Spinal nerves branch off from the spinal cord to innervate the rest of the body. These complex networks of nerves enable the brain to receive sensory inputs from the skin and to send motor controls for muscle movements. In the cervical spine, there are eight pairs of spinal nerves labeled C1 to C8, which innervate the neck, shoulder, arm, hand, and more.

See Spinal Anatomy and Back Pain

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Nerve Root and Spinal Nerve Anatomy

Each level of the cervical spine has four nerve roots—two on each side—that branch off from the spinal cord. The two types of nerve roots on each side include:

  • Ventral root (located in front) that carries motor signals from the brain to that nerve root’s myotome, which is the group of muscles that it controls
  • Dorsal root (located in back) that carries sensory signals back to the brain from that nerve root’s dermatome, which innervates the specific region of skin that it covers

See Spinal Cord and Spinal Nerve Roots

The ventral root and dorsal root branch off separately from the spinal cord then merge together in the intervertebral foramen, a small bony opening between the two adjacent vertebrae. When the ventral and dorsal roots merge, the combined nerve is called the spinal nerve. From there, the spinal nerve branches into a network of nerves that innervate its dermatome (for sensations) and myotome (for motor controls).

When discussing symptoms with a patient, it is common for doctors and other medical experts to simplify the terminology by referring to a single nerve root rather than two, or by using the terms for nerve root and spinal nerve interchangeably.

Cervical Nerve Functions

A dermatome is the area of sensory nerves near the skin that are supplied by a specific spinal nerve root. For example, the C5 dermatome is supplied by the C5 nerve root.

Cervical spinal nerves, also called cervical nerves, provide functional control and sensation to different parts of the body based on the spinal level where they branch out from the spinal cord. While innervation can vary from person to person, some common patterns include:

  • C1, C2, and C3 (the first three cervical nerves) help control the head and neck, including movements forward, backward, and to the sides.3 The C2 dermatome handles sensation for the upper part of the head, and the C3 dermatome covers the side of the face and back of the head.4 (C1 does not have a dermatome.)

    See The C1-C2 Vertebrae and Spinal Segment

  • C4 helps control upward shoulder movements.3 C4 (along with C3 and C5) also helps power the diaphragm—the sheet of muscle that stretches to the bottom of the rib cage for breathing.3 The C4 dermatome covers parts of the neck, shoulders, and upper part of arms.4
  • C5 helps control the deltoids (which form the rounded contours of the shoulders) and the biceps (which allow bending of the elbow and rotation of the forearm).3 The C5 dermatome covers the outer part of the upper arm down to about the elbow.4

    See All About the C2-C5 Spinal Motion Segments

  • C6 helps control the wrist extensors (muscles that control wrist extension) and also provides some innervation to the biceps.3,5 The C6 dermatome covers the thumb side of the hand and forearm.4

    See All About the C5-C6 Spinal Motion Segment

  • C7helps control the triceps (the large muscle on the back of the arm that straightens the elbow) and wrist extensor muscles.3,5 The C7 dermatome goes down the back of the arm and into the middle finger.4

    See All About the C6-C7 Spinal Motion Segment

  • C8 helps control the hands, such as finger flexion (handgrip).3,5 The C8 dermatome covers the pinky side of the hand and forearm.4

    See All About the C7-T1 Spinal Segment (Cervicothoracic Junction)

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If a cervical nerve becomes irritated or compressed, it may cause pain and/or dysfunction that correlates to its dermatome for sensations and/or myotome for motor control.

See Spinal Cord Compression and Dysfunction from Cervical Stenosis

References:

  1. Magee DJ. Cervical Spine. In: Magee DJ, ed. Orthopedic Physical Assessment. 5th ed. St. Louis, MO. Saunders Elsevier; 2008: 130-202.
  2. Felten DL, O’Banion MK, Maida MS. Peripheral Nervous System. In: Netter’s Atlas of Neuroscience. 3rd ed. Elsevier; 2016:153-231. doi:10.1016/b978-0-323-26511-9.00009-6
  3. Childress MA, Becker BA. Nonoperative management of cervical radiculopathy. Am Fam Physician. 2016; 93(9):746-54.
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