Sympathetic Blocks

The autonomic nervous system (ANS) is the part of the nervous system that regulates involuntary functions. It is composed of the sympathetic and the parasympathetic nervous systems (SNS and PNS, respectively). The sympathetic nervous system, in addition to its vital role as part of the autonomic nervous system and the emergency response, is thought to be involved in numerous pathologic, painful conditions. These conditions are referred to as Sympathetically Mediated Pain (SMP). SMP is often considered a result of a vicious circle of events, which include changes in peripheral and central somatosensory processes. This assumption is based upon the observations that the pain is spatially correlated with signs of autonomic dysfunction, blocking the efferent sympathetic supply to the affected area would relieve the pain. Sympathetic blocks emerged as a way to help diagnose and treat several painful conditions, including complex regional pain syndrome (CRPS), phantom pain, neuralgias, herpes zoster, and even fibromyalgia. Additionally, sympathetic blockades have been used to improve perfusion, treat angina and malignant arrhythmias, and posttraumatic stress disorder (PTSD) symptoms. This review contains 1 table and 68 references. Key words: Sympathetic nervous system, sympathetically mediated pain, sympathetic blocks, neuropathic pain, chronic pain, stellate ganglion block, celiac plexus block, lumbar sympathetic block, superior hypogastric plexus block