open access

Vol 82, No 2 (2023)
Original article
Submitted: 2021-11-03
Accepted: 2022-02-02
Published online: 2022-02-17
Get Citation

The spinal accessory nerve and its entry point into the posterior triangle of the neck

S. Ellis1, C. Brassett1, N. Glibbery1, J. Cheema1, S. Madenlidou1
·
Pubmed: 35187635
·
Folia Morphol 2023;82(2):256-260.
Affiliations
  1. Human Anatomy Centre, Department of Physiology, Development and Neuroscience, University of Cambridge, United Kingdom

open access

Vol 82, No 2 (2023)
ORIGINAL ARTICLES
Submitted: 2021-11-03
Accepted: 2022-02-02
Published online: 2022-02-17

Abstract

Background: The course of the spinal accessory nerve in the neck is long and
superficial rendering it at high risk of injury during procedures performed in the
posterior triangle. The majority of spinal accessory nerve injuries are iatrogenic in
nature. This is associated with significant morbidity including reduction in shoulder
movements, drooping of the shoulder, winging of the scapula and neuropathic
pain. Knowledge of the nerve anatomy reduces the risk of intra-operative nerve
injury. Traditional teaching describes the point of entry into the posterior triangle
as the intersection between the upper and middle third of the posterior border
of sternocleidomastoid. The aim of this study was to determine whether this is
in fact the case and if so, whether this landmark can reliably be used to identify
the spinal accessory nerve in order to improve patient outcomes.
Materials and methods: The spinal accessory nerve was identified unilaterally
in 26 cadavers. The total length of sternocleidomastoid was measured as well
as the length along the posterior border from the inferior aspect of the mastoid
process to the point at which the accessory nerve enters the posterior triangle
of the neck. These measurements were used to calculate the ratio of the entry
point of the nerve into the posterior triangle along the length of the posterior
border of sternocleidomastoid from its superior insertion point. The mean ratio
was 0.35 with 95% confidence intervals of 0.33 to 0.36.
Results and Conclusions: Our findings confirm the traditional description of the
entry point of the spinal accessory nerve into the posterior triangle of the neck. We
describe a so-called ‘safe zone’ inferior to the midpoint of the posterior border of
sternocleidomastoid within which the spinal accessory nerve is unlikely to be found,
thereby reducing the risk of iatrogenic injury

Abstract

Background: The course of the spinal accessory nerve in the neck is long and
superficial rendering it at high risk of injury during procedures performed in the
posterior triangle. The majority of spinal accessory nerve injuries are iatrogenic in
nature. This is associated with significant morbidity including reduction in shoulder
movements, drooping of the shoulder, winging of the scapula and neuropathic
pain. Knowledge of the nerve anatomy reduces the risk of intra-operative nerve
injury. Traditional teaching describes the point of entry into the posterior triangle
as the intersection between the upper and middle third of the posterior border
of sternocleidomastoid. The aim of this study was to determine whether this is
in fact the case and if so, whether this landmark can reliably be used to identify
the spinal accessory nerve in order to improve patient outcomes.
Materials and methods: The spinal accessory nerve was identified unilaterally
in 26 cadavers. The total length of sternocleidomastoid was measured as well
as the length along the posterior border from the inferior aspect of the mastoid
process to the point at which the accessory nerve enters the posterior triangle
of the neck. These measurements were used to calculate the ratio of the entry
point of the nerve into the posterior triangle along the length of the posterior
border of sternocleidomastoid from its superior insertion point. The mean ratio
was 0.35 with 95% confidence intervals of 0.33 to 0.36.
Results and Conclusions: Our findings confirm the traditional description of the
entry point of the spinal accessory nerve into the posterior triangle of the neck. We
describe a so-called ‘safe zone’ inferior to the midpoint of the posterior border of
sternocleidomastoid within which the spinal accessory nerve is unlikely to be found,
thereby reducing the risk of iatrogenic injury

Get Citation

Keywords

spinal accessory nerve, anatomy, posterior triangle, iatrogenic injury

About this article
Title

The spinal accessory nerve and its entry point into the posterior triangle of the neck

Journal

Folia Morphologica

Issue

Vol 82, No 2 (2023)

Article type

Original article

Pages

256-260

Published online

2022-02-17

Page views

2359

Article views/downloads

1349

DOI

10.5603/FM.a2022.0014

Pubmed

35187635

Bibliographic record

Folia Morphol 2023;82(2):256-260.

