The cervical plexus is formed by which spinal nerve roots?

• A. C5-T1 nerves
• B. C1-C5 nerves
• C. L1-L4 nerves
• D. L4-S4 nerves

Answer: (B)

The main idea is that a cervical nerve plexus is created by the ventral rami of the upper cervical nerves, which come together to supply the neck region and some deeper structures. In this region, the fibers most commonly come from the first four cervical nerves, but there is often a contribution from the fifth cervical nerve as well. That extra C5 input helps form nerves that descend toward the diaphragm (through the phrenic nerve) and other neck nerves. Because of this combined pattern, the roots C1 through C5 best describe where the cervical plexus gets its fibers. The other root sets belong to different plexuses (brachial from C5-T1, lumbar from L1-L4, sacral from L4-S4), so they don’t describe the cervical plexus.