Brachial Plexus

Question 0

Roots of brachial plexus

Answer 0

Formation
Anterior rami of c5 to t1
Usually pass through gap between anterior and middle scalene muscles with the subclavian artery
Sympathetic fibers carried by each root of the plexus are received from gray rami of the middle and inferior cervical ganglia as the roots pass through the scalene muscles

Question 1

Begins and extends

Answer 1

Lateral cervical region and extends into the axilla

Question 2

Trunks

Answer 2

In inferior part of neck, roots unite to form three trunks
C5+c6- superior trunk
Continuation of c7 root- middle trunk
C8+t1- inferior trunk

Question 3

Divisions of trunks

Answer 3

Each trunk divides into anterior and posterior divisions as the plexus passes through the cervicoaxillary canal posterior to the clavicle
Anterior divisions supply the anterior (flexor) compartments of the upper limb and posterior divisions supply the posterior (extensor) compartments of the upper limb

Question 4

Cords

Answer 4

Divisions of the trunks form three cords of the brachial plexus soon the axilla
Anterior divisions of superior and middle trunks unite to form lateral cord
Anterior division of inferior trunk continues as medial cord
Posterior divisions of all three trunks unite to form the posterior cord
Named for relation to second part of axillary artery

Question 5

Branches

Answer 5

Four branches of the supraclavicular part of the plexus arise from the roots and trunks if the plexus: dorsal scapular nerve, long thoracic nerve, nerve to the subclavius and suprascapular nerve. Approachable through neck
Muscular branches arise from anterior rami of c5 to t1 to supply scalene and longus colli muscles
Branches of the infra clavicular part of the plexus arise from the cords of the brachial plexus and are approachable through the axilla

Question 6

Variations in brachial plexus

Answer 6

Anterior rami of c4 or t2 may contribute
Prefixed brachial plexus: c4 to c8
Post fixed brachial plexus: c6 to t2; inferior trunk may be compressed by 1st rib, producing neurovascular symptoms in upper limb
Variations also occur in formation of trunks, divisions and cords, in origin and or combination of branches and in the relationship to the axillary artery and scalene muscles

Question 7

Brachial plexus injuries: c5 and c6

Answer 7

Result from excessive increase in angle between neck and shoulder. Shoulder hits something and stops, but head and trunk continue to move. Stretches or ruptures superior parts of plexus or avulses ( tears) roots of plexus from spinal cord
Waiters tip position: limb hangs by side in medial rotation
Can also occur in newborns after delivery: Erb-Duchenne palsy: paralysis of muscles of shoulder and arm supplied by c5, c6

Question 8

Brachial plexus injuries to inferior parts

Answer 8

Klumpke paralysis
Less common
Occur when upper limb is suddenly pulled superiorly
Injure c8 and t1
Avulses roots of spinal nerves from spinal cord
Short muscles of hand are affected and claw hand results

Question 9

Brachial plexus block

Answer 9

Injection of anesthetic solution into or immediately surrounding axillary sheath interrupts nerve impulses and produces anesthesia of structures supplied by branches of cords of plexus. Tourniquet to keep it there
Inter scalene, supraclavicular, axillary

Question 10

Dorsal scapular nerve

Answer 10

Supraclavicular branch
Originates off posterior aspect of anterior ramus of c5 with frequent c4 contribution
Pierces middle scalene, descends deep to levator scapulae and rhomboids
Innervates rhomboids, levator scapulae

Question 11

Long thoracic nerve

Answer 11

Supraclavicular branch
Originates off of posterior aspect of c5, c6, c7
Superior two rami pierce middle scalene, passes through Cervico axillary canal, descending posterior to c8 and t1 anterior rami, runs inferiorly on superficial surface of serratus anterior
Innervates serratus anterior

Question 12

Suprascapular nerve

Answer 12

Supraclavicular branch
Originates off if superior trunk, receiving fibers from c5, c6, and often c4
Passes laterally across lateral cervical region (posterior triangle of neck), superior to brachial plexus, then through scapular notch, deep to transverse scapular ligament
Innervates supraspinatus and infraspinatus muscles and glenohumeral joint

