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Surgical Anatomy of the Spinal Accessory Nerve in the Posterior Triangle of the Neck
Original Article
Surgical Anatomy of the Spinal Accessory Nerve in the Posterior Triangle of the Neck Atchara Aramrattana, Pichit Sittitrai1 and Kanchana Harnsiriwattanagit, Departments of Anatomy and 1Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
OBJECTIVE: The major complication of neck dissection and surgery at the posterior triangle of the neck is severe disability of the shoulder or “shoulder syndrome”, which results from spinal accessory nerve injury. Surgical landmarks of the nerve in this area were studied. METHODS: Fifty-six fresh Thai cadavers (112 necks) were dissected to identify the anatomical relationship of the spinal accessory nerve and its commonly used landmarks. RESULTS: The spinal accessory nerve was found within 3.6 cm (mean, 1.43 cm) above Erb’s point. The distance between the spinal accessory nerve entering the trapezius muscle and the clavicle was between 2.6 cm and 6.9 cm (mean, 4.5 cm). CONCLUSION: Our data were different from those described in the literature. Reconsideration of these two important landmarks can help to minimize iatrogenic injury of the spinal accessory nerve. [Asian J Surg 2005; 28(3):171–3] Key Words: shoulder syndrome, spinal accessory nerve
Introduction Spinal accessory nerve dysfunction is one of the most frequent complications of radical neck dissection for metastatic carcinoma to the cervical lymph node.1 Patients who suffer nerve sacrifice are often afflicted with “shoulder syndrome”.1,2 This syndrome results from trapezius paralysis which consists of limited shoulder abduction, shoulder droop, and a dull ache around the shoulder.2–4 Conservation neck dissections, which are classified as modified radical and selective neck dissection, were developed to preserve the nerve and prevent this painful and disabling syndrome in cases where lymph nodes in the spinal accessory chain were not grossly involved by the tumour.4 During neck dissection, the spinal accessory nerve is usually identified in the posterior triangle of the neck.4,5 Knowl-
edge of its surgical anatomy is needed for nerve preservation, as well as being applicable to cervical lymph node biopsy and other surgical procedures in this particular area.
Anatomy The spinal accessory nerve exits at the jugular foramen with the ninth and tenth nerve as well as the internal jugular vein. After crossing the internal jugular vein, it descends obliquely downward and backward to the upper part of the deep surface of the sternocleidomastoid muscle. After supplying the muscle, the nerve turns inferiorly and laterally, running through the posterior triangle before entering the trapezius muscle, which it innervates. In the posterior triangle, it lies superficially between two layers of deep cervical fascia, embedded in loose connective tissue.6,7 The spinal accessory nerve may receive branches from the cervical plexus deep into the sternocleido-
Address correspondence and reprint requests to Dr. Pichit Sittitrai, Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, 110 Intavaroros Road, Chiang Mai 50200, Thailand. E-mail: [email protected] • Date of acceptance: 23 February 2005 © 2005 Elsevier. All rights reserved.
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the posterior border of the sternocleidomastoid near this point. We found that the spinal accessory nerve was located above Erb’s point in 101 necks (90.2%), below Erb’s point in one neck (0.9%) and at Erb’s point in 10 necks (8.9%). The nerve exiting above Erb’s point was found between 0.3 cm and 3.6 cm (mean, 1.43 cm) (Table 1).
Distance between spinal accessory nerve entering trapezius muscle and clavicle
Figure. Anatomical landmarks of the spinal accessory nerve in the posterior triangle of the neck. A = distance between Erb’s point and the spinal accessory nerve; B = distance between the spinal accessory nerve and the clavicle.
mastoid muscle. It is still unclear whether the cervical plexus contributions carry motor or sensory fibre into the spinal accessory nerve.1
Materials and methods The posterior triangle of 112 necks was dissected in 56 fresh Thai cadavers to identify the course of the spinal accessory nerve. There were 35 males and 21 females. Their ages ranged from 38 to 93 years (mean, 67 years). The anatomical landmarks were documented and comprised the relationship of the spinal accessory nerve to the bundle of sensory nerves from the cervical plexus, and the level of the nerve entering the trapezius muscle (Figure). Calipers were used for accurate measurement.
