The mechanisms of radicular pain, with Annina Schmid [Repost!]
54 min
We’re still working on the cover design for our upcoming book Understanding Sciatica - a frustratingly long back-and-forth process with the designer that I wish I’d started much earlier… In the meantime, I thought I’d re-send this podcast that Annina and I recorded in September 2020. It’s still the most popular episode of the pod. Might nerve pain be the most interesting thing in the world? Below are the timestamps for the Q&A, with some relevant pictures and links. (Please by aware if you are reading this through your podcast app, the pictures and links may not show). If you have not heard from Annina before, I recommend her episode of The Physio Matters Podcast as a good introduction on this topic. Today’s podcast takes more of a deep dive! Timestamps 0.00 - 2:55: intro 2:55: is radicular pain neuropathic? I reference Annina and Brigitte Tampin's classification for low back related leg pain which you can see more about here Annina mentions the NeuPSIG grading system for neuropathic pain: 6:48: ectopic activity from abnormal impulse generating sites Ectopic means "in the wrong place". Ectopic activity means action potentials arising from the wrong place in the nerve. For example, instead of arising in the peripheral terminals as they should, action potentials can be generated in the nerve trunk or the dorsal root ganglion. In entrapment neuropathies, this will typically happen when a patch of the nerve becomes demyelinated and ion channels lodge in that part of the cell membrane. This picture shows the process in a nerve that has been completely cut, but the concept is the same for nerves that are merely crowded out. 9:07: mechanisms of stress-induced radicular pain I mention a paper by Elspeth McLachlan which found that after sciatic nerve ligation, noradrenergic axons in rats sprout into the dorsal root ganglion and form basket-like structures which can activate sensory neurons. 12:19: allodynia, wind up and other neuropathic pain features in radicular pain 14:5...