Anatomic topographical relationship of the intraspinal accessory root to the upper cervical roots and to the vessels of the cranial cervical region.

The object of this investigation was to provide a statistical interpretation of macroscopic anatomic findings in the cranial cervical region, which is very rich in variation. In this way rare nervous and vascular variations could be related statistically. The first cervical posterior root demonstrated the most striking variations, which, according to anlage and connection with the accessory nerve, was divided into four anlage types of formation. In this way it was shown that in only 23% of the cases, no posterior C-1 root had been formed. It was further demonstrable that in at least part of the cases the accessory nerve was sensibly mixed with the first posterior root. Furthermore, nervous structures and peculiarities in the vessels were investigated. Special courses taken by the posterior inferior cerebellar artery, in addition to those already known, were statistically interpreted. Nervous as well as vascular contact and courses were analyzed, especially in relation to their topography to the accessory nerve, in order to provide clinicians with possibilities for explanations of irritations or compressions of this cranial nerve.