Keywords

spinal accessory nerve
anatomy
posterior triangle
iatrogenic injury

Authors

S. Ellis
C. Brassett
N. Glibbery
J. Cheema
S. Madenlidou

References (23)
  1. Abakay MA, Güneş S, Küçük C, et al. Accessory nerve anatomy in anterior and posterior cervical triangle: a fresh cadaveric study. Turk Arch Otorhinolaryngol. 2020; 58(3): 149–154.
  2. Amuti TM, Butt F, Otieno BO, et al. The relation of the extracranial spinal accessory nerve to the sternocleidomastoid muscle and the internal jugular vein. Craniomaxillofac Trauma Reconstr. 2019; 12(2): 108–111.
  3. Canella C, Demondion X, Abreu E, et al. Anatomical study of spinal accessory nerve using ultrasonography. Eur J Radiol. 2013; 82(1): 56–61.
  4. Dailiana ZH, Mehdian H, Gilbert A. Surgical anatomy of spinal accessory nerve: is trapezius functional deficit inevitable after division of the nerve? J Hand Surg Br. 2001; 26(2): 137–141.
  5. Goldstein DP, Ringash J, Bissada E, et al. Scoping review of the literature on shoulder impairments and disability after neck dissection. Head Neck. 2014; 36(2): 299–308.
  6. Grossman JAI, Ruchelsman DE, Schwarzkopf R. Iatrogenic spinal accessory nerve injury in children. J Pediatr Surg. 2008; 43(9): 1732–1735.
  7. Johal J, Iwanaga J, Tubbs K, et al. The accessory nerve: a comprehensive review of its anatomy, development, variations, landmarks and clinical considerations. Anat Rec (Hoboken). 2019; 302(4): 620–629.
  8. Khavanin N, Carl HM, Yang R, et al. Surgical "safe zone": rapid anatomical identification of the lesser occipital nerve. J Reconstr Microsurg. 2019; 35(5): 341–345.
  9. Kierner AC, Zelenka I, Heller S, et al. Surgical anatomy of the spinal accessory nerve and the trapezius branches of the cervical plexus. Arch Surg. 2000; 135(12): 1428–1431.
  10. London J, London NJ, Kay SP. Iatrogenic accessory nerve injury. Ann R Coll Surg Engl. 1996; 78(2): 146–150.
  11. Lu L, Haman SP, Ebraheim NA. Vulnerability of the spinal accessory nerve in the posterior triangle of the neck: a cadaveric study. Orthopedics. 2002; 25(1): 71–74.
  12. Lloyd S. Accessory nerve: anatomy and surgical identification. J Laryngol Otol. 2007; 121(12): 1118–1125.
  13. Mirjalili SA, Muirhead JC, Stringer MD. Ultrasound visualization of the spinal accessory nerve in vivo. J Surg Res. 2012; 175(1): e11–e16.
  14. Moore KL, Dalley AF. Clinically orientated anatomy. 3rd ed. Lippincott Williams and Wilkins, Philadelphia 1992.
  15. Morris LGT, Ziff DJS, DeLacure MD. Malpractice litigation after surgical injury of the spinal accessory nerve: an evidence-based analysis. Arch Otolaryngol Head Neck Surg. 2008; 134(1): 102–107.
  16. Nahum AM, Mullally W, Marmor L. A syndrome resulting from radical neck dissection. Arch Otolaryngol. 1961; 74: 424–428.
  17. Overland J, Hodge JC, Breik O, et al. Surgical anatomy of the spinal accessory nerve: review of the literature and case report of a rare anatomical variant. J Laryngol Otol. 2016; 130(10): 969–972.
  18. Popovski V, Benedetti A, Popovic-Monevska D, et al. Spinal accessory nerve preservation in modified neck dissections: surgical and functional outcomes. Acta Otorhinolaryngol Ital. 2017; 37(5): 368–374.
  19. Romanes GF, Cunningham DJ. Cunningham’s textbook of anatomy, 12th ed. Oxford University Press, Oxford 1981.
  20. Sharp E, Roberts M, Żurada-Zielińska A, et al. The most commonly injured nerves at surgery: A comprehensive review. Clin Anat. 2021; 34(2): 244–262.
  21. Soo KC, Hamlyn PJ, Pegington J, et al. Anatomy of the accessory nerve and its cervical contributions in the neck. Head Neck Surg. 1986; 9(2): 111–115.
  22. Symes A, Ellis H. Variations in the surface anatomy of the spinal accessory nerve in the posterior triangle. Surg Radiol Anat. 2005; 27(5): 404–408.
  23. Tubbs RS, Salter EG, Wellons JC, et al. Superficial landmarks for the spinal accessory nerve within the posterior cervical triangle. J Neurosurg Spine. 2005; 3(5): 375–378.

Regulations

Important: This website uses cookies. More >>

The cookies allow us to identify your computer and find out details about your last visit. They remembering whether you've visited the site before, so that you remain logged in - or to help us work out how many new website visitors we get each month. Most internet browsers accept cookies automatically, but you can change the settings of your browser to erase cookies or prevent automatic acceptance if you prefer.

By VM Media Group sp. z o.o., Grupa Via Medica, Świętokrzyska 73, 80–180 Gdańsk, Poland

tel.: +48 58 320 94 94, faks: +48 58 320 94 60, e-mail: viamedica@viamedica.pl