At the top of the interscalene groove the brachial plexus presents as the C5 and the C6 spinal nerve branches – and usually the C6 is split in two branches
The three profiles of C5 and C6 are usually lined up like a string of black pearls sandwiched between the anterior scalene muscle and the middle scalene muscle
The string of black pearls made up by the spinal nerve branches of C5 and C6
