Some Variations in the Formation of the Brachial Plexus in Infants*

573 Abstract: The anatomical variations of the brachial plexus in human have clinical significance to surgeons, radiologists and anatomists. We studied some variations in the formation of 130 brachial plexuses in sixty-five infant cadavers (34 males, 31 females; aged 1-7 days). The brachial plexus consisted of the 5, 6, 7, and 8 cervical spinal nerves and 1 thoracic spinal nerve (69.23%). We found that among the 130 plexuses, 30.77% also received a contribution from C4 (Fig.1, A ) . The variations in the formation of brachial plexuses were classified into three groups. Group 1 had a variation in the formation of the median nerve (10.77%), with fusion of three branches; one each coming from the lateral and medial cords; and one coming directly from a branch of the anterior division of the middle trunk (Fig.3,A). Group 2 had three anterior division cords: a) the lateral cord formed from anterior division of the upper trunk (Fig.2, A); b) an “intermediate” cord formed from the anterior division of the middle trunk and c) the medial cord formed from the anterior division of the lower trunk (3.07%). In group 3, there was a rare variation of the medial cord (1.54%) which receives an anastomotic branch from the posterior division of the middle trunk (Fig.4, B). The anomalies of the human brachial plexus have clinical importence in diagnosis of injuries of the brachial plexus.