with his dog and then and his pain and numbness would come on He had learned to cope with this by bending over to stroke his dog or fiddle with its collar for a few minutes and then the symptoms would ease. He could then walk another 500 yards before they started again.

X-rays and an MRI scan showed spinal stenosis - he went on to see a spinal surgeon.


Diagnosis of lumbar spinal stenosis

Many of the physical tests we perform in the clinic will give us a good idea if this is the root of the problem.

  • Taking a thorough history and finding out if the aggravating and easing activities match the expected pattern.

  • Neurological tests such as reflexes, sensation and power can show changes.

  • Straight leg raise tests may be positive in a foraminal stenosis.

  • However, in order to get a definitive diagnosis you need imaging such as X-ray or Lumbar MRI scan.

  • Spinal stenosis symptoms may be similar to those caused by a reduction in blood supply to the legs (vascular disease and intermittent claudication) therefore it is important that this is ruled out.

spinal canal stenosis MRI
© Nevit Dilmen via Wikimedia Commons
this image shows a neck central canal stenosis
MRI but the same principles apply in the lower back

Lumbar Spinal Stenosis Treatment

If the symptoms are not severe usually conservative treatment is tried first.

  • This involves physiotherapy with advice on stretching exercises and posture etc.

  • If this does not offer relief an injection may be considered to reduce pain from a nerve root.

  • Failing this the next course of treatment is spinal stenosis surgery.

What is the difference between stenosis, sciatica and peripheral neuropathy?

Central spinal stenosis tends to affect both legs, although foraminal stenosis can give similar symptoms of sciatica.

Peripheral neuropathy tends to have a different presentation and a much more distinct sock pattern of sensory changes.

In truth though these are just general patterns, everyone is different and there is no perfect checklist which tells us what the problem is, its more a case of building a picture from many different considerations of symptoms and history.

So in order to tease these things apart and get a proper diagnosis you need to go and see a doctor.

Understand a Normal MRI scan Video - helpful when picturing the problem

 

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Links to more lumbar spinal stenosis information

PubMed Health

This is a good evidence based primer spinalstenosis.org

Patient information

 

More Causes of Numbness

Lower Back Pain Toolkit Home Page

All case studies on this site are fictional and are based on my combined experiences - they do not describe any one individual.

01-Feb-2013

 

 

 

 

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