The body has two nervous systems, the voluntary and the involuntary. The voluntary system controls all actions that we are aware of and also nociceptive pain. The involuntary (autonomic) system handles involuntary functions, such as how fast the heartbeats. The autonomic system has two components, the sympathetic system and the parasympathetic, which parallel to the “fight or flight” responses. The sympathetic system will speed the heart up; the parasympathetic system slows it down.
The sympathetic system also can carry pain information. Pain carried by the diffuse, slow sympathetic system is poorly localized, often dull or burning pain.
We can treat this type of pain by injecting the sympathetic system to block and treat pain in different parts of the body, including the head and arms (stellate ganglion injections), the abdomen (the splanchnic nerves or celiac plexus), the pelvis (the hypogastric plexus), the legs (lumbar sympathetic ganglia) and the perineum (Ganglion Impar).
The sympathetic nerves have multiple other functions, including blood flow. Most sympathetic injections would cause warmth in the area supplied by the nerve, because of increased blood flow.
Injections of the stellate ganglion, which is in the neck, will cause a Horner’s Syndrome, which involves dropping of the eyelid on the injected side, a small pupil, reddening of the eye and dryness on the same side of the face, all because of blockade of the effects of the sympathetic nervous system.
Sympathetic injections appear to allow the sympathetic system to “reset” itself. Several injections may be required. If these repeated injections do not bring long-term relief, one can proceed to a sympathetic ganglion ablation.
Sympathetic ganglion ablations involve using radiofrequency thermocoagulation (RFTC) to heat up, block, and destroy the sympathetic nerves. RFTC is a relatively safe way of obtaining a longer-term sympathetic blockade and prolonged pain relief.