Brachial Plexus

Question 1

Brachial Plexus Basics

Answer 1

Spinal Nerve Basics: merge of dorsal and Ventral roots

Network of interconnected nerves

Anterior rami split: anterior division (flexors) and posterior division (extensors)

Question 2

Spinal Segments and Distribution Of Upper Limb

Answer 2

Receives most of innervation from C5-T1

Proximal muscles tend to be innervated by more superior nerve segments (C5,C6) Intermediate (C6,C7) and distal muscles tend to be innervated by more inferior segments (C8,T1)

Question 3

Composition of the Brachial Plexus

Answer 3

Root: formed from anterior rami

Trunks: superior (C5,C6), middle (C7) and inferior (C8,T1)

Divisions: anterior and posterior. Posterior gets contribution from all 3 trunks

Cords: lateral cord (all anterior divisions) posterior (all posterior divisions) and medial (all anterior divisions). Named in reference to the axillary artery

Terminal Branches: musculocutaneous, Median, Ulnar, Radial and Axillary

Question 4

Terminal Branches

Answer 4

Musculocutaneous Nerve (C5-C7): comes from lateral cord

Axillary Nerve (C5,C6): comes from posterior cord (innervates shoulder)

Radial Nerve (C5-T1): Innervates everything in the posterior compartment pretty much

Median Nerve (C6-T1): lateral and medial cord

Ulnar (C8,T1): just off medial cord

Question 5

Proximal Branches of the Brachial Plexus

Answer 5

See pics

Question 6

Musculocutaneous Nerve

Answer 6

Motor innervation: Supplying all the muscles of anterior compartment of arm (usually involve flexion of the elbow)

Cutaneous Innervation: skin on lateral forearm (lateral cutaneous nerve of the forearm: branch of the musculocutaneous)

On deep surface of biceps and superficial surface of brachialis

Question 7

Axillary Nerve

Answer 7

Innervates the deltoid and teres minor
Skin on upper lateral arm
Clinically important landmark: travels near SURGICAL NECK of humerus with posterior circumflex humeral artery

Question 8

Radial Nerve

Answer 8

Innervates muscles in the posterior compartment of arm and forearm (extensors)
Skin on: lateral and posterior arm, posterior forearm, dorsolateral hand
Clinically important landmark: travels in radial groove on posterior aspect of the humerus with the deep brachial artery. By midshaft fracture of humerus could be injured

Question 9

Radial Nerve Continued

Answer 9

In the forearm splits into superficial branch (sensory to dorsolateral hand) and deep branch (Motor to muscle most period compartment muscles in the forearm)

Changes names to POSTERIOR INTEROSSEOUS NERVE once it pierces the supinator muscle and enters the posterior compartment

Question 10

Median Nerve

Answer 10

Innervates most muscles in the anterior forearm (Flexors) and some muscles in lateral hand
Skin on lateral palm and tips of digits 1-3
Clinically important landmark: travels through the carpal tunnel

Question 11

Median Nerve in Hand

Answer 11

Common/proper palmar digital nerves innervate skin
Palmar cutaneous branch goes to skin at base of thumb/central palm: branches proximal to carpal tunnel, Innervates skin in the central palm area
Recurrent branch innervates the thenar muscles

Question 12

Ulnar Nerve

Answer 12

Innervates 1.5 muscles (FCU and Medial half of FDP) in the anterior forearm and most intrinsic hand muscles
Skin on medial hand
Clinically important landmark: travels just posterior to the medial epicondyle of the humerus

Question 13

Ulnar Nerve in the Hand

Answer 13

Splits into several named branches that innervate:
Most intrinsic hand muscles
Skin on medial part of hand and 1.5 digits

Question 14

Cords

Answer 14

Picture

Question 15

Subscapular Nerves

Answer 15

Off posterior cord
C5(upper) and C6 (lower)

Innervates subscapularis and teres major (both medially rotate and adduct the arm)

Question 16

Thoracodorsal Nerve

Answer 16

off posterior cord
C6-C 8
Innervates latissimus dorsi (extend, adduct and medially rotate arm)

Question 17

Pectoral Nerves

Answer 17

Medial pectoral: off medial cord. C8, T1. Innervates: pectoralis major and minor

Lateral pectoral: off lateral cord. C5-C7. Innervates pectoralis major.

Muscle actions: major-adducts, medially rotates the arm (also flex/extend arm). Minor-stabilizes the scapula

Question 18

Cord lesions

Answer 18

Medial cord: C8-T1. Ulnar nerve affected. Median as well. No symptoms associated with radial nerve because this stuff is happening after the C8-T1 levels, it’s not that C8-T1 are gone.

Lateral: musculocutaneous nerve affected. Also have another part of median nerve affected. Mostly involves C5,C6 and some C7

Posterior: affected the radial nerve and then Axillary Nerve

Question 19

Roots and Trunks

Answer 19

Supra scapular nerve

Dorsal scapular nerve: actually arising off of C5

Long thoracic nerve: C5,6,7

Question 20

Dorsal Scapular Nerve

Answer 20

Off root of C5

Innervates rhomboid major and minor (retract scapula, depress glenoid cavity)
Levator scapulae (elevates scapula)

Question 21

Long Thoracic Nerve

Answer 21

off roots C5-C7
Innervates: serratus anterior (protracted scapula)

Damage to this nerve results in a specific condition called WINGED SCAPULA

Question 22

SupraScapular Nerve

Answer 22

Off superior trunk

C5,C6

Innervates: supraspinatus (initiates abduction of arm) and infraspinatus (laterally rotates the arm)

Question 23

Trunk Lesions

Answer 23

Musculocutaneous: C5-7
Axillary: C5,C6
Radial: C5-T1
Median: C5/6-T1
Ulnar: C8,T1

Question 24

Superior Trunk Damage

Answer 24

C5 and C6 affected. Take out axillary. You’ll have problems with deltoid. Some sensory issues with skin around shoulder. Will affect musculocutaneous as well but it gets a little C7 so it’ll be spared a little.

Erb’s Palsy

Question 25

Inferior Trunk Damage

Answer 25

C8 and T1. Mostly ulnar affected. All of ulnar will be knocked out. Some of median (recurrent branch in hand). Radial nerve doesn’t innervate and intrinsic muscles of hand (no posterior intrinsic muscles) but there are some that might be affected

Klumpke’s Palsy