C4 spinal nerve

At a glance

Level system

C4 nerve (named for its spinal cord segment)

Where it leaves the canal

The C4 nerve exits between the C3 vertebra and the C4 vertebra, above the C4 vertebra.Betts et al. 2022, §13.4

Distance down the canal before it exits

16 mmMeasured on one model: the Visible Human male, imaged as a supine cadaver. Not a normal range; drawn root, schematic

ISNCSCI key sensory point

Over the acromioclavicular jointRupp et al. 2021; Kirshblum et al. 2011

Roots, ganglia and nerves are drawn schematically from each segment to its exit; their paths are not traced from imaging.

What the sources say

“The same occurs for C3 to C7, but C8 emerges between the seventh cervical vertebra and the first thoracic vertebra.” Betts et al. 2022, §13.4

“All of the spinal nerves are combined sensory and motor axons that separate into two nerve roots.” Betts et al. 2022, §13.4

“The sensory axons enter the spinal cord as the dorsal nerve root.” Betts et al. 2022, §13.4

“The motor fibers, both somatic and autonomic, emerge as the ventral nerve root.” Betts et al. 2022, §13.4

“The cervical plexus is composed of axons from spinal nerves C1 through C5 and branches into nerves in the posterior neck and head, as well as the phrenic nerve , which connects to the diaphragm at the base of the thoracic cavity.” Betts et al. 2022, §13.4

Connections to the rest of the body

• Spinal nerves and plexuses

  Phrenic nerve: neck segments drive breathing

  The diaphragm is driven by the phrenic nerve, a branch of the cervical plexus. Its roots are classically C3, C4 and C5; dissection studies find two-root and one-root patterns too.

  Betts et al. 2022, §13.4; Sharma et al. 2025 · Show on the body

• Spinal nerves and plexuses

  Brachial plexus: the nerves of the arm

  Spinal nerves from the lower neck and first thoracic segment regroup in the brachial plexus and become the nerves of the arm.

  Betts et al. 2022, §13.4 · Show on the body

• Key sensory points (ISNCSCI)

  Key sensory points: one patch of skin per segment

  The examination tests light touch and pinprick at one key point per segment on each side, from C2 behind the ear to S4–5 beside the anus. The points here were placed on this body by following the standard’s written descriptions from bony landmarks, so they are approximate.

  Rupp et al. 2021; Kirshblum et al. 2011 · Show on the body

Read more

• Breathing and the spinal cord

  How the brainstem's breathing rhythm reaches the diaphragm and rib muscles through the cord. Why the phrenic nerve's origin in the mid-neck matters after a spinal cord injury.