return to: Posterolateral Neck Dissection

Trapezius muscle innervation:

Tubbs et al (2011) identified that 'athough most agree that the spinal accessory nerve is the primary innervation of the trapezius, the additional contribution from cervical nerves has yet to reach a general consensus". Through cadaver study of 15 specimens, these investigators identified cervical motor nerve innervation of all trapezius muscles studied. Fibers from C2 and C-3 usually joined the spinal accessory nerve before its penetration into the trapezius muscle, whereas fibers containing just C3 and C-4 innervation usually entered separately. Fiber analysis identified that all cervcial fibers innervating the trapezius muscle contained motor fibers (carbonic anhydrase activity).

Dominant innervation of the trapezius muscle comes from the spinal accessory nerve with variable contributions coming from the C2, 3, and 4 nerves. Analysis of intraoperative nerve stimulation by Kim et al (2014) identified that the three portions of the trapezius labelled 'descending', 'transverse' and 'ascending' were all innervated by the spinal accessory nerve among 24 patients studied intraoperatively during neck dissection. C4 contributions to the trapezius were present in 20 of 24 patients (16 of the patients with all three parts of the trapezius supplied). C2 contributions were present in only 2 of 24 patients (with no patient showing response in all three parts) and C3 contributions in 11 of 24 patients (with 8 patients showing response in all three parts).

References

Tubbs RS, Shoja MM, Loukas M, Lancaster J, Mortazavi MM, Hattab EM and Cohen-Gadol AA: Study of the cervical plexus innervation of the trapexius muscle. J Nerosurg: Spine / Vol 14 / May 2011

Kim JH, Choi KY, Lee KH, Lee DJ, Park BJ and Rho YS: Motor innervation of the trapezius muscle: intraoperative motor conduction study during neck dissection. ORL Otorhinolaryngol Relat Spc. 2014;76(1):8-12  Epub 2014