ORIGINAL ARTICLE

Year : 2019  |  Volume : 3  |  Issue : 2  |  Page : 55-57

Safer dissection of spinal accessory nerve from sternocleidomastoid muscle during neck dissection

Akhlak Hussain¹, Ashish Singhal¹, Nida Siddiquee², Bimlesh Thakur^1
1 Department of Surgical Oncology, Dr. RMLIMS, Lucknow, Uttar Pradesh, India
² Department of Paediatrics, Dr. RMLIMS, Lucknow, Uttar Pradesh, India

Correspondence Address:
Dr. Akhlak Hussain
Department of Surgical Oncology, Dr. RMLIMS, Lucknow - 226 010, Uttar Pradesh
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/aiao.aiao_17_18

Background: The spinal accessory nerve (SAN) may damage during its dissection from the sternocleidomastoid (SCM) muscle during modified neck dissection type II due to their intimate relation. Routinely, it is dissected from the anterior aspect of the SCM. The aim of this study is to describe and simplify the safer dissection of the SAN from the SCM muscle. Objectives: We proposed a different method of dissection describing it to be posterior approach. Materials and Methods: Posterior dissection of SAN was done as routine. Conclusion: Although more studies are required to depict the superiority of one over another, we found this method to be easier and time-saving approach.

Keywords: Modified neck dissection, spinal accessory nerve, sternocleidomastoid

Introduction

Materials and Methods

Results and Discussions

1. Internal jugular vein (IJV)^[1]



1. Ventral, 39.8%
2. Dorsally, 57.4%
3. Through IJV, 2.8%.



2. SCM



1. Through the belly – 54.1%^[1]–66%:^[2] Branching within SCM
2. Branching before entering the SCM; thus, trapezius branch travels posterior to SCM remaining superficial to cervical C4 root (22%).^[2] Lee et al.^[1] described that in 45.9% of the cases, the nerve sent branches to the SCM muscle without penetrating it.

1. Most describe the preservation of SAN through its identification in the lower neck, near its entry at the anterior border of the trapezius muscle, with a description of subsequent retrograde dissection.^{[8],[9],[10],[11]} The landmarks include (a) the distance between the clavicle and the point where the SAN passes under or pierces the anterior border of the trapezius (locates to within 2–5 cm of the clavicle in the majority) and (b) the relationship of the SAN to the point of emergence of the greater auricular nerve at the posterior border of the SCM (greater auricular point) (the SAN is always located above this point, usually within 2 cm of it)
2. With the increasing use of selective neck dissection, some described the method of identifying the nerve anterior to the SCM, finding the nerve high in the neck with anterograde dissection.^{[12],[13],[14]} The landmark here is the silvery white tendinous part (upper third of cleido-occipitalis) at the superior aspect of the SCM at its anteromedial surface. Immediately deep to the tendinous portion, one or more vessels are noted. These originate from the occipital artery and supply the SCM segmentally. Immediately deep to this point, the SAN is noted consistently passing into the SCM between the superficial sheet and the deeper sternocleidomastoid fibers Superior landmark is the transverse process of the  Atlas ^{More Details} (C1).^[15] This is easily palpable, and the IJV consistently sits anterior to it. Both the internal carotid artery and the SAN are intimately associated with the IJV at this point, deep to the posterior belly of digastric but anterior transverse process of C1.
3. Description of approach to dissect SAN from SCM.

1. Anterior approach: This is quite a common way to dissect SAN. Dissection and identification of the SAN in the posterior triangle is the main requisite for this approach. It involves following the SAN, identified in the posterior triangle, on artery forceps or Lahey forceps. All the bulk of SCM is divided anterior to the nerve, following the whole of its course, without dividing the attachments of SCM. The only advantage we could found is the easy of division of the SCM which remains fixed as the SCM attachments are not divided. This approach involves the division of the major bulk or almost the whole of the SCM which remains anterior to the SAN. This involves more handling of the nerve and thus more chances of neuropraxia. Moreover, the course of SAN in the SCM is not straight, and the attachment of cervical branches is not consistent, so this approach may have more chances of injury to the cervical contributions. It surely involves more time, and more dissection is required to dissect the major bulk of the SCM
2. Posterior approach: It involves the division of both clavicular and mastoid attachments of SCM and elevating it from the floor. Then, identification and dissection has to be started. In our experience, we found only a small slip of SCM posterior to the nerve, which has to be divided, thus easy to separate the nerve, and the reflections of the branches are more prominent and easier to identify [Figure 1]. Lesser handling may lead to less neuropraxia and more chances to preserve the branches. Moreover, posterior triangle dissection is not required for this type of approach.

Figure 1: The dissected sternocleidomastoid along with spinal accessory nerve from the posterior aspect Click here to view

References

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