Lumbar spine and Lumbar spinal cord - There IS a Difference

Okay, now I might be about to confuse everybody - tho I hope not.  nd I hope that I attached a picture of what I am saying to the top.

We always say there are no MS lesions in the Lumbar spine, yet we sometime read where someone has referred to an MS lumbar spine lesion.  Here is what's up.

First, think of the bony spinal column with the vertebrae surrounding the spinal canal.  We all can picture this as it is our backbone.  This is rightly referred to as our SPINE.  There are four main sections of the bony spine, the cervical part (8 vertebra) the 12 vertebrae of the thoracic spine, the 6 vertebrae of the lumbar spine and the 5 fused vertebra of the sacral spine.  Well, and there's the dinky little talibone, called the coccyx.

Now, we know that the spinal cord runs down inside the vertebrae.  However, the spinal cord is shorter than the full length of the bony spine.  It extends to just about the level of the 12th thoracic bone ending by the beginning of the first lumbar vertebra.

When we talk about MRIs of the spinal cord, then, we are only talking about needing to image the cervical and thoracic spine to capture the entire spinal cord in the imaging.  MRIs of the Lumbar bony spine will not capture any part of the Central Nervous System or the spinal cord.  (Now in reality, MRIs of the lumbar spine often do capture a little bit of the bottom end of the spinal cord by accident.  That is why we will occasionally hear about lower thoracic MS lesions on a report from the lumbar spine.)

Confused yet?  Actually, I think we all have this much pretty securely in our minds.

But, what we don't often think about is that the spinal CORD has the nerves that go out to the entire body within it, even though it is short.  The top part of the cord has the cervical section, the middle the thoracic nerves and the bottom of the cord actually does have white matter in it that sends out the nerves that travel down the rest of the canal before they exit through the holes in the bony lumbar spine and the bony sacral spine.  These nerves flow downward and are referred to as the cauda equina (the horse's tail).

So, in reality there IS a section of the spinal CORD that can accurately be refered to as the LUMBAR section, even though it is not at the level of the bony lumbar spine.  So, it is not inaccurate to refer to the "lumbar section".  However, I think some doctors are still confused about this and still go about looking for MS lesions by doing Lumbar MRIs.  That is completely incorrect.

Comments confusing the two "lumbar" sections have come up recently on the forum and I have been meaning to explain this.

The best diagramn that I have found showing the relationship of the spinal "cord" to the bony spinal column is this:  (scroll down a bit to see this)

http://www.apparelyzed.com/spinalcord.html

Look at the picture and see the canal and see that the nerves that will leave the lumbar and sacral spinal column have left the spinal "cord" way up in the lower section of the spinal cord at the level of the thorax.

Now for the questions.

Quix

[Eyesnlegs]

Thanks for another gem

I met up with a friend I had not seen since our babies were at pre-school the other day - too many years ago to mention here - lol - and after chatting for a while she asked me about my cane.

Now that was an interesting conversation as it seems she was suspected of MS too but was dx with Adhesive arachnoiditis and she had to travel the length of the UK to see a University Prof who linked up with a US expert to get the dx.

She have me an education in the lower spine anatomy.

Thanks so much Quix I will pass this on to her too.

Pat x

[Quixotic1]

Here is a link that discusses where all the nerves pass through and what attaches to what.

and it is the source of the pic above.  I should have referenced it in my post.

http://www.apparelyzed.com/spinalcord.html

Q

[Quixotic1]

Also, our T-Lynn (youngatheart) has both diagnoses, MS AND Adhesive Arachnoiditis.  Bummer.  AA is horribly painful.  If you do a search of this community on it you can read her descriptions.

Quix

[Eyesnlegs]

Thank you

[jensequitur]

Thanks, Quix!  I've been doing lots of research on this lately, as my right knee is weak and numb.  (Just got the MRI report yesterday!)

It's very specifically the right knee, which I understand is L3.  But I hear that the thoracic spine can go as low down as L3, right?

[essdipity]

That's not what I understood.

I think what Quix is saying, and am open to any and all corrections, is that nerves that start at the T-spine come down through the cord and exit at the L-spine.

ess

[jujuminx]

Wow!  Thanks so much for sharing this.  When my neurologist ordered a cervical and thoracic MRI I wondered why he didn't just do the whole thing.  Now I know and apparently he knows what he is doing.  Nice to know.

Julie

[jensequitur]

I probably didn't express myself very well!  What I meant was that a lesion at T11 could affect parts of your body that were ennervated by the lumbar.  Although that graphic doesn't allow for a lesion at T11 to affect L3.

[Quixotic1]

Jen - the diagramn is not a "perfect" representation.  The level of T11 to T12 does sprout off the nerves that descend in the canal to exit through the lumbar and sacral bony spine.

No the spinal cord does not usually extend that low (L3) in nonmalformed people.  It will sometimes end right at the L1 level.

The point is that the lower back's nerves have their origin in the lower part of the spinal cord.  That lower part of the spinal cord is still at the same level of the lower thoracic bony spine..  the nerves exit the cord and travel down loose in the canal until they arrive at the level of their exit.

So a thoracic spinal "cord" lesion can affect things, like the bladder or the parts of the foot, that have their exit out into the body down through the "sacral bony spine".

I know this is confusing.

Quix

[Lulu54]

Q-
Is there going to be a test on this one?  I will have to study this over and over to get it entirely, but this is a very good start for me.  

The links are very good, too.  They go very well with your explanation. This should also be a HP.

Now, can we go for ice cream?  My brain needs  a break.  LOL

-L

[jensequitur]

Hey, Quix - so my lesion at T11 could affect my knee specifically?

[Quixotic1]

Jen - I have spoken at the level of understanding of the anatomy involved that I have.  Your question presses me into an answer I don't have.  And you know how I feel about  trying to dierectly map lesions to symptoms.  My neuro feels that most of the lesions on the thoracic cord are too small to be seen and they are difficult to image at best.

My answer - I don't know.  I was only trying to convey the point that there is a part of the bottom of the spinal cord that deals with the nerves that will exit the lumbar and the sacral bony spinal column.

Sensation at the knee is by nerves that "exit" at L3 and L4 which is tyically below the bottom of the cord.  I can't tell you exactly where they are in the cord.  

But, aslo remember that higer lesions can affect the lower structures because the nerves originate much higher - usually in the brain and travel down the entire length of the cord until they exit the cord.

Quix

[Heather3418]

Fantastic piece.  Great information and easy to understand.

You're right, it's all hard to understand and to picture in one's mind.  I learned early that MS lesions are usually confined to the cervical and thoracic region or any area in the spine that has some white matter in it.

Is the "horse tail" called grey matter?  If not, what is it called.

Thank you for taking the time to spell all this out for us.  You are a god-send and I love you more than my Eddie Bauer luggage.  I really do.

Hugs,
Heather
(Earth Mother)

[jensequitur]

Thanks, sweetie!  You've already helped a lot.  I agree with you on the mapping lesions to symptoms thang - it just makes neuros want to look for a lesion to explain every symptom.

Isn't the horse tail called cauda equina?

[Quixotic1]

wow......I'm ranking higher than Eddie Baier luggage!!!  I own some of that.  I am sooo honored.

Heather - You asked the very question that I have not chased down yet.  And that is whether the nerve fibers in the cauda equina (yes, Jen) have yet become peripheral nerves or if they are still part of the CNS.  It depends where the vertebral ganglia are.  I will look, but would appreciate it if anyone alreadys knows.

Q :))

[jensequitur]

I've been looking for more information, but online resources are pretty slim.  They all say basically the same thing.