Dermatromes & Myotomes

Question 1

C1 Dermatome

Answer 1

Vertex of the skull

Question 2

C2 Dermatome/Myotome

Answer 2

Dermatome: Temple, forehead, occiput
Myotome: Longus colli, SCM, rectus capitis

Question 3

C3 Dermatome/Myotome/Paresthesia

Answer 3

Dermatome: Entire neck extending under the mandible
Myotome: Trapezius, splenius capitis
Paresthesia: Cheek, side of neck

Question 4

C4 Dermatome/Myotome/Paresthesia

Answer 4

Dermatome: Shoulder, clavicular and upper scapular areas
Myotome: Trapezius and levator scapulae
Paresthesia: Horizontal band along clavicle and upper scapula

Question 5

C5 Dermatome/Myotome/Reflexes affected

Answer 5

Dermatome: Deltoid area, anterior aspect of entire arm to base of thumb
Myotome: Supraspinatus, infraspinatus, deltoid, biceps
Reflexes affected: Biceps and Brachioradialis

Question 6

C6 Dermatome/Myotome/Reflexes affected/Paresthesia

Answer 6

Dermatome: Anterior arm, radial side of hand to thumb and index finger
Myotome: Biceps, supinator, wrist extensors
Reflexes affected: Biceps and Brachioradialis
Paresthesia: Thumb and index finger

Question 7

C7 Dermatome/Myotome/Reflexes affected/Paresthesia

Answer 7

Dermatome: Lateral arm and forearm to index, long and ring fingers
Myotome: Triceps and wrist flexors
Reflexes affected: Triceps
Paresthesia: Index, long and ring fingers

Question 8

C8 Dermatome/Myotome/Paresthesia

Answer 8

Dermatome: Medial arm and forearm to long, ring, and little fingers
Myotome: Ulnar deviators, thumb extensors, thumb adductors
Paresthesia: Little finger alone or with two adjacent fingers

Question 9

T1 Dermatome

Answer 9

Dermatome: Medial side of forearm to base of little finger

Question 10

T2 Dermatome

Answer 10

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

Question 11

T3-T12 Dermatomes

Answer 11

Dermatome:
T3-T6 upper thorax
T5-T7: costal margin
T8-T12: abdomen and lumbar region

Question 12

L1 Dermatome/Paresthesia

Answer 12

Dermatome: Back, over trochanter and groin
Paresthesia: Groin

Question 13

L2 Dermatome/Myotome/Paresthesia

Answer 13

Dermatome: Back, front of thigh to knee
Myotome: Psoas, hip adductors
Paresthesia: Anterior hip

Question 14

L3 Dermatome/Myotome/Paresthesia/Reflexes Affected

Answer 14

Dermatome: Back, upper buttock, anterior thigh and knee, medial lower leg
Myotome: Psoas, quadriceps, thigh atrophy
Paresthesia: Medial knee and anterior lower leg
Reflexes Affected: Knee jerk sluggish, positive PKB, pain in full SLR

Question 15

L4 Dermatome/Myotome/Paresthesia/Reflexes Affected:

Answer 15

Dermatome: Medial buttock, lateral thigh, medial leg, dorsum of foot, big toe
Myotome: Tibialis anterior, extensor hallucis
Paresthesia: Medial aspect of calf and ankle
Reflexes Affected: SLR limited, neck flexion painful, ankle decreased, crossed leg raising pain

Question 16

L5 Dermatome/Myotome/Paresthesia/Reflexes Affected:

Answer 16

Dermatome: Buttock, posterior and lateral thigh, lateral aspect of leg, dorsum of foot, medial half of sole, first, second and third toes
Myotome: Extensor hallucis, peroneals, gluteus medius, dorsiflexors, hamstrings, and calf atrophy
Paresthesia: Lateral aspect of leg and medial three toes
Reflexes Affected:

Question 17

S1 Dermatome/Myotome/Paresthesia/Reflexes Affected:

Answer 17

Dermatome: Lateral and plantar aspect of foot
Myotome: Calf and hamstrings, wasting of gluteals, hamstrings and plantar flexors
Paresthesia: Lateral two toes, lateral foot, lateral leg to knee, plantar aspect of foot
Reflexes Affected: SLR limited, Achilles reflex weak or absent

Question 18

S2 Dermatome/Myotome/Paresthesia/Reflexes Affected

Answer 18

Dermatome: Buttock, thigh and posterior leg
Myotome: Calf and hamstrings, wasting of gluteals, hamstrings and plantar flexors
Paresthesia: Lateral leg, knee and heel
Reflexes Affected: SLR limited, Achilles reflex weak or absent

Question 19

S3 Dermatome

Answer 19

Dermatome: Groin, posteromedial thigh to knee

Question 20

S4 Dermatome/Myotome/Paresthesia

Answer 20

Dermatome: Perineum, genitals, lower sacrum
Myotome: Bladder, rectum
Paresthesia: Saddle area, genitals