Not a bad day overall, despite waking up with intense right shoulder pain. I wish I could understand the terms for Joint range of motion, but just like knowing my left from my right, I cannot fathom ad and ab and ex and flex, and rotation just sends me round the bend. So all I can say is that certain movements were more stabbingly painful the others, the stabs coming behind the clavicle and down under the shoulder blade. It’s an odd pain, the type of pain that includes sudden weakness and loss of strength, which I believe to be a sudden motor nerve conduction block or slowing.
There was a good explanation on an old CMT UK Comment article from a geneticist, I think her name was Neva Haites, perhaps my memory fails me, but it does seem to be the type of name that is hard to forget.
She describes the myelin as being like a swiss roll, due to the way it spirals around the axon, making ever greater layers of compact myelin (cake). The ingredient, that helps it all stick together is the Jam, in nerve terms this has pmp22 as an integral component.
In HNPP the jam is rather thin and not viscous enough to stick the layers of cake together particularly well and it tends to thin out and run more easily. If the cake is compressed all the jam starts to squidge out of the way, eventually falling out of the end. In the case of the nerve it would mean that the extracellular goo (words fail me) bunches up against other squidged out regions of extracellular goo (Jam) and form areas where the goo is bunched up, and areas with a depletion of goo (pmp22 jam). Regions with little jam cause the cake layers (myelin) not to stick together. Bunched up areas of Pmp22 jam look like sausage shaped swellings (tomacula = a latin sausage). This isn’t good for nerve conduction. Eventually regions of cake without enough jam fall apart from one another, ie myelin becoming uncompacted, disintegrates, eventually exposing the axon (demyelination).
If the pressure is not strong enough to separate the goo into sausages, does that mean that the goo will squidge for a while then slowly seep back, and eventually allow reasonable nerve conduction speeds. While the goo is squidged the nerve conduction is temporarily impeded. It can never fully recover and eventually will clump into sausages (tomacula) after further episodes of compressive force. Perhaps this is the repetitive, short lasting palsy (or disturbance in nerve conduction) which gradually develops into permanent weakness. In this case the weakness is slowly progressive being accumulative in onset, as opposed to the sudden but long lasting and potentially permanent weakness induced by stronger compressive forces or pressure.
Sensory nerve involvement will affect A-delta myelinated nerves as well as the larger A-Alpha and A-beta myelinated mechano-sensory nerves. The A-delta nerves will include those nerves which transmit fast pain signals, causing repetitive stabbing, pins and needles, and electric type pain, as opposed to the non-myelinated c-type small fibers which signal slow dull and throbbing pain.
Isn’t this fast electric stabbing pain with pins and needles the same as that experienced when the ‘funny bone’ is hit? That’s what it feels like to me. With HNPP there are many ‘funny bones’, at all the points these A-delta pain nerves are pinched, trapped, temporarily struck, or pressed.
So it’s all about cake… Anyone fancy a cuppa tea with their cake.
This exploration of cakey runny jam pain, does not include other modes of secondary pain, muscular pain, joint pain and recruited pain as a result of sudden, intermittent,and permanent nerve conduction dysfunction. These can be managed once the primary pain is recognised and understood.
All this talk of cake…. it must be Sunday.