RESUMO
Median nerve is commonly formed by the union of the lateral and medial cord of the brachial plexus, which embrace the third part of the axillary artery. Formation of a median nerve’s loop is a very rare condition. We present a cadaveric case, in which the right median nerve was found at the upper arm forming a fusiform neural loop penetrated by a superficial brachial artery, which continued over the forearm as the radial artery. The literature concerning nerve loops and traversing arteries is discussed, as well as the relevant embryology. We consider that such nerve loops constitute vulnerable sites of the nerve trunk since it is compressed by the pulsation of the abnormal traversing artery. Moreover, neurosurgeons should keep in mind that in case of existing arterial variation, variation of the associated neural structures may co-exist.