I just arrived back from teaching in San Diego, hosted by my amazing friend there, Rajam, who organizes the San Diego Pain Summit. Be sure to attend the one she's organizing for 2016. Robert Sapolsky will be speaking! He's awesome. So are all those other speakers! Don't miss out or you'll kick yourself.
There are only 2 weeks left to register at the early bird rate. I kid you not. After that, it's going up.
You know how ideas can chase each other around and around in one's head until they make a hole in your thinking?
I think that has happened to me again fairly recently. The idea I had turned into a cartoon.
I really do think the NS is still pretty much like this. It seems seamless in its operation most of the time, as a communication system, but that danged old ancient physiology can derail it and then the seams show.
And pain is the clue. At least, according to me. And bear in mind, I'm no expert. I just like to read, and think.
I made another cartoon, this one about the physiology of tissue healing. I threw in a few ideas about how as long as you have enough blood flow, you won't have any nociception that will "hurt" you, as long as you don't bang that sore toe or whatever...
This is all well and good. Things resolve, discomfort ebbs, eventually disappears, all is well once again eventually.
What happens if this process occurs INSIDE A NERVE?
1. Nerves are loaded with nociceptive neurons innervating their walls, and the vessels that pierce through them to feed neurons.
2. Nerves are long narrow cylinders, very self-contained.
3. They have lots of circulation - neurons need lots of oxygen and glucose to function.
4. The circulation gets in, and out, of nerves, through narrow regional vessels, which are highly subject to mechanical deformation.
4. The circulation to nerves is easily distorted. At any given point in time, some part of the peripheral neural tree is being somewhat deprived, while the rest enjoys abundance. As long as one moves about and or rests in enough varied ways, no harm befalls any part of the neural tree. In fact, it needs the challenge and the stimulation of being affected mechanically.
What happens if you develop bad stationary resting habits?
What happens if you always...
1. sit with the same foot tucked up under the other leg?
2. carry your bag on the same shoulder?
3. sleep on the same side?
4. stand with one hip up and the other down?
5. wear a toolbelt dragging you down on only one side?
6. lean on the same elbow all the time?
7. have your head turned the same way watching TV for a couple decades?
8. sit with the same leg crossed, and have for the last 25 years?
These things we do can really take a toll after awhile. If circulation is skewed too long one way for too long and too repeatedly, I can see how the products of nociceptive activation WITHIN A NERVE might not be cleared away in a timely fashion.
Then, "silent" nociceptors might activate, part of a positive biological feedback loop. Not good, those positive feedback loops...
The signs of inflammation are rubor, calor, tumor, and yes, dolor. Loss of function is considered a fifth cardinal sign.
Imagine inflammation occurring inside a nerve.
It's called "neuritis".
Now, put that together with the fact that a nerve is a very enclosed structure. How can the products of inflammation be swished away, from an enclosed space like the inside of a nerve, if fresh blood can't even get in there because of swelling? Or because regional vessels that drain the nerve have been tensioned and become narrowed or occluded, aka "mechanical deformation"? Mechanical deformation secondary to some muscle guarding the spinal cord has given rise to because it's trying to help, reflexively?
How can you move, in order to bring fresh blood into an inflamed nerve, if you can't, because of reflexive motor inhibition because the spinal cord got way too excited and is trying to protect you with reflex inhibition/spasm?
We can't get rid of nociception or peripheral hyperalgesia or neurogenic inflammation because tissues need all that "nerve net" behaviour, to become healthy again if injured. We can't lose that. But inside nerve trunks, it can all turn into an echo chamber!! Lotsa neurons all covered in sensitizing debris from other neurons, all of them raw and screaming! Like babies in wet diapers with their diaper rash stinging their undercarriages! Nothing cleans up nerves like fresh blood flow washing away the physiological byproducts of inflammation, but fresh blood can't get in, because... well... swelling. Tumor. And the old blood can't get out.
And it is not obvious swelling, because it's inside a nerve.
And not only all that, but also, the neurons will think they're starving because fresh blood can't get in with new supplies. It's a perfect storm.
I've checked the IASP site for this, and found out that neuritis is indeed a "thing".
"Note: Neuritis (q.v.) is a special case of neuropathy and is now reserved for inflammatory processes affecting nerves."Again.. : "Neuritis is a special case of neuropathy"
Even though nociception is involved, in terms of nociceptors' ability to create and add to an inflammatory response, IASP is clear that neuritis is not nociceptive "pain". Nociceptive pain is:
"Pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors."I don't think I agree entirely, because I know that nerve coverings are derived from mesoderm. Which makes them "tissue".
However, I won't quibble about it.
Mesodermal derivative is usually an innocent bystander - I blame ectodermal derivative for everything pain-related, including neuritis, because of all that ancient nerve net (the clay tablet and stylus) hooked up to the state of the art smart phone type central NS we all enjoy (or don't enjoy, depending on what is going on inside the whole enclosed system).
OK, so the question remains: How can we get rid of something like this that is excruciatingly painful, comes along seemingly spontaneously, and we can't just shake it off, because (hello?) we can't move that bit?
Well, we have to make an appointment and go see someone we hope will have some answers.
Hopefully, if it's medication, it will be effective and not mind-numbing.
Hopefully, it won't be an appointment for imaging, where all sorts of perfectly innocuous grey hair and wrinkles on the inside of the body might show up and be conflated with this awful pain experience.
Hopefully it won't be a surgical recommendation in the absence of actual life-threatening pathology.
Hopefully it will be a good human primate social groomer who:
1. Understands physiological processes and pain mechanisms
2. Can reduce stress by providing clear explanations and pain education
3. Can move the nerves carefully without adding more nociceptive input, enough that..
4. He or she can help some of it go away immediately, restore hope, reduce stress
5. Recommend safe and stress-free and easy movement homework
6. Cares enough to inquire about habitual postures and body-useage and can advise the individual in pain on how to change their own behaviour to avoid any relapse in the long term.