The brachial plexus is a system of five nerve roots that exit from the spinal cord beginning with the C5 nerve root, which exits between the C4 and C5 vertebrae. The five nerve roots are known as C5, C6, C7, C8 and T1.
Nerve roots C5 and C6 make up the upper trunk (row) of the brachial plexus.
- They are the most frequently injured nerves (often called Erb’s palsy).
- These nerves tell the shoulder to move and elbow to bend.
Nerve root C7 makes up the middle trunk (row) of the brachial plexus.
- This nerve tells the wrist to move and elbow to straighten.
Nerve roots C8 and T1 make up the lower trunk (row) of the brachial plexus.
- These nerves tell the hand and fingers to move.