The sympathetic nervous system has been implicated in numerous pain syndromes while interruption of the sympathetic flow has been proven to relieve certain pain syndromes. Such pain syndromes are referred to as Sympathetically Maintained Pain Syndromes (SMP).
Sympathetically maintained pain presents clinically with neuropathic pain picture i.e. burning, Stabbing, shooting in nature. There is no gold standard criteria to determine if the neuropathic pain syndrome is SMP or not.
The classical targets for sympathetic blockade are the sphenopalatine ganglia (for vascular headache, and cranial neuralgias), stellate (cervicothoracic) sympathetic ganglia (for SMP and vascular disorders, in the upper extremities), celiac/splanchnic plexus (abdominal SMP and visceral malignant and non- malignant pain), lumbar sympathetic ganglia (lower extremity SMP and related pain syndromes), superior hypogastric (for pelvic pain and pelvic visceral malignancies), and ganglia impar (peri-anal and rectal pain).