Ooh, that's interesting. Immediately made me wonder about the difference.
Found someone on the web having tried to find it out saying "from what I gathered the only difference between the two is that you get a pressure/squeezing sensation in your chest with IN". Someone else answered a sharp sternal pain was first seen by docs as being "costo", but as it continued and no tests found anything (but I doubt they would...) they were recommended to see a neurosurgeon for IN. Someone else said they assume costo is less long lasting, so it's easier to get meds with the diagnosis IN. However also mentions Tietze syndrome and calls all 3 blanket terms for rib/chest pain, cos it's hard even for docs to see the difference. With nerve component pregabalin/Lyrica might help.
painscale has a summary of all three. But tbh comparing I can only see that Tietze means there's a sternum swelling, whilst I can't see any diagnostic difference between costo and IN.
What is described on painscale if it hurts when you move and they press they can diagnose IN. Wow. epainassist says 1) general blood tests for inflammation, 2) eye tests if eye, 3) lumbar puncture for meningitis and encephalitis. 4) EMG, nerve conduction, 5) nerve biopsy, 6) scans.
My rheums did #1, my sleep lab psychiatrist 3, my neurologists 4 and 6, but found nothing.
And somehow I very much doubt they're gonna be doing anything specific for ribs/chest.
So I spose if we think there is nerve involvement trying a supp like capsaicin is a good test.
For me personally, treating a nerve is not going deep enough to the cause. Many of my more extreme and long term local pains seemed as if nerves were involved, and some people I know are very quick to recommend cortisone for everything. Again, my experience is that with the right bodywork, the muscles and nerves recover and don't need (much) substances. You gotta be up to bodywork