Endoscopic thoracic sympathectomy (ETS) is a minimally invasive surgical procedure that involves the interruption of the sympathetic nerve chain in the thoracic region. It is performed to treat excessive sweating (hyperhidrosis) and certain cases of Raynaud's disease. The procedure involves making small incisions in the chest, inserting an endoscope, and cutting or clamping the sympathetic nerves responsible for the symptoms.