Spinal nerve root
C4
Muscle contributions
Reported motor contributions, grouped by region. Muscles commonly receive more than one root; these groups are not a serial nerve pathway.
Anterior and lateral neck
- Longus capitis
- Longus colli
- Middle scalene
Respiratory
- Diaphragm
Scapular region
- Levator scapulae
Source-dependent contributions
- Rhomboid major; rhomboid minor — UW includes C4–C5; other references emphasize C5.
- Supraspinatus — UW includes C4–C6; many references give C5–C6.
Other deep posterior neck muscles have segmental posterior-ramus supply; the reviewed references do not resolve every muscle or fascicle to an individual root.