Accessory nerve - wikipedia Accessory nerve Accessory nerve View of the human brain from below. The accessory nerve emerges from the medulla of the brainstem, and is visible at the bottom of the image in blue. Details Innervates sternocleidomastoid muscle, trapezius muscle Identifiers Latin nervus accessorius MeSH A08. 800.800. 120.060 TA A14. 2.01. 184 FMA 6720 Anatomical terms of neuroanatomy ( edit on Wikidata ) Cranial nerves CN 0 -- Terminal CN I -- Olfactory CN II -- Optic CN III -- Oculomotor CN IV -- Trochlear CN V -- Trigeminal CN VI -- Abducens CN VII -- Facial CN VIII -- Vestibulocochlear CN IX -- Glossopharyngeal CN X -- Vagus CN XI -- Accessory CN XII -- Hypoglossal Overview Table The accessory nerve is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is considered the eleventh of twelve pairs of cranial nerves, or simply cranial nerve XI, as part of it was formerly believed to originate in the brain. The sternocleidomastoid muscle tilts and rotates the head, while the trapezius muscle, connecting to the scapula, acts to shrug the shoulder. Traditional descriptions of the accessory nerve divide it into a spinal part and a cranial part. The cranial component rapidly joins the vagus nerve, and there is ongoing debate about whether the cranial part should be considered part of the accessory nerve proper. Consequently, the term `` accessory nerve '' usually refers only to nerve supplying the sternocleidomastoid and trapezius muscles, also called the spinal accessory nerve. Strength testing of these muscles can be measured during a neurological examination to assess function of the spinal accessory nerve. Poor strength or limited movement are suggestive of damage, which can result from a variety of causes. Injury to the spinal accessory nerve is most commonly caused by medical procedures that involve the head and neck. Injury can cause wasting of the shoulder muscles, winging of the scapula, and weakness of shoulder abduction and external rotation. The accessory nerve is derived from the basal plate of the embryonic spinal segments C1 -- C6. Contents 1 Structure 1.1 Nucleus 1.2 Variation 1.3 Development 2 Function 2.1 Classification 3 Clinical significance 3.1 Examination 3.2 Injury 4 History 5 Additional images 6 References 7 External links Structure See also : Spinal root of accessory nerve and Cranial root of accessory nerve The fibres of the spinal accessory nerve originate solely in neurons situated in the upper spinal cord, from where the spinal cord begins at the junction with the medulla oblongata, to the level of about C6. These fibres join together to form rootlets, roots, and finally the spinal accessory nerve itself. The formed nerve enters the skull through the foramen magnum, the large opening at the skull 's base. The nerve travels along the inner wall of the skull towards the jugular foramen. Leaving the skull, the nerve travels through the jugular foramen with the glossopharyngeal and vagus nerves. The spinal accessory nerve is notable for being the only cranial nerve to both enter and exit the skull. This is due to it being unique among the cranial nerves in having neurons in the spinal cord. After leaving the skull, the cranial component detaches from the spinal component. The spinal accessory nerve continues alone and heads backwards and downwards. In the neck, the accessory nerve crosses the internal jugular vein around the level of the posterior belly of digastric muscle. As it courses downwards, the nerve pierces through the sternocleidomastoid muscle while sending it motor branches, then continues down until it reaches the trapezius muscle to provide motor innervation to its upper part. Nucleus Main article : Spinal accessory nucleus The fibres that form the spinal accessory nerve are formed by lower motor neurons located in the upper segments of the spinal cord. This cluster of neurons, called the spinal accessory nucleus, is located in the lateral aspect of the anterior horn of the spinal cord, and stretches from where the spinal cord begins ( at the junction with the medulla ) through to the level of about C6. The lateral horn of high cervical segments appears to be continuous with the nucleus ambiguus of the medulla oblongata, from which the cranial component of the accessory nerve is derived. Variation In the neck, the accessory nerve crosses the internal jugular vein around the level of the posterior belly of digastric muscle, in front of the vein in about 80 % of people, and behind it in about 20 %, and in one reported case, piercing the vein. Traditionally, the accessory nerve is described as having a small cranial