Utilization of intraoperative electroneurography to understand the innervation of the trapezius muscle.

The radical neck dissection is an operation for the management of lymph node metastases from primary sites involving the oral cavity, larynx, and other areas of the head and neck. In this procedure, the spinal accessory nerve is removed along with other structures. In modified neck dissection the spinal accessory nerve is preserved. Patients undergoing the modified neck dissection have had variable functional outcomes from little or no pain or disability, to significant muscle dysfunction. Our group hypothesized that patients with good functional outcomes following modified neck dissection may have had motor contributions from C2, C3, or C4 branches, while those with less favorable outcomes did not. To demonstrate the presence of motor input and its significance both from the spinal accessory nerve and the branches of the cervical plexus, we utilized intraoperative electroneurography. We find that although there is motor contribution from C2, C3, and C4 to the trapezius muscle, it was not consistent or significant.