C7 dermatome and nerve root

Cervical spinal root

Where is the C7 dermatome?

The C7 dermatome covers the middle finger, and a strip down the back of the forearm. Its ISNCSCI key sensory point is the back of the middle finger’s proximal phalanx. Its key movement is elbow extension (triceps brachii). The C6/C7 disc is the one that usually compresses C7.

C7 at a glance
Type	Cervical spinal root
Key sensory point	The back of the middle finger’s proximal phalanx
Key movement	Elbow extension
Tendon reflex	Triceps reflex
Usual disc	C6/C7

Try in: Dermatome and Myotome Map Explorer →

C7 myotome: the muscles it supplies

C7 is a major root for 12 of the 19 muscles below and a minor root for the rest.

Muscles C7 supplies, and every root each takes
Muscle	From C7	All its roots
Serratus anterior	Major	C5 to C7
Pectoralis major, sternal part	Major	C7 and C8; C6 and T1 in part
Pectoralis minor	Major	C7 and C8; T1 in part
Latissimus dorsi	Major	C7; C6 and C8 in part
Coracobrachialis	Major	C6 and C7
Triceps brachii	Major, ISNCSCI key muscle	C7; C6 and C8 in part
Pronator teres	Major	C6 and C7
Extensor carpi radialis brevis	Major	C6 and C7
Extensor digitorum	Major	C7; C8 in part
Extensor carpi ulnaris	Major	C7; C8 in part
Flexor carpi radialis	Major	C6 and C7
Palmaris longus	Major	C7 and C8
Subscapularis	Minor	C5 and C6; C7 in part
Teres major	Minor	C5 and C6; C7 in part
Supinator	Minor	C6; C5 and C7 in part
Extensor carpi radialis longus	Minor	C6; C5 and C7 in part
Flexor carpi ulnaris	Minor	C8; C7 and T1 in part
Flexor digitorum superficialis	Minor	C8; C7 and T1 in part
Flexor digitorum profundus	Minor	C8; C7 and T1 in part

Tendon reflexes through C7

Tendon reflexes C7 carries, how each is tested and its roots
Reflex	Role of C7	Tap	Response	Roots
Triceps reflex	Main root	The triceps tendon just above the point of the elbow	The elbow straightens	C6, C7 and C8, mainly C7

Why a C6/C7 disc compresses C7

Cervical roots leave the spine above the vertebra of the same number, so the C7 root leaves between the C6 and C7 vertebrae, right beside the C6/C7 disc. A disc bulging backwards and to the side presses on it there, which is why a C6/C7 disc gives C7 symptoms.

What a C7 root lesion does

Sensation. Numbness or tingling in the C7 band. Usually a smaller patch than the whole band, because C6 and C8 overlap it: Sherrington found in 1893 that cutting a single root in monkeys left no skin entirely without feeling.
Strength. Elbow extension, the standard’s key movement for C7 (triceps brachii). Also weaker where C7 is a major supply: serratus anterior, pectoralis major, sternal part, pectoralis minor, latissimus dorsi, coracobrachialis, pronator teres, extensor carpi radialis brevis, extensor digitorum, extensor carpi ulnaris, flexor carpi radialis and palmaris longus.
Reflexes. The triceps reflex is reduced or absent.

A teaching map. Root territories overlap and vary between people, and a root lesion is diagnosed by examination and imaging, not by a map. Numbness between the legs or around the anus, new bladder or bowel problems, or quickly spreading weakness need emergency care.

Neighboring dermatomes

C6: the outer forearm, the thumb and the index finger
C8: the ring and little fingers, the inner edge of the hand and the inner forearm

Where published maps disagree

Maps disagree whether C7 reaches up the back of the forearm or stays in the hand.
The index finger is C6 in some maps and C7 in others.
The ring finger is C8 in some maps, C7 in others, or split between them.

Dermatome and Myotome Map Explorer, with C7 lit on a front and back body map
Every dermatome, with the disc levels and key movements side by side
Cervical Spine and Skull Base Explorer, the neck’s vertebrae, which the cervical roots leave between, in 3D
Upper Limb Muscles Explorer, the arm’s muscles in 3D
Reflex Arc Simulator, the loop a tendon reflex runs through the spinal cord
Muscles Worked by Exercise 3D Explorer, a whole body colored by root, in its root mode

Sources. Key sensory points and key movements: International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), American Spinal Injury Association, 2019 revision. Muscles: Aids to the Examination of the Peripheral Nervous System, Medical Research Council and the Guarantors of Brain, 5th ed. (2010), cross-checked with Kendall et al. (2005). Reflex roots: Walker (1990), Clinical Methods, 3rd ed., Table 72.1, and StatPearls, “Physiology, Deep Tendon Reflexes”; the main root as the MSD Manual’s “How to Assess Reflexes” names it. Overlap: Sherrington (1893), Phil Trans R Soc Lond B 184:641-763.