The C3 dermatome forms a collar over the upper and middle neck, front and back, below the C2 area. It reaches down toward the supraclavicular fossa. Its skin is supplied mainly through the cervical plexus.
| Nerve root | C3 |
|---|---|
| Area | Upper and middle neck, front and back |
| How to test | Light touch and pinprick are compared side to side at the ISNCSCI key sensory point: in the supraclavicular fossa (just behind the clavicle) at the midclavicular line. |
| Nerve Supply | Lesser occipital nerve; Great auricular nerve; Transverse cervical nerve; Supraclavicular nerves |
Carries touch, pain and temperature sensation from this strip of skin to the spinal cord through the C3 dorsal root.
C3 radiculopathy is uncommon but gives neck pain and altered sensation around the neck, sometimes with occipital headache. The cervical plexus nerves that carry C3 fibres are at risk during neck surgery and are the target of superficial cervical plexus blocks. Dermatome maps differ between sources (Foerster, Keegan and Garrett, and modern evidence-based maps disagree), and neighbouring dermatomes overlap, so borders are approximate.
Compression of the C3 root, usually by C2-C3 foraminal narrowing or arthritis, causing neck pain and numbness in a collar-like band.
An injury at C3 or above affects this dermatome and also threatens breathing, since the diaphragm is supplied by C3-C5.
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