The ansa subclavia: a review of the literature.

The ansa subclavia, subclavian loop, Vieussens' ansa or Vieussens' loop is a nerve cord that connects the middle cervical and inferior cervical sympathetic ganglia, forming a loop around the subclavian artery. The structure of the ansa subclavia is evolutionarily conserved from rats, guinea pigs, the porcine species and dogs to humans. A common application in physiological studies is to electrically stimulate the ansa subclavia in animal models as a robust protocol to modulate stimulatory cardiac sympathetic input. Despite a large number of physiological studies utilizing the ansa subclavia, only very brief descriptions have been devoted to it in standard anatomy texts. An extensive search found only one report in the English language literature concerning the anatomy of the ansa subclavia. The aim of this report, therefore, was to provide a comprehensive review of the clinical anatomy of the ansa subclavia and to discuss its potential physiological functions.