Spinal levels to the muscles of the hand?

• A. C5 and C6
• B. C6 and C7
• C. C7 and C8
• D. C8 and T1

Answer: (D)

Focus on the nerves that actually control the intrinsic muscles of the hand. Those muscles are innervated mainly by the ulnar and median nerves, which carry fibers from the lower trunk of the brachial plexus: C8 and T1. The ulnar nerve supplies most of the intrinsic hand muscles (like the interossei and many intrinsic muscles of the hypothenar region), while the median nerve provides the thenar muscles and the lateral two lumbricals. The radial nerve does not innervate the intrinsic hand muscles; it is involved with posterior forearm extensors and some dorsal hand muscles but not the intrinsic group.

So the spinal levels relevant to the hand muscles are C8 and T1. A lesion at these roots would chiefly affect intrinsic hand movements (e.g., finger abduction/adduction and lumbrical/thenar function).