The term spinal accessory nerve plexus may be defined as the spinal accessory nerve with all of its intra- and extracranial connections to other nerves, principally cranial, cervical, and sympathetic. The term, however, is not new (1). This review discusses its anatomy and blood supply in head and neck cancer and atherosclerosis. For many centuries, the knowledge gleaned from studies of neural and vascular systems in general and their embryology has given us the tools to describe this plexus. For example, early descriptions of cranial nerves were incomplete (2, 3) until 1778 when von Soemmering established the now accepted number of cranial nerves as 12 (4). This knowledge helped to enable scholars to understand the anatomy of the spinal accessory nerve.
In parallel, understanding the circulatory system was already evolving at the time Herophilus of Chalcedon described the confluence of veins at the cerebral occiput, the "torcular Herophili," in the fourth century B.C. (5). Much later, Andreas (1514-1564) in the first known systematic anatomy text of the western world (6) vehemently corrected some of Galen’s misstatements concerning the nervous and circulatory systems, which had been accepted as dogma for the previous thousand years (7). Vasculature of the nervous system has continued to intrigue anatomists from then to the present (8–15). Rather recently, Lasjaunias and others (16) added concepts of arterial territories and directional blood flow, and Taylor et al. (17) described three-dimensional independent vascular territories called angiosomes. Collectively, these studies, too, have emphasized the critical importance of the blood supply to the plexus.
During the past century, the importance of almost all of the plexus to head, neck, and upper extremity function has come to be understood. As a consequence, surgery has become more conservative. Now, both as little of the plexus and as few of its closely related structures are removed as is possible during neck dissections to prevent iatrogenic injury to the plexus. This progression of conservatism is traced historically. Earlier work will also be mentioned later in the review in connection with modern surgery involving the spinal accessory nerve plexus because of the relevance of the two in the modern context.
Most of the studies done in the past half century, however, rather than systematically describing the entire plexus and its vasculature, have been more narrowly focused on specific clinical problems. One such recent instance is the work of Katsuka et al. (18) on the anatomy of the jugular foramen. Regarding embryology, Padget’s 1948 embryologic work (19), the most complete studies of which the author is aware, suggested that developmental variations might cause clinically significant aberrations or anomalies, as aneurysms, a theory now being confirmed by imaging studies (20). A much more recent embryologic review is far less complete than Padget’s (21).
Other topics relating to the circulatory and neural anatomy of the spinal accessory nerve plexus, i.e., the lymphatic circulation and the sympathetic nerves, reviewed by Hidden (22) and Collins (23), respectively, will be discussed later in relation to surgery involving the plexus.