Can't help with info about lumbar sympathetic blocks but just wanted to ask if you have been checked out for a vascular blood flow issue causing the chronic leg pain?
I ask because, whille I don't have a leg pain issue from it myself, I have renal Nutcracker Syndrome (NCS) and this can be a 'mystery cause' of leg pain. Or if not this, then iliac vein compression (May-Thurner Syndrome) can be another (standalone) mystery cause of leg pain, and not uncommon to also occur as a comorbidity in those with NCS as well.
My large arteries and arterioles are all normal. Similar to what long covid patients describe, I have a pain and temperature sense dysregulation. After a hot shower I often experience a lacy skin rash over my legs. Sometimes my feet either look white or flushed after getting out of bed.
Perhaps viruses can affect/alter the autonomic nervous system permanently. Does this also partially explain changes to CNS interoception? Is this the reason why some MECFS patients respond to but are not cured by benzodiazepines?
I hope more researchers study this possibility further but in the meantime I am trying to gauge the risk of trying a procedure that may alleviate some chronic misery.