Preservation of spinal accessory and level 2b-sparing neck dissection: The balance beyond oncology and functionality.

Abstract

We applaud Dziegielewski et al. for meticulously collating an arduous trial, pointing out subtle details and generating a high level of evidence supporting the occurrence of shoulder dysfunction in patients undergoing submuscular recess dissections.1 Although the literature supporting the omission of level 2b is fractionated,2 to our knowledge studies have failed to provide concrete evidence with regard to oncological safety and long-term shoulder dysfunction in avoiding submuscular recess dissection.3, 4 Studies till date have indicated that there may be functional disability associated with any type of neck dissection. Specifically in patients wherein dissection is done around spinal accessory nerve, or with its handling and when subjected to a certain degree of traction. The degree of shoulder dysfunction is higher in modified radical neck dissection compared with a selective neck dissection (SND) or superselective neck dissection.5 The results of the study by Dziegielewski et al convincingly demonstrated that level 2b–sparing SND causes less shoulder impairment than SND that includes level 2b. The authors dissected 270 degrees around the nerve and acknowledged that the partial devascularization of the spinal accessory nerve (SAN) on the superior aspect of level 2a resulted in dysfunction among the patients in the level 2b–sparing group.1 Nevertheless, these patients had better shoulder function compared with those who underwent level 2b dissection. In our view factors beyond the degree of dissection around the nerve may play an additive role. Impairment of the intraneural microvascular flow, resulting in ischemia and subsequent axonal rupture and degeneration, causes the neuropathy. When level 2b is left untouched, apart from skeletonization, the vascularity to the nerve from the occipital and lingual vessels remains intact. This concept could further explain why the patients in the level 2b–sparing group had better shoulder function despite a 270-degree dissection around the nerve. Another exciting highlight in the present study was the relationship between active range of motion and mechanical contractures in the shoulder joint. With active physiotherapy, the patients experienced no significant limitations in their passive range of motion possibly due to the minimization of fibrotic changes and improved soft-tissue mobility. However, rigorous physiotherapy was no alternative to having a functional SAN. The fundamental movements found to be most affected during the trial period were active abduction and active external rotation. Impairment in the SAN alone and limitations in active abduction have been well corroborated, but nerves supplying muscles involved in active external rotation of the shoulder originate from the brachial plexus. The contributions from the cervical plexus to the brachial plexus could explain this unusual finding and raises the question of whether cervical rootlets should also be meticulously preserved during neck dissection. The answer is yes. Often, surgeons ignore the importance of the preservation of cervical rootlets. Studies have suggested better outcomes in shoulder function, both subjectively and objectively, when the cervical rootlets were preserved.6 The emphasis should not be just regarding the SAN, but to functionally preserve all oncologically safe structures during neck dissection. We differ with the current authors on the idea of omitting level 2b in the purview of the low incidence of isolated lymph node metastasis. Although the main highlight of their study was not the oncological safety of the omission of level 2b, the study was underpowered to draw robust conclusions. In their limited sample, more than 55% of the patients (11 of 20 patients) in the level 2b–sparing group received adjuvant radiotherapy or chemoradiotherapy. This in itself could mask the actual oncological effects of sparing level 2b. In addition, multiple head and neck subsites have the varying potential of causing metastasis to level 2b, thus diluting the effect on oncological safety. Evidence currently is divided regarding the role of the omission of level 2b based on arguable oncological safety. The study by Dziegielewski et al1, through an exemplary model, has emphasized the importance of the SAN in improving functional outcomes. However, the results of the study have to be considered in light of a low sample size and multiple anatomical locations of head and neck squamous cell carcinoma. Although not emphasized, the findings by Dziegielewski et al1 demonstrated the additional importance of the preservation of cervical rootlets.7, 8 The oncological safety of sparing level 2b should be compared in an adequately powered, prospective, randomized controlled trial before moving on to functional studies.9 This is to prevent the spread of the wrong concept regarding the superiority of level 2b–sparing neck dissection. The essence of our surgical endeavour indeed should be true functional preservation after corroborative oncological safety. No specific funding was disclosed. The authors made no disclosures.