The C6 dermatome covers the lateral forearm, the thumb and usually part of the index finger. A handy memory aid is that a thumb held up makes a 6 with the index finger. Most of the area lies on the radial side of the forearm, ending in the thumb.
| Nerve root | C6 |
|---|---|
| Area | Lateral (radial) forearm, thumb and the radial side of the index finger |
| How to test | Light touch and pinprick are compared side to side at the ISNCSCI key sensory point: on the dorsal surface of the proximal phalanx of the thumb. |
| Nerve Supply | Musculocutaneous nerve (lateral cutaneous nerve of forearm); Radial nerve (superficial branch); Median nerve (digital branches) |
Carries touch, pain and temperature sensation from this strip of skin to the spinal cord through the C6 dorsal root.
C6 radiculopathy, most often from a C5-C6 disc herniation or spondylosis, causes pain and tingling down to the thumb with weak wrist extension and a reduced biceps or brachioradialis reflex. Carpal tunnel syndrome can mimic it, but median nerve numbness spares the forearm and the thenar skin supplied by the palmar cutaneous branch. 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 C6 root at C5-C6 causing pain into the thumb, wrist extensor weakness and reduced biceps and brachioradialis reflexes.
Median nerve compression at the wrist causes thumb and index finger tingling that can be confused with C6 radiculopathy, but the forearm is spared.
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