In addition to the seven cervical vertebrae, cervical anatomy features eight cervical nerve roots (C1-C8) that branch from the spinal cord and control motor and sensory abilities for different parts of the body.
Each cervical nerve is named based on the lower cervical vertebra that it runs between. As an example, the C6 nerve root runs between the C5 vertebra and the C6 vertebra.
Cervical Nerve Functions
Each level of the cervical spine actually has two nerve roots—one on each side—that branch off from the spinal cord.
Keeping with the aforementioned example at the C5-C6 level, each C6 nerve root exits the spinal canal through a bony hole (foramina) on both sides of the neck. From there, the C6 nerve root feeds into nerves that run down their own side’s shoulder, arm, and hand.
Cervical nerves provide control and sensation to different parts of the body based on the spinal level from where they branch out. More specifically:
- C1, C2, and C3 (the first three cervical nerves) control the head and neck, including movements forward, backward, and to the sides. These nerves also play key roles in breathing. The C2 dermatome handles sensation for the upper part of the head, and the C3 dermatome covers the side of the face and behind the head. (C1 does not have a dermatome.)
- C4 helps control the shoulders as well as the diaphragm—the sheet of muscle that stretches to the bottom of the rib cage—for breathing. The C4 dermatome covers the neck and top of the shoulders.
- C5 controls upper body muscles like the deltoids (which form the rounded contours of the shoulders) and the biceps (which allow flexion of the elbow and rotation of the forearm). The C5 dermatome covers the shoulders and outer part of the arm down to about the elbow or close to the wrist.
- C6 controls the wrist extensors (muscles like the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris that control wrist extension and hyperextension) and also provides some innervation to the biceps. The C6 dermatome covers the top of the shoulders and runs down the side of the arm and into the thumb side of the hand.
- C7 controls the triceps (the large muscle on the back of the arm that allows for straightening of the elbow). The C7 dermatome goes from the shoulder down the back of the arm and into the middle finger.
- C8 controls the hands. The C8 dermatome covers the lower part of the shoulder and goes down the arm into the pinky side of the hand.
When any of the highly sensitive cervical nerves are irritated (possibly from a herniated cervical disc or cervical stenosis), neck pain and other symptoms may ensue, with functioning possibly affected in different ways.
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Cervical Spinal Cord Injury
The spinal cord is a bundle of nerves that send signals from the brain to the rest of the body. If a cervical vertebra is fractured by trauma, such as in a car accident, a fall, a diving accident that jars the head, or any other significant cervical injury, the spinal cord can be damaged. This type of injury can result in impaired functioning depending on which cervical vertebra has been injured.
Spinal cord injuries are typically classified by the spinal nerve root level at which function is lost or impaired. For example, a C6 spinal cord injury would result in loss of the C6 nerve root’s function and all of the nerve roots below. A person with a C6 spinal cord injury would be able to breathe and move the head and shoulders well, but there would be struggles with moving the arms and likely no ability to move the trunk or legs. Sensations beneath the shoulders would also likely be impaired or lost.
A spinal cord injury at any of the top three levels (C1, C2, or C3) is usually fatal unless the ability to breathe is quickly restored by an emergency medical responder.
A full review of cervical fractures is beyond the scope of this article.
It should also be noted that trauma to cervical vertebrae occurs less often than cervical pain and other symptoms resulting from changes that occur with aging, such as the development of bone spurs in the neck and cervical osteoarthritis.