The C7 myotome is tested by elbow extension, the ISNCSCI key movement for C7, through the triceps brachii. C7 also supplies wrist flexion and finger extension. The triceps reflex tests the same root.
| Nerve root | C7 |
|---|---|
| Area | Elbow extension (ISNCSCI key muscles: elbow extensors) |
| How to test | With the elbow bent, the patient straightens the arm against resistance at the forearm. Strength is graded 0-5 on the Medical Research Council scale and compared side to side. |
| Muscles | |
| Nerve Supply | Radial nerve; Median nerve |
Straightens the elbow and contributes to wrist flexion and finger extension.
C7 is the most often affected cervical root, usually from a C6-C7 disc, giving triceps weakness, middle finger numbness and a reduced triceps reflex. In spinal cord injury, preserved C7 lets a person push up and transfer independently. Myotome charts vary slightly between sources, and most muscles receive more than one root, so a single root lesion usually weakens rather than paralyses.
Compression at C6-C7 causing triceps weakness, middle finger numbness and a reduced triceps reflex.
A high radial nerve lesion, as from crutch pressure, weakens triceps along with wrist and finger extensors.
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