Over and over again the subject of “pinched nerve”, “slipped disc”, or back/neck pain comes up. Often, absent a physical model to show a person, I find myself straining to give a verbal description to the suffering patient, so that he or she might better understand that lancinating electrical shock that radiates down their arm or leg. This usually degenerates into a quasi-artistic and ersatz modern-dance-physical-demonstration of the vertebral column.
It goes something like this:
The bones of the spinal column (the vertebrae) are like a totem pole. You know, that stack of sections of thick logs with carved and painted faces and arms, each one squatting upon the head of the other like building blocks. (It is at this point I assume the appropriate posture).
Now, between each “totem” is a cushion, separating the flat head of the lower one from the flat butt of the higher one perched on his head. (I’d want a pillow there, too). This is the “disc”, made of cartilage mostly around the rim and a spongy gel-like substance in the middle for shock absorption and flexibility. (Picture a jelly doughnut).
(This is where it gets really artsy): Each totem (vertebrae) has a pair of thick arms called “pedicles” that extend toward the back, clasping their hands so that the trunk of the totem and the encircled arms form a shape not unlike a napkin ring.(Now I look a bit like a praying frog). The rings formed by the clasped arms of the totems, one on top of the other, line up. This is the “spinal canal”, the passageway through which the spinal cord descends from brain to tailbone.
(It gets really tough here): Imaging that each pair of thick arms extending backwards has another pair of arms extending upward and a stubby pair of legs (just feet, really) extending downward. (Now I look a bit like and Egyptian painting or hieroglyph, or Steve Martin doing “King Tut” with his arms extended in angular posture toward the sky).
The arms of each totem reaching up from below are braced against and connected by a flexible joint-like structure to the legs or feet of the totem above. These are called “facet joints.” (At this point I am doing crazy gyrations alternating arms up and arms down demonstrating the posture of the totems, one on top of the other… I haven’t figured out how to do this in any manner that’s not totally ridiculous… Mr. Martin would be proud).
There’s a relatively small space left over between these extended and joined arms and legs and the body of the vertebrae above and below, out of which come the nerve roots that extend from the spinal cord itself. It’s when one of these nerve roots gets pinched that problems occur.
It could be a herniated disc. (I’ll devote another blog to the concept of “hernia”.) That’s when that pillow cushion (the jelly doughnut) bulges out from its normal confines separating heads and butts to push on one of the nerve roots or even on the spinal cord itself. It could be a bone spur on the back of the vertebrae or on one or more facets (usually the result of arthritis or degenerative disease of the spine) that causes a narrowing of that space through which the nerve roots travel.
That’s a “pinched nerve.”
One other thing that’s not a pinched nerve but often hurts just as much is back or neck spasm (the so-called “crick-in-the-neck”). Think of it this way:
All along those stacked totems, connecting their outer edges one to the other is a layer of connective tissue (ligaments) and short muscle fibers. Their purpose is to keep those vertebrae lined up at the proper angle even when the back or neck twists or bends, so that the spinal cord is protected as it travels down the stack of “napkin rings”. These ligaments and muscles are chock full of extremely sensitive nerve fibers that will detect any hint of misalignment (such as could happen if you stretch, bend, or reach in an awkward way, or sleep wrong, or get hit from behind). Detecting such movement, these nerve fibers send out a panic “lock-down” signal accompanied by major pain.
They’re just doing their job. Making you stay still. Protecting your spine until all is well. And making you miserable and immobile until the “all clear” signal is given. This can sometimes take weeks. The pain keeps you from moving and doing more damage. It stinks.
If the pain doesn’t go away or that radiating pain down the arm or leg comes on… it’s not just a spasm. It’s a “pinched nerve”.
Now, is that perfectly clear?
Maybe I should just keep anatomical models in every exam room.