This is a prospective study, in which 100 consecutive selective neck dissections done for in 91 patients (82 patients underwent ipsilateral neck dissection and 9 patients underwent bilateral neck dissection) with radiological N+ necks with resectable Oral Squamous Cell Carcinoma presenting at our Head and Neck Surgical Oncology Department between January 2018 to March 2018 were included in the study. Bilateral neck dissections for the purpose of this study have been considered as two neck dissections.

Treatment naïve patients with resectable oral squamous cell carcinoma.

Non-squamous cell pathology/ non oral cavity pathology.

Ethical clearance was not sought for this pilot study, as this study intended to be a modification of already well-established surgical technique, which has been in practice at our centre, prior to this designed study.

Sub-platysmal flaps were raised in the standard manner. The anterior border of the Sternocleidomastoid (SCM) muscle was delineated. The SCM was divested of its fascia. The avascular plane, between the SCM and Internal Jugular Vein (IJV), was opened by sharp dissection [1]. Here on according to the technique practiced at our institution, the posterior belly of the digastric muscle was identified and retracted. At this point the level of the hyoid bone was identified and a node parallel to this level lateral to the IJV was identified. The loose areolar tissue on the inner aspect of the SCM, which separates it from the internal jugular vein, was further opened up at the level of the identified node and the Spinal Accessory Nerve (SAN) was identified directly beneath the node at its entry point into the SCM [Table/Fig-1a-c].

[Table/Fig-1]:

a) Blue arrow-retracted SCM, black arrow-retracted IJV, White arrow-undissected lymph node lying above SAN in a left neck dissection. b) Black arrow-retracted IJV, blue arrow-retracted SCM, white arrow-babcock forceps holding dissected node lying above SAN, pointed by Addison forceps. Right Neck Dissection. c) Black arrow-IJV, blue arrow-retracted SCM, white arrow-node lying above SAN, yellow arrow-digastric tendon at the level of hyoid bone. Left neck dissection.

In this study, 91 consecutive patients with N+ neck, underwent 100 selective neck dissection. 82 patients underwent ipsilateral neck dissection and 9 patients underwent bilateral neck dissection [Table/Fig-1,2]. For the purpose of this study bilateral neck dissection has been considered as two neck dissections (82 ipsilateral neck dissections+9 bilateral neck dissections=total 100 neck dissections). Strictly following the above described technique alone, we were able to identify the SAN near its entry point into the SCM in 96 neck dissection procedures. Except for in four neck dissections were a nodal conglomerate was found to be surrounding the nerve and the SAN had to be sacrificed for oncological safety. Pre-operative scans, for these four patients were suggestive of the presence of nodal conglomerate at level II, however it is not possible to identify the course of the nerve in a Contrast Enhanced Computer Tomography (CECT) image, which is the more common pre-operative imaging modality used. Identification of the nerve although possible on Magnetic Resonance Imaging (MRI), is not a routine practice and MRI is not advised to the patient just for identification of the nerve unless otherwise indicated.

In our experience, despite the presence of multiple nodes in level II, it is only rarely that the nerve passes through a nodal conglomerate and that only becomes evident on the operating table during dissection. These 4 neck dissections had been staged N2b clinically with the primary being T4a buccal mucosa OSCC [Table/Fig-3].

Identification of SAN is an important step in neck dissection. Its anatomic implication with regards to neck dissection is that it delineates level IIa and IIb in the neck. Its intraoperative identification serves two purposes:

Its rapid identification while preserving its nerve sheath and innervation to Sternocleidomastoid (SCM) and Trapezius is vital for post-operative quality of life of the patient [4]. The most consistent landmarks for its identification are greater auricular nerve at erb’s point and its entry point into trapezius in the lower neck [5]. With consistent use of Selective Neck Dissections (SND) in N+ necks and Super Selective Neck Dissections (SSND) in salvage settings, the need for identification of SAN at higher levels of neck by simpler means in anterograde manner is felt, however only few papers in literature discuss this issue [6,7].

The method described in this study requires identification of a level IIa lymph node, which has been consistently found at the level of the hyoid bone, lateral to IJV following retraction of SCM, in the avascular plane. We were able to identify the SAN by direct deeper dissection to this node in 96 out of 100 neck dissection procedures. In the remaining four cases the nerve was found to be traversing through a nodal conglomerate in this region and had to be sacrificed for oncological safety.

In the superior neck, the transverse process of the (C1) has been described in the literature as the key landmark [8,9]. However, palpatory identification of the transverse process with intact level IIb is difficult and often not possible in short fat necks where in-adequate extension of the neck is often not achievable. In contrast it is much easier to identify the node at this level, which in our experience was found to be consistently lying over the SAN at the level of hyoid bone.

The small sample size inherently limits any conclusion drawn from this study to be generalised. Thus this study can be treated as a pilot study. Further studies with larger sample size are required to prove level IIa node as consistent landmark for SAN identification as lymph nodes in general are not considered to be consistent in their location. This study only includes N+ necks and further investigations are warranted to identify the presence or absence of this node in clinically N0 necks.

In our search of the published literature, while preparing the manuscript of this study, we have not come across mention of any such technique involving the constant presence of this node in N+ necks while doing Selective Neck Dissection (I-IV) used to identify the SAN. The purpose of this study was to establish this technique as a standard operating procedure for identification of SAN We even have a separate nomenclature for it, the ‘Trainee Node.’