Dermatomes and Myotomes of the Upper Limb

Question 1

What is a dermatome?

Answer 1

A dermatome is an area of skin supplied by sensory fibers from a single spinal nerve.

Question 2

What is a myotome?

Answer 2

A myotome is a group of muscles primarily innervated by motor fibers from a single spinal nerve.

Question 3

How are dermatomes of the upper limb organized?

Answer 3

Upper limb dermatomes are arranged in a segmental pattern from the neck down to the fingers.

Question 4

How are myotomes of the upper limb organized?

Answer 4

Upper limb myotomes are arranged proximally to distally, corresponding to specific spinal levels.

Question 5

Which spinal nerves contribute to the dermatomes of the upper limb?

Answer 5

The dermatomes of the upper limb are supplied by spinal nerves C3-T2.

Question 6

Which spinal nerves contribute to the myotomes of the upper limb?

Answer 6

The myotomes of the upper limb are supplied by spinal nerves C5-T1.

Question 7

What is the dermatome distribution of C3 and C4 in the upper limb?

Answer 7

C3 and C4 supply the skin over the shoulder and base of the neck.

Question 8

What is the dermatome distribution of C5 in the upper limb?

Answer 8

C5 supplies the skin over the lateral shoulder and upper arm.

Question 9

What is the dermatome distribution of C6 in the upper limb?

Answer 9

C6 supplies the lateral forearm and thumb.

Question 10

What is the dermatome distribution of C7 in the upper limb?

Answer 10

C7 supplies the middle finger and central palm.

Question 11

What is the dermatome distribution of C8 in the upper limb?

Answer 11

C8 supplies the little finger and medial forearm.

Question 12

What is the dermatome distribution of T1 in the upper limb?

Answer 12

T1 supplies the medial side of the forearm and lower arm.

Question 13

What is the dermatome distribution of T2 in the upper limb?

Answer 13

T2 supplies the medial upper arm and axillary region.

Question 14

Which spinal level is tested by sensory examination over the lateral shoulder?

Answer 14

C5 is tested by sensory examination over the lateral shoulder.

Question 15

Which spinal level is tested by sensory examination over the lateral forearm and thumb?

Answer 15

C6 is tested by sensory examination over the lateral forearm and thumb.

Question 16

Which spinal level is tested by sensory examination over the middle finger?

Answer 16

C7 is tested by sensory examination over the middle finger.

Question 17

Which spinal level is tested by sensory examination over the little finger?

Answer 17

C8 is tested by sensory examination over the little finger.

Question 18

Which spinal level is tested by sensory examination over the medial forearm?

Answer 18

T1 is tested by sensory examination over the medial forearm.

Question 19

Which spinal level is tested by sensory examination over the medial arm?

Answer 19

T2 is tested by sensory examination over the medial arm and axilla.

Question 20

What is the main myotome responsible for shoulder abduction?

Answer 20

C5 is the primary myotome responsible for shoulder abduction (deltoid, supraspinatus).

Question 21

What is the main myotome responsible for elbow flexion?

Answer 21

C6 is the primary myotome responsible for elbow flexion (biceps brachii, brachialis).

Question 22

What is the main myotome responsible for elbow extension?

Answer 22

C7 is the primary myotome responsible for elbow extension (triceps brachii).

Question 23

What is the main myotome responsible for wrist extension?

Answer 23

C6 is the primary myotome responsible for wrist extension (extensor carpi radialis longus and brevis).

Question 24

What is the main myotome responsible for wrist flexion?

Answer 24

C7 is the primary myotome responsible for wrist flexion (flexor carpi radialis and ulnaris).

Question 25

What is the main myotome responsible for finger flexion?

Answer 25

C8 is the primary myotome responsible for finger flexion (flexor digitorum profundus and superficialis).

Question 26

What is the main myotome responsible for finger extension?

Answer 26

C7 is the primary myotome responsible for finger extension (extensor digitorum).

Question 27

What is the main myotome responsible for finger abduction?

Answer 27

T1 is the primary myotome responsible for finger abduction (dorsal interossei).

Question 28

How can dermatomes be clinically tested?

Answer 28

Dermatomes are tested using light touch or pinprick sensation on specific skin regions.

Question 29

How can myotomes be clinically tested?

Answer 29

Myotomes are tested by assessing muscle strength in movements associated with each spinal nerve level.

Question 30

What is the significance of dermatomal and myotomal testing in diagnosing nerve root lesions?

Answer 30

Dermatomal and myotomal testing helps localize nerve root compression or injury in spinal cord disorders.