There are eight pairs of cervical nerves, labeled C1 through C8. They exit through small openings between the vertebrae in your neck and are responsible for sensation and movement in your head, neck, shoulders, arms, and hands. They also control your ability to breathe.
Why Eight Nerves but Only Seven Vertebrae
Your neck contains seven cervical vertebrae, so having eight cervical nerves catches many people off guard. The explanation comes down to how the first seven nerves exit the spine. C1 through C7 each exit above the vertebra they’re named after: the C1 nerve exits above the C1 vertebra, the C2 nerve exits above C2, and so on. That pattern leaves one nerve unaccounted for after C7, the last cervical vertebra. The eighth cervical nerve, C8, exits below the C7 vertebra. From that point downward in the spine, every nerve exits below its corresponding vertebra, which is why the rest of the body doesn’t have this mismatch.
These 8 pairs are part of a larger system of 31 total spinal nerve pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
What the Upper Cervical Nerves Control (C1 to C4)
The upper four cervical nerves form a network called the cervical plexus. These nerves handle sensation across your scalp, neck, and upper shoulders, and they power muscles involved in swallowing and, critically, breathing.
On the sensory side, C2 and C3 supply feeling to the upper neck, a small area of the jaw beneath each ear, and the back of the head. C3 and C4 cover the lower neck, upper chest, and upper back. Some branches cross over the collarbone to supply the skin over the shoulder.
On the motor side, branches from C1 to C3 control a group of small muscles in the front of your throat that help with swallowing and speaking. The most important motor nerve in this group is the phrenic nerve, which originates primarily from C4 with contributions from C3 and C5. The phrenic nerve is the sole motor supply to your diaphragm, making it essential for breathing. Dissection studies confirm that C4 provides the largest contribution to this nerve, though the exact combination of roots varies from person to person.
What the Lower Cervical Nerves Control (C5 to C8)
The lower four cervical nerves, along with the first thoracic nerve (T1), form the brachial plexus, the network that controls your shoulders, arms, and hands. C5 and C6 merge into an upper trunk, C7 continues alone as the middle trunk, and C8 joins with T1 to form the lower trunk. These trunks then branch and recombine into the major nerves of your arm.
Each root level has a distinct role in arm movement. C5 primarily drives the muscle that bends your elbow (the brachioradialis). C5 and C6 together power wrist extension and forearm rotation. C8 controls finger grip strength and the small muscles on the pinky side of your hand. If a single nerve root is compressed, the resulting weakness often follows a predictable pattern. Someone with C6 nerve root irritation, for instance, typically experiences mild weakness in wrist extension and forearm rotation while other arm movements remain normal.
Skin Regions Each Nerve Supplies
Each cervical nerve root maps to a specific strip of skin called a dermatome. These maps aren’t perfectly precise, since neighboring nerves overlap, but they follow a consistent general pattern that’s useful for pinpointing where a problem originates.
- C1: Many people lack a C1 sensory nerve entirely. When present, it covers a small area at the center of the back of the head.
- C2 to C3: Upper neck, a small patch of jaw below each ear, and the back of the head.
- C3 to C4: Lower neck, upper chest, and upper back.
- C4 to C5: Shoulders and upper arms.
- C5 to C6: Thumb side of the upper arm and forearm, and the thumb itself.
- C6 to C7: Thumb side of the forearm, plus the index and middle fingers.
- C8: Ring finger, little finger, and the pinky side of the hand and forearm.
This is why a pinched nerve in the neck can cause tingling or numbness in a very specific part of your arm or hand. The location of the symptoms points back to which nerve root is affected.
Why This Numbering Matters
Understanding the eight cervical nerve pairs isn’t just an anatomy trivia point. When a disc herniates or a bone spur narrows the opening where a nerve exits, the symptoms follow the map laid out by dermatomes and muscle groups. Numbness along the thumb side of your forearm suggests a C6 issue. Weakness in your grip and tingling in your ring finger points toward C8. The phrenic nerve’s origin at C3 to C5 explains why high spinal cord injuries can compromise breathing, since damage at or above that level can cut off the signal to the diaphragm.
The fact that C1 through C7 exit above their vertebrae while C8 exits below C7 also has practical consequences for imaging and diagnosis. A disc bulge between C5 and C6, for example, typically affects the C6 nerve root, not C5, because C6 is the nerve exiting at that level. This numbering quirk is unique to the cervical spine and often determines which specific nerve root is being compressed.