Fig. 4.

(a-c) The roots and trunks of the normal brachial plexus (BP) on magnetic resonance imaging. (d) cadaver specimen, anterolateral view. 1 – the C4 spinal nerve (not contributing to the BP), 2 – the C5 root, 3 – the C6 root, 3a- the anterior division of the middle trunk, 4 – the C7 root, 5 – the upper trunk, 6 – the middle trunk, 7 – the C8 root, 8 – the Th1 root, 9 – the ganglia of the spinal nerves C5-C8, 10 – the phrenic nerve, 11 – the suprascapular artery, 12 – the ascending cervical artery, 13 – the subclavian vein, 14 – the internal jugular vein, and 15 – the nerve point of the neck. Ant.; anterior, post.; posterior, sup.; superior, inf.; inferior.