The sympathetic nervous system is generally considered the “fight-or-flight” part of the nervous system and responds to neurotransmitters such as epinephrine (adrenaline) and norepinephrine (noradrenaline). Sympathetic nerves are located throughout the body, and help to regulate blood flow and sweat glands. They are also found in the eye, and affect the size of the pupil to let more light into the eye. We have found that the sympathetic nerves often travel alongside nerves that communicate chronic pain, and are hypothesized to contribute to a painful process when there is some disruption of normal functioning of these nerves.
The term, ganglion, refers to a collection of nerves, in this case, of the sympathetic nerves. They are located in front of the spine and are accessible by the pain specialist for injection of local anesthetic, in an attempt to interfere with the ongoing transmission of pain. When the Sympathetic Ganglion is exposed to local anesthetic, the effect of the sympathetic neurotransmitters is blocked, and pain relief may occur. The blood vessels in the area of blockade begin to dilate, the skin warms, and eye changes may occur as side effects to the local anesthetic (temporary effect).
Sympathetic ganglion blockade is often performed for a painful disorder known as Complex Regional Pain Syndrome (CRPS), formerly known as Reflex Sympathetic Dystrophy (RSD) and causalgia. This syndrome is usually characterized by hypersensitivity of the skin, a burning or cold sensation, pain with motion, skin and nail changes, abnormal hair growth, and abnormal temperature regulation, usually confined to the affected part of the body. This syndrome is often caused by prior trauma or surgery.