Subclavian loop
Subclavian loop, also known as Vieussens' ansa after French anatomist Raymond Vieussens, is a nerve cord that is a connection between the middle and inferior cervical ganglion which is commonly fused with the first thoracic ganglion and is then called the stellate ganglion. The subclavian ansa forms a loop around the subclavian artery; whence its name. This communicating branch downwards anteromedial to the vertebral artery makes a loop around the subclavian artery from anterior to posterior and then lies medially to the internal [thoracic artery] respectively. Sometimes there are two communicating branches encompassing the vertebral artery, one from anterior and the other from posterior.