Brachial Plexus

Question 1

Brachial plexus is derived from?

Answer 1

Ventral rami of C5-T1

Question 2

Upper limb dermatome

Answer 2

C5-T1

Question 3

How do the dermatomes invade the upper limb?

Answer 3

Dermatomes invade upper limb in pre- to post-axial manner
PRE = lateral and thumb side
POST = medial and pinky side

Question 4

Brachial plexus general innervation

Answer 4

C5 = shoulder
C6-8 = fingers
T1 = medial side of arm

Question 5

Myotomes

Answer 5

Set of muscles innervated by a specific nerve root associated with specific movements

Question 6

Myotome of C5

Answer 6

Abduction, lateral rotation

Question 7

Myotome of C6

Answer 7

Wrist extension

Question 8

Myotome of C7

Answer 8

Wrist flexion, finger extension, elbow extension (important for cervical spinal cord injuries – push out of bed or chair, if intact can use wheelchair)

Question 9

Myotome of C8

Answer 9

Digital flexion

Question 10

Myotome of C6-8

Answer 10

Medial rotation, adduction

Question 11

Reflexes and their nerve associations

Answer 11

C5 = bicecps
C6 = brachioradialis
C7 = triceps

Question 12

Brachial plexus organization

Answer 12

Roots, trunks, divisions, cords, branches (REMEMBER: Remember To Drink Cold Beer)

Question 13

Roots of brachial plexus

Answer 13

Ventral rami from C5-T1

Question 14

Trunks of brachial plexus (with origins)

Answer 14

Upper (C5-6), middle (C7), lower (C8-T1)

Question 15

Cords of brachial plexus (with origins)

Answer 15

Lateral (C5-7), medial (C8-T1), posterior (C5-8) – all are named with respect to relationship with AXILLARY A

Question 16

Cords of brachial plexus (with origins)

Answer 16

Lateral (C5-7), medial (C8-T1), posterior (C5-8)

Question 17

Branches from roots (2)

Answer 17

Dorsal scapular (C5), long thoracic (C5-7)

Question 18

Branches from roots

Answer 18

Dorsal scapular (C5), long thoracic (C5-7)

Question 19

Branch from lateral cord

Answer 19

Lateral pectoral (C5-6)

Question 20

Branch from lateral cord

Answer 20

Lateral pectoral

Question 21

Branches from medial cord (3)

Answer 21

Medial pectoral, medial antebrachial cutaneous (to forearm), medial brachial cutaneous (to arm) – ALL C8-T1

Question 22

Branches from posterior cord (3)

Answer 22

Upper subscapular (C5-6), lower subscapular (C5-6), thoracodorsal (C6-8)

Question 23

Posterior cord terminal branches

Answer 23

Axillary and radial nerves

Question 24

Axillary nerve actions

Answer 24

Motor to deltoid and teres minor mm, cutaneous to lateral arm

Question 25

Radial nerve actions

Answer 25

Motor to posterior arm and forearm, half of brachialis m, cutaneous to dorsolateral hand and posterior forearm

Question 26

The “M” of the brachial plexus

Answer 26

Musculocutaneous, median, and ulnar

Question 27

Median nerve actions

Answer 27

Motor to anterior forearm (thenar muscles and lateral 2 lumbricals), cutaneous to lateral palm and lateral 3.5 digits – MOST OF FOREARM

Question 28

Pattern of median and ulnar nerves (in relation to forearm/hand)

Answer 28

Median n = most of forearm, some of hand

Ulnar n = most of hand, some of forearm

Question 29

Pattern of median and ulnar nerves (in relation to forearm/hand)

Answer 29

Median n = most of forearm, some of hand

Ulnar n = most of hand, some of forearm

Question 30

Ulnar nerve actions

Answer 30

Motor to flexor carpi ulnaris, half of flexor digitorum profundus, all intrinsic hand muscles, cutaneous to medial palm, medial 1.5 digits, and dorsum of medial half of hand

Question 31

Thoracic outlet syndrome

Answer 31

Constriction of narrow area between first rib, clavicle, and scalene muscles where neurovasculature passes – mostly affects C8-T1 (median and ulnar nerves) but can also compress subclavian vasculature – causes pain, numbness, muscle weakness, edema, cold skin, etc.

Question 32

Cervical rib

Answer 32

Extra rib that may compress subclavian a or brachial plexus

Question 33

Erb-Duchenne (Erb’s) palsy

Answer 33

Happens in C5-6 during delivery or when head and shoulders are forcibly extended apart – causes lack of ability to abduct and laterally rotate arm – presents as “waiter’s tip” hand because C7 takes over

Question 34

Klumpke paralysis

Answer 34

“Strap-hanger’s syndrome” – happens in C8-T1 in lower trunk, causes loss of finger flexion, abduction, and adduction to form claw hand (hyperextension of metacarpalphalangeal joints due to loss of flexors and radial deviation of wrist due to loss of flexor carpi ulnaris)

Question 35

Horner syndrome

Answer 35

Loss of sympathetics from T1 (causes ptosis, lack of sweat/anhydrosis, constricted pupil/miosis)