A 23-year-old man is brought to the emergency department after sustaining stab injuries in a street fight. The patient feels lightheaded and dizzy. His blood pressure is 100/60 mm Hg and pulse is 115/min. Physical examination shows profuse bleeding from penetrating wounds over the left neck and shoulder area. Intravenous fluids are administered, and a blood transfusion is initiated. Urgent surgical exploration is performed, and the injured blood vessel is repaired. Further exploration shows complete transection of the nerve indicated by the arrow in the image below. Which of the following actions is most likely to be weakened as a result of this patient's nerve injury?

Question

A 23-year-old man is brought to the emergency department after sustaining stab injuries in a street fight.  The patient feels lightheaded and dizzy.  His blood pressure is 100/60 mm Hg and pulse is 115/min.  Physical examination shows profuse bleeding from penetrating wounds over the left neck and shoulder area.  Intravenous fluids are administered, and a blood transfusion is initiated.  Urgent surgical exploration is performed, and the injured blood vessel is repaired.  Further exploration shows complete transection of the nerve indicated by the arrow in the image below.  Which of the following actions is most likely to be weakened as a result of this patient's nerve injury?

Quizplus · Accepted Answer

11ec160b_3599_8e9b_9249_935dfa269b83_MD0001_00 The radial nerve is the largest branch of the brachial plexus and receives fibers from C5-T1. It innervates all of the extensor muscles of the upper limb below the shoulder and provides sensory innervation to the skin of the posterior arm, forearm, and dorsal lateral hand. This nerve tracks within the radial groove on the humerus; therefore, it is vulnerable to traumatic injury (eg, penetrating stab wound) at the humeral midshaft. The nerve can also be injured during its superficial course within the axilla. Patients with proximal radial neuropathy typically have weakness during wrist and finger extension (wrist drop) and variable sensory loss over the posterior arm and forearm. (Choices A, B, D, and E) Damage to the median or ulnar nerve can result in weakness on wrist flexion. Damage to the median nerve can also result in weakness on thumb opposition, whereas ulnar nerve damage may limit finger abduction and thumb adduction. Educational objective: The radial nerve provides sensory innervation to the skin of the posterior arm, forearm, and dorsal lateral hand and provides motor innervation to all of the extensor muscles of the upper limb below the shoulder. Damage to the proximal radial nerve (eg, at the axilla or midshaft humerus) may result in wrist drop. __________ References: Clinical features of wrist drop caused by compressive radial neuropathy and its anatomical considerations. (http://www.ncbi.nlm.nih.gov/pubmed/24851150) Anatomical, clinical, and electrodiagnostic features of radial neuropathies. (http://www.ncbi.nlm.nih.gov/pubmed/23177029)

A 23-Year-Old Man Is Brought to the Emergency Department After