The term “Brachial plexus” means grouping of nerves to the arm. Brachial meaning of or related to the arm, and plexus meaning a grouping of nerves. The brachial plexus is a complex intertwining of sensory and motor nerve structures from the fifth through the first thoracic spinal nerves.
The brachial plexus originates at the Cervical C5 through Thoracic T1 spinal nerve roots and exit the posterior portion of the neck. These nerve roots are named by the location where they exit the spinal column. While there is some variation from person to person, the nerve roots are fairly constant in the muscle groups that they innervate, or carry signals to. These nerve roots come together and separate along their course from the neck. They form trunks, divisions, cords and finally branches, coursing through to the shoulder, arm and hand. We use EMG studies to trace the signal through the nerves to their ends where the impulses are converted to muscle function. This allows us to evaluate the extent of individual injuries.
Each nerve root carries a signal and activates a specific muscle group of the upper extremity. The C5 nerve root elicits deltoid function as shoulder abduction, extension and external rotation. The C6 nerve root elicits shoulder adduction and flexion, elbow flexion, and forearm supination. C6 and C7 provide internal rotation of the shoulder. C7 contributes to elbow, wrist and finger extension. Finally, C8 and T1 elicit wrist and finger flexion and intrinsic muscle function.