Conclusions. We encountered shoulder syndrome after functional neck dissection (FND) less frequently than reported in the literature. This technique is a favorable treatment choice for appropriately selected patients with head and neck cancer with cervical metastasis. It depends on careful dissection of neurovascular tissues during surgery and preserved shoulder function due to chronic neurological degeneration caused by surgery. Also, radiotherapy has an evident negative effect on the accessory nerve. Objectives. To perform postoperative electrophysiological tests on the spinal accessory nerve (SAN) after FND and postoperative radiotherapy. Subjects and methods. A study group of 16 patients with head and neck cancer who underwent 22 FNDs and 10 volunteers in the control group were evaluated. The SAN latency and amplitude were measured and then upper trapezius muscle electromyography (EMG) was performed on all the patients and the volunteers. Results. The EMG results of the study group revealed 19 cases with normal findings, 1 with total and 2 with partial axonal degeneration. The amplitude levels of the SAN in the study group showed statistically significant decrease when compared with the control group. The latency levels of the SAN in the four patients who received postoperative radiotherapy were significantly longer than those in cases who did not receive this therapy.