Myotomes and Dermatomes: Key Muscles, Movements, and Nerve Roots

C1-C2 Myotome

Cervical flexion.

L1-L2 Myotome

Hip flexion.

C3 Myotome

Cervical side flexion.

L3 Myotome

Knee extension.

C4 Myotome

Scapular elevation.

L4 Myotome

Ankle dorsiflexion.

L5 myotome

big toe extension

C5 Myotome

shoulder abduction

C5 Myotome

Shoulder abduction.

C6 Myotome

Elbow flexion and wrist extension.

S1 Myotome

Ankle eversion and plantarflexion, hip extension.

S2 Myotome

Knee flexion.

S3 Myotome

No specific test action; intrinsic foot muscles (except abductor hallucis).

C7 Myotome

Elbow extension and wrist flexion.

C8 Myotome

Thumb extension.

T1 Myotome

Finger abduction.

C1 Dermatome

Vertex of skull.

C2 Dermatome

Temple, forehead, occiput.

C3 Dermatome

Entire neck, posterior cheek, temporal area, prolongation forward under mandible.

C4 Dermatome

Shoulder area, clavicular area, upper scapular area.

C5 Dermatome

Deltoid area, anterior aspect of entire arm to base of thumb.

C6 Dermatome

Anterior arm, radial side of hand to thumb and index finger.

L1 Dermatome

Back, over trochanter and groin.

L2 Dermatome

Back, front of thigh to knee.

L3 Dermatome

Back, upper buttock, anterior thigh and knee, medial lower leg.

L4 Dermatome

Medial buttock, lateral thigh, medial leg, dorsum of foot, big toe.

L5 Dermatome

Buttock, posterior and lateral thigh, lateral aspect of leg, dorsum of foot, medial half of sole, first, second, and third toes.

S1 Dermatome

Buttock, thigh, and leg posterior.

S2 Dermatome

Same as S1 (Buttock, thigh, and leg posterior).

C8 Dermatome

Medial arm and forearm to index, long, and ring fingers.

T1 Dermatome

Medial side of forearm to base of little finger.

S3 Dermatome

Groin, medial thigh to knee.

T2 Dermatome

Medial side of upper arm to medial elbow, pectoral and midscapular areas.

S4 Dermatome

Perineum, genitals, lower sacrum.

T8-T12 Dermatome

Abdomen and lumbar region.

T3-T6 Dermatone

Upper thorax

T5-T7 Dermatome

costal margin (lower ribs)

C7 Dermatome

lateral arm and forearm to index, long (middle) and ring fingers

What is a dermatome?

A region of skin whose sensory innervation derives from a single spinal nerve root.

How is a dermatome related to the spinal cord?

It corresponds to a single dorsal root ganglion and a single spinal cord level.

What supplies the dermatomes on one side of the body?

A single spinal nerve.

What can the pattern of sensory loss indicate?

It helps determine where in the nervous system the lesion is located.

What is a peripheral nerve distribution?

A region of skin supplied by a named peripheral nerve, formed from multiple nerve roots.

What are the main divisions of dermatomes in the body?

Head & Neck, Trunk, Upper Extremity, Back, Lower Extremity.

What spinal levels correspond to the saddle region?

S2-S4.

What is the role of the dorsal root ganglion in sensory innervation?

It contains the cell bodies of sensory neurons that innervate the skin.

What is the clinical relevance of understanding dermatomes?

It aids in diagnosing nerve injuries and understanding sensory loss patterns.