SCALENE MUSCLES AND THE BRACHIAL-PLEXUS - ANATOMICAL VARIATIONS AND THEIR CLINICAL-SIGNIFICANCE

Anatomical variations may be clinically significant, but many are inad equately described or quantified. Variations in neck anatomy are impor tant to surgeons performing surgical procedures in this region. Thirty -two female and 19 male adult cadavers were studied. The commonly desc ribed anatomical relationship of the brachial plexus (BP) lying betwee n the anterior scalene (AS) and middle scalene (MS) muscles was found in only 60% of instances. Scalenus minimus was present in 46% of insta nces (bilateral in 14 cadavers). The most common variation was the pen etration of the AS by the C5 and/or C6 ventral rami. The C5 and C6 roo ts may fuse before piercing AS (15% cases, bilateral in 4 cadavers), o r the C5 root alone pierce the belly of AS (13% cases, bilateral in 3 cadavers). The roots also may pierce AS independently (6% cases, bilat eral in 1 cadaver). In 3%, the C5 root was found to be completely ante rior to AS. (C) 1997 Wiley-Liss, Inc.