component that descends from the medulla and briefly connects with the spinal accessory component before branching off of the nerve to join the vagus nerve. A study, published in 2007, of twelve subjects suggests that in the majority of individuals, this cranial component does not make any distinct connection to the spinal component ; the roots of these distinct components were separated by a fibrous sheath in all but one subject. Development The accessory nerve is derived from the basal plate of the embryonic spinal segments C1 -- C6. Function The accessory nerve supplies the sternocleidomastoid and trapezius muscles The spinal component of the accessory nerve provides motor control of the sternocleidomastoid and trapezius muscles. The trapezius muscle controls the action of shrugging the shoulders, and the sternocleidomastoid the action of turning the head. Like most muscles, control of the trapezius muscle arises from the opposite side of the brain. Contraction of the upper part of the trapezius muscle elevates the scapula. The nerve fibres sternocleidomastoid however are thought to change sides ( Latin : decussate ) twice. This means that the sternocleidomastoid is controlled by the brain on the same side of the body. Contraction of the stenocleidomastoid fibres turns the head to the opposite side, the net effect meaning that the head is turned to the side of the brain receiving visual information from that area. The cranial component of the accessory nerve, on the other hand, provides motor control to the muscles of the soft palate, larynx and pharynx. Classification Among investigators there is disagreement regarding the terminology used to describe the type of information carried by the accessory nerve. As the trapezius and sternocleidomastoid muscles are derived from the pharyngeal arches, some investigators believe the spinal accessory nerve that innervates them must carry specific special visceral efferent ( SVE ) information. This is in line with the observation that the spinal accessory nucleus appears to be continuous with the nucleus ambiguus of the medulla. Others, consider the spinal accessory nerve to carry general somatic efferent ( GSE ) information. Still others believe it is reasonable to conclude that the spinal accessory nerve contains both SVE and GSE components. Clinical significance Examination The accessory nerve is tested by evaluating the function of the trapezius and sternocleidomastoid muscles. The trapezius muscle is tested by asking the patient to shrug their shoulders with and without resistance. The sternocleidomastoid muscle is tested by asking the patient to turn their head to the left or right against resistance. One - sided weakness of the trapezius may indicate injury to the nerve on the same side of an injury to the spinal accessory nerve on the same side ( Latin : ipsilateral ) of the body being assessed. Weakness in head - turning suggests injury to the contralateral spinal accessory nerve : a weak leftward turn is indicative of a weak right sternocleidomastoid muscle ( and thus right spinal accessory nerve injury ), while a weak rightward turn is indicative of a weak left sternocleidomastoid muscle ( and thus left spinal accessory nerve ). Hence, weakness of shrug on one side and head - turning on the other side may indicate damage to the accessory nerve on the side of the shrug weakness, or damage along the nerve pathway at the other side of the brain. Causes of damage may include trauma, surgery, tumours, and compression at the jugular foramen. Weakness in both muscles may point to a more general disease process such as amyotrophic lateral sclerosis, Guillain - Barre syndrome or poliomyelitis. Injury Main article : Accessory nerve disorder Injury to the spinal accessory nerve commonly occurs during neck surgery, including neck dissection and lymph node excision. It can also occur as a result of blunt or penetrating trauma, and in some causes spontaneously. Damage at any point along the nerve 's course will affect the function of the nerve. The nerve is intentionally removed in `` radical '' neck dissections, which are attempts at exploring the neck surgically for the presence and extent of cancer. Attempts are made to spare it in other forms of less aggressive dissection. Injury to the accessory nerve can result in neck pain and weakness of the trapezius muscle. Symptoms will depend on at what point along its length the nerve was severed. Injury to the nerve can result in shoulder girdle depression, atrophy, abnormal movement, a protruding scapula, and weakened abduction. Weakness of the shoulder girdle can lead