What action is associated with the C8 myotome?

The C8 myotome is primarily associated with the muscles that control finger flexion and, more specifically, the movements related to the fingers. The action of finger abduction, which involves spreading the fingers apart, is influenced by the innervation from the C8 nerve root. This nerve root contributes to the function of certain muscles in the hand, particularly the interossei muscles that facilitate finger abduction.

In contrast, the shoulder shrug is primarily related to the upper trapezius muscle, which is innervated by the accessory nerve and upper cervical segments. Elbow flexion is mainly governed by the C5 and C6 nerve roots, which supply the biceps brachii and brachialis muscles. Wrist extension involves the radial nerve, which predominantly correlates with the C6 to C8 levels, but the C8 myotome specifically highlights control of finger and hand movements more than wrist actions. Hence, finger abduction is the most accurate choice for the action associated with the C8 myotome.