1012 T HE NERVE SYSTEM 



innominate or subclavian arteries: by mediastinal tumors: by bronchocele: or by cancer of the 

 upper part of the oesophagus, when the paralysis is often unilateral. The nerve may be acci- 

 dentally divided during the operation for goitre. 



THE ELEVENTH OR SPINAL ACCESSORY NERVE (N. ACCESSORIUS) 



(Figs. 743, 744). 



The eleventh or spinal accessory nerve consists of two parts, one the accessory 

 part to the vagus, and the other the spinal portion. 



The bulbar or vagal accessory part (ramus interims) is the smaller of the two. 

 It is accessory to the vagus. Its superficial origin (Fig. 743) is by four or five 

 delicate filaments from the side of the medulla oblongata, below the roots of the 

 vagus. Its deep origin is described in detail on page 881. It passes outward 

 1:6 the jugular foramen, where it interchanges fibres with the spinal portion or 

 becomes united to it for a short distance; it is also connected, in the foramen, 

 with the upper ganglion of the vagus by one or two filaments. It then passes 

 through the foramen (Fig. 744), and becoming again separated from the spinal 

 portion it is continued over the surface of the ganglion of the trunk of the vagus, 

 being adherent to its surface, and is distributed principally to the pharyngeal 

 and superior laryngeal branches of the vagus. Through the pharyngeal branch 

 it probably supplies the Azygos uvulae and Leva tor palati muscles (see p. 400). 

 Some few filaments from it are continued into the trunk of the vagus below the 

 ganglion, to be distributed with the recurrent laryngeal nerve to supply most 

 of the laryngeal muscles and probably also with the cardiac nerves. 



The spinal portion (ramus externus) is firm in texture. Its superficial origin 

 (Fig. 743) is by several filaments or rootlets from the lateral tract of the cord, 

 as low down as the sixth cervical nerve. Its deep origin (Fig. 648) may be traced 

 to the intermediolateral tract of the gray substance of the cord. The rootlets 

 of origin join and form a trunk which ascends in the subdural space between the 

 ligamentum denticulatum and the anterior roots of the spinal nerves, enters the 

 skull through the foramen magnum, and is then directed outward to the jugular 

 foramen, through which it passes. lying in the same sheath as the vagus, but 

 separated from it by a fold of the arachnoid. In the jugular foramen it receives 

 one or two filaments from the vagal accessory portion. At its exit from the jugular 

 foramen it passes backward, either in front of or behind the internal jugular vein, 

 and descends obliquely behind the Digastric and Stylohyoid muscles to the upper 

 part of the Sternomastoid muscle. It pierces that muscle, and passes obliquely 

 across the posterior triangle, to terminate in the deep surface of the Trapezius 

 muscle. During its passage through the Sternomastoid muscle it gives several 

 branches to the muscle, and joins in its substance with branches from the second 

 cervical. In the posterior triangle it joins with the second and third cervical 

 nerves, while beneath the Trapezius it forms a sort of plexus with the third and 

 fourth cervical nerves, and from this plexus fibres are distributed to the muscle. 



Applied Anatomy. Division of the external branch of the spinal accessory nerve causes 

 paralysis of the Sternomastoid and Trapezius muscles; not absolute paralysis, for these muscles 

 also receive nerves from the cervical plexus. In cases of spasmodic torticollis in which all pal- 

 liative treatment has failed, division or excision of a portion of the external branch of the spinal 

 accessory nerve has been suggested by Keen. This may be done either along the anterior or 

 posterior border of the Sternomastoid muscle. The former operation is performed by making 

 an incision from the apex of the mastoid process, three inches in length, along the anterior border 

 of the Sternomastoid muscle. The anterior border of the muscle is defined and pulled back- 

 ward, so as to stretch the nerve, which is then to be sought for beneath the Digastric muscle, 

 about two inches below the apex of the mastoid process. The other operation consists in 

 making an incision along the posterior border of the muscle, so that the centre of the incision cor- 

 responds to the middle of this border of the muscle. The superficial structures having been 



