MSFinals-2960
A 20-year-old man without significant history presents with complaints of pain in his left forearm and hand that is relieved by changing the position of his arm. During examination, there is a loss of sensation on the medial aspect of his hand, and a cervical rib is suspected. To confirm involvement of the C8 and T1 roots of the brachial plexus rather than a palsy of the ulnar nerve, which motor test should be used?