The C4 myotome corresponds to which shoulder movement?

• A. Finger abduction and adduction
• B. Shoulder elevation (upper trapezius)
• C. Elbow flexion and wrist extension
• D. Shoulder abduction and external rotation

Answer: (B)

C4 is a shoulder-related myotome that mainly controls the ability to shrug the shoulders, which is shoulder elevation produced by the upper trapezius. In a neuromuscular exam, asking the patient to elevate the shoulders against resistance tests this C4 function, helping localize nerve root involvement to C4.

Other movements listed map to different nerve roots: finger abduction/adduction involves the intrinsic hand muscles (primarily C8–T1); elbow flexion and wrist extension involve C5–C6 (biceps and wrist extensor muscles); and shoulder abduction with external rotation mainly involves C5–C6 (deltoid for abduction and infraspinatus for external rotation).