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.
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.
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:
Vertebra from the top down showing the
spinal canal space in a normal spine.
The nerve roots leave the spinal column through a gap between the vertebrae which is called the foramen.
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).
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.
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.
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.
Therefore things that make it feel worse tend to be:
Things that make it feel better tend to be:
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.
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.
Many of the physical tests we perform in the clinic will give us a good idea if this is the root of the problem.
© Nevit Dilmen via Wikimedia Commons
this image shows a neck central canal stenosis
MRI but the same principles apply in the lower back
If the symptoms are not severe usually conservative treatment is tried first.
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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This is a good evidence based primer spinalstenosis.org
All case studies on this site are fictional and are based on my combined experiences - they do not describe any one individual.