Question 13

Subclavian nerve

Answer 13

Supraclavicular branch
Originates off of superior trunk, receiving fibers from c5, c6 and often c4
Descends posterior to clavicle and anterior to brachial plexus and subclavian artery, often giving accessory root to phrenic nerve
Innervates subclavius and sternoclavicular joint (accessory phrenic root innervates diaphragm)

Question 14

Lateral pectoral nerve

Answer 14

Infra clavicular branch
originates from side branch of lateral cord, receiving fibers from C5, C6, C7
pierces costocoracoid membrane to reach deep surface of pectoral muscles
a communicating branch to the medial pectoral nerve passes anterior to axillary artery and vein
primarily innervates pectoralis major, but some lateral pectoral nerve fibers pass to pectoralis minor via branch to medial pectoral nerve

Question 15

musculocutaneous nerve`

Answer 15

infraclavicular branch
originates from terminal branch of lateral cord, receiving fibers from c5-c7
innervates muscles of anterior compartment of arm (coracobrachialis, biceps brachii, and brachialis); skin of lateral aspect of forearm
exits axilla by piercing coracobrachialis, descends between biceps brachii and brachialis, continues as lateral cutaneous nerve of forearm

Question 16

median nerve

Answer 16

infraclavicular branch
Lateral root is a terminal branch of lateral cord (C6, C7 fibers)
medial root is a terminal branch of medial cord (c8, t1 fibers)
innervates muscles of anterior forearm compartment (except for flexor carpi ulnaris and ulnar half of flexor digitorum profundus), five intrinsic muscles in thenar half of palm and palmar skin

Question 17

medial pectoral nerve

Answer 17

infraclavicular branch
arises from side branches of medial cord, receiving fibers from C8, T1
innervates pectoralis minor and sternocostal part of pectoralis major
passes between axillary artery and vein, then pierces pectoralis minor and enters deep surface of pectoralis major

Question 18

medial cutaneous nerve of arm

Answer 18

infraclavicular branch
arises from side branches of medial cord, receiving fibers from C8, T1
innervates skin of medial side of arm, as far distal as medial epicondyle of humerus and olecranon of ulna
smallest of plexus, runs along medial side of axillary and brachial veins

Question 19

median cutaneous nerve of forearm

Answer 19

infraclavicular branch
arises from side branches of medial cord, receiving fibers from C8, T1
innervates skin of medial side of forearm, as far distal as wrist
initially runs with ulnar nerve but pierces deep fascia with basilic vein, and enters subcutaneous tissue

Question 20

ulnar nerve

Answer 20

infraclavicular branch
arises: larger terminal branch of medial cord, receiving fibers from C8, T1 and often C7
innervates flexor carpi ulnaris and ulnar half of flexor digitorum profundus (forearm); most intrinsic muscles of hand; skin of hand medial to axial line of digit 4

Question 21

upper subscapular nerve

Answer 21

infraclavicular branch
side branch of posterior cord, receiving fibers from C5
innervates superior portion of subscapularis
passes posteriorly, entering subscapularis directly

Question 22

lower subscapular nerve

Answer 22

infraclavicular branch
side branch of posterior cord, receiving fibers from C6
passes inferolaterally, deep to subscapular artery and vein
innervates inferior portion of subscapularis and teres major

Question 23

thoracodorsal nerve

Answer 23

infraclavicular branch
side branch of posterior cord, receiving fibers from C6, C7, C8
innervates latissimus dorsi

Question 24

axillary nerve

Answer 24

infraclavicular branch
terminal branch of posterior cord, receiving fibers from C5, C6
innervates glenohumeral joint, teres minor and deltoid muscles, skin of superolateral arm (over inferior part of deltoid)
passes through quadrangular space, gices rise to superior lateral brachial cutaneous nerve, then winds around surgical neck of humerus deep to deltoid

Question 25

radial nerve

Answer 25

infraclavicular branch
larger terminal branch of posterior cord (largest of plexus), receiving fibers from C5-T1
innervates all muscles of posterior compartments of arm and forearm, skin of posterior and inferolateral arm, posterior forearm, and dorsum of hand lateral to axial line of digit 4
divides into superficial (cutaneous) and deep (motor) branches