The C7 dermatome centres on the middle finger, front and back, and runs as a narrow strip up the middle of the back of the forearm. It often includes parts of the index and ring fingers. It is the central dermatome of the hand.
| Nerve root | C7 |
|---|---|
| Area | Middle finger, palmar and dorsal surfaces, and a strip up the middle of the posterior forearm |
| 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 middle finger. |
| Nerve Supply | Median nerve (palmar digital branches); Radial nerve (posterior cutaneous nerve of forearm and dorsal digital branches) |
Carries touch, pain and temperature sensation from this strip of skin to the spinal cord through the C7 dorsal root.
C7 is the most commonly affected cervical root, usually from a C6-C7 disc herniation. Typical findings are middle finger numbness, weak elbow extension and a reduced triceps reflex. 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 C7 root at C6-C7 causing pain down the back of the arm into the middle finger, triceps weakness and a reduced triceps reflex.
Narrowing of the cervical canal can cause patchy numbness in the hands, including the C7 area, along with clumsiness and gait problems.
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