C2 dermatome and nerve root

Cervical spinal root

Where is the C2 dermatome?

The C2 dermatome covers the back of the scalp, behind the ear and the angle of the jaw. Its ISNCSCI key sensory point is at least 1 cm to the side of the occipital protuberance, or 3 cm behind the ear. No disc compresses C2: no disc lies between the first and second vertebrae.

C2 at a glance
Type	Cervical spinal root
Key sensory point	At least 1 cm to the side of the occipital protuberance, or 3 cm behind the ear
Key movement	None graded: the standard grades C5 to T1 and L2 to S1
Tendon reflex	None tests it on its own
Usual disc	None: no disc lies between the first and second vertebrae

Try in: Dermatome and Myotome Map Explorer →

C2 myotome: the muscles it supplies

ISNCSCI grades no key movement for C2: it grades only C5 to T1 and L2 to S1.

C2 is only a minor root for the sternocleidomastoid.

Muscles C2 supplies, and every root each takes
Muscle	From C2	All its roots
Sternocleidomastoid	Minor	C2 and C3 in part

Sternocleidomastoid: its motor supply is the accessory nerve, cranial nerve XI; C2 and C3 add to it.

C2 and the tendon reflexes

No tendon reflex tests C2 on its own.

Why no disc compresses C2

C2 leaves the spine between the first and second cervical vertebrae, where there is no disc, so a disc never presses on it. Its skin is the back of the scalp, through the greater occipital nerve, and the angle of the jaw and the ear, through the great auricular nerve.

What a C2 root lesion does

Sensation. Numbness or tingling in the C2 band. Usually a smaller patch than the whole band, because C3 overlaps it: Sherrington found in 1893 that cutting a single root in monkeys left no skin entirely without feeling.
Strength. No muscle the bedside examination grades depends mainly on C2.
Reflexes. No tendon reflex depends on C2.

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

C3: the neck, front and back, down to the collarbones

Dermatome and Myotome Map Explorer, with C2 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
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.