to traction injury of the brachial plexus. Because diagnosis is difficult, electromyogram or nerve conduction studies may be needed to confirm a suspected injury. Outcomes with surgical treatment appear to be better than conservative management, which entails physiotherapy and pain relief. Surgical management includes neurolysis, nerve end - to - end suturing, and surgical replacement of affected trapezius muscle segments with other muscle groups. Damage to the nerve can cause torticollis. History English anatomist Thomas Willis in 1664 first described the accessory nerve, choosing to use `` accessory '' ( described in Latin as nervus accessorius ) meaning in associated with the vagus nerve. In 1848, Jones Quain described the nerve as the `` spinal nerve accessory to the vagus '', recognizing that while a minor component of the nerve joins with the larger vagus nerve, the majority of accessory nerve fibres originate in the spinal cord. In 1893 it was recognised that the heretofore named nerve fibres `` accessory '' to the vagus originated from the same nucleus in the medulla oblongata, and it came to pass that these fibres were increasingly viewed as part of the vagus nerve itself. Consequently, the term `` accessory nerve '' was and is increasingly used to denote only fibres from the spinal cord ; the fact that only the spinal portion could be tested clinically lent weight to this opinion. Additional images Course and distribution of the glossopharyngeal, vagus, and accessory nerves. The accessory nerve ( top left ) travels down through the jugular foramen with the other two nerves, and then passes down, usually over the internal jugular vein, to supply the sternocleidomastoid and trapezius muscles Side of the neck, with accessory nerve seen between the sternocleidomastoid and trapezius muscles The brain and upper spinal cord in a cadaver specimen. The accessory nerve can be seen as a number of rootlets arising from the medulla. References ^ Jump up to : Gray 's Anatomy 2008, p. 459. Jump up ^ `` Spinal Accessory Nerve ''. Structure of the Human body, Loyola University Medical Education Network. Archived from the original on 16 June 2007. Retrieved 2007 - 06 - 17. ^ Jump up to : Terence R. Anthoney ( 1993 ). Neuroanatomy and the Neurologic Exam : A Thesaurus of Synonyms, Similar - Sounding Non-Synonyms, and Terms of Variable Meanings. Boca Raton : CRC - Press. pp. 69 -- 73. ISBN 0 - 8493 - 8631 - 4. Jump up ^ London J, London NJ, Kay SP ( 1996 ). `` Iatrogenic accessory nerve injury ''. Annals of the Royal College of Surgeons of England. 78 ( 2 ) : 146 -- 50. PMC 2502542. PMID 8678450. ^ Jump up to : Kelley, Martin J. ; Kane, Thomas E. ; Leggin, Brian G. ( February 2008 ). `` Spinal Accessory Nerve Palsy : Associated Signs and Symptoms ''. Journal of Orthopaedic & Sports Physical Therapy. 38 ( 2 ) : 78 -- 86. doi : 10.2519 / jospt. 2008.2454. ^ Jump up to : Ryan S, Blyth P, Duggan N, Wild M, Al - Ali S ( 2007 ). `` Is the cranial accessory nerve really a portion of the accessory nerve ? Anatomy of the cranial nerves in the jugular foramen ''. Anatomical Science International. 82 ( 1 ) : 1 -- 7. doi : 10.1111 / j. 1447 - 073X. 2006.00154. x. PMID 17370444. ^ Jump up to : Talley, Nicholas ( 2014 ). Clinical Examination. Churchill Livingstone. pp. 424 -- 5. ISBN 978 - 0 - 7295 - 4198 - 5. ^ Jump up to : Finsterer, Josef ; Grisold, Wolfgang ( 2015 ). `` Disorders of the lower cranial nerves ''. Journal of Neurosciences in Rural Practice. 6 ( 3 ) : 377. doi : 10.4103 / 0976 - 3147.158768. ^ Jump up to : Gray 's Anatomy 2008, p. 460. Jump up ^ Saman M, Etebari P, Pakdaman MN, Urken ML ( 2010 ). `` Anatomic relationship between the spinal accessory nerve and the jugular vein : a cadaveric study ''. Surgical and Radiologic Anatomy. 33 ( 2 ) : 175 -- 179. doi : 10.1007 / s00276 - 010 - 0737 - y. PMID 20959982. Jump up ^ Skórzewska, A ; Bruska, M ; Woźniak, W ( 1994 ). `` The development of the spinal accessory nerve in human embryos during 5th week ( stages 14 and 15 ) ''. Folia morphologica. 53 ( 3 ) : 177 -- 84. PMID 7883243. Jump up ^ Kelley, Martin J. ; Kane, Thomas E. ; Leggin, Brian G. ( February 2008 ). `` Spinal Accessory Nerve Palsy : Associated Signs and Symptoms ''. Journal of Orthopaedic & Sports Physical Therapy. 38 ( 2 ) : 78 -- 86. doi : 10.2519 / jospt. 