Anatomic Variability of the Accessory Nerve: Implications for Dissection of Level IIB

During neck dissection, level IIB lymphadenectomy necessitates manipulation of the spinal accessory nerve that might be avoided and might cause postoperative disability. Current literature does not describe the effect of variation in the spinal accessory nerve in the upper neck. We sought to measure the effect of the dimensions of level IIB on nodal yield in level IIB and on patient reported neck symptoms.

We measured the boundaries of level IIB of 150 patients undergoing neck dissection. Level II was dissected and separated into levels IIA and IIB intraoperatively. Patient-reported symptoms were assessed in 50 patients using the Neck Dissection Impairment Inventory. We computed descriptive statistics, and sought to identify correlation with the number and proportion of level IIB nodes and the number of metastatic nodes. Level IIB dimensions were analyzed as predictors of postoperative symptoms.

We measured 184 sides, with 37.7% of level II nodes found in level IIB. Mean accessory nerve length across level II was 2.5 cm. Every additional 1 cm in accessory nerve length was associated with two more level IIB nodes. At all accessory nerve lengths, meaningful numbers of nodes were present in level IIB. Accessory nerve length and other factors did not correlate with NDII scores.

Longer lengths of accessory nerve across level IIB correlated with greater nodal yield. However, data did not point to an accessory nerve length cutoff below which level IIB dissection could be avoided. In addition, the dimensions of level IIB did not correlate with postoperative neck symptoms.

2 Laryngoscope, 134:154-159, 2024.