FIG 4. A and B, STIR images of the brachial plexus (A) and nerves entering upper arm (B). The components of the brachial plexus (arrows in A) have a higher signal intensity than that of skeletal muscle, whereas nerves in the upper arm (arrows in B), emerging from the brachial plexus and nearly parallel to B₀, are isointense or slightly hyperintense to muscle.