Spinal accessory nerve

The accessory nerve (or Spinal accessory nerve) is the eleventh of twelve cranial nerves. It leaves the cranium through the jugular foramen along with the glossopharyngeal nerve (IX) and vagus nerve (X).

Parts
Traditional descriptions distinguish two parts to the accessory nerve:
 * A spinal part, that innervates the muscles around the neck -- specifically, the sternocleidomastoid muscle (sternomastoid) and trapezius muscle on the ipsilateral side.


 * A cranial part, made of rootlets that quickly combine with the vagus nerve.The cranial part of nerve XI can be thought of doing the exact same things as the vagus. In fact, a recent reinvestigation of human material fails to detect any connection of this cranial part with the spinal part, reassigns it entirely to the vagus nerve and dismisses altogether the existence of cranial roots for the accessory nerve.

Testing the accessory nerve
Getting a person to shrug their shoulders while you push down tests trapezius. When a person turns their head, especially against force, sternocleidomastoid should be prominent.