Review Question - QID 1414

Examination of finger abduction would be normal in a patient with an isolated superior trunk brachial plexus injury. Finger abduction is performed by the ulnar nerve, which is supplied by the inferior trunk of the brachial plexus.

Superior trunk brachial plexus injuries are thought to occur secondary to traction when an athlete sustains a lateral flexion injury of the neck. Transient injuries are often referred to as "stingers" or a "burner." Symptoms of these injuries are referable to the motor and sensory functions of the axillary, musculocutaneous, and supra-scapular nerves.

Hershman reviewed the etiology of brachial plexus injuries. They showed that superior trunk brachial plexus injuries are usually transient, with 95% of people regaining full neurological recovery with conservative management.

Schenck showed that injuries to the superior trunk will mainly affect muscles supplied by C5 and C6, such as the deltoid, biceps brachii, brachialis, and brachioradialis muscles. Decreased sensation will occur over the lateral shoulder, lateral aspect of the upper limb, as well as the radial half of the volar forearm with these injuries.

Illustration A demonstrates a lateral traction injury that can precipitate this type of superior brachial plexus injury. Illustration B shows a schematic of the brachial plexus. The nerves supplied by the superior trunk of the brachial plexus include the axillary, musculocutaneous, and supra-scapular nerves.

Incorrect Answers:
Answer A: Decreased sensation over the lateral aspect of shoulder = axillary nerve.
Answer B: Decreased biceps reflex = C5 +/- C6 reflex arc.
Answer C: Weakness to shoulder abduction = axillary nerve.
Answer D: Decreased sensation over the radial aspect of the forearm = lateral antebrachial cutaneous nerve of the forearm (branch of musculocutaneous nerve).