Anatomy and evolution of accessory nerve: cranial or spinal origins?: a review

The accessory nerve is traditionally described as having both spinal and cranial roots, with the spinal root originating from the upper cervical segments of the spinal cord and the cranial root originating from the dorsolateral surface of the medulla oblongata. The spinal and cranial rootlets converge before entering the jugular foramen or within it. This conventional view has been challenged by finding no cranial contribution to the accessory nerve. Clinical, anatomical, functional and evolutionary implications are discussed in the present study.