Results Relationship of spinal accessory nerve to sensory nerve bundle from cervical plexus The point where the bundle of sensory nerves from the cervical plexus emerges from the posterior border of the sternocleidomastoid is called Erb’s point.8 The spinal accessory nerve exits
Table 1. Relationship between the spinal accessory nerve and Erb’s point
Above Erb’s point Below Erb’s point
172
Right side (cm)
Left side (cm)
0.6–3.6 0.7
0.3–3.0 –
When measured from the clavicle along the anterior border of the trapezius muscle to the point where the spinal accessory nerve entered the muscle, the distance ranged between 2.6 cm and 6.9 cm (mean, 4.5 cm) on both sides (Table 2).
Discussion Preservation of the spinal accessory nerve during neck dissection and lymph node biopsy is justified whenever possible to prevent shoulder disability. The course of the nerve and its variation should be identified precisely during dissection in order to avoid iatrogenic injury. The spinal accessory nerve is located superficially as it courses through the posterior triangle of the neck. The skin flap elevated over this region must be kept relatively thin to avoid injury to the nerve.5 There are two important anatomical landmarks that locate the spinal accessory nerve in this area: first, Erb’s point; and second, the distance between the nerve entering the trapezius muscle and the clavicle.5,8,9 Erb’s point is where the bundle of sensory nerves from the cervical plexus emerges from the posterior border of the sternocleidomastoid muscle, midway between the mastoid process and the clavicle. From previous reports,1,8,9 the spinal accessory nerve exits within 2 cm above the posterior border of the muscle. In our study, the nerve was found below Erb’s point in one neck, and at or above Erb’s point (within 3.6 cm) in 111 necks (99.1%). The distance between the clavicle and the point where the spinal accessory nerve enters the trapezius muscle is usually within 2–4 cm.9 However, we found this distance to be between 2.6 cm and 6.9 cm.
Table 2. Distance between the spinal accessory nerve entering the trapezius muscle and the clavicle
Distance above the clavicle
Right side (cm)
Left side (cm)
2.6–6.7
3.0–6.9
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■ SURGICAL ANATOMY OF THE SPINAL ACCESSORY NERVE ■
Our two surgical landmarks for localizing the spinal accessory nerve showed significant differences in distance when compared with those described in the literature where the data had been obtained from Caucasians.1,5,8,9 These differences could have arisen from our precise dissection and measurements, and could be from racial characteristics. Careful dissection with good knowledge of the course of the nerve, accurate measurement by using calipers, and reconsideration of the distance of these two useful landmarks could help to prevent injury to the spinal accessory nerve during neck dissection and surgery in the posterior triangle of the neck, especially in Thai and Asian people.
References 1. Nason RW, Abdulrauf BM, Stranc MF. The anatomy of the accessory nerve and cervical lymph node biopsy. Am J Surg 2000;180:241–3.
ASIAN JOURNAL OF SURGERY VOL 28 • NO 3 • JULY 2005
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2. Nahum AM, Mullally W, Marmor L. A syndrome resulting from radical neck dissection. Arch Otolaryngol 1961;74:424–8. 3. Skolnik EM, Tenta LT, Wineinger DM, Tardy ME. Preservation of XI cranial nerve in neck dissections. Laryngoscope 1967;77:1304–13. 4. Brandenburg JH, Lee CYS. The eleventh nerve in radical neck surgery. Laryngoscope 1981;91:1851–9. 5. 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 2001;2:137–41. 6. Hollinshead WH. Anatomy for Surgeons. New York: Harper and Row, 1968. 7. Weitz JW, Weitz SL, McElhinney AJ. A technique for preservation of spinal accessory nerve function in radical neck dissection. Head Neck Surg 1982;5:75–8. 8. Becker GD, Pareli GJ. Technique of preserving the spinal accessory nerve during radical neck dissection. Laryngoscope 1979;89: 827–31. 9. Soo KC, Hamlyn PJ, Pegington J, Westbury G. Anatomy of the accessory nerve and its cervical contributions in the neck. Head Neck Surg 1986;9:111–5.
