2B or Not 2B? Shoulder Function After Level 2B Neck Dissection: A Randomized Controlled Study

The lymphatic fluid of upper aerodigestive tract (UADT) drains into various levels of the neck. When cancer occurs in the UADT, the potential for local metastatic spread to the neck exists, thus necessitating treatment of the neck. Ideally all potential neck structures, which could harbor cancer cells or provide a dock for recurrence, would be eradicated. Unfortunately, such radical treatments have shown to cause extreme rates of morbidity with little extra oncologic benefit. Thus, head and neck oncologists have strived to create treatment paradigms, which maximize cure rates while minimizing morbidity. Finding this intricate balance has translated to selective neck dissection (SND) and post-operative RT.1

Increased understanding of lymphatic drainage patterns in the head and neck has lead to widespread use of SND. Through removal of lymphatics in neck levels with the highest risk of harboring cancer cells, based on primary tumor site, important neck structures may be preserved. As such, the treatment remains oncologically sound and avoids the morbidity associated with its predecessor, the radical neck dissection. 1

One of the structures preserved in the SND is the spinal accessory nerve (SAN), which is responsible for providing motor innervation to the sternocleidomastoid (SCM) and trapezius muscles. Thus, it is intricately involved in shoulder function. The nerve exists the skull base at the jugular foramen and obliquely passes through neck level II. It then passes posterior to the SCM and eventually enters the trapezius muscles. Through this trajectory, it divides level II into IIa (anterior to the SAN) and IIb (posterior to the SAN).

It is known that shoulder function significantly deteriorates when level V is dissected.2 This is likely due to traction and devascularization injury of the longest portion of the SAN in the neck. As such, practice has become such that level V is left intact in cases where it does not harbor detectable disease or when occult disease incidence is very low. Due to the intimate relationship of IIb with the SAN, there is also potential for injury to the nerve in this area.2 As such, debate has arisen to the necessity of including IIb in the neck dissection specimen. Studies have shown that the prevalence of occult nodal disease in IIb ranges from 0-8.7.5% depending on the overall n stage of the neck.3-5 These figures have lead head and neck surgeons to weigh the benefits of not excising lymphatic tissue with low nodal metastatic rates versus excising the area and decreasing post-operative shoulder function.6

Because the incidence of occult metastases in IIb is low3-5, it has become standard of care in many centers to spare IIb, if it is oncologically feasible, in SND to preserve shoulder function. Because these patients receive post-operative RT it is thought that the RT will address any occult disease. Unfortunately, relying on RT poses two problems:

• occult disease may not respond to the RT
• leaving level IIb intact provides a lymphatic route of recurrence despite undergoing RT By surgically removing all portals of lymphatic disease spread these issues above can be eliminated.

The goal of this study is to demonstrate that the minimal manipulation of the SAN associated with IIb dissection will not have a significant impact on post-operative shoulder function. If this is the case, the standard of practice should be changed to include IIb in the SND specimen in cases where level IIa is dissected as well. This would eliminate any further lymphatic tissue, which may harbor disease.

Note: At the University of Alberta, some head and neck surgeons prefer to spare IIb in SND, while others prefer to resect it. Thus, the protocol in this study does not manipulate current standards of practice.

*Reference numbers correspond to articles in the "Citations" section. The citations are in order of appearance in the above text.

Inclusion criteria

• Head and neck cancer to be treated with primary surgical resection, SND and post-operative radiation therapy (RT).
• N0 neck disease on side of the dominant hand
• Willingness to participate in post-operative physiotherapy

Exclusion criteria

• IIb positive disease found on clinical exam, CT Scan or intraoperatively (gross appearance or positive margins of frozen section of level IIa)
• Previous neck RT
• Previous chemotherapy
• Invasion of spinal accessory nerve (SAN) by neck malignancy (evident on physical exam, CT scan or intraoperatively (gross appearance).
• Previous neck dissection
• Previous SAN injury or dysfunction
• Preoperative signs or formal diagnosis of myopathy or neuropathy
• Previous shoulder injury (muscular or bony)
• Level V neck dissection
• Recognized intraoperative sectioning of the SAN
• Unable to provide informed consent
• Cardiac pacemaker (contra-indication to EMG/Nerve conduction)
• Radial forearm free flap on dominant arm