Endoscopic thoracic sympathectomy (ETS) is a surgical procedure in which a portion of the sympathetic nerve trunk in the thoracic region is destroyed. ETS is used to treat excessive sweating in certain parts of the body (focal hyperhidrosis), facial blushing, Raynaud's disease and reflex sympathetic dystrophy. By far the most common complaint treated with ETS is sweaty palms (palmar hyperhidrosis). The intervention is controversial and illegal in some jurisdictions. Like any surgical procedure, it has risks; the endoscopic sympathetic block (ESB) procedure and those procedures that affect fewer nerves have lower risks. Sympathectomy physically destroys relevant nerves anywhere in either of the two sympathetic trunks, which are long chains of nerve ganglia located bilaterally along the vertebral column (a localisation which entails a low risk of injury) responsible for various important aspects of the peripheral nervous system (PNS). Each nerve trunk is broadly divided into three regions: cervical (neck), thoracic (chest), and lumbar (lower back). The most common area targeted in sympathectomy is the upper thoracic region, that part of the sympathetic chain lying between the first and fifth thoracic vertebrae. Indications The most common indications for thoracic sympathectomy are focal hyperhidrosis (that specifically affects the hands and underarms), Raynaud syndrome, and facial blushing when accompanied by focal hyperhidrosis. It may also be used to treat bromhidrosis, although this usually responds to non-surgical treatments, and sometimes people with olfactory reference syndrome present to surgeons requesting sympathectomy. There are reports of ETS being used to achieve cerebral revascularization for people with moyamoya disease, and to treat headaches, hyperactive bronchial tubes, long QT syndrome, social phobia, anxiety, and other conditions. Surgical procedure ETS involves dissection of the main sympathetic trunk in the upper thoracic region of the sympathetic nervous system, irreparably disrupting neural messages that ordinarily would travel to many different organs, glands and muscles. It is via those nerves that the brain is able to make adjustments to the body in response to changing conditions in the environment, fluctuating emotional states, level of exercise, and other factors to maintain the body in its ideal state (see homeostasis). Because these nerves also regulate conditions like excessive blushing or sweating, which the procedure is designed to eliminate, the normative functions these physiological mechanisms perform will be disabled or significantly impaired by sympathectomy. There is much disagreement among ETS surgeons about the best surgical method, optimal location for nerve dissection, and the nature and