Spinal Accessory Nerve Monitoring in Selective and Modified Neck Dissection

Objectives: To determine whether a threshold increase in current is required to stimulate the spinal accessory nerve (SAN), comparing current on initial identification of the SAN and after completion of the dissection and before closure for selective neck dissection (SND), zones 1, 2, and 3, and modified radical neck dissection (MRND), zones 1, 2, 3, 4, and 5, and compare clinical outcome measures for “shoulder syndrome” for SND and MRND. Study Design: Prospective study of 22 consecutive patients receiving SND or MRND by one surgeon at one institution. Methods: Electrophysiologic recording of current on initial identification of the SAN was compared with the current recorded at the completion of the procedure and before closure for SND and MRND. Clinical correlation measured and compared parameters of “shoulder syndrome” (shrug, flexion, abduction, winging, and pain) for SND and MRND at 2 months. Results: Zero of 11 (0%) patients with SND and 3 of 11 (27%) patients with MRND had significant threshold increases (>0.4 mAmp) on completion of the dissection. One of 11 (9%) patients with SND and 3 of 11 (27%) with MRND had less than 90 degrees of shoulder abduction, scapular winging, or significant pain. Conclusions: Electrophysiologic integrity of the SAN does not completely correlate with clinical outcome measures for “shoulder syndrome.” It is significant that 17 of 19 (89%) patients without an electrophysiologic threshold increase did not develop “shoulder syndrome.” This study demonstrated less electrophysiologic threshold shift and “shoulder syndrome” with SND compared with MRND.