Spinal accessory nerve neuropathy following neck dissection

The most common complication of neck dissection is shoulder dysfunction due to manipulation of spinal accessory nerve, resulting in trapezius muscle atrophy mainly in procedures involving the posterior neck triangle. AIM: This study used electromyography to evaluate the injury to the spinal accessory nerve following neck dissection. MATERIALS AND METHODS: Prospective case series of 51 patients submitted to 60 neck dissections followed by physical therapy evaluation of shoulder dysfunction. Nerve integrity was evaluated before and after the surgery by means of surface EMG registering the electric activity of the trapezius muscle during voluntary contraction. The patients were grouped according to the type of neck dissection, presence of shoulder pain, impairment during abduction movement and hypotrophy/ atrophy of the trapezius muscle. RESULTS: Action potential had median values of 54.3 microV before surgery and 11.6 microV after it (p<0.001). There was a mean decrease of 70% comparing to preoperative values. The median was 12.5 microV after dissection including level IIb, and 8.9 microV after dissection including levels IIb and V (p<0.002). CONCLUSION: Surface EMG is a sensitive and painless method for spinal accessory nerve dysfunction evaluation. The results suggest the usefulness of the trapezius muscle electromyography to confirm diagnosis and early physical therapy intervention in neuropathies of the spinal accessory nerve.