A 42-year-old woman complains of pain and stiffness in her neck. She was injured sliding into second base headfirst during her company softball game. Radiographs reveal no fractures of her spine. However, upon physical examination her right shoulder is drooping and she has difficulty in elevating that shoulder. If you ordered an MRI, it would most likely reveal soft tissue damage to which of the following nerves?

The thoracodorsal nerve innervates the latissimus dorsi, which has no action on the shoulder girdle. The spinal accessory nerve is the eleventh cranial nerve (CNXI) and innervates both the trapezius and sternocleidomastoid muscles. The loss of CNXI results in drooping of the shoulder due to paralysis of the trapezius. In addition to the clinical findings of the MRI, one can test the innervation of this nerve by asking the patient to shrug his or her shoulders against resistance (testing the trapezius), as well as turning his or her head against resistance (testing the sternocleidomastoid). The dorsal scapular nerve innervates the levator scapulae muscle, as well as the rhomboids. The greater occipital nerve is a sensory nerve innervating the posterolateral aspect of the scalp. The axillary nerve is a branch of the brachial plexus and innervates the deltoid and teres minor. It is not involved in shoulder elevation.