• accessory nerve
• electromyography
• trapezius atrophy
• wrestling

A 17 year old youth presented complaining of vague chest and back pain. His medical history was unremarkable except for a sports injury three to four months previously. The injury occurred during wrestling when his opponent had fallen on his chest and neck region. On physical examination, we noted an asymmetric neckline on the right, the result of atrophy in the superior portion of the right trapezius muscle. Neck and bilateral shoulder movement, both passive and active, were not limited and were painless. There were no functional deformities such as winging scapula or drooping shoulder. No loss of motor function was detected in the right sternocleidomastoid muscle or during right shoulder elevation. Radiographic examination produced no relevant findings. We next performed electromyography (EMG), the likely diagnosis being an injury to the right accessory nerve. The needle EMG was consistent with an almost completely regenerated upper portion of the trapezius muscle compared with the contralateral side. The patient was given a regimen of shoulder strengthening exercises and followed up.

The superficial course of the spinal accessory nerve in the posterior cervical triangle makes it susceptible to injuries. The most common cause is an iatrogenic injury during surgery. Donner et al,¹ in a series of 83 patients with extracranial spinal accessory nerve injuries, reported the underlying causes to be lymph node biopsy in 42 cases, tumour excision in 14 cases, and carotid endarterectomy, face lift surgery, and irradiation (one case each). They also summarised the other causes as: traumatic, 13; stretch/contusion, 6; stab or glass wound, 1; shotgun, 1; compression, 1; weight lifting, 1; Hansen’s disease, 1; mononeuritis, 1.

The accessory nerve is a motor nerve which innervates the trapezius and the sternocleidomastoid muscles. Interestingly, injury to this nerve does not usually result in functional loss of the latter muscle. This is usually attributed to the fact that the nerve is usually injured in the posterior triangle after it has innervated the muscle and/or the observation that the muscle receives dual input from the accessory nerve and the cervical roots.¹ Consequently, patients present with an ipsilateral trapezius palsy—that is, an asymmetric neckline, a drooping shoulder, winging of the scapula, and weakness of forward elevation²—immediately after or within one week of the trauma.¹

Patient evaluation entails electrodiagnostic studies in addition to the clinical findings, EMG often showing an increase in polyphasic waves and decreased recruitment.³ Ultrasonography has recently been proposed as an adjunct in the diagnosis.⁴ Because of untoward consequences in chronic cases, surgery is recommended if patients fail to improve after one year of conservative treatment.^2,5

We consider this case to be noteworthy in certain aspects. Firstly, the patient did not present with a trapezius palsy; it was a late silent physical finding that we uncovered. Secondly, as in a few of the cases in the above series,¹ only the upper trapezius atrophy was present which did not preclude shoulder function. This is usually because there are other innervation sources or because of the presence of a divided accessory nerve.^1,6 Thirdly, we believe that our case implies the likelihood of a relatively benign course in younger patients. Lastly, together with another case report of a wrestler,⁷ the possibility of this type of injury occurring during sporting activity is highlighted. We therefore alert sports physicians to such a clinical scenario, for which prompt evaluation and management should always be the prerequisite.