2008.2454. The upper trapezius elevates, the middle trapezius retracts, and the lower trapezius depresses. In unison, the pri - mary function of the trapezius is to up - wardly rotate the scapula during shoulder elevation, forming a force couple with the serratus anterior Jump up ^ William T. Mosenthal ( 1995 ). A Textbook of Neuroanatomy : With Atlas and Dissection Guide. Washington, DC : Taylor & Francis. p. 12. ISBN 1 - 85070 - 587 - 9. Jump up ^ Duane E. Haines ( 2004 ). Neuroanatomy : an atlas of structures, sections, and systems. Hagerstown, MD : Lippincott Williams & Wilkins. ISBN 0 - 7817 - 4677 - 9. Jump up ^ Joshi SS, Joshi SD ( 2001 ). `` Muscle Dorso - Fascialis -- A Case Report ''. Journal of the Anatomical Society of India. 50 ( 2 ) : 159 -- 160. ^ Jump up to : Martin, Ryan M. ; Fish, David E. ( 2 November 2007 ). `` Scapular winging : anatomical review, diagnosis, and treatments ''. Current Reviews in Musculoskeletal Medicine. 1 ( 1 ) : 1 -- 11. doi : 10.1007 / s12178 - 007 - 9000 - 5. Jump up ^ Davis, Matthew C. ; Griessenauer, Christoph J. ; Bosmia, Anand N. ; Tubbs, R. Shane ; Shoja, Mohammadali M. ( January 2014 ). `` The naming of the cranial nerves : A historical review ''. Clinical Anatomy. 27 ( 1 ) : 14 -- 19. doi : 10.1002 / ca. 22345. Jump up ^ Jones Quain ( 1848 ). Richard Quain ; William Sharpey, eds. Elements of Anatomy. 2 ( 5th ed. ). London : Taylor, Walton, and Maberly. p. 812. Books Gray 's anatomy : the anatomical basis of clinical practice. editor - in - chief, Susan Standring ( 40th ed. ). London : Churchill Livingstone. 2008. ISBN 978 - 0 - 8089 - 2371 - 8. External links Wikimedia Commons has media related to Nervus accessorius. MedEd at Loyola GrossAnatomy / h_n / cn / cn1 / cn11. htm lesson6 at The Anatomy Lesson by Wesley Norman ( Georgetown University ) cranialnerves at The Anatomy Lesson by Wesley Norman ( Georgetown University ) ( XI ) Anatomy photo : 28 : 13 - 0115 at the SUNY Downstate Medical Center `` 11 - 1 ''. Cranial Nerves. Yale School of Medicine. Archived from the original on 3 March 2016. Notes on Accessory Nerve The cranial nerves terminal Nuclei Septal nuclei Course no significant branches olfactory Nuclei Anterior olfactory nucleus Course olfactory bulb olfactory tract optic Nuclei Lateral geniculate nucleus Course optic chiasm optic tract oculomotor Nuclei Oculomotor nucleus Edinger -- Westphal nucleus Branches superior parasympathetic root of ciliary ganglion / ciliary ganglion inferior trochlear Nucleus Branches no significant branches trigeminal Nuclei PSN Spinal trigeminal nucleus MN TMN Course trigeminal ganglion Branches ophthalmic maxillary mandibular abducens Nucleus Branches no significant branches facial near origin intermediate nerve geniculate inside facial canal greater petrosal pterygopalatine ganglion nerve to the stapedius chorda tympani lingual nerve submandibular ganglion at stylomastoid foramen posterior auricular suprahyoid digastric stylohyoid parotid plexus temporal zygomatic buccal mandibular cervical Nuclei Facial motor nucleus Solitary nucleus Superior salivary nucleus vestibulocochlear Nuclei Vestibular nuclei Cochlear nuclei cochlear nerve striae medullares lateral lemniscus vestibular Scarpa 's ganglion glossopharyngeal before jugular fossa ganglia superior inferior after jugular fossa tympanic tympanic plexus lesser petrosal otic ganglion stylopharyngeal branch pharyngeal branches tonsillar branches lingual branches carotid sinus Nuclei Nucleus ambiguus Inferior salivatory nucleus Solitary nucleus vagus before jugular fossa ganglia superior inferior after jugular fossa meningeal branch auricular branch neck pharyngeal branch pharyngeal plexus superior laryngeal external internal recurrent laryngeal ( inferior ) superior cervical cardiac thorax inferior cardiac pulmonary vagal trunks anterior posterior abdomen celiac renal hepatic anterior gastric posterior gastric Nuclei Nucleus ambiguus Dorsal nucleus of vagus nerve Solitary nucleus accessory Nuclei Nucleus ambiguus Spinal accessory nucleus cranial spinal hypoglossal Nucleus Branches lingual Retrieved from `` https://en.wikipedia.org/w/index.php?title=Accessory_nerve&oldid=808879383 '' Categories : Accessory nerve Cranial nerves Hidden categories : Good articles Medicine infobox template using GraySubject or GrayPage Articles containing Latin - language text Use dmy dates from April 2017 Talk Contents About Wikipedia Azərbaycanca Català Čeština Deutsch Eesti Español فارسی Français Galego Bahasa Indonesia Italiano עברית Latina Lietuvių Magyar Nederlands 日本 語 Norsk Norsk nynorsk Polski Português Русский Српски / srpski Srpskohrvatski / српскохрватски Svenska Tagalog తెలుగు Українська 中文 Edit links This page was last edited on 5 November 2017, at 19 : 49. 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Question: where does the spinal accessory nerve come from
Answer: basal plate of the embryonic spinal segments C1–C6