A 47-year-old man comes to the emergency department 2 hours after the onset of severe neck pain that began while he was lifting a heavy tool at his construction job. The pain is exacerbated when he turns his neck or coughs and now radiates over his right shoulder and arm. He has a 3-year history of intermittent neck pain that is relieved by ibuprofen use. He is in severe distress. When asked to turn his head, he turns it slowly to avoid pain. Muscle strength is 4/5 in the elbow flexor and wrist extensor muscles on the right. Deep tendon reflexes are decreased in the right biceps and brachioradialis muscles. Which of the following is the most likely cause of these findings?
A) Central cord syndrome
B) Compression of the lower brachial plexus
C) Compression of the musculocutaneous nerve
D) Compression of the upper brachial plexus
E) Herniated disc at C5–6