It is a group of nerves located on each side of your cervical-thoracic vertebrae (the bones in your neck and chest part of your spine).  Signals from the brain stop there before going to the rest of your body.  Information for this ganglion is also relayed to the rest of the body including the face, brain, head, neck, arms, and chest.  You have one of these on each side of your neck.

It is a way to interrupt the signals going in and out from the stellate ganglion by numbing the ganglion with a local anesthetic such as lidocaine, ropivacaine, or bupivacaine.  This is performed under live ultrasound guidance at least in practice, but it can also be performed with fluoroscopy or live x-ray guidance.  This procedure is an injection but it is tolerated very well even awake.  We also block the C3 or C4 area which contains the superior cervical plexus and the sympathetic tract or road to the brain.  This is not technically part of the actual SGB, but has been shown to improve results by Dr. Eugene Lipov, MD.