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Surgical Anatomy of the Spinal Accessory Nerve in the Posterior Triangle of the Neck Atchara Aramrattana, Pichit Sittitrai1 and Kanchana Harnsiriwattanagit, Departments of Anatomy and 1Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
OBJECTIVE: The major complication of neck dissection and surgery at the posterior triangle of the neck is severe disability of the shoulder or “shoulder syndrome”, which results from spinal accessory nerve injury. Surgical landmarks of the nerve in this area were studied. METHODS: Fifty-six fresh Thai cadavers (112 necks) were dissected to identify the anatomical relationship of the spinal accessory nerve and its commonly used landmarks. RESULTS: The spinal accessory nerve was found within 3.6 cm (mean, 1.43 cm) above Erb’s point. The distance between the spinal accessory nerve entering the trapezius muscle and the clavicle was between 2.6 cm and 6.9 cm (mean, 4.5 cm). CONCLUSION: Our data were different from those described in the literature. Reconsideration of these two important landmarks can help to minimize iatrogenic injury of the spinal accessory nerve. [Asian J Surg 2005; 28(3):171–3] Key Words: shoulder syndrome, spinal accessory nerve
Introduction Spinal accessory nerve dysfunction is one of the most frequent complications of radical neck dissection for metastatic carcinoma to the cervical lymph node.1 Patients who suffer nerve sacrifice are often afflicted with “shoulder syndrome”.1,2 This syndrome results from trapezius paralysis which consists of limited shoulder abduction, shoulder droop, and a dull ache around the shoulder.2–4 Conservation neck dissections, which are classified as modified radical and selective neck dissection, were developed to preserve the nerve and prevent this painful and disabling syndrome in cases where lymph nodes in the spinal accessory chain were not grossly involved by the tumour.4 During neck dissection, the spinal accessory nerve is usually identified in the posterior triangle of the neck.4,5 Knowl-
edge of its surgical anatomy is needed for nerve preservation, as well as being applicable to cervical lymph node biopsy and other surgical procedures in this particular area.
Anatomy The spinal accessory nerve exits at the jugular foramen with the ninth and tenth nerve as well as the internal jugular vein. After crossing the internal jugular vein, it descends obliquely downward and backward to the upper part of the deep surface of the sternocleidomastoid muscle. After supplying the muscle, the nerve turns inferiorly and laterally, running through the posterior triangle before entering the trapezius muscle, which it innervates. In the posterior triangle, it lies superficially between two layers of deep cervical fascia, embedded in loose connective tissue.6,7 The spinal accessory nerve may receive branches from the cervical plexus deep into the sternocleido-
Address correspondence and reprint requests to Dr. Pichit Sittitrai, Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, 110 Intavaroros Road, Chiang Mai 50200, Thailand. E-mail: [email protected] • Date of acceptance: 23 February 2005 © 2005 Elsevier. All rights reserved.
ASIAN JOURNAL OF SURGERY VOL 28 • NO 3 • JULY 2005
070/2001
171
■ ARAMRATTANA et al ■
the posterior border of the sternocleidomastoid near this point. We found that the spinal accessory nerve was located above Erb’s point in 101 necks (90.2%), below Erb’s point in one neck (0.9%) and at Erb’s point in 10 necks (8.9%). The nerve exiting above Erb’s point was found between 0.3 cm and 3.6 cm (mean, 1.43 cm) (Table 1).
Distance between spinal accessory nerve entering trapezius muscle and clavicle
Figure. Anatomical landmarks of the spinal accessory nerve in the posterior triangle of the neck. A = distance between Erb’s point and the spinal accessory nerve; B = distance between the spinal accessory nerve and the clavicle.
mastoid muscle. It is still unclear whether the cervical plexus contributions carry motor or sensory fibre into the spinal accessory nerve.1
Materials and methods The posterior triangle of 112 necks was dissected in 56 fresh Thai cadavers to identify the course of the spinal accessory nerve. There were 35 males and 21 females. Their ages ranged from 38 to 93 years (mean, 67 years). The anatomical landmarks were documented and comprised the relationship of the spinal accessory nerve to the bundle of sensory nerves from the cervical plexus, and the level of the nerve entering the trapezius muscle (Figure). Calipers were used for accurate measurement.
Results Relationship of spinal accessory nerve to sensory nerve bundle from cervical plexus The point where the bundle of sensory nerves from the cervical plexus emerges from the posterior border of the sternocleidomastoid is called Erb’s point.8 The spinal accessory nerve exits
Table 1. Relationship between the spinal accessory nerve and Erb’s point
Above Erb’s point Below Erb’s point
172
Right side (cm)
Left side (cm)
0.6–3.6 0.7
0.3–3.0 –
When measured from the clavicle along the anterior border of the trapezius muscle to the point where the spinal accessory nerve entered the muscle, the distance ranged between 2.6 cm and 6.9 cm (mean, 4.5 cm) on both sides (Table 2).
Discussion Preservation of the spinal accessory nerve during neck dissection and lymph node biopsy is justified whenever possible to prevent shoulder disability. The course of the nerve and its variation should be identified precisely during dissection in order to avoid iatrogenic injury. The spinal accessory nerve is located superficially as it courses through the posterior triangle of the neck. The skin flap elevated over this region must be kept relatively thin to avoid injury to the nerve.5 There are two important anatomical landmarks that locate the spinal accessory nerve in this area: first, Erb’s point; and second, the distance between the nerve entering the trapezius muscle and the clavicle.5,8,9 Erb’s point is where the bundle of sensory nerves from the cervical plexus emerges from the posterior border of the sternocleidomastoid muscle, midway between the mastoid process and the clavicle. From previous reports,1,8,9 the spinal accessory nerve exits within 2 cm above the posterior border of the muscle. In our study, the nerve was found below Erb’s point in one neck, and at or above Erb’s point (within 3.6 cm) in 111 necks (99.1%). The distance between the clavicle and the point where the spinal accessory nerve enters the trapezius muscle is usually within 2–4 cm.9 However, we found this distance to be between 2.6 cm and 6.9 cm.
Table 2. Distance between the spinal accessory nerve entering the trapezius muscle and the clavicle
Distance above the clavicle
Right side (cm)
Left side (cm)
2.6–6.7
3.0–6.9
ASIAN JOURNAL OF SURGERY VOL 28 • NO 3 • JULY 2005
070/20
■ SURGICAL ANATOMY OF THE SPINAL ACCESSORY NERVE ■
Our two surgical landmarks for localizing the spinal accessory nerve showed significant differences in distance when compared with those described in the literature where the data had been obtained from Caucasians.1,5,8,9 These differences could have arisen from our precise dissection and measurements, and could be from racial characteristics. Careful dissection with good knowledge of the course of the nerve, accurate measurement by using calipers, and reconsideration of the distance of these two useful landmarks could help to prevent injury to the spinal accessory nerve during neck dissection and surgery in the posterior triangle of the neck, especially in Thai and Asian people.
References 1. Nason RW, Abdulrauf BM, Stranc MF. The anatomy of the accessory nerve and cervical lymph node biopsy. Am J Surg 2000;180:241–3.
ASIAN JOURNAL OF SURGERY VOL 28 • NO 3 • JULY 2005
070/2001
2. Nahum AM, Mullally W, Marmor L. A syndrome resulting from radical neck dissection. Arch Otolaryngol 1961;74:424–8. 3. Skolnik EM, Tenta LT, Wineinger DM, Tardy ME. Preservation of XI cranial nerve in neck dissections. Laryngoscope 1967;77:1304–13. 4. Brandenburg JH, Lee CYS. The eleventh nerve in radical neck surgery. Laryngoscope 1981;91:1851–9. 5. 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 2001;2:137–41. 6. Hollinshead WH. Anatomy for Surgeons. New York: Harper and Row, 1968. 7. Weitz JW, Weitz SL, McElhinney AJ. A technique for preservation of spinal accessory nerve function in radical neck dissection. Head Neck Surg 1982;5:75–8. 8. Becker GD, Pareli GJ. Technique of preserving the spinal accessory nerve during radical neck dissection. Laryngoscope 1979;89: 827–31. 9. Soo KC, Hamlyn PJ, Pegington J, Westbury G. Anatomy of the accessory nerve and its cervical contributions in the neck. Head Neck Surg 1986;9:111–5.
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