title: The sheath of the brachial plexus: fact or fiction?
abstract: BACKGROUND
  The concept of the axillary "sheath" has been a central tenet of brachial plexus regional anesthesia for many years. Recent investigations have cast doubt on its nature and existence. This study further examines the issue.
  
  
  METHODS
  Computerized axial tomographic dye studies were performed using continuous catheter systems for the sciatic nerve and the brachial plexus. The resultant images were compared and contrasted.
  
  
  RESULTS
  The images of the two catheter systems were the same, with the exception that one was of the upper extremity and the other was of the lower extremity.
  
  
  CONCLUSIONS
  The sciatic nerve is not surrounded or enveloped by a "sheath"--it lies in the tissue plane between rigid anatomical structures. Similarly, the brachial plexus lies in the tissue plane between the rigid anatomy of the chest wall, scapula, humerus, and pectoral fascia. This finding is inconsistent with the concept of the axillary sheath.
authors.affiliation: Department of Anaesthesia, Nelson Hospital, New Zealand. philip.cornish@nmhs.govt.nz
authors.forename: Philip B
authors.initials: PB
authors.lastname: Cornish
authors.forename: Christopher
authors.initials: C
authors.lastname: Leaper
mesh_terms: D001917:Brachial Plexus / Q000033:anatomy & histology*; D002404:Catheterization; D006801:Humans; D009407:Nerve Block / Q000379:methods*; D012584:Sciatic Nerve / Q000033:anatomy & histology; D